Exoplanets & Planet Formation
Workshop 2023

Book of Abstracts

December 16-19, 2023
Beijing, China

Format for each submission:
Family-Name, Given-Name(s) / Email / Institute
Title
Abstract

Orals (in the sequence of the program):--------------------------------Dong Ruobing / rbdong@uvic.ca / University of Victoria
Some recent JWST and ALMA observations of protoplanetary disks
ALMA and JWST have been the powerhouse of protoplanetary disk observations. I will
introduce two programs in which we use JWST and ALMA to image disks. In one of them, we
use JWST to characterize a sample of protoplanetary disks with gaps and spiral arms, and to
search for the predicted spiral-driving and gap-opening planets. In the other program, we use
ALMA to study the gas kinematics in a protoplanetary disk potentially gravitationally unstable.
--------------------------------Harsono, Daniel / dharsono@gapp.nthu.edu.tw / NTHU
Composition of planet-forming disks from ALMA and JWST
Planets are formed in accretion disks around young stars. Recent results suggest that theplanet formation process begins in the earliest stages of star formation. ALMA has unveiled adiversity in the characteristics of planet-forming disks around young stars. Meanwhile, JWST
is starting to provide us with the ingredients of these planets by studying the composition oficy dust grains and the hot inner disk. I will present recent results with ALMA and JWST thatexamine the composition of young planet-forming disks.
--------------------------------Yang, Haifeng / hfyangpku@gmail.com / Peking University
Eccentric dust ring and scattering-induced polarization in the IRS 48 transition disk
Crescent-shaped structures in transition disks hold the key to studying the putative
companions to the central stars. The dust dynamics, especially that of different grain sizes, isimportant to understanding the role of vortices in planet formation. In this work, we present
deep polarized dust continuum observation with high resolution towards the Oph IRS 48
system. For the first time, we are able to trace and detect emission along the entire orbit
crossing the crescent-shaped structure. The orbit is hightly eccentric with an eccentricity of
0.27. In addition, we detect a compact emission toward the central star with a dust mass of
1.5e-8 solar mass, or 0.005 earth mass. The polarization comes mostly from self-scatteringof dust grains, with grain sizes of about 100 micron. We show that the dust scale height has
a strong impact on the polarization. We are able to constrain the dust scale height accurately,
which gives the turbulent viscosity alpha of about 10^-4~10^-3. Together, our observations
reveal a turbulent vortex in a highly eccentric orbit in the transition disk system IRS 48.
--------------------------------Muto, Takayuki / muto@cc.kogakuin.ac.jp / Kogakuin University
Methods to Explore the Disk Asymmetries and its Application to a Young Protoplanetary Disk
Substructures in protoplanetary disks have indications on physical processes at work in disks
such as vortex formation, dust accumulation, and planet formation. Disk substructures havealso been under active debate observationally since ALMA has enabled to deliver the high1spatial resolution data. Yet, it is still difficult to obtain the structures in the spatial scales
comparable to the Solar System (~several au) with standard CLEAN imaging methods. In
this presentation, we propose a method to extract non-axisymmetric structures in the disk bydirect visibility analyses. We show it is possible to find asymmetric structures with the spatial
scale comparable to or less than the beam size of standard CLEAN methods. We also show
the application of the methods to a young protoplanetary disk system, which is indicated tohave an asymmetric ring-like structure at the deeply embedded phase of its evolution.
--------------------------------Yang, Jun / junyang@pku.edu.cn / Peking University
Cloud behaviour on tidally locked rocky exoplanets
Determining the behaviour of convection and clouds is one of the biggest challenges in our
understanding of exoplanetary climates. Given the lack of in situ observations, one of themost preferable approaches is to use cloud-resolving or cloud-permitting models (CPM).
Here we present CPM simulations in a quasi-global domain with high spatial resolution(4 × 4 km^2 grid) and explicit convection to study the cloud regime of 1:1 tidally locked rocky
planets orbiting around low-mass stars. We show that the substellar region is covered bydeep convective clouds and cloud albedo increases with increasing stellar flux. The CPM
produces relatively lower cloud liquid water concentration, smaller cloud coverage, lower
cloud albedo and deeper H2O spectral features than previous general circulation model
simulations using empirical convection and cloud parameterizations. Furthermore, cloudstreets—long bands of low-level clouds oriented nearly parallel to the direction of the meanboundary-layer winds—appear in the CPM and substantially affect energy balance andsurface precipitation at a local level.
--------------------------------Yan, Fei / yanfei@ustc.edu.cn / University of Science and Technology of China
Characterizing the dayside atmospheres of ultra-hot Jupiters
Characterizing exoplanet atmosphere is a frontier subject in the exoplanet field. By observing
the spectra of exoplanet atmospheres, we can probe their chemical compositions as well as
physical conditions such as temperature structures, global circulations, and atmosphericescape. In this talk, I will present the recent research on ultra-hot Jupiter, which is a class ofgiant exoplanets with extremely high temperatures. We have conducted a survey of a dozen
ultra-hot Jupiters using ground-based high-resolution spectrographs, such as CRIRES+,CARMENES, HARPS-N. By observing their thermal emission spectra, we detected various
chemical species, including Fe, Si, CO, OH. Particularly, we found that temperature inversion
layers are common on their dayside hemispheres.
--------------------------------Tan, Xianyu / xianyut@sjtu.edu.cn / Shanghai Jiao Tong University
Meteorology of brown dwarfs
Most brown dwarfs (BDs) and directly imaged exoplanets characterized so far lack significant
external stellar irradiation and their atmospheres are sculpted by the internal heat flux. They
provide valuable testbeds to understand the climate physics of planetary atmospheres in the
self-luminous regime. Recent surveys have revealed that variability is common among theseobjects with a small fraction having exceptionally large variability amplitudes. Spectroscopic
information on the variability has also been obtained from space-based and ground-based
facilities. JWST spectroscopic time-series observations of these objects will lead to further
breakthrough discoveries. Observations are more than rich to pose critical questions about
the climate dynamics of these atmospheres, but theory and modeling are relatively behind.
Our recent theoretical development suggested that cloud radiative feedback coupled withatmospheric dynamics could lead to a self-sustained dynamical system, and such a system
2would generate large-scale turbulence and traveling waves, producing variability withmorphology and amplitudes that could broadly explain some of the observed variability. Our
general circulation model is further developed to have a nongrey radiative transfer, therefore
being able to predict spectroscopic variability and spectrum as a result of such a dynamicalsystem and directly compare to observations.We use VHS1256b, which is the BD with thelargest variability amplitude detected so far, as a template to illustrate how we can use
spectrum and variability simultaneously to constrain the atmospheric properties.
--------------------------------Wei, Xing / xingwei@bnu.edu.cn / Beijing Normal University
Hot Jupiters' radius anomaly and exomoons' retention
I will talk about the two recent projects, why hot Jupiters' radii are larger than Jupiter's but not
too large, and how exomoons can be retained around their host planet.
--------------------------------Chiang, Eugene / echiang@astro.berkeley.edu / UC Berkeley
Accreting protoplanets
The hunt is on for protoplanets in young, gas-rich discs. How bright these planets are, andwhat they will grow to become, depend on their gas accretion rates, which may be in the
runaway regime. We discuss how planet accretion may play out in gas discs, and theprospects of detecting protoplanets via their broadband spectral energy distributions.
--------------------------------Wang, Yu / wang-y21@mails.tsinghua.edu.cn / Tsinghua University
Atmospheric recycling of volatiles by pebble-accreting planets
Planets, embedded in their natal discs, harbour hot envelopes. When pebbles are accretedby these planets, the contained volatile components may sublimate, enriching the envelope
and potentially changing its thermodynamical properties. However, the envelopes of
embedded planets actively exchange material with the disc, which would limit the buildup ofa vapour-rich atmosphere. To properly investigate these processes, we have developed a
new phase change module to treat the sublimation process with hydrodynamical simulations.
Combined with the recently developed multidust fluid approach, we conduct 2D selfconsistent hydrodynamic simulations to study how pebble sublimation influences the watercontent of super-Earths and sub-Neptunes. We find the extent and the amount of vapour thata planet is able to hold on to is determined by the relative size of the sublimation front andthe atmosphere. When the sublimation front lies far inside the atmosphere, vapour tends tobe locked deep in the atmosphere and keeps accumulating through a positive feedback
mechanism. On the other hand, when the sublimation front exceeds the (bound) atmosphere,
the ice component of incoming pebbles can be fully recycled and the vapour content reaches
a low, steady value. Low disc temperature, small planet mass, and high pebble flux render
the planet atmosphere vapour-rich while the reverse changes render it vapour-poor. The
phase change module introduced here can also be employed to model the chemicalcomposition of the gas in the vicinity of accreting planets and solid enhancement aroundsnowlines.
--------------------------------Chen, Kan / kan.chen.21@ucl.ac.uk / University College London
Planet Gap-opening Feedback on Disk Thermal Structure and Composition(Exo-)planets inherit their budget of chemical elements from a protoplanetary disk. The disk
temperature determines the phase of each chemical species, which sets the composition of3

solids and gas available for planet formation. We investigate how gap structures, which arecommon in recent disk observations, alter the thermal and chemical structure of a disk.
Planet-disk interaction is a leading hypothesis of gap formation and so such changes could
present a feedback that planets have on planet-forming material. Both the planet gapopening process and the disk thermal structure are well studied individually, but how the gapopening process affects disk thermal structure evolution remains an open question. We
develop a new modelling method by iterating hydrodynamical and radiative transfer
simulations to explore the gap-opening feedback on disk thermal structure. We carry out
parameter studies by considering different planet locations $\rp$ and planet masses $\Mp$.
We find that for the same $\rp$ and $\Mp$, our iteration method predicts a wider and deeper
gap than the non-iteration method. We also find that the inner disk and gap temperature fromthe iteration method can vary strongly from the non-iteration or disk without planets, which
can further influence dust-trap conditions, iceline locations, and distribution of various ices,such as \ce{H2O}, \ce{CO2}, and CO on large dust grains (“pebbles”). Through that, a gapopening planet can complicate the canonical picture of the non-planet disk C/O ratio andinfluence the composition of the next generation of planetesimals and planets.
--------------------------------Hammer, Michael / mhammer44444@gmail.com / ASIAA
How to form compact & other longer-lived planet-induced vortices: VSI, planet migration, or
re-triggers, but not feedback
Past computational studies of planet-induced vortices have shown that the dust asymmetries
associated with these vortices can be long-lived enough that they should be much morecommon in mm/sub-mm observations of protoplanetary discs, even though they are quiterare. Observed asymmetries also have a range of azimuthal extents even thoughcomputational studies have shown planet-induced vortices should be preferentiallyelongated. In our recent study, we use 2-D and 3-D hydrodynamic simulations to test whether
those dust asymmetries should really be so long-lived or so elongated. With higher resolution(29 cells per scale height) than our previous work, we find that vortices can be more compact
by developing compact cores when higher-mass planets cause them to re-form, or if they areseeded by tiny compact vortices from the vertical shear instability (VSI), but not through dust
feedback in 3-D as was previously expected in general. Any case with a compact vortex orcore(s) also has a longer lifetime. Even elongated vortices can have longer lifetimes withhigher-mass planets or if the associated planet is allowed to migrate, the latter of which can
prevent the dust asymmetry from decaying as the planet migrates away from the vortex.
These longer dust asymmetry lifetimes are even more inconsistent with observations. Our
ongoing work suggests this discrepancy is not easy to explain with cooling, perhaps insteadsuggesting that discs have an intermediate amount of effective viscosity that prevents
vortices from being more prevalent in protoplanetary discs.
--------------------------------Liu, Hauyu Baobab / baobabyoo@gmail.com / Sun Yat-sen University, Kaohsiung
A tale of pebble formation
A complete model of planet formation needs to explain the co-existence of water/carbon
deficient planets such as Earth and Mars and the icy giants such as Neptune and Uranus.
This implies that we need to understand the coagulations of the water-ice-coated and waterice-free dust grains. I will base on observational case studies to suggest that the water-icefree dust grains in the innermost part of the protoplanetary disks can grow to larger than 1
mm size without being limited by the classical fragmentation/bouncing barrier. The
coagulation of water-ice-coated dust seems to be limited by the fragmentation/bouncing
barriers in general, while icy-pebble formation in some localized regions appears possible.
While I do not yet have a good idea about the physical mechanism that promotes theformation of the icy-pebble, it seems to me that icy-pebble tends to show azimuthally
4asymmetric distributions.
--------------------------------Lin, Min-Kai / mklin@asiaa.sinica.edu.tw / ASIAA
Streaming instability: Reborn
The ‘streaming instability’ (SI) between dust and gas in protoplanetary disks is the leadingmechanism to form planetesimals — the building blocks of planets. However, the simplicity of
the SI is challenged by the complex physics involved in a realistic protoplanetary disk. I
describe how turbulence, vertical structure, and thermodynamics can hinder the SI; but also
how accretion flows and magnetic fields can help to revive it, albeit in modified forms, whichshould be investigated in future simulations.
--------------------------------Li, Rixin / rixin@berkeley.edu / UC Berkeley
From Dust to Planetesimals, from Young to Evolved Protoplanetary Disks
The first step in planet formation is to build planetesimals from dust grains in protoplanetarydisks. The origin and demographics of planetesimals are crucial to understanding the Solar
System, exoplanetary systems, and circumstellar disks. In this talk, I will present our latest
works on planetesimal formation via the streaming instability, a mechanism to
aerodynamically concentrate dust and produce planetesimals. By contextualizing our models
in disks at various evolutionary stages, I will show that planet formation is well underway inmassive young disks, and small bodies in the pristine Cold Classical Kuiper Belt formed latein the solar nebula's lifetime. I will then discuss the implications and links between our results
and recent disk observations, as well as Solar System explorations.
--------------------------------Huang, Pinghui / phhuang10@gmail.com / University of Victoria
Dust Clumping in Outer Turbulent Protoplanetary DisksThe Vertical Shear Instability (VSI) is a robust hydrodynamic phenomenon that occurs withina range of tens to hundreds of astronomical units (AU) in protoplanetary disks, significantly
impacting disk accretion and evolution. The Rossby Wave Instability (RWI) has the capability
to generate anticyclonic vortices, effectively trapping dust and thereby promoting dust
concentration and growth. Simultaneously, the Streaming Instability (SI) offers a promisingmechanism for creating strong dust clumps, which contribute to the formation ofplanetesimals. In this study, we utilized the newly developed multifluid dust module inAthena++ to conduct 3D global simulations, showcasing the coexistence of VSI, RWI, and SI
within protoplanetary disks. Although the weak zonal flows induced by VSI and the subtle
dusty vortices arising from RWI may not achieve complete dust trapping, these mild pressure
variations do make significant contributions to dust clumping driven by SI. When all three
instabilities coexist, they result in more pronounced dust clumping compared to scenarios
where only a single instability is active.
--------------------------------Lai, Dong / dong@astro.cornell.edu / Cornell University/TDLIHot Jupiters and Super-Earths: Spin-Orbit Dynamics in Exoplanetary Systems
I will discuss two topics on exoplanetary systems. The first concerns hot Jupiters, giant
planets with orbital periods of a few days. Observations have revealed that many hot Jupiters
have orbits that are highly misaligned with the rotation of their host stars. How did such large
stellar obliquities come about? What do they inform about the formation of hot Jupiters? The
second topic deals with planetary obliquity, which reflects the planet's dynamical history, and5

can strongly influence the atmosphere condition and climate of the planet. Many Sun-likestars are observed to host close-in super-Earths (or Earth-like planets) as part of a multiplanetary system. Can such super-Earths (or similar habitable planets around M stars)
sustain significant obliquities?
--------------------------------Dai, Fei / fdai@caltech.edu / Caltech
Dynamical Evolution of Near Resonant Planetary Systems
Convergent disk migration has long been suspected to be responsible for forming planetarysystems with a chain of mean-motion resonances. Dynamical evolution over time could
disrupt the resonant configuration to form the non-resonant Kepler multi-planet systems. We
contrast two planetary systems TOI-1136 and TOI-4495. TOI-1136 is a 700-Myr old G starwith 6 transiting planets in a chain of mean-motion resonances. The orbital period ratios
deviate from exact commensurability by only 1e-4, smaller than the deviations of 1e-2 seen
in mature Kepler near-resonant systems. TOI-1136 appears to be a pristine example of theorbital architecture emerging from convergent disk migration before dynamical processes
disrupt the resonance. The resonant chain also contains a very delicate 7:5, 2nd orderresonance that favors a gentle Type-I migration in a low-density disk with an inner edge at
about 0.05AU. On the other hand TOI-4495, ~2Gyr, has two planets that have apparently
broken away from mean-motion resonance. We discuss how these two systems could
represent snaps of dynamical evolution of hundreds of Kepler-like systems--------------------------------Huang, Xiumin / huangxm@pmo.ac.cn / PMO, CAS
The EKL mechanism explains the retrograde orbits and retrograde rotation of the planets
around the binary star.
The Eccentric Kozai-Lidov (EKL) mechanism plays an essential role in exploring significant
oscillations of the mutual inclination between the planet and the secondary. We perform
qualitative analysis and extensive numerical integrations to investigate the flip conditions andtimescales of γ Cep Ab’s orbit. The timescale for the first orbital flip decreases along with theincrease of the perturbation Hamiltonian. The flipping orbits of γ Cep Ab are confirmed tohave a large possibility to retain stable based on surfaces of section and the secular stability
criterion. For general S-type planetary systems with a1/a2 ≤ 0.1, where the most intense
excitation of i occurs when a1/a2 = 0.1 and e2 ~ 0.8. The planetary obliquity is also asignificant factor in determining the physical properties of planetary surfaces and the climate.
Secular dynamical theories are helpful to predict the evolution of the planetary obliquity,especially when direct detections are limited by the observation accuracy. The EKL and theequilibrium tide are coupled to investigate the diverse secular evolution paths of planetary
obliquity. For close-in S-type terrestrial planets in binary star systems, the planetary obliquity
could first undergo the excitation to be retrograde, then enters the quasi-equilibrium state
between 40° and 60°. The maximum obliquity can reach 130° when ttide/tkl > 10000.
Qualitative simulation results indicate the maximum obliquity increases with the semi-major
axis ratio a1/a2 and the perturbing body's eccentricity e2. For general S-type terrestrials with
a1~0.1 au and a2<45 au, the retrograde possibility could be 73%. Spin evolution trends ofseveral observed hot-Jupiters in binary star systems are estimated as well.
--------------------------------Wang, Su / wangsu@pmo.ac.cn / Purple Mountain Obervatory, CAS
The Formation of Hot Jupiter and Its Companions
Gas giants in transiting multi-planetary systems are intrinsically much rarer compared to thetypical transiting multiple planetary systems only host Super-Earth/Sub-Neptunes discoveredby Kepler mission. Compared with the small planet multiple systems, the occurrence rate of6multiple planetary systems with gas giants with longer periods increases and there is a pileup near the 2:1 mean motion resonance. In this work, we investigate the three-dimensional
configuration formation of short-period gas giant and its low-mass companions under the
influence of the orbital migration of planets in the protoplanetary disk, and the post orbital
evolution influenced by the atmospheric mass loss and tidal effect induced by the central
star. We find that in the orbital migration phase, the mutual inclination excitation is related tothe competition between the eccentricity damping timescale and the migration timescale, andthe mass ratio between planets. And the mutual inclinations between the gas giant and its
low-mass companions are hard to be excited to larger than six degrees. More planet pairs innear 3:2 MMR have higher opportunities to be in non-coplanar with a mutual inclination of
few degrees than they are in 2:1 MMR. After the gas disk vanished, the atmospheric massloss and tidal effect are two key factors that influence the final orbital configurations. Withhigher mass loss fraction and hotter jupiter, the mutual inclination can be excited to higher
value which is a possible reason of more gas giant multiple planetary system with longer
periods have been found. The simulation results is consistent with the observed period ratio
obtained from Kepler mission with a mass loss fraction less than 15% of its total mass.
Based on the estimation of the expected TTV amplitude of the resulted systems, we predictat least 1-2 systems existed in TESS data with a single transiting super-earth within period of
10 days with TTV amplitude higher than three minutes due to a non-transiting gas giant.
--------------------------------Fang, Min / mfang@pmo.ac.cn / Purple Mountain Observatory
Disk winds from protoplanetary disks
Planet systems are formed from the dust and gas present in protoplanetary disks
surrounding young stars. The evolution and eventual dispersal of these protoplanetary disks
strongly influence their formation. Among the physical processes that govern the evolution
and dispersal of protoplanetary disks, disk winds have been identified as one of the key
factors supported by observations and theories. In this talk, I will provide an overview of theadvancements in our understanding of disk winds from observational perspective.
--------------------------------Chen, Yuan / ychen@strw.leidenuniv.nl / Leiden Observatory
Tracing complex organic molecules (COMs) from ice to gas in YSOs with JWST and ALMA
How the chemistry in the universe evolves from diffuse interstellar medium to a life-harboring
environment on our Earth? Star formation stages from molecular clouds to protostars tocircumstellar disk and protoplanets are the key stages in this cosmic chemical evolution. In
particular, complex organic molecules (COMs), typically defined as carbon-bearing
molecules with at least six atoms, have gained their popularity over the past several decades
due to their importance of linking atoms and simple molecules with prebiotic species. So far,more than 80 COMs have been detected in various environments. The emission lines ofrotational transitions of gas-phase COMs can be observed in (sub)millimeter wavelengths
using radio telescopes, in which the most powerful one is the Atacama Large
Millimeter/submillimeter Array (ALMA). With its high sensitivity and resolution (both spatialand spectral), ALMA has detected a rich inventory of COMs in star-forming regions, mostly inClass 0 protostars. The detection of COMs in the solid phase (i.e., in ices) was only
confirmed for methanol (CH3OH), the simplest COM, but is now becoming possible for otherCOMs with the James Webb Space Telescope (JWST) and its Mid-InfraRed Instrument(MIRI). Tracing COMs in both phases in YSOs will help us probe their formation history andshed light on how the chemistry evolves from simple to complex in the universe. This talk willshow the results from latest ALMA and JWST observations with a nonexclusive focus on
oxygen-bearing COMs (O-COMs), which are the most abundant and therefore detectable forboth telescopes. By comparing the ratios between O-COMs and the reference species suchas water and methanol, we find that most of the COMs are likely to be formed in ices during
7

the early stages of star formation. However, the gas-phase reprocessing may also act onsome species, which needs to be studied more statistically in a larger sample.
--------------------------------Wang, Mutian / mutianwang@smail.nju.edu.cn / Nanjing Univerisity
The Accretion History of EX Lup: A Century of Bursts, Outbursts, and Quiescence
EX Lup is the archetype for the class of young stars that undergoes repeated accretion
outbursts of ∼ 5 mag at optical wavelengths and that last for months. Despite extensive
monitoring that dates back 130 years, the accretion history of EX Lup remains mostly
qualitative and has large uncertainties. We assess historical accretion rates of EX Lup by
applying correlations between optical brightness and accretion, developed on multi-band
magnitude photometry of the ∼ 2 mag optical burst in 2022. Two distinct classes of bursts
occur: major outbursts (ΔV ∼5 mag) have year-long durations, are rare, reach accretion ratesof ∼ 1e−7 M⊙ yr−1 at peak, and have a total accreted mass of around 0.1 Earth masses.
The characteristic bursts (ΔV ∼ 2 mag) have durations of ∼ 2−3 months, are more common,
reach accretion rates of ∼ 1e−8 M⊙ yr−1 at peak, and have a total accreted mass of around1e−3 Earth masses. The distribution of total accreted mass in the full set of bursts is poorly
described by a power law, which suggests different driving causes behind the major
outbursts and characteristic bursts. The total mass accreted during two classes of bursts isaround two times the masses accreted during quiescence.
--------------------------------Calcino, Josh / josh.calcino@gmail.com / Tsinghua University
Kinematic Signatures of Circumbinary Discs: Spiral arms, Fast Flows, and Doppler Flips
Kinematic studies of protoplanetary discs are becoming a valuable method for uncovering
hidden companions. While there exists a subtantial amount of literature on the understandingof planet-disc interactions and their observational implications, little attention has been madetowards circumbinary discs. Using 3D hydrodynamical simulations post-processed with
Monte Carlo radiative transfer, I found several kinematic and morphological features that canidentify circumbinary discs. I will show that Doppler flips, spiral arms, eccentric gas motion,and vortex-like kinematic signatures are commonly seen. These complex kinematic
structures may explain some of the observed, and potentially misinterpreted, kinematic
signatures seen in the literature.
--------------------------------Wu, Yanqin / wu@astro.utoronto.ca / University of Toronto
Shinning lights on proto-planetary Disks
I will discuss how multiple observational puzzles may be related to the effects of stellar
irradiation on disks, and how the planet hypothesis may not be the ultimate answer.
--------------------------------Deng, Hongping / hpdeng353@shao.ac.cn / Shanghai Astronomical Observatory
Are warps in class II circumstellar discs inherited from their formation?
Circumstellar discs, the cradle of planets, are likely formed warped due to the accretion of
misaligned infall and streamers. Understanding the evolution of warped circumstellar discs isthus crucial for the planet formation theory. We show via direct hydrodynamic simulations
that warps in young circumstellar discs are efficiently damped by spiral density waves within
thousands of years. As the disc evolves, when its self-gravity is negligible, a parametricinstability takes over to align the disc rapidly. As a result, it is unlikely to pass on any
misalignment in the formation stage to the widely observed warped, million-year-old class II
8

discs. One potential solution to this puzzle is the formation of misaligned giant planets via
disc fragmentation, which can break up the internal flow for disc alignment and maintainwarps.
--------------------------------Li, Jiaru / jiaru.li@northwestern.edu / CIERA - Northwestern University
Resonant Excitation of Planetary Eccentricity due to a Dispersing Eccentric Protoplanetary
Disk: a New Mechanism of Generating Large Planetary Eccentricities
I will present a new mechanism of generating large planetary eccentricities. This mechanism
applies to planets within the inner cavities of their companion protoplanetary disks. A massive
disk with an inner truncation may become eccentric due to non-adiabatic effects associatedwith gas cooling, and can retain its eccentricity in long-lived coherently-precessing eccentricmodes; as the disk disperses, the inner planet will encounter a secular resonance with theeccentric disk when the planet and the disk have the same apsidal precession rates; theeccentricity of the planet is then excited to a large value as the system goes through theresonance. We solve the eccentric modes of a model disk for a wide range of masses. We
then adopt an approximate secular dynamics model to calculate the long-term evolution ofthe "planet + dispersing disk" system. The planet attains a large eccentricity (up to 0.6) in our
calculations, even though the disk eccentricity is quite small (~0.05).
--------------------------------Lee, Man Hoi / mhlee@hku.hk / The University of Hong Kong
Resonant Chains and the Convergent Migration of Planets in Protoplanetary Disks
An increasing number of compact planetary systems with multiple planets in a resonant
chain have been detected. The resonant chain must be maintained by convergent migrationof the planets due to planet-disk interactions, if it is formed before the dispersal of the
protoplanetary gas disk. For type I migration in an adiabatic disk, we show that an analytic
criterion for convergent migration can be developed by requiring that any part of the resonant
chain should be convergently migrating toward the remaining part. The criterion depends
primarily on the logarithmic gradients of the surface density and temperature profiles of thedisk, and it is independent of the absolute values of the surface density and temperature. The
analytic criterion is applied to the Kepler-60, Kepler-80, Kepler-223, TOI-178, and
TRAPPIST-1 systems. Due to the variation of planetary masses within the resonant chains,
we find that convergent migration typically requires rather extreme values of the logarithmic
gradients that have little or no overlap with common disk models. Finally, we show that there
is a empirical relationship between the distance of the innermost planet from the central starand the stellar mass for the observed resonant chain systems, which supports the idea thatthe resonant chains are formed and maintained by stalling the migration of the innermost
planet near the inner edge of the disk truncated by the magnetic fields of the protostar.
--------------------------------Fujii, Yuri / fujii.yuri.2z@kyoto-u.ac.jp / Kyoto University
Reexamination of Cosmic-Ray Ionization Rate in Protoplanetary Disks with Sheared
Magnetic Fields
The magnetic fields in protoplanetary disk are stretched to the azimuthal directions due to thevelocity shear. Thus, the cosmic rays entering into the disk need to detour while propagating
to the midplane. However, most of the previous studies assume that cosmic rays travel to the
midplane straightly from the vertical direction. We investigate the effects of magnetic-field
configurations on the ionization rate by cosmic rays in protoplanetary disks. First, weconsider cosmic-ray propagation from the interstellar medium (ISM) to the protoplanetarydisks in the case that magnetic fields threading the protoplanetary disk are connected to its
parent molecular cloud, and show that the cosmic-ray density around the disk should be 4
9

times lower than the isotropic ISM value. Then, we compute the attenuation of cosmic rays inprotoplanetary disks. Our result show that the detouring effectively enhances the column
density by about two orders of magnitude. We employ a typical ionization rate by cosmic rays
in diffuse ISM, which is considered too high to be consistent with observations ofprotoplanetary disks, and find that the cosmic rays are significantly shielded at the midplane.
In the case of the disk around IM Lup, the midplane ionization rate is very low for inner to~100 au, while the value is as large as a diffuse ISM in the outer radii. Our results are
consistent with the recent ALMA observation that indicates the radial gradient in the cosmicray ionization rate. The high ionization rate in the outer radii of disks may activate themagnetorotational instability that was thought to be suppressed due to ambipolar diffusion.
These results will have a strong influence on the dynamical and chemical evolutions ofprotoplanetary disks.
--------------------------------Okuzumi, Satoshi / okuzumi@eps.sci.titech.ac.jp / Tokyo Institute of Technology
Thermal evolution of protoplanetary disks
Understanding how the thermal structure of protoplanetary disks evolves is essential for
addressing the fundamental question of how and where planets of varying compositions
form. Classical solar system formation theory assumed that the solar nebula's snow line
resided at the current position of the asteroid belt. However, models of disk evolution showthat the snow line's location is, in fact, highly uncertain and depends on the disk's heating
and cooling processes. In this presentation, I will discuss our recent efforts to model thethermal evolution of protoplanetary disks, with a specific focus on MHD-induced Joule
heating, planet-induced shock heating, and self-shadowing caused by dust pileups.
--------------------------------Lee, Yueh-Ning / ynlee@ntnu.edu.tw National / Taiwan Normal University
Non-ideal MHD and the size of early protoplanetary disks
Many mechanisms have been proposed to alleviate the magnetic catastrophe, that prevents
the Keplerian disk from forming inside a collapsing magnetized core. Such propositions
include inclined field and non-ideal magnetohydrodynamics effects, and have been
supported with numerical experiments. Models have been proposed for typical disk sizes
when a field threads the rotating disk, parallel to the rotation axis, while observations at thecore scales do not seem to show any correlation between the directions of angularmomentum and the magnetic field. In this talk, I will present a new model that considers
vertical and horizontal fields and discuss their effects on the protoplanetary disk size.
--------------------------------Zhang, Shangjia / shangjia.zhang@unlv.edu / University of Nevada, Las Vegas
Vertical Shear Instability in Stellar-Irradiated Protoplanetary Disks
Vertical Shear Instability (VSI) is a promising candidate for the source of turbulence inprotoplanetary disks. We use Athena++ radiation module to study VSI in full and transition
disks, considering radiation transport and stellar irradiation. With stellar irradiation, thelocation of the inner rim is crucial for the disk thermal structure. The thermal structure has astrong impact on velocity components and turbulence levels. With a temperature gradient in
the vertical direction, the typical n=1 corrugation mode disappears in realistic disk setups.
The shear can be the strongest near the tau=1 surface for the star, which leads to a strong
accretion. At several gas scale heights, radial-azimuthal turbulence stress is stronger thanthat in the vertically isothermal simulations, closer to the vertical-azimuthal stress (~1e-2). In
the midplane, the stresses can be weak (~1e-4-1e-3). The weak turbulence in the midplane
and the closer-to-isotropic turbulence levels are consistent with highly settled dust layers
from dust continuum observations.
10--------------------------------Hirano, Teruyuki / hd17156b@gmail.com / Astrobiology Center / National Astronomical
Observatory of Japan
Exoplanet Detection and Characterization by the InfraRed Doppler (IRD) Instrument on
SubaruIRD is a fiber-fed near-infrared spectrograph covering 950-1730 nm with a spectral resolutionof R~70000. It is designed to achieve an exceptional radial-velocity (RV) precision (1-2 m/s)
in the near infrared for mid-to-late M dwarf stars, which are generally faint in the visible. With
IRD, we have conducted 1) a blind Doppler survey for mid-to-late M dwarfs, 2)
validations/confirmations of transiting-planet candidates identified by K2/TESS, and 3) orbital
and atmospheric characterizations of transiting planets. In this talk, I will summarize thelatest progress in these projects with an emphasis on the characterization of transiting
planets. I will also present the future prospect of exoplanet observations by IRD.
--------------------------------Teng, Huanyu / hyteng@bao.ac.cn / National Astronomical Observatories, Chinese Academyof Sciences
The Progress of East Asian Planet Search Network
East Asian Planet Search Network (EAPS-Net) surveys late-G (including early-K) giant stars
with precise radial velocities, aiming to search for planets around intermediate-mass stars intheir evolved stages. The EAPS-Net began 20 years ago, with 48 exoplanetary systems
discovered by telescopes in east Asia. In this presentation, we report the latest discoveries
from the EAPS-Net and statistical information from planet survey around evolved stars.
--------------------------------Hu, Qingru / huqr20@mails.tsinghua.edu.cn / Tsinghua University
TOI-677 b: A spin-orbit aligned yet eccentric warm Jupiter in a dynamically hot system
With the development of high-resolution spectroscopic observations, the RossiterMcLaughlin (RM) measurement for wide-orbiting warm Jupiters becomes feasible. The RM
measurement can tell us the sky-projected angle between the stellar spin and the planet orbit
norm, which encodes valuable information about angular momentum transfer of the system.
From a combined fit of observations from the PFS/Magellan spectrograph and the
ESPRESSO/VLT spectrograph, we derived a low sky-projected stellar obliquity of$\lambda\sim3.2\degree$ and a moderately high eccentricity of $e\sim0.460$ for TOI-677 b,
making it part of an emerging puzzling class of wide-orbiting giant planets that exhibit large
orbital eccentricities and yet low stellar obliquities. We suggest that TOI-677 b may have had
its orbital eccentricity excited through either disk-planet interactions or ZLK oscillations with amutually inclined companion.
--------------------------------Wu, Zexuan / wuzexuan@pku.edu.cn / Department of Astronomy, School of Physics, Peking
University
Gaia22dkvLb: A Microlensing Planet Potentially Accessible to Radial-Velocity
Characterization
Microlensing is sensitive to “cold” planets extended to a few AUs and provides
complementary probes of unexplored parameter space for exoplanets. However,microlensing reveals little about planet dynamics and the system architecture, which areroutinely recovered using Radial-Velocity (RV) techniques. The majority of microlensing
planets are discovered in bulge field, where the host stars are typically low-mass stars
located far away, thus challenging for RV follow-ups. Here we report the newly discovered11

microlensing planetary system Gaia22dkv. Our analysis yields a Jovian planet with a turn-off
host at r’~14, and it is far brighter than any previously discovered microlensing planet host.
With the exceptional brightness and the Jovian mass ratio, this system is potentiallyaccessible to high-precision RV facilities, e.g., VLT ESPRESSO, enabling dynamic
characterization of the microlensing planet. Additionally, RV data would allow for the searchof inner planets of the cold jupiter, as suggested by the “inner-outer correlation” inferred from
Kepler and RV discoveries.
--------------------------------Li, Yaping / liyp@shao.ac.cn / Shanghai Astronomical Observatory
3D Global Simulations of Accretion onto Gap-opening Planets: Implications for
Circumplanetary Disc Structures and Accretion Rates
We perform a series of 3D simulations to study the accretion of giant planet embedded inprotoplanetary discs (PPDs) over gap-opening timescales. We find that the accretion massflux mainly comes from the intermediate latitude above the disc midplane. The
circumplanetary disc (CPD) for a super-thermal planet is rotation-supported up to $\sim$2030\% of the planet Hill radius. While both mass inflow and outflow exists in the CPD
midplane, overall trend is an outflow that forms a meridional circulation with high-latitude
inflows. We confirm the absence of accretion outburst from disc eccentricity excited bymassive planets in our 3D simulations, contrary to the consensus of previous 2D simulations.
This suggests the necessity of 3D simulations of accretion even for super-Jupiters. The
accretion rates of planets measured in steady-state can be decomposed into the ``geometric"and ``density depletion" factors. Through extensive parameter survey, we identify a powerlaw scaling for the geometric factor $\propto q_{\rm th}^{2/3}$ for super-thermal planets($q_{\rm th}$ being the thermal mass ratio), which transforms to $\propto q_{\rm th}^{2}$ forless massive cases. The density depletion factor is limited by the disc accretion rate for
mildly super-thermal planets, and by gap-opening for highly super-thermal ones.Moderate
planetary eccentricities can enhance the accretion rates by a factor of $2-3$ through making
the gap shallower, but does not impact the flow geometry. We have applied our simulations
results to accreting protoplanet system PDS 70 and can satisfactorily explain the accretion
rate and CPD size in observations.
--------------------------------Chen, Yixian / yc9993@princeton.edu / Princeton University
Twists and Turns in the Circumplanetary Flow Pattern
Extensive studies have shown that when a planet is embedded within a protoplanetary disk,
the azimuthal flow in its close vicinity would be prograde, or in other words, aligned with theglobal orbital angular momentum. However, this is not trivial as the background Keplerian
shear is effectively retrograde, and the tidal gravity field must significantly influence the flow
to maintain its prograde nature. Using 3D global hydrodynamic simulations with adaptive
mesh refinement, we show that when the planet eccentricity is large enough thecircumplanetary flow becomes retrograde due to impact velocity relative to the backgroundflow, affecting planetary spin evolution and satellite formation; Likewise, the presence ofstrong turbulence also introduces constantly fluctuating impact velocities, leading to therandomization of the circumplanetary flow pattern as well as migration torque in the Type I
regime.
--------------------------------Aoyama, Yuhiko / yaoyama@pku.edu.cn / Peking University
Planet-disk interaction in windy disks
Young giant planets in protoplanetary disks (PPDs) can open disk gaps and drive planet
migration, which are of key to understanding planet formation. However, planet-disk
12interaction has been nearly exclusively studied in the viscous disk framework, despite theemerging new paradigm that disk evolution is primarily driven by magnetized disk winds. We
conduct 3D non-ideal magnetohydrodynamic (MHD) simulations of planet-disk interaction in
the presence of MHD winds applicable to the outer disks. Our results show that the planetdraws the magnetic flux into its orbit, enhancing the radial accretion flow within the planetinduced density gap. This faster accretion deepens the gap, disrupts the horseshoe turn flow,
and alters the accretion pathway to the planet. Implications to planet migration, kinematic
signatures, and circumplanetary disks will also be discussed.
--------------------------------Chen, Zhuo / chenzhuo_astro@tsinghua.edu.cn / Tsinghua University
Circumplanetary disks around gas giants
During the final stages of its formation, a gas giant will typically develop a circumplanetary
disk (CPD) around the planet, which can accrete some of the surrounding material.
Meanwhile, satellites can grow and evolve within the CPD. Currently, there are few
observational constraints on the temperature, density, and state of CPDs. In the hope of
uncovering the interior of the CPDs, we conduct axis-symmetric 2D radiation hydrodynamic
simulations. Our simulations suggest that the CPD of a gas giant may have temperatures ashigh as 1400K, which can sublimate high-temperature-resistant dust such as silicates. In
addition, the spin of the gas giant can affect the transfer of mass and angular momentum in
CPD-gas giant interactions. In this report, I will show the process of gas giant accretion
through CPDs and discuss the formation and evolution of gas giants and their satellites
under more realistic conditions.
--------------------------------YU, Cong / yucong@mail.sysu.edu.cn / Sun Yat-sen University
Boundary Layers of Circumplanetary Disks with Azimuthal Magnetic Field around Spinning
Planets
The accretion of material from disks onto weakly magnetized objects invariably involves its
traverse through a material surface, known as the boundary layer (BL). Our prior studies
have revealed that two distinct global wave modes for circumplanetary disks (CPDs) with
BLs exhibit opposite behaviors in spin modulation. We perform a detailed analysis about theeffect of magnetic fields on these global modes, highlighting how the magnetic resonances
and turning points could complicate the wave dynamics. It is found that the angularmomentum flux oscillates near the corotation resonance with increasing magnetic fieldstrength. We also examine the perturbation profile to demonstrate the amplification ofmagnetic fields within the BL. The dependence of growth rates on the width of the BL, theMach number, the magnetic field strength, and the spin rate are systematically investigated.
We find that stronger magnetic fields tend to result in lower terminal spin rates. We stress thepotential possibility of magnetized CPDs for the formation of primordial rings, moons, andangular momentum belts. The implications for the spin evolution and quasi-period oscillations
observed in compact objects are also briefly discussed. Our calculations advance thecomprehension of magnetohydrodynamical (MHD) accretion processes and lay a foundationfor observational studies and numerical simulations.
--------------------------------Ormel, Chris / chrisormel@tsinghua.edu.cn / Tsinghua University
Origin of the TRAPPIST-1 planet system
The exoplanet system around the low-mass star (0.09 solar) TRAPPIST-1 is perhaps themost iconic example of a compact, multi-planet system. The planets are found at close
distances from the star (but some at moderate irradiation levels) and are all in mean motion
resonances. Modelling of transit timings variations and photometry have resulted in, for13

astronomical standards, unprecedented constraints on the planets masses, compositions,and their dynamical states. These constraints allow us to reconstruct how the systemassembled. I will present numerical simulations that reproduce the physical and dynamical
properties of the TRAPPIST planets. It is found that the latter is only possible in a formation
context, that is, the present dynamical state of the TRAPPIST-1 system has been determinedin its first few million years and seen little change thereafter.
--------------------------------Pan, Mengrui / panmr@zju.edu.cn / Zhejiang University (ZJU)
Planet formation around M dwarfs
The study of planets around stars with differing masses reveals significant variations in thetypes of planets and the architectures of planetary systems. To unravel the planet formation
around low-mass stars and provide insights into the observed planetary populations, we
perform N-body simulations to identify differences in the statistical distribution of synthetic
planets in different models. We also explore the optimal disk conditions for giant planet
formation in the framework of pebble-driven core accretion. Our research contributes to abetter understanding of the diversity of planets and the configuration of planetary systems
around M dwarfs, shedding light on the intricacies of planetary formation in suchenvironments.
--------------------------------Ogihara, Masahiro / ogihara@sjtu.edu.cn / TDLI
Formation of diverse planetary systems from a ring in a disk with peaked gas density profile
It is known that the orbital characteristics of the terrestrial planets of the solar system can bewell explained by considering a ring-like distribution of material at a distance of about 1 aufrom the star. Such localized material distribution can be achieved by dust concentration andlocal planetesimal/protoplanet formation in a protoplanetary disk with a density peak at about
1 au. In such peaked disks, inward migration of protoplanets can be avoided and the
localized orbital distribution is maintained after type I migration. If such peaked disks arecommon, then the orbital distribution of low-mass planets in other exoplanet systems should
also be explained by the same model. In this study, we perform N-body simulations of planet
formation to investigate whether the orbital distributions of various planetary systems can be
reproduced from a ring considering the peaked gas disk profile. Our simulation results showthat the characteristics of the solar system terrestrial planets can be well reproduced. In
addition, depending on the setting of the simulations, it is also possible to explain the originof the orbital characteristics of super-Earths in close-in orbits in the same model.
--------------------------------Jiang Haochang / Haochang.Jiang@eso.org / ESO; Tsinghua
Chicken or Eggs? Formation of Planets from Pebble Rings
Rings are a prevalent feature observed in both protoplanetary and debris disks, hinting at an
intrinsic connection between them. In the protoplanetary disk phase, these rings serve as
accumulation sites for pebbles, fostering planetesimal formation and subsequent planet
assembly. We investigate the viability of planet formation inside ALMA rings, where pebbles
are trapped either by a Gaussian-shaped pressure bump or through strong dust
backreaction. Planetesimals are assumed to form at the mid-plane of the ring via thestreaming instability. Through N-body simulations, we explore the growth of theseplanetesimals via collisional mergers and pebble accretion. The concentrated pebbles andthe reduced headwind within the ring enhance the efficiency of planetesimal growth bypebble accretion as soon as they are born, ultimately yielding the ring as an efficientplanetary core factory. A broad and massive planetesimal belt is left at the planet-forming
ring's location. Remarkably, the majority of directly imaged planets coexist with debris disks,
14

exemplified by the four giants residing in HR 8799. The presence of a mean motion
resonance chain and an ALMA-resolved debris ring beyond these four planets renders HR
8799 an ideal candidate for the application of our model. We will also present a dedicatedmodel that the cores of these four giants originated within a planetesimal-forming pebble ringand evolved to their current state.
--------------------------------Xie, Ji-Wei / jwxie@nju.edu.cn / Nanjing University
Planetary Census Through Time and Space aided by LAMOST-Gaia-Kepler
Since the discovery of the first exoplanet (51 Peg b) orbiting a solar star in 1995, the study of
exoplanets has been one of the most active frontiers. To date, over 5000 exoplanets havebeen discovered and thousands of candidates are yet to be confirmed. The map of known
exoplanets has expanded significantly from the solar neighborhood (100-200 pc) to a muchlarger area (orders of 1000 pc) in the Galaxy thanks to the improvement of observational
technology. We are therefore entering a new era of exoplanet census in the Milky Way
Galaxy. In the Galactic context, one of fundamental questions in studying exoplanets is: what
are the differences in the properties of planetary systems at different positions in the Galaxy
with different ages? The answer to this question will provide insights on the formation andevolution of the ubiquitous and diverse exoplanets in different Galactic environments. In thispresentation, I will introduce our recent work aiming to address this question, which has been
aided by the LAMOST, Gaia and Kepler surveys.
--------------------------------Chen, Di-Chang / dcchen@nju.edu.cn / Nanjing University
The evolution of hot Jupiters revealed by the age distribution of their host stars
The unexpected discovery of hot Jupiters challenged the classical theory of planet formation
inspired by our solar system. Until now, the origin and evolution of hot Jupiters are still
uncertain. Determining their age distribution and temporal evolution can provide more clues
into the mechanism of their formation and subsequent evolution. Using a sample of giant
planets around Sun-like stars collected from the kinematic catalogs of the Planets AcrossSpace and Time (PAST) project, we find that hot Jupiters are preferentially hosted byrelatively younger stars in the Galactic thin disk. We subsequently find that the frequency of
hot Jupiters declines with age. In contrast, the frequency of warm/cold Jupiters shows nosignificant dependence on age. Such a trend is expected from the tidal evolution of hot
Jupiters’ orbits, and our result offers supporting evidence using a large sample. We also
perform a joint analysis on the planet frequencies in the stellar age-metallicity plane. The
result suggests that the frequencies of hot Jupiters and warm/cold Jupiters, after removing
the age dependence are both correlated with stellar metallicities. Moreover, we show that theabove correlations can explain the bulk of the discrepancy in hot Jupiter frequencies inferredfrom the transit and radial velocity (RV) surveys, given that RV targets tend to be more metalrich and younger than transits.
--------------------------------Dong, Jiayin / jdong@flatironinstitute.org / Flatiron InstituteDeciphering Origins of Hot Jupiters through Stellar Obliquity Distribution
Recently, multiple lines of observational evidence suggest that high-eccentricity tidal
migration is an inevitable pathway for forming hot Jupiters. However, the mechanism that
excites the highly elliptical orbits of proto-Hot Jupiters remains unclear. Several candidate
mechanisms have been proposed, including the von Zeipel-Lidov-Kozai effect, secularchaos, planet-planet scattering, among others. We leverage the stellar obliquity informationof hot Jupiters to identify the dominant mechanism responsible for eccentricity excitation.
15

First, we demonstrate that the population-level stellar obliquity distribution can be inferredpurely from projected obliquities, as measured by the Rossiter-McLaughlin effect, even in theabsence of stellar inclination information. This is because the projected stellar obliquity
provides a more significant constraint on the true stellar obliquity compared to stellar
inclination. Next, we introduce a hierarchical Bayesian framework capable of inferring stellar
obliquity at the population level. When applied to exoplanetary systems with RM-effectmeasurements, it reveals that misaligned systems are nearly isotropically distributed, with nopronounced clustering near 90 degrees. We find that the deviation from Albrecht+21 results
stems from biases in their sample selection. Lastly, we interpret the stellar obliquity
distribution to shed light on the origins of hot Jupiters. Our findings highlight planet-planet
interactions as a significant mechanism in the formation of hot Jupiters.
--------------------------------Feng, Fabo / ffeng@sjtu.edu.cn / Tsung-Dao Lee Institute, Shanghai Jiao Tong University
A population of mutually inclined multi-planet systems
Our solar system is home to an intriguing population of multiple cold giants, which are gas
giant planets characterized by their long orbital periods. Detecting these cold giants has
proven to be a challenging task, given their extended orbits and elusive nature. However,recent advancements in high-precision astrometry, facilitated by Gaia's mission and the 24year gap between the Hipparcos and Gaia missions, have enabled us to identify dozens ofthese systems with multiple giant planets. We have identified a subset of these systems withhigh mutual inclinations, indicating a dynamically hot history probably induced by planetplanet or planet-disk interactions. These findings raise questions about the uniqueness of oursolar system, as it appears to possess an exceptional level of coplanarity when compared tothese newly discovered, more dynamically active systems.
--------------------------------Ida, Shigeru / ida@elsi.jp / ELSI, Tokyo Tech
The origin of significant carbon depletion in the inner Solar system
Tamami Okamoto (1,2) & Shigeru Ida (1) / presented by Ida
1. ELSI, Tokyo Institute of Technology
2. Cote d’Azur Observatory
The Earth and asteroid parent bodies in the inner Solar System are depleted in carbon by a
few orders of magnitude compared to the Sun and the ISM dust. This is a big puzzle,
because observations suggest that a half of carbon materials in molecular clouds are inrefractory forms such as amorphous hydrocarbon grains and complex organics, which canbecome building blocks of rocky bodies. We have investigated the carbon depletion
processes through 3D Lagrangian simulation of dust particles in turbulent disks and foundthat two orders of magnitude carbon depletion robustly occurs inside the snow line if silicate
dust grains ejected from icy pebbles at the snow line are much smaller than the icy pebbles
due to the difference in the collisional fragmentation limit between silicate and ice, while thedepletion by the variations of the refractory carbon carriers or temporal strong disk heating
events such as FU Orionis bursts are uncertain.
--------------------------------Wang, Lile / lilew@pku.edu.cn / Peking University
Computational Microscopic Foundations of Planets and their Formation
Planets and their formation processes are complicated and require detailed treatments ofvarious coupled microphysical mechanisms for convincing results of theoretical studies. We
will discuss the methods of constructing the microscopic foundations for the studies of16

protoplanetary disks and planet atmospheres computationally, as well as their applications inconnecting theories to observations directly.
--------------------------------Nomura, Hideko / hideko.nomura@nao.ac.jp / National Astronomical Observatory of Japan
Carbon Isotope Chemistry: From Protoplanetary Disks to Asteroid Ryugu
Origin of materials in our solar system is one of our ultimate questions. Thanks to recent
ALMA observations with high sensitivity, some complex organic molecules as well as manyrare isotopologues have been detected towards protoplanetary disks. Looking for chemicalsimilarities/differences between pristine materials in our solar system and materials in
protoplanetary disks is one of the possible approaches to tackle the question. In particular,
the isotope ratios provide a powerful tool. Recent ALMA observations suggest bimodal
fractionation of carbon isotopes in CO and HCN molecules; 12CO/13CO ratio shows a lower
value (~20) while H12CN/H13CN does higher value (~ 86) inside ~100 au of the TW Hya
disk, compared with the local interstellar value (~69), which could be caused by thermal
isotope exchange reaction under a low temperature environment with C/O > 1 (Yoshida et al.
2022). Such bimodal fractionation can be transported in more complex molecules found in
our solar system. I will discuss a possible connection to the materials in the Japanese
Hayabusa 2 sample return mission exploring to the asteroid Ryugu.
--------------------------------Tatsuuma, Misako / misako.tatsuuma@gmail.com / RIKEN iTHEMS
Formation process of small solar system bodies and pebbles via self-gravitational
compression of dust aggregates
Constraining the formation process of comets and asteroids in the solar system is crucial forunderstanding the size growth and porosity evolution of planetesimals. One widely accepted
scenario for planetesimal formation is the pebble accretion scenario, but the formation
process of pebbles from submicrometer-sized dust grains remains unknown. In this work, weinvestigate the formation process of comets, asteroids, and pebbles by calculating theinternal density of planetesimals made from dust aggregates. We calculate the bulk densityand diameter of dust aggregates by equating their compressive strength with their selfgravity and compare them with the observational and explorational results of asteroids,
comets, and trans-Neptunian objects. As a result, we numerically obtain the relation between
the bulk density and diameter depending on material parameters such as monomer radius,material density, and surface energy, and also succeed in deriving an analytical formula. By
comparing our results with the bulk density and diameter of asteroids and comets and theporosity of observed pebbles, we find a unified formation scenario of planetesimals including
pebbles. First, 0.1-µm-sized dust grains coagulate and grow into dust aggregates, and thenthe first-generation planetesimals composed of dust aggregates form. The first-generation
planetesimals include Ryugu’s parent body and possibly include comets’ parent bodies.
Second, the first-generation planetesimals fragment into pebbles, they coagulate and growinto pebble aggregates, and then the second-generation planetesimals composed of pebble
aggregates form. The second-generation planetesimals can be comets.
--------------------------------Dong, Chuanfei / dcfy@bu.edu / Boston University
Atmospheric escape from M-dwarf exoplanets and implications for habitability
In the last two decades, the field of exoplanets has witnessed a tremendous creative surge.
Research in exoplanets now encompasses a wide range of fields ranging from astrophysics
to heliophysics and climate science. One of the primary objectives of studying exoplanets is
to determine the criteria for habitability, and whether certain exoplanets meet theserequirements. The classical definition of the Habitable Zone (HZ) is the region around a star17

where liquid water can exist on the planetary surface given sufficient atmospheric pressure.
However, this definition largely ignores the impact of the stellar wind and stellar magnetic
activity on the erosion of an exoplanet's atmosphere. Amongst the many factors that
determine habitability, understanding the mechanisms of atmospheric loss is of paramountimportance. We will discuss the impact of exoplanetary space weather on atmospheric loss
and long-term climate evolution, which offers fresh insights concerning the habitability of
exoplanets, especially those orbiting M-dwarfs, such as Proxima b, TOI-700 d, and the
TRAPPIST-1 planets. We will address a wide range of planetary parameters, including
atmospheric composition, magnetization, size, and obliquity. For each of these cases, we will
demonstrate the importance of the exoplanetary space weather on atmospheric ion loss andhabitability.
--------------------------------Liu, Pengyu / pengyu.liu@ed.ac.uk / University of Edinburgh, Leiden University
Direct imaging and atmosphere structures of giant exoplanets and brown dwarfs
Direct imaging is a promising technique to detect and characterise earth-like planets directlyin the future. A dozen of exoplanets have been detected by direct imaging. Unlike themajority of exoplanets detected by radial velocity and transiting, they are wide-separation
planets with a few Jupiter mass. In this talk, I will present recent direct imaging surveys andresults. Then I will present a near-infrared variability survey of young planetary-mass objects.
These free-floating objects are analogues to directly imaged planets but are easier tocharacterise. From L to T spectral types, brown dwarfs experisence drastic atmospherechanges, from clear to cloudy and to clear. Photometric monitoring of brown dwarfs showthat variability is common in brown dwarfs. As young planetary-mass objects, they have alower surface gravity than their field dwarf counterparts. Surface gravity plays an importantrole in the atmospheric structure of L- and T-type objects. We conduct continuous monitoringfor 18 objects with spectral types from L5 to T8 and detect four new variables and twovariable candidates. Combining with previous variability surveys of field and young L and T
objects, we find that young objects tend to be more variable than field objects within peak-topeak variability amplitude ranges of 0.5%–10% and period ranges of 1.5–20 hr. For the firsttime, we constrain the variability rate of young T dwarfs to be 56% compared to 25% for field
T dwarfs. This work supports the critical role of surface gravity on the atmospheric structurefrom L to T spectral types. I will also discuss variability monitoring of directly imaged
exoplanets in the end.
--------------------------------Guo, Jianheng / guojh@ynao.ac.cn / Yunnan Observatories, CAS
Characterizing regimes of hydrodynamic escape of low mass exoplanets by the upgraded
Jeans parameter
Distinguishing between the driving mechanisms responsible for the hydrodynamic escape ofhydrogen-rich atmospheres of low-mass, close-in exoplanets is complicated due to theinvolvement of many physical factors. Characterizing hydrodynamic escape using essential
physical parameters can provide deep insights into the driving mechanisms and patterns ofescape. My simulations show that the hydrodynamic escape can be driven by thermal energy
deposited in the lower layers of the atmosphere due to the own core luminosity of the planet
or bolometric heating from the star even in the absence of other energy sources, as long as
the planet's Jeans parameter is below 3. If the Jeans parameter exceeds 3, three distinct
regimes can be identified by introducing an upgraded Jeans parameter that takes into
account tidal forces. When the upgraded Jeans parameter is less than 3 or greater than 6,
the main driver of the atmospheric escape is tidal forces or XUV radiation of the host star,
respectively. In the range of 3 to 6, both factors can trigger the escape of the atmosphere.
Planets with high gravitational potential and low stellar irradiation are more likely to undergo
subsonic escape, although transonic escape is common among most planets. Moreover, the18

ionization status is significantly dependent on both upgraded Jeans parameter and thegravitational potential. The calculation results are applied to fit the uncertain parameters of
the energy-limited equation.
--------------------------------Huang, Chenliang / huangcl@shao.ac.cn / Shanghai Astronomical Observatory
A hydrodynamic study of the atmospheric escape of the hot Jupiter WASP-121b
The escape of the atmosphere plays a crucial role in planetary evolution. Recent
advancements in high spectral resolution transmission spectrum observation have provided
an exceptional opportunity to investigate the structure of exoplanet upper atmospheres andtheir escape processes. In this talk, I will introduce a sophisticated forward model by
expanding the capability of a one-dimensional model of the upper atmosphere andhydrodynamic escape, to include important processes of atomic metal species.
Using this model, we can interpret the detected atomic features in the transmission spectrumof WASP-121b, which originate from material outside the planet's Roche lobe. By studying
these atomic signatures, we can explore the impact of metals and excited hydrogen on theupper atmosphere, gain insights into the mechanisms of atmospheric escape, andemphasize the significance of the high mass-loss rate caused by Roche lobe overflow.

Posters, Disk & Planet Formation--------------------------------Chung, Chia-Ying / sharon0311chung@gmail.com / ASIAA
Constraining dust masses and grain growth in Class II protoplanetary disks by the(sub)millimeter broadband Taurus-Auriga survey
We have performed a new SMA 200–400 GHz survey of 47 Class II sources in the TaurusAuriga region. The improved precision tightens the constraints on the (sub)millimeter spectral
indices. Intriguingly, we found that the observed spectral indices are mostly populated in an
extremely narrow range of 2.1 ± 0.2; only a handful of spatially resolved (e.g., diameter >250au) disks present larger spectral indices. Using population synthesis, we argue that the mostprobable interpretation for the observational results is that the (sub)millimeter luminosities
are dominated by very optically thick (e.g., τ ≳10) dust thermal emission. This immediately
implies that the previous dust mass estimates, assuming optically thin, may beunderestimated by at least one order of magnitude. The largely retained dust mass budget in
the Class II disks may be the consequence that dust coagulation outside of the water
snowline is still limited by the classical bouncing/fragmentation barrier. Indeed, our population
synthesis indicates that the maximum grain sizes in our sample may be a few times smaller
than 100 microns. These results may be essential to developing theories of planet formation.
--------------------------------Doi, Kiyoaki / doi.kiyoaki.astro@gmail.com / NAOJ
Constraints on the dust size distributions in the HD 163296 disk from wavelength-dependent
spatial distribution of ALMA continuum images
Planet formation begins with dust coagulation in protoplanetary disks. Therefore,
observational constraints on the dust size distribution in the disks can be a clue forunderstanding planet formation. While previous studies estimated the dust size from thespectral index derived from multi-wavelength observations or dust polarization observations,they still have large uncertainties. In this study, we present a new method to constrain the
dust size distribution from the dust spatial distribution. High-resolution observations with
ALMA revealed ring-like structures. These rings are thought to be formed by the dust
19

trapping at gas pressure maxima. Since larger dust grains are trapped more effectively in thegas pressure bump, they form narrower rings. As a result, the dust rings appear narrower atlonger wavelength observations since observations are sensitive to the dust grains whose
size is comparable to the observed wavelength. Since the difference of the apparent ringwidths on the observed wavelengths depends on the dust size distribution, we can constrain
the dust size from the ratio of the dust ring widths between two wavelengths. We analyze
high-resolution Band 4 (2.1 mm) and Band 6 (1.3 mm) images of the HD 163296 disk andfind that the widths of the inner dust ring are similar between the two wavelengths, but theouter dust ring is 1.2 times narrower in Band 4 than in Band 6. Using simple dust ring models
that assume size-dependent dust trapping, we derive constraints on the dust size
distribution, such as maximum dust size and dust size power law. We constrain that 0.9 mm< a_max < 5 mm and p < 3.3 in the inner ring, and a_max > 3×10^1 mm and 3.4 < p < 3.7 inthe outer ring. The larger maximum dust size in the outer ring implies a spatial dependency indust growth, potentially influencing the formation location of the planetesimals, and theexponent of the size distribution suggests that dust growth is inhibited by dust fragmentation.
--------------------------------Hu, Ying-Chi / yingchihu@asiaa.sinica.edu.tw / National Tsinghua University (NTHU)
Dust Grain Growth in Early Disk? A Multi-Wavelength study of the HH 212 Disk
The growth of dust grains during the initial stages of star formation is an important process inplanet formation. However, various properties of dust particles in young protostellar disks,such as their composition, grain sizes, and porosity, remain uncertain. Recent studies of dust
polarization detection in the Class 0 HH 212 disk in ALMA Band 7 (Lee et al. 2018a, 2021)
have suggested the importance of self-scattering from growing dust grains. Here, we aim toinvestigate this possible grain growth by modeling the continuum maps of the disk obtainedat multiple wavelengths, ranging from 0.85 (ALMA Band 7) to 9 mm (VLA Band Ka). We havederived the opacity and albedo of the dust in this disk. The low opacity index suggests thepresence of mm/cm-sized grains, while the low albedos indicate grain sizes smaller than 100
μm. We propose a possible vertical grain size distribution to explain this contradiction. We
note that the possibility of uniformly distributed porous dust grains cannot be ruled out.
--------------------------------Hung, Yi-Ping / b102030019@g-mail.nsysu.edu.tw / Department of Physics, Sun Yat-Sen
University, Kaohsiung
Radiative Transfer Model of Embedded Gravitational Unstable Disks
The previous observational studies may have systematically underestimated the dust andgas masses in the embedded and naked protoplanetary disks. The evolution of (embedded)
protoplanetary disks may be regulated by gravitational instability instead of viscosity. To
testify these possibilities, it is becoming important to seek observational signatures in themodels of gravitationally unstable disks, which is relatively less explored at this moment ascompared to the viscous disk models. We use the publicly available radiative transfer
simulation code, RADMC-3D, to produce mock observations for the 1D parameterized modelof gravitationally unstable disks published by Xu and Kunz (2021). The major assumptions inthis model include marginal gravitational instability, vertical hydrostatic equilibrium, and local
thermodynamic equilibrium (LTE). The advantage of the model we adopted is that it permits
self-consistently constructing the 3D density and temperature distributions using a small
number of free parameters. This poster makes a demonstration of our present achievement.
--------------------------------Kim, Seongjoong / kimseongjoong@mail.tsinghua.edu.cn / Tsinghua University
The application of 2D parametric disk model to multiple CO line data
The temperature and density structures of protoplanetary disks are fundamental components
20for understanding the planet formations and disk evolutions. Recent molecular line
observations done by ALMA have opened a new window to examine the disk verticalstructure with the estimation of line-emitting surfaces. In this study, we establish acomprehensive parametric disk model including temperature, density, and CO isotopic
abundances. We do the fitting of model parameters with the Markov chain Monte-Carlo
method by comparing the model image to the observed CO isotopologue lines (12CO, 13CO,
and C18O lines) in the RU Lup disk. Although the model result is limited by the poor angularresolution, this case study provides another possible way to estimate the disk physicalconditions from the observations.
--------------------------------Ma Xiaoyi / xiaoyima@uvic.ca / University of Victoria
Vortex-induced rings and gaps in a protoplanetary disk
The co-existence of crescents and rings has been observed in protoplanetary disks in dust
continuum emission. The crescents in continuum emission have been proposed to be thedust-trapping vortices generated by Rossby Wave Instability (RWI). We hypothesize that theRWI vortices could produce rings and gaps by driving density waves, analogous to planets.
We study the properties of density waves and substructures induced by a vortex in 2Dhydrodynamic simulations for both global disks and shearing boxes performed by Athena++.
In this work, we aim to find rings and gaps induced by vortices in disks comparable toobservations.
--------------------------------Mori, Shoji / shoji9m@gmail.com / Tohoku university
Temperature structure of magnetized protoplanetary disks
Understanding the thermal structure of protoplanetary disks (PPDs) is crucial for elucidating
the formation of rocky planets. We present 2D global radiative magnetohydrodynamic (MHD)
simulations of the inner region of PPDs, taking into account all three non-ideal MHD effects,
irradiation and Joule heating due to the global magnetic structure. The thermal structure
consistent with the disk dynamics is calculated using a simplified radiative transfer methodthat is computationally efficient. Our simulations show that strong Joule heating occurs
primarily in the strong current layer at the disk surface, where the global magnetic fields
bend, which does not significantly heat the disk midplane. This is the case whether thepoloidal magnetic field is aligned or anti-aligned. As a result, the temperature structure of
PPDs, even at a few au, is mainly determined by irradiation heating. In addition, thestructure of the irradiated surface is affected by the high-density disk wind, and the intensityof irradiation heating depends on the MHD disk wind structure. This suggests the need toconstruct a disk temperature model that takes into account the MHD behavior of the disk.
--------------------------------Ni, Yang / ny22@mails.tsinghua.edu.cn / Tsinghua University,
Gravitational Instability of the Irradiated Protoplanetary Disk via Meshless Methods
Planet formation in young protoplanetary disks (PPDs) may proceed via the gravitational
instability (GI) followed by disk fragmentation. While disk fragmentation requires relatively
rapid radiative cooling, the subsequent evolution of these fragmented clumps remains
enigmatic, primarily due to the lack of proper treatment of radiation transport. In this work, we
successfully apply the two-moment radiation transport scheme with the M1 closure using themeshless finite mass (MFM) method in the Lagrangian code GIZMO and enable a secondorder M1 radiation hydrodynamics scheme. We have extensively tested the code including
the thermal equilibrium of PPDs under stellar irradiation in local and global settings, and will
present preliminary results of our GI simulations.
21

--------------------------------Smallwood, Jeremy / jlsmallwood@asiaa.sinica.edu.tw / ASIAA
The evolution misaligned protoplanetary disks around binary star systems
The majority of stars born in dense stellar clusters are part of binary star systems.
Circumbinary discs of gas and dust commonly surround binary star systems and are
responsible for accreting material onto the binary. The gas flow dynamics from thecircumbinary disc onto the binary components have significant implications for planet
formation scenarios in binary systems. Misalignments between the circumbinary disc and thebinary orbital plane are commonly observed. A misaligned circumbinary disc undergoes
nodal precession. For a low initial inclination, the precession is around the binary angularmomentum vector, while for a sufficiently high initial inclination, the precession is around theeccentricity vector. Dissipation causes the disc to evolve to align coplanar to the binary
orbital plane or perpendicular (i.e., polar) to the binary orbital plane. I present 3-dimensionalhydrodynamical simulations and linear theory on the evolution of highly misaligned
circumbinary discs. I show that polar-aligned circumbinary discs are favorable environments
for forming polar circumbinary (P-type) planets. Moreover, misaligned and polar circumbinarymaterial flows around each binary component, forming misaligned and polar circumstellar
discs. These circumstellar discs undergo long-lived Kozai-Lidov oscillations that may prompt
the formation of giant circumstellar (S-type) planets in binary star systems. The evolution of
protoplanetary discs in and around binary star systems bears important implications forplanet formation.
--------------------------------Su, Zehao / suzh22@mail.bnu.edu.cn / Beijing Normal University(1) Self-gravity Protoplanetary Disk with Cooling: Linear Perturbation Analysis
Self-gravity and thermodynamics are both important in protoplanetary disks. Their combined
effects have been studied in many hydrodynamic simulations. We investigate the most
unstable modes in disks with a wide range of star-mass ratios and dimensionless coolingtimescales using linear perturbation analysis. We find that the dominance of the most
unstable modes change from small-scale ones (those with high azimuthal wave number 'm')which are mostly suppressed when β is around 1, to large-scale ones (those with small
azimuthal wave number 'm') which are mostly suppressed when β is larger than 1 as the
disk-star mass ratio increases. Implications for disk evolution and planet formation will be
discussed.
(2) Dynamical Consequence of Shadows Cast to the Outer Protoplanetary Disks
Many protoplanetary disks (PPD) show evidence of shadows in ourter disks observed inscattered lights that are cast from the disk inner region, while in the meantime present
substructures of various kinds in the submillimeter. As stellar irradiation is the primary heating
source for outer PPDs, the presence of such shadows thus suggest inhomogeneous heatingof the outer disk in azimuth. We study the dynamical consequence of shadows cast to theouter protoplanetary disks as potential cause of disk substructure formation. We run idealized
2D disk simulations of the outer disk with azimuthally-varying cooling prescription. We findthat shadows can potentially lead to the formation of a variety of types of substructure
including rings, spirals and crecents, depending on the viscosity, cooling time, etc.
Implications for disk observations and future perspectives will be discussed.
--------------------------------Wang, Shengtang / wangst19@mails.tsinghua.edu.cn / Tsinghua University
Gas dynamics of innermost protoplanetary disk
The innermost region of protoplanetary disks (PPDs, <1AU) is characterized by the complex
22

interplay of various physical processes, including radiation transport, thermal and nonthermal ionization chemistry, and non-ideal magnetohydrodynamics (MHD). It is the region
where most exoplanets have been discovered, yet its physics remains poorly understood.
We have implemented radiation transport by M1 closure in the Athena++ MHD code. By
conducting local shearing-box simulations at representative disk radii that fully incorporate
the relevant microphysics, we present preliminary results indicating that the bulk disk can
become magneto-rotational instability (MRI) active and "dead" dependent on the thermal
history of disk evolution.
--------------------------------Zhang, Jiayue / zhangjy23@mails.tsinghua.edu.cn / Department of Astronomy, Tsinghua
University, Peking, China
A two-component dust model to model the vertical structure of protoplanetary disks
Protoplanetary disk contains a large amount of gas and dust. These disks host dust particles
of varying sizes, ranging from micrometers to (sub-)millimeters. Particles will settle anddiffuse in the disk under the effect of gravity and turbulent motion. At millimeter (mm)wavelength, dust emission is concentrated at the midplane, while at near-IR wavelengths,
the disk becomes very extended. The simultaneous thinness at mm-wavelength, but the
thickness of disks in near-IR/scattered light defies an explanation. In this study, we construct
a two component model of small grains and large pebbles to simulate the vertical distributionof micrometer-sized dust grains and (sub-)mm-sized pebbles within a protoplanetary disk.
We consider that two components will exchange mass due to collisions. In this model, in theregion near the midplane, small grains population decreases because of sweep-up by
pebbles, while in the upper regions, the small grains population increase due to high velocity
erosive collisions.With this model we attempt to meet observation constraints from near-IR to
sub mm-wavelength given by VLT/SPHERE and ALMA. By adjusting parameters such as
particle sizes and turbulent properties, we attempt to match the two-component transportmodel with observational data.
--------------------------------Zheng, Xinyu / zheng-xy20@mails.tsinghua.edu.cn / Tsinghua University / Leiden
Observatory
Ionization of the innermost protoplanetary disks
Ionization plays a critical role in the gas dynamics of protoplanetary disks (PPDs), which isfurther related with disk evolution and planet formation. While non-thermal ionization
mechanisms, such as X-rays and cosmic rays, dominate the bulk regions of PPDs, theinnermost regions (<0.1AU) are characterized by high temperatures (>1000K) with thermal
ionization of alkali species, ion emission and thermionic emission from the dust. Suchprocesses are expected to dramatically enhance the disk ionization fraction, leading to a
revival of the magneto-rotational instability. To better understand the complex ionization
processes in this region, we develop a comprehensive ionization chemical network that
accounts for both non-thermal ionization and high-temperature effects. Using this model, we
calculate the ionization fraction and the resulting magnetic diffusivities throughout the fullrange of physical conditions present in PPDs and discuss the implications on the gas
dynamics of the innermost disk regions. Our findings provide a robust microphysical basis for
future magnetohydrodynamical simulations.
--------------------------------Li, Tianhao / lth23@mails.tsinghua.edu.cn / Tsinghua University
Observational signatures of dust clumping in protoplanetary disks
The prevalence of substructures in protoplanetary disks (PPDs) suggests dust trapping insuch substructures, which is expected to further trigger dust clumping and potentially23

planetesimal formation. However, such clumping is expected to occur on spatial scales muchsmaller than the observational resolution, thus dust clumping is not directly detectable. We
post-process non-ideal magnetohydrodynamic simulations of dust trapping and clumping
under weakly MRI-turbulent dust rings with multi-species dust through radiative transfer
calculations using the RADMC-3D code. We compare calculation results using simulation
data versus a model without dust clumping. While the two results are morphologically similar,
the spatial map of spectral indices holds promise to distinguish dust clumping from a smooth
dust profile.
--------------------------------Liu, Hanpu / liuhanpu@stu.pku.edu.cn / Peking University
The dusty Rossby wave instability (DRWI): linear analysis and simulations of turbulent dusttrapping rings in protoplanetary disks
Recent numerical simulations have revealed that dust clumping and planetesimal formation
likely proceed in ring-like disc substructures, where dust gets trapped in weakly turbulent
pressure maxima. The streaming instability has difficulty operating in such rings with external
turbulence and no pressure gradient. To explore potential paths to planetesimal formation inthis context,we analyse the stability of turbulent dust-trapping rings under the shearing sheet
framework. We self-consistently establish the pressure maximum and the dust ring inequilibrium, the former via a balance of external forcing versus viscosity and the latter via
dust drift versus turbulent diffusion. We find two types of >~H-scale instabilities (H being thepressure scale height), whichwe term the dusty Rossby wave instability (DRWI). Type I isgeneralised from the standard RWI, which is stationary at the pressure maximum anddominates in relatively sharp pressure bumps. Type II is a newly identified travelling modethat requires the presence of dust. It can operate in relatively mild bumps, including many
that are stable to the standard RWI, and its growth rate is largely determined by theequilibrium gas and dust density gradients. We further conduct two-fluid simulations thatverify the two types of the DRWI. While Type I leads strong to dust concentration into a largegas vortex similar to the standard RWI, the dust ring is preserved in Type II, and meanwhile
exhibiting additional clumping within the ring. The DRWI suggests apromising path towards
formation of planetesimals/planetary embryos and azimuthally asymmetric dust structurefrom turbulent dust-trapping rings.
--------------------------------Qiao, Lin / lin.qiao@qmul.ac.uk / Queen Mary University of London
Disc evolution and planet formation under the impacts of stellar cluster environments
Most stars (and their protoplanetary discs) form in large stellar clusters with high stellar
density, and there has been growing attention on how these dense cluster environments caninfluence disc evolution, planet formation and possibly the final planetary system. The“external” UV radiation field emitted by the massive stars in such clusters can affectprotoplanetary discs via external photoevaporation, where UV radiation heats and disperses
material from disc surfaces, depleting disc mass and truncate the disc radius. In a
dynamically evolving stelar cluster, discs are exposed to time varying FUV radiation. Discs
initially embedded in the cloud can be shielded for some time before stellar feedback
processes disperse the cloud, exposing discs to strong FUV radiation. Recent studies shown
shielding can protect discs from high mass loss rates at least for early stage disc evolution,
but how this affect planet formation and diversity is still largely unknown. We haveinvestigated how planet core formation via pebble accretion is affected by external
photoevaporation, and how its effects can be mitigated by disc shielding time, and we also
extend our investigations of these effects on forming multiple planetary systems.
--------------------------------24

Wu, Hening / heningwu@mail.bnu.edu.cn / Beijing Normal University
Effects of Thermodynamics On the Accretion of Gas Giants
The runaway process is a crucial stage in the formation of planets, as it is during this phasethat the gas giants acquire majority of their masses. Accretion onto the planet is dependent
on the circumplanetary disk(CPD) and is influenced by spiral density waves induced byplanets whose intensity and structure are strongly impacted by the thermodynamics of the
protoplanetary disk(PPD). We carry out a series of 2D and 3D simulations with FARGO3D
and Athena++ to test the impact of thermodynamics in the runaway stage. Our research
focuses on investigating the accretion rates, structures of CPDs and the mechanisms ofaccretion in different cooling time scales. This analysis aids in our understanding of theaccretion process in CPD and the growth of gas giants.
--------------------------------Liu, Huigen / huigen@nju.edu.cn / Nanjing University
Title: Understanding the Planetary formation and evolution in Clusters
Abstract: Stars form in cluster environments, and the clusters can provide homogeneous andaccurate parameters of cluster members, to investigate the correlation between planetarysystems and hosts. In this talk, I will briefly introduce the UPiC program to explore the planet
formation and evolution correlated with the open clusters and associations, via simulations
and statistics based on Kepler-TESS-Gaia sample. The simulations reveal the stability ofcold planets in OCs, as well as the disk lifetime in cluster environment due to external
photoevaporation. Combining Kepler and Gaia data, we provide observational evidences of
the influence on Kepler's planet occurrence rate due to dynamical history. We also collect alargest exoplanet catalogues in clusters and associations to do statistics, and constrain themechanism of formation of HJs and Hot-Neptune desert.
--------------------------------He, Yaxing / yaxinghe@sjtu.edu.cn / Tsung-Dao Lee Institute
Exploring radius valley formation from collisions between super-Earths and planetary
embryos using N-body simulations
From detailed analysis of observed exoplanets, low-mass planets have a bimodal size
distribution, with peaks at about 1.3 and 2.4 Earth radii, and a valley at about 2 Earth radii.
The origin of this radius valley can be explained by the dissipation of H/He atmospheres fromsuper-Earths. Recent N-body simulations of super-Earth/sub-Neptune formation suggest that
eccentric planetary embryos may remain after the dissipation of protoplanetary disks. Whenthese embryos collide with super-Earths, impact erosion of the super-Earth’s atmosphere canoccur. In this study, we investigate whether the origin of the radius gap can be explained by
impact erosion due to collision between embryos and super-Earths. We perform N-bodysimulations to simulate the long-term orbital evolution of super-Earths and embryos, andanalyze the size evolution due to impacts. We find that high-eccentricity embryos can collidewith super-Earths, resulting in atmospheric dissipation and a decrease in the size of superEarths. On the other hand, the presence of embryos can cause collisions between superEarths, which can increase the size of super-Earths due to core growth. Whether theobserved radius valley can be explained by this mechanism depends on the properties (e.g.,
distribution, number, eccentricity) of the remaining embryos after the disk dissipation.
--------------------------------Kambara, Yuki / yuki.kambara@grad.nao.ac.jp / The University of Tokyo
Planet formation from planetesimal rings
In the standard scenario of planet formation, it is assumed that planetesimals form
throughout the protoplanetary disk and are smoothly distributed. Recently, however, a25

number of models have been proposed in which planetesimals form only at limited locations,such as gas pressure bumps, snow lines, and so on, and planetesimals are concentrated
and distributed in a ring-like structure. Moreover, simulations have shown that the mass
distribution of terrestrial planets in the solar system can be reproduced by arranging
protoplanets in a narrow ring. In the observations, it is revealed that ring structures areuniversal in protoplanetary disks. These results support the existence of ring-like structuresduring planet formation. If planetesimals are distributed in a ring-like structure, thedistribution of resulting protoplanets and planets would be different from ones in the standard
scenario that assumes a smooth disk. However, the evolution of planetesimal rings has notbeen investigated in detail. In this study, we aim to illustrate the accretion process of ringdistributed planetesimals and the structure of the resulting planetary systems. We are
performing a series of high-resolution N-body simulations and calculated the evolution of
ring-distributed planetesimals. In the poster, we will report the results of our current
calculations and discuss the evolution of planetary systems and the dependence of theirstructure on the initial distribution.
--------------------------------Li, Min / minphyli@163.com / Jilin Normal University
Stellar outbursts and chondrite composition
The temperatures of observed protoplanetary disks are not sufficiently high to produce theaccretion rate needed to form stars, nor are they sufficient to explain the volatile depletion
patterns in CM, CO, and CV chondrites and terrestrial planets. We revisit the role that stellar
outbursts, caused by high accretion episodes, play in resolving these two issues. These
outbursts provide the necessary mass to form the star during the disk lifetime, and provide
enough heat to vaporize planet-forming materials. We show that these outbursts canreproduce the observed chondrite abundances at distances near one AU. These outbursts
would also affect the growth of calcium-aluminum-rich inclusions (CAIs) and the isotopic
compositions of carbonaceous and non-carbonaceous chondrites.
--------------------------------Yi, Tian / yit23@mails.tsinghua.edu.cn / Tsinghua University
On the Dynamical History of Kepler-221 Planet System
Kepler-221 is a G-type star hosting four planets. In this planet system, planet b, c and e arein (or near) a 6:3:1 three-body resonance while the intermediate planet d is not part of theresonance chain. This configuration cannot naturally be explained by traditional migration
theory. To reach this resonance configuration, we propose a scenario in which there wereoriginally five planets in the system which started out in a chain of first-order resonances.
After disk dispersal, the resonance chain became unstable and two planets quickly merged
to become the current planet d. In addition, the b/c/e three-body resonance was reestablished because of effective damping from stellar (obliquity) tides. We run N-bodysimulations using REBOUND to investigate the parameter space under which this scenario
can operate. We find that the re-establishing of the 3-body resonance is the key step, whichputs strong constraint on the mass of planets and their effective tidal Q parameters. In
particular, we find that the planets in the system have a similar mass of around 9𝑀⊕, withtidal damping preferentially operating on planet c. Such methods can also be applied to otherplanet systems in resonance, such as K2-138.
--------------------------------Xu, Yuru / 202031160015@mail.bnu.edu.cn / Beijing Normal University
Wave propagation and transmission in a rotating polytropic spherical shell
Wave propagation can simultaneously transport momentum and energy, therefore it may
have important effects on stellar or planetary interior structures and evolutions. It is quite26

common for a star or planet to have a multi-layer structure, and yet propagation andtransmission of internal waves in these layers have not been fully explored. In this work, we
study the wave propagation and transmission by solving the linearized equations of acompressible, self-gravitating, uniformly rotating polytropic spherical shell. We use a 2D
pseudo-spectral method which allow us to calculate the adiabatic and inviscid oscillation
modes. The influence of Coriolis force in the equation of motion is fully taken into account but
the centrifugal force and rotation distortion of the equilibrium state is neglected for simplicity.
We consider interior models with polytropic index n = 1.5 (convective), n = 2.5, 3, 4
(radiative), and n transiting from 4 to 1.5 at the RCB. We characterize the energy flux andkinetic energy of these waves and find that energy flux carried by high-frequency acoustic
wave (p mode) but kinetic energy carried by low-frequency gravity wave (g mode), inertial
wave (r mode) or mixed gravito-inertial wave (GIWs). It is also shown that rotation canfacilitate wave propagation and enhance wave transmission.

Posters, Exoplanets--------------------------------An, Dongsheng / andongsheng@live.com / Nanjing University
The Eccentricity–Metallicity Trend for Small Planets Revealed by the LAMOST–Gaia–Kepler
SampleOrbital eccentricity is one of the basic planetary properties, whose distribution may shed lighton the history of planet formation and evolution. Here, in a series of works on Planetary Orbit
Eccentricity Trends (dubbed POET), we study the distribution of planetary eccentricities andtheir dependence on stellar/planetary properties. In the first work of the POET series, weinvestigate whether and how the eccentricities of small planets depend on stellar metallicities(e.g., [Fe/H]). Previous studies on giant planets have found a significant correlation between
planetary eccentricities and their host metallicities. Nevertheless, whether such a correlation
exists for small planets (e.g., super-Earths and sub-Neptunes) remains unclear. Here,benefiting from the large and homogeneous LAMOST–Gaia–Kepler sample, we characterize
the eccentricity distributions of 244 (286) small planets in single (multiple) transiting systems
with the TDR method. We confirm the eccentricity–metallicity trend whereby the eccentricities
of single small planets increase with stellar metallicities. Interestingly, a similar trend between
eccentricity and metallicity is also found in the radial velocity sample. We also found that themutual inclination of multiple transiting systems increases with metallicity, which predicts amoderate eccentricity–metallicity rising trend. Our results of the correlation between
eccentricity (inclination) and metallicity for small planets support the core accretion model forplanet formation, and they could be footprints of self (and/or external) excitation processes
during the history of planet formation and evolution.
--------------------------------Dai, Yuan-Zhe / astrodyz@outlook.com / Nanjing University
Understanding the Planetary Formation and Evolution in Star Clusters(UPiC)-I: Evidence of
Hot Giant Exoplanets Formation Timescales
Planets in young star clusters could shed light on planet formation and evolution since starclusters can provide accurate age estimation. However, the number of transiting planets
detected in clusters was only ~30, too small for statistical analysis. Thanks to theunprecedented high-precision astrometric data provided by Gaia DR2 and Gaia DR3, many
new Open Clusters(OCs) and comoving groups have been identified. The UPiC project aims
to find observational evidence and interpret how planets form and evolve in cluster
environments. In this work, we cross-match the stellar catalogs of new OCs and comoving
groups with confirmed planets and candidates. We carefully remove false positives andobtain the biggest catalog of planets in star clusters up to now, which consists of 73
27

confirmed planets and 84 planet candidates. After age validation, we obtain the radius--age
diagram of these planets/candidates. We find an increment of the fraction of Hot
Jupiters(HJs) around 100 Myr and attribute the increment to the flyby-induced high-e
migration in star clusters. An additional small bump of the fraction of HJs after 1 Gyr isdetected, which indicates the formation timescale of HJ around field stars is much larger thanthat in star clusters. Thus, stellar environments play important roles in the formation of HJs.
The Hot-Neptune desert occurs around 100 Myr in our sample. Combining photoevaporationand high-e migration may sculpt the Hot-Neptune desert in clusters.
--------------------------------Gao, Yichen / 2301110308@stu.pku.edu.cn / Peking University
Moist convective variability on mini-Neptunes with a 1D model
Hydrogen has a significantly smaller molecular weight than most condensable gases. Thiscan lead to convective inhibition, in which the presence of a heavy condensable gas (likeH2O vapor) suppresses convection inside a light H2-dominated atmosphere. Convective
inhibition is believed to play an essential part in explaining the Great White Spots on Saturnand could similarly lead to variable convection phenomena on gas giants or mini-Neptunes
with high amounts of condensables. However, the dynamics of convective inhibition are still
poorly understood. Here we investigate the variability of moist convection in H2-H2O
atmospheres with a 1D time-stepping model. We have developed a flexible moist convection
code based on Ding & Pierrehumbert (2016). Even this very simple model shows cyclic
variations in convection. By making some simplifications, we are able to categorize moist H2atmospheres into several categories, including convective oscillations with different periods
and possible multiple equilibria. We will discuss how these vertical and temporalcharacteristics are affected by parameters such as incoming solar radiation, total optical
thickness, surface pressure, etc.
--------------------------------GU, ZIYING / guziying@g.ecc.u-tokyo.ac.jp / The University of Tokyo
Atmospheric Characterization of K2-100b in the Neptunian Desert with High-Resolution
SpectroscopyWith the discovery of thousands of exoplanets with various diversities, one of the mostimportant problems beyond planet hunting is detection and characterization of the planetaryatmospheres. Among the various methods to characterizing exoplanet atmospheres,transmission and emission spectroscopy for transiting planets has a unique advantage,
enabling us to characterize their atmospheres using spectra during their transit or eclipse.
Such research has been typically carried out on Hot Jupiters, massive planets close to their
host stars (a < 0.1 AU). As the improvement of instrumentation, smaller and lighter planets
are being possible to be characterized through this method as well. Unlike Hot Jupiters,
planets with periods of < 10 d and masses of 0.03 − 0.3 Mjup (or equivalently 9.5 − 95 M⊕)
are evidently fewer than neighboring region. Such a phenomenon is coined as Neptunian
Desert and planets in this desert are called Hot Neptunes. We present an atmosphericcharacterization of a Hot Neptune, K2-100 b. This transiting planet discovered by the K2
mission is orbiting around a young star (0.8 Gyr, a member of the Praesepe cluster) with asemi-major axis of ∼ 0.02 AU and a period of ∼ 1.67 d. The planet radius is estimated to be
3.88 ± 0.16 R⊕ and its mass is recently estimated to be 21.8 ± 6.2 M⊕. The planet issituated in the middle of the Neptunian Desert and critically important to understand if such aplanet has an atmosphere and what their compositions are. Because of its youth and its
location in the desert, it might also provide information of the origin of Hot Neptunes. We
would like to search for molecules and to confine properties of K2-100 b with CrossCorrelation Function (CCF) analysis in its high-resolution near-infrared spectra obtained with
the infrared high-dispersion spectrometer IRD on the Subaru 8.2-m telescope during thetransit phases. Starting with two-dimensional echelle format spectral data, one-dimensional
28

spectra were subtracted with a pipeline dedicated for IRD (PyIRD). Then further reductions,like masking sky emission lines, blaze function correction and masking outliers, were carriedout. After that, data were passed through a de-trending algorithm, SYSREM, to remove
systematic effects like stellar signals and telluric lines. Model spectra were generated withtarget species including H2O, FeH, CO, CO2, HCN and CH4, and pre-processed before
applying CCF. The results show non-detection for above 6 species. Although there are two
suspicious signals of H2O and HCN, they are ruled out by injection test. Non-detection
results and injection tests suggest the important information about K2-100 b as below. i) If
the assumption of H-He dominated atmosphere is correct, water abundance is low andhazes or clouds may exist in low pressure (higher altitude), preventing us from retrieving
features in relatively flat spectra. ii) If the assumption of H-He dominated atmosphere iswrong, K2-100 b may have an atmosphere consisting of heavier molecules, unlike Hot
Jupiters. If this is the case, K2-100 b probably formed through loss of H-He envelope during
its evolution. In order to conclude this, more extensive observations of K2-100 b and agreater number of observations on Hot Neptunes are necessary.
--------------------------------Hu, Zhecheng / hzc22@mails.tsinghua.edu.cn / Tsinghua University
OGLE-2015-BLG-0845: A Bulge M dwarf From Combination of Xallarap and Parallax EffectWe report a precise determination of both the mass and distance of the single-lensmicrolensing event OGLE-2015-BLG-0845, achieved through a combined analysis modelingboth xallarap and parallax effects. Our analysis indicates that the lensing object is likely an
M-dwarf situated in the Galactic Bulge. The measured mass of the lens is 0.13 +- 0.05
M_sun, and its distance is 7.4 +/- 1.0 kpc. We demonstrate that the xallarap effect serves toeffectively break the inherent mass-distance degeneracy commonly encountered in
microlensing events, together with the parallax effect. Furthermore, we estimate thatapproximately 4% of such microlensing events present the xallarap effect amenable tocharacterization through future joint observations employing both radial velocity techniquesand continued microlensing studies.
--------------------------------Huang, Helong / huanghl22@mails.tsinghua.edu.cn / Department of Astronomy, Tsinghua
University
A fast cloud model for exoplanet atmosphere retrieval
Exoplanet atmosphere has been investigated by a number of ground-based and spacebased telescopes. With the launch of JWST, we are embracing an era of precise
measurement of exoplanet atmosphere’s transition and emission spectrum. The potential
presence of cloud poses major uncertainty to the retrieval of atmosphere properties, as it cansmooth out the spectral features. We proposed a new cloud model to be used in the retrievalof exoplanet. The model follows the transport of cloud particles, composed of various
condensates, the condensation of which is calculated from supersaturation ratio. A relaxation
method is utilized to find a steady state solution with computational speed fast enough to be
used in atmospheric retrieval. Our model is robust again a wide range of parameters, flexible
to be used in different kinds of planets and versatile to include a variety of cloud species.
--------------------------------Ji, Chenyang / jicy23@mails.tsinghua.edu.cn / Tsinghua University
Radial Velocity Precision of CHORUS with Different Pupil Slicing Designs
Precise radial velocity (RV) surveys are trying to find Earth 2.0 in the next decade, which
requires extremely high resolution spectrographs. We carry out simulations to compare two
instrumental designs of CHORUS. The Canarian Hybrid Optical high-Resolution Ultra-stable
Spectrograph, which will be installed on the Gran Telescopio de Canarias in 2027. CHORUS
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is under construction by NAOC and NIAOT in China, and it is expected to reach a RV
precision of lower than 10cm/s in visible band. The two different designs differ primarily in thenumber of pupil slicing (3 vs. 2) and spectral resolution (120,000 vs. 90,000). We found that
the RV precision obtained under the 3-slice setting is better than the 2-slice setting, as
expected, and the 3-slice setup would reach the instrument target of 10 cm/s precision at amore reasonable SNR. We used Kurucz’s solar template to synthesize observational spectrawith input Doppler shift and various SNRs. Then we extracted RVs using the crosscorrelation method. We will carry out further simulations to test other aspects in the
instrumental designs of CHORUS, and our work could help assessing the photon-limited RV
precision and performances of other similar instruments.
--------------------------------Jin, Sheng / jins@ahnu.edu.cn / Anhui Normal University
Adaptive Parallel Tempering Markov Chain Monte Carlo with Nii-C
This talk introduces an adaptive parallel tempering Markov Chain Monte Carlo (APT-MCMC)
code Nii-C that enables rapid convergence in the sampling of complex distributions. The NiiC code has two outstanding features. First, an efficient control system is implemented that
can adaptively adjust the step sizes of the proposal distributions for all model parametersacross all parallel tempering chains. This can ensure that the real-time sampling acceptance
rates are within an ideal range. Second, it is a pure C language implementation using the
Message-Passing Interface (MPI) protocol, which guarantees its fast execution speed. To
facilitate the adaptation of the Nii-C code to different posterior distributions faced by various
Bayesian analysis models, the user-defined prior and likelihood functions were designed to
be as independent as possible and isolated into two separate source files. Tracking of thesamplers in a linear regression model and a hierarchical statistical model demonstrates theadvantages of Nii-C in terms of speed and convergence capability.
--------------------------------Lee, Sanghee / lee.s.ay@m.titech.ac.jp / Tokyo Institute of Technology
Magnetic activity variability of Sun-like stars by intensive H alpha line monitoring
We report intensive monitoring of the activity variability in the H alpha line for 13 Sun-likestars using the 1.88-m reflector at Okayama Branch Office, Subaru Telescope, during the last
four years 2019-2022. Our aim was to investigate features of the stellar magnetic activity
behaviors from various aspects, including activity cycles, amplitudes of activity variability, andexoplanet detection. We correlated the H alpha line variability of each star with the stellar
activity levels derived from the Ca II H&K line, suggesting its efficiency as a magnetic activity
indicator. Each target star exhibited distinct magnetic activity, suggesting the possibility ofshort-term activity cycles in F-type stars and temporal absence/existence of the cycle period.
With respect to the stars with a hot Jupiter, we could not find any signature of the star-planet
magnetic interaction. It is speculated that the magnetic activity variability in the H alphaobservation is related to the stellar intrinsic activity rather than the existence of the hot
Jupiter. We also found the range of the amplitudes of the H alpha variability that may or may
not induce a stellar noise to the RV with the precision of few m/s.
--------------------------------Li, Yufeng / yufengli@bnu.edu.cn / Beijing Normal University
Radio Astronomy of Exoplanets
Radio observations provide a unique avenue to surpass the limitations of opticalobservations, allowing us to probe the magnetic fields of planets. This report delves into theapplication of radio astronomy in unveiling the characteristics of exoplanets. We introduce
how the radio data is employed to investigate exoplanets. We also discuss ongoing radio
observation projects and look forward to the future, where radio observations hold promise in30

providing valuable data for a deeper understanding of exoplanets and their potential
habitable conditions.
--------------------------------Lin, Zitao / lzt22@mails.tsinghua.edu.cn / Tsinghua University
PFS Radial Velocity Survey on Long-period Giant Planets
Understanding cold Jupiters, a population similar to our own Jupiter, is important for studying
exoplanet demographics or planet formation. Long-term radial velocity (RV) surveys provide
powerful constraints on the occurrence and properties of cold Jupiters. Here we present theinitial results from a long-term high-precision RV survey of 468 stars using the Magellan
Planet Finder Spectrograph (PFS). We report our sample selection criteria, planet-searchingalgorithm, the resulting catalog containing confirmed or newly identified exoplanets andsubstellar companions, and the search completeness of each system. Our data containaround 17000 RV measurements with a median baseline of 12 years. Our survey result
stands as an independent, homogeneous dataset, with a relatively low selection bias. Thisdistinctive dataset represents an invaluable resource for diverse statistical investigations. In
our following papers, we will delve deeper into the occurrence rate and property distributionsof giant planets. These findings will provide reassuring independent and/or new evidence for
giant planet formation in tandem with findings from other similar RV surveys.
--------------------------------Liu, Jiajia / jiajialiu@ustc.edu.cn / University of Science and Technology of China
Introduction to the SOlar Terrestrial Habitability Explorer (SOTHE)
Among more than 5000 exoplanets discovered up to now, around 60 are believed to bepotentially habitable. The Sun-Earth system provides a unique example based on which
detailed insights into the properties, formation, evolution, and thus habitability of exoplanets
could be gained. However, simultaneously observing the Sun as a star and the Earth as an
exoplanet has been rare. In this talk, I will briefly introduce the SOlar Terrestrial Habitability
Explorer (SOTHE) to be deployed to the Sun-Earth L1 point. SOTHE will carry 5 payloads toobtain the spectra of the Sun and the Earth at the same time, together with images of the
Earth at a number of unique passbands and the local plasma and magnetic field parametersat the L1 point. The core scientific goal of SOTHE is to conduct the first-ever simultaneous
spectral observations of the Sun and Earth to explore key characteristics related to thehabitability of the Sun-Earth system and provide a unique baseline for habitable exoplanets
exploration.
--------------------------------Liu, Jiachen / jiachen@stu.pku.edu.cn / Peking University
Convection and Clouds under Different Planetary Gravities
In this study, we employ a cloud-resolving model to investigate how gravity influences
convection and clouds in a small-domain (96 × 96 km) radiative–convective equilibrium. Our
experiments are performed with a horizontal grid spacing of 1 km, which can resolve large(>1km2) convective cells. We find that under a given stellar flux, sea surface temperature
increases with decreasing gravity. This is because a lower-gravity planet has larger water
vapor content and more clouds, resulting in a larger clear-sky greenhouse effect and astronger cloud warming effect in the small domain. By increasing stellar flux under different
gravity values, we find that the convection shifts from a quasi-steady state to an oscillatory
state. In the oscillatory state, there are convection cycles with a period of several days,
comprised of a short wet phase with intense surface precipitation and a dry phase with nosurface precipitation. When convection shifts to the oscillatory state, the water vapor content
and high-level cloud fraction increase substantially, resulting in rapid warming. After the31transition to the oscillatory state, the cloud net positive radiative effect decreases withincreasing stellar flux, which indicates a stabilizing climate effect. In the quasi-steady state,
the atmospheric absorption features of CO2 are more detectable on lower-gravity planets
because of their larger atmospheric heights. While in the oscillatory state, the high-levelclouds mute almost all of the absorption features, making the atmospheric components hard
to characterize.
--------------------------------Liu, Quanyi / mailto:liuqy0723@163.com / Nankai University
The Feasibility Analysis of Constraining the Shape of a Jupiter Analog with JWST Transit
The shape of a planet can provide massive clues about itself and its system, including thespinning, interior structure, and even its evolutionary history. An oblate planet can cause thetransit light curve asymmetric and distortions in the ingress and egress, which is detectablewith JWST observation accuracy. We perform oblateness signal injection and recovery in thecase of a Jupiter analog, Kepler-167e. We simulate the light curve of a Kepler-167e-likeplanet with a certain oblateness, with the photometric noise of JWST/NIRSpec and the stellar
red noise corresponding to a Kepler-167-like star. The fitting results of light curves in different
oblateness show that we can significantly detect the oblateness of a planet in a condition of
the Angle between the planet's axis of rotation and the plane of revolution greater than 20
degrees. This enables us to characterize exoplanets more comprehensively.
--------------------------------Ren, Haibin / rhb23@mails.tsinghua.edu.cn / Tsinghua University
Implementation of Automatic Differentiation in Microlensing Light Curve Calculation
Microlensing offers a unique avenue for exploring exoplanets beyond the snowline and theirimplications for planetary formation. To harness its full potential in the era of growing
observational data, we present a Jax implementation of V. Bozza's adaptive samplingalgorithm (VBBinaryLensing) with automatic differentiation. This library can be combined withcurrent mainstream optimization algorithms, and its adaptive differentiation function will also
allow for more efficient implementation of optimization algorithms, such as Hamiltonian
Monte Carlo. This is of great significance for accelerating the analysis and opening new
horizons in gravitational microlensing analysis.
--------------------------------Song, Xinyi / songxinyi@pku.edu.cn / Peking University
Asymmetry and Variability in the Transmission Spectra of Tidally Locked Habitable Planets
Spatial heterogeneity and temporal variability are general features in planetary weather andclimate, due to the effects of planetary rotation, uneven stellar flux distribution, fluid motion
instability, etc. In this study, we investigate the asymmetry and variability in the transmission
spectra of 1:1 spin–orbit tidally locked (or called synchronously rotating) planets around lowmass stars. We find that for rapidly rotating planets, the transit atmospheric thickness of theevening terminator (east of the substellar region) is significantly larger than that of themorning terminator (west of the substellar region). The asymmetry is mainly related to thespatial heterogeneity in ice clouds, as the contributions of liquid clouds and water vapor are
smaller. The underlying mechanism is that there are always more ice clouds on the evening
terminator, due to the combined effect of coupled Rossby–Kelvin waves and equatorial
superrotation that advect vapor and clouds to the east, especially at high levels of theatmosphere. For slowly rotating planets, the asymmetry reverses (the morning terminatorhas a larger transmission depth than the evening terminator), but the magnitude is small oreven negligible. For both rapidly and slowly rotating planets, there is strong variability in thetransmission spectra. The asymmetry signal is nearly impossible to be observed by theJames Webb Space Telescope (JWST), because the magnitude of the asymmetry (about 1032ppm) is smaller than the instrumental noise and the high variability further increases thechallenge.
--------------------------------Tang, Jiaxin / tangjx22@mails.tsinghua.edu.cn / Tsinghua University
RVxTESS I: Modeling Asteroseismic Signals with Simultaneous Photometry and RVs
The Radial Velocity (RV) method, measuring the Doppler Shifts from stellar spectra, is widelyused for the detection and characterization of exoplanets. For low-mass planets, RV
detection typically requires cm/s precision, whereas the stellar jitter becomes an issue at them/s level. Thus, it is essential to mitigate such stellar jitter in order to detect Earth-like planets
using RVs. Our project focuses on the asteroseismic signals of stellar jitter, including stellar
oscillation and granulation. We study HD 5562 with fitting the model of stellar jitter to theobservational data from the Transiting Exoplanet Survey Satellite (TESS) and RVs from theCarnegie Planet Finder Spectrograph on the Magellan II Telescope (Magellan/PFS). We
perform a Gaussian Process (GP) regression on the star's photometric and RV data to
describe its asteroseismic signals. The simultaneous fit model suggests that the primarymode of its oscillation is around 15 minutes or around 1000 muHz. We have reduced the RV
scatter from 2.03 m/s to 0.50 m/s by fitting a GP model, which was trained on the TESS light
curves, to the RV time series. We also explore multiple ways to model the oscillation in thephotometry and how it could be transferred effectively to the RV domain. In addition, we seek
to extend the method to test the detectability of Super-Earths around evolved stars. Our
project is part of the RVxTESS program (RVxTESS.com), which combines simultaneous
TESS photometry with ground-based RV observations to study stellar jitter.
--------------------------------Yan, Dongdong / yand@ynao.ac.cn / Yunnan Observatories, Chinese Academy of Sciences
Modeling the H-alpha and He 10830 transmission spectra of a hot JupiterIn this talk, I will show our work of modeling of H-alpha and He 10830 transmission spectrumof a hot Jupiter. The work helps to constrain the stellar XUV and Ly-alpha flux, H/He ratio andmass loss rate of the exoplanetary atmosphere, and provides clues to the escaping
atmosphere of hydrogen and helium. To do this, we use the XUV driven hydrodynamic
simulation to obtain the atmospheric structures, solve the rate equations of non-local thermal
equilibrium related to hydrogen and helium to calculate the detailed level population, andthen conduct the radiative transfer simulation to model the transmission spectrum of H-alphaand He 10830. The Monte Carlo simulations of Ly-alpha radiative transfer are performed to
calculate the Ly-alpha mean intensity distribution inside the planetary atmosphere, necessary
in estimating the hydrogen level population.
--------------------------------Yang, Jia-Yi / yangjy@nju.edu.cn / Nanjing University
Planets Across Space and Time (PAST) IV: The Occurrence and Architecture of Kepler
Planetary Systems as a Function of Kinematic Age Revealed by the LAMOST-Gaia-Kepler
SampleOne of the fundamental questions in astronomy is how planetary systems form and evolve.
Measuring the planetary occurrence and architecture as a function of time directly addresses
this question. In the fourth paper of the Planets Across Space and Time (PAST) series, weinvestigate the occurrence and architecture of Kepler planetary systems as a function ofkinematic age by using the LAMOST-Gaia-Kepler sample. To isolate the age effect, otherstellar properties (e.g., metallicity) have been controlled. We found the following results. (1)The fraction of stars with Kepler-like planets (Fkep) is about 50% for all stars; no significant
trend is found between Fkep and age. (2) The average planet multiplicity (Np) exhibits adecreasing trend (~2σ significance) with age, which decreases from ~3 for stars younger
33

than 1 Gyr to Np~1.8 for stars about 8 Gyr. (3) The number of planets per star (η=Fkep*Np)
also shows a decreasing trend (~2-3σ significance), which decreases from η~1.6-1.7 foryoung stars to η~1.0 for old stars. (4) The mutual orbital inclination of the planets (σ_{i,k})increases from 1.2(+1.4,-0.5) to 3.5(+8.1,-2.3) as stars aging from 0.5 to 8 Gyr with a best fit
of log(σ_{i,k})=0.2+0.4*log(Age/1Gyr), and interestingly, the Solar System also fits such atrend. The nearly independence of Fkep~50% on age implies that planet formation is robust
and stable across the Galaxy history. The age dependence of Np and σ_{i,k} demonstrates
planetary architecture is evolving, and planetary systems generally become dynamicallyhotter with fewer planets as they age.
--------------------------------Zhan, Ruizhi / 2201110322@stu.pku.edu.cn / Peking University
Novel Atmospheric Dynamics Shape Habitable Zone Inner Edge Around White Dwarfs
White dwarf stars offer a unique opportunity to search nearby stellar systems forbiosignatures. Due to white dwarfs’ small size, planets orbiting these stars are much easier tocharacterize via transmission spectra than planets orbiting main sequence stars. The
potential habitability of white dwarf planets, however, is still poorly understood. Here we use
the ExoCAM, a 3D global climate model (GCM), to investigate the inner edge of the habitablezone (HZ) around white dwarfs. Since white dwarfs are low-luminosity and compact,
habitable planets orbiting them are most probably tidally locked and rapidly rotating withorbital periods ranging from hours to days. We find that the runaway greenhouse limit for
white dwarfs lies in-between that for rapidly rotating non-tidally locked planets and slowly
rotating tidally locked planets reported in previous research. The upper atmospheres of whitedwarf planets are also much drier than for main sequence stars, which means most whitedwarf planets never experience a moist greenhouse state. We explain these features as
resulting from a novel atmospheric dynamical regime. When tidally locked planets rotate
rapidly (orbital period ~< 1 day), the hottest point on the planetary surface shifts from theequator to the subtropics which leads to the formation of anti-Hadley Cells on the planet’s
dayside and strongly modifies the dayside cloud cover. The inner edge of the habitable zone
around white dwarfs is therefore strongly affected by planetary rotation, the dynamics ofwhich cannot be resolved in 1D models.

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