bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Volume-limited Sample of Ultracool Dwarfs. II. The Substellar Age and Mass Functions in the Solar Neighborhood
Authors: Best William M. J. , Sanghi Aniket , Liu Michael C. , Magnier Eugene A. , Dupuy Trent J. 
Published: May 2024

Abstract
We present the most precise constraints to date for the mass and age distributions of single ultracool dwarfs in the solar neighborhood, based on an updated volume-limited sample of 504 L, T, and Y dwarfs within 25 pc. We develop a Monte Carlo approach using the

〈
V

/

V

max

〉

statistic to correct for incompleteness and obtain a space density of

(

1.83

−
0.15

+
0.16

)
×

10

−
2

pc−3 for spectral types L0–Y2. We calculate bolometric luminosities for our sample, using an updated “super-magnitude” method for the faintest objects. We use our resulting luminosity function and a likelihood-based population synthesis approach to simultaneously constrain the mass and age distributions. We employ the fraction of young L0–L7 dwarfs as a novel input for this analysis that is crucial for constraining the age distribution. For a power-law mass function

dN

dM

∝

M

−
α

, we find

α
=

0.58

−
0.20

+
0.16

, indicating an increase in numbers toward lower masses, consistent with measurements in nearby star-forming regions. For an exponential age distribution b(t) ∝ e
−β
t
we find β = −0.44 ± 0.14, i.e., a population with fewer old objects than often assumed, which may reflect dynamical heating of the Galactic plane as much as the historical brown dwarf birthrate. We compare our analysis to that of Kirkpatrick et al., who used a similar volume-limited sample. Although our mass function measurements are numerically consistent, their assumption of a flat age distribution is disfavored by our analysis, and we identify several important methodological differences between our two studies. Our calculation of the age distribution of solar neighborhood brown dwarfs is the first based on a volume-limited sample.
The Impact of Extended H2O Cross Sections on Temperate Anoxic Planet Atmospheres: Implications for Spectral Characterization of Habitable Worlds
Authors: Broussard Wynter , Schwieterman Edward W. , Ranjan Sukrit , Sousa-Silva Clara , Fateev Alexander , Reinhard Christopher T. 
Published: May 2024

Abstract
JWST has created a new era of terrestrial exoplanet atmospheric characterization, and with it, the possibility to detect potential biosignature gases like CH4. Our interpretation of exoplanet atmospheric spectra, and the veracity of these interpretations, will be limited by our understanding of atmospheric processes and the accuracy of input modeling data. Molecular cross sections are essential inputs to these models. The photochemistry of temperate planets depends on photolysis reactions whose rates are governed by the dissociation cross sections of key molecules. H2O is one such molecule; the photolysis of H2O produces OH, a highly reactive and efficient sink for atmospheric trace gases. We investigate the photochemical effects of improved H2O cross sections on anoxic terrestrial planets as a function of host star spectral type and CH4 surface flux. Our results show that updated H2O cross sections, extended to wavelengths >200 nm, substantially impact the predicted abundances of trace gases destroyed by OH. The differences for anoxic terrestrial planets orbiting Sun-like host stars are greatest, showing changes of up to 3 orders of magnitude in surface CO levels, and over an order of magnitude in surface CH4 levels. These differences lead to observable changes in simulated planetary spectra, especially important in the context of future direct-imaging missions. In contrast, the atmospheres of planets orbiting M-dwarf stars are substantially less affected. Our results demonstrate a pressing need for refined dissociation cross-section data for H2O, where uncertainties remain, and other key molecules, especially at mid-UV wavelengths >200 nm.
Kinematic Age of the β-Pictoris Moving Group
Authors: Lee Jinhee , Song Inseok 
Published: May 2024

Abstract
Accurate age estimation of nearby young moving groups (NYMGs) is important as they serve as crucial testbeds in various fields of astrophysics, including the formation and evolution of stars and planets, as well as loose stellar associations. The β-Pictoris moving group (BPMG), being one of the closest and youngest NYMGs, has been extensively investigated, and its estimated ages have a wide range from ∼10–25 Myr, depending on the age estimation methods and data used. Unlike other age dating methods, kinematic traceback analysis offers a model-independent age assessment hence the merit in comparing many seemingly discordant age estimates. In this study, we determine the kinematic ages of the BPMG using three methods: probabilistic volume calculation, mean pairwise distance calculation, and covariance matrix analysis. These methods yield consistent results, with estimated ages in the range of 14–20 Myr. Implementing corrections to radial velocities due to gravitational redshift and convectional blueshift increases the ages by ∼2–4 Myr. Conversely, considering data uncertainties decreases the estimated ages by 1–2 Myr. Taken together, our analysis determined the kinematic age of the BPMG to be

16.3

−
2.1

+
3.4

Myr. This age is significantly younger than the commonly accepted age of the BPMG (∼24 Myr) determined primarily from the lithium depletion boundary analysis. This younger kinematic age may point to the discrepancy between the luminosity evolution and lithium depletion models or the presence of unaccounted systematic error in the method. This result underscores the necessity for systematic reevaluations of age-dating methods for nearby, young moving groups.
Pickup Ion Modulation on Plateau-like Turbulence in the Martian Magnetosheath
Authors: Li Hui , Jiang Wence , Yang Zhongwei , Liu Xiaodong , Verscharen Daniel , Wang Chi 
Published: May 2024

Abstract
The distribution of magnetic energy across scales, represented by the turbulence spectrum, provides insights into magnetic field dynamics in astrophysical and space plasma. While the Earth’s magnetosheath exhibits a conventional two-slope spectrum, the Martian magnetosheath often displays a prominent plateau-like spectrum. However, the underlying physical mechanism remains unresolved. Based on MAVEN observations, we present appealing evidence of pickup ions (PUIs) modulating the plateau-like spectrum through proton cyclotron waves (PCWs). PCWs, driven by unstable pickup H+ ion distributions, significantly influence the formation of plateau-like spectra. Both case and statistical studies suggest that the spectral evolution is affected by the relative abundance of pickup O+ ions. A substantial presence of pickup O+ ions can suppress PCWs driven by pickup H+ ions, resulting in a decline in the slope of the plateau spectrum. Particle-in-cell simulations confirm the role of PUI-modulated PCWs in the plateau-range energy injection. Our results provide new insight into the impact of PUIs on magnetic turbulence evolution and associated energy transfer processes in space and astrophysical plasma.
A Recipe for Eccentricity and Inclination Damping for Partial-gap Opening Planets in 3D Disks
Authors: Pichierri Gabriele , Bitsch Bertram , Lega Elena 
Published: May 2024

Abstract
In a previous paper, we showed that, like the migration speed, the eccentricity damping efficiency is modulated linearly by the depth of the partial gap a planet carves in the disk surface density profile, resulting in less efficient e-damping compared to the prescription commonly used in population synthesis works. Here, we extend our analysis to 3D, refining our e-damping formula and studying how the inclination damping efficiency is also affected. We perform high-resolution 3D locally isothermal hydrodynamical simulations of planets with varying masses embedded in disks with varying aspect ratios and viscosities. We extract the gap profile and orbital damping timescales for fixed eccentricities and inclinations up to the disk scale height. The limit in gap depths below which vortices appear, in the low-viscosity case, happens roughly at the transition between classical type-I and type-II migration regimes. The orbital damping timescales can be described by two linear trends with a break around gap depths ∼80% and with slopes and intercepts depending on the eccentricity and inclination. These trends are understood on physical grounds and are reproduced by simple fitting formulas whose error is within the typical uncertainty of type-I torque formulas. Thus, our recipes for the gap depth and orbital damping efficiencies yield a simple description for planet–disk interactions to use in N-body codes in the case of partial-gap opening planets that is consistent with high-resolution 3D hydrosimulations. Finally, we show examples of how our novel orbital damping prescription can affect the outcome of population synthesis experiments.
Challenges to Inflation in the Post-Planck Era
Authors: Liu Jingwei , Melia Fulvio 
Published: May 2024

Abstract
Space-based missions studying the cosmic microwave background (CMB) have progressively refined the parameter space in conventional models of inflation shortly (∼10−37 s) after the Big Bang. While most inflationary scenarios proposed thus far in the context of general relativity have since been ruled out, the basic idea of inflation may still be tenable, albeit with several unresolved conundrums, such as conflicting initial conditions and inconsistencies with the measured CMB power spectrum. In the new slow-roll inflationary picture, inflation arising in plateau-like potentials requires an initiation beyond the Planck time. This delay may be consistent with the cutoff,

k

min

, measured recently in the primordial power spectrum. However, the actual value of

k

min

would imply an initiation time too far beyond the Big Bang for inflation to solve the horizon problem. In this paper, we also describe several other undesirable consequences of this delay, including an absence of well-motivated initial conditions and a significant difficulty in providing a viable mechanism for properly quantizing the primordial fluctuations. Nevertheless, many of these inconsistencies may still be avoided if one introduces nonconventional modifications to inflation, such as a brief departure from slow-roll dynamics, possibly due to a dramatic change in the inflationary potential, inflation driven by multiple fields, or a nonminimal coupling to gravity. In addition, some of these difficulties could be mitigated via the use of alternative cosmologies based, e.g., on loop quantum gravity, which replaces the initial Big Bang singularity with finite conditions at a bounce-like beginning.
Hybrid Star Models in the Light of New Multimessenger Data
Authors: Li Jia Jie , Sedrakian Armen , Alford Mark 
Published: May 2024

Abstract
Recent astrophysical mass inferences of compact stars HESS J1731-347 and PSR J0952-0607, with extremely small and large masses respectively, as well as the measurement of the neutron skin of Ca in the CREX experiment challenge and constrain the models of dense matter. We examine the concept of hybrid stars—objects containing quark cores surrounded by nucleonic envelopes—as models that account for these new data along with other inferences. We employ a family of 81 nucleonic equations of state (EOSs) with variable skewness and slope of symmetry energy at saturation density and a constant speed-of-sound EOS for quark matter. For each nucleonic EOS, a family of hybrid EOSs is generated by varying the transition density, the energy jump, and the speed of sound. These models are tested against the data from GW170817 and J1731-347, which favor low-density soft EOS and J0592-0607 and J0740+6620, which require high-density stiff EOS. The addition of J0592-0607's mass measurement to the constraints has no significant impact on the parameter space of the admissible EOS, but allows us to explore the potential effect of pulsars more massive than J0740+6620, if such exists. We then examine the occurrence of twin configurations and quantify the ranges of masses and radii that they can possess. It is shown that including J1731-347 data favors EOSs that predict low-mass twins with M ≲ 1.3 M
⊙ that can be realized if the deconfinement transition density is low. If combined with large speed of sound in quark matter such models allow for maximum masses of hybrid stars in 2.0–2.6 M
⊙.
Observations of GRB 221009A by the MAVEN-SEP Instrument at Mars
Authors: Alnussirat Samer T. , Rahmati Ali , Larson Davin , Dunn Patrick A. , Lee Christina O. , Tomsick John , Agapitov O. 
Published: May 2024

Abstract
We report on the detection of the Brightest Of All Time (the BOAT) gamma-ray burst (GRB) 221009A by the MAVEN Solar Energetic Particle (SEP) silicon (Si) detectors. The SEP instrument on board the MAVEN spacecraft at Mars is designed to measure charged particle fluxes and energies. In this work, we show that the SEP Si detectors have detected populations of secondary charged particles and low-energy primary photons from the GRB. Our analysis relies on a series of simplified Geant4 Monte Carlo simulations. We show that electromagnetic and hadronic interactions between the GRB photons and the spacecraft’s passive material and Si detectors produced the detected secondary particles.
Analytical Study of Damped Standing Longitudinal MHD Waves in Flowing Coronal Loops: The Effect of Thermal Conduction
Authors: Bahari Karam 
Published: May 2024

Abstract
The longitudinal magnetohydrodynamic (MHD) oscillations of coronal loops have been investigated in dissipative flowing loops. Thermal conduction has been considered as the damping mechanism of the wave. We aim to construct the damped longitudinal waves by superposing two propagating waves that propagate in opposite directions. The two propagating components must have the same oscillation frequencies and damping rates, which has been described impossible by some authors, but we have used a technique to overcome this difficulty. The equations of motion are combined to obtain a differential equation for the velocity perturbation. Using the weak damping condition, the perturbation method is used to solve the dispersion relation. In the leading order approximation, the oscillation frequency of the standing waves is determined. In the first-order approximation, we let both the oscillation frequency and wavelength of the propagating waves be perturbed due to the presence of thermal conduction, which enables us to determine the damping rate of the standing waves. Our results show that the plasma flow is an essential parameter in determining the effectiveness of the damping mechanism. Also, the exact solutions of the dispersion relation have been determined without using weak damping assumption. Interestingly the two solutions are the same. Introducing plasma flow to the coronal loop causes the period ratio of the fundamental mode to the first overtone to decrease more.
The TESS-Keck Survey. XX. 15 New TESS Planets and a Uniform RV Analysis of All Survey Targets
Authors: Polanski Alex S. , Lubin Jack , Beard Corey , Akana Murphy Joseph M. , Rubenzahl Ryan , Hill Michelle L. , Crossfield Ian J. M. , Chontos Ashley , Robertson Paul , Isaacson Howard , Kane Stephen R. , Ciardi David R. , Batalha Natalie M. , Dressing Courtney , Fulton Benjamin , Howard Andrew W. , Huber Daniel , Petigura Erik A. , Weiss Lauren M. , Angelo Isabel , Behmard Aida , Blunt Sarah , Brinkman Casey L. , Dai Fei , Dalba Paul A. , Fetherolf Tara , Giacalone Steven , Hirsch Lea A. , Holcomb Rae , Kosiarek Molly R. , Mayo Andrew W. , MacDougall Mason G. , Močnik Teo , Pidhorodetska Daria , Rice Malena , Rosenthal Lee J. , Scarsdale Nicholas , Turtelboom Emma V. , Tyler Dakotah , Van Zandt Judah , Yee Samuel W. , Coria David R. , Dulz Shannon D. , Hartman Joel D. , Householder Aaron , Lange Sarah , Langford Andrew , Louden Emma M. , Siegel Jared C. , Gilbert Emily A. , Gonzales Erica J. , Schlieder Joshua E. , Boyle Andrew W. , Christiansen Jessie L. , Clark Catherine A. , Fernandes Rachel B. , Lund Michael B. , Savel Arjun B. , Gill Holden , Beichman Charles , Matson Rachel , Matthews Elisabeth C. , Furlan E. , Howell Steve B. , Scott Nicholas J. , Everett Mark E. , Livingston John H. , Ershova Irina O. , Cheryasov Dmitry V. , Safonov Boris , Lillo-Box Jorge , Barrado David , Morales-Calderón María 
Published: May 2024

Abstract
The Transiting Exoplanet Survey Satellite (TESS) has discovered hundreds of new worlds, with TESS planet candidates now outnumbering the total number of confirmed planets from Kepler. Owing to differences in survey design, TESS continues to provide planets that are better suited for subsequent follow-up studies, including mass measurement through radial velocity (RV) observations, compared to Kepler targets. In this work, we present the TESS-Keck Survey’s (TKS) Mass Catalog: a uniform analysis of all TKS RV survey data that has resulted in mass constraints for 126 planets and candidate signals. This includes 58 mass measurements that have reached ≥5σ precision. We confirm or validate 32 new planets from the TESS mission either by significant mass measurement (15) or statistical validation (17), and we find no evidence of likely false positives among our entire sample. This work also serves as a data release for all previously unpublished TKS survey data, including 9,204 RV measurements and associated activity indicators over our three-year survey. We took the opportunity to assess the performance of our survey and found that we achieved many of our goals, including measuring the mass of 38 small (<4 R
⊕) planets, nearly achieving the TESS mission’s basic science requirement. In addition, we evaluated the performance of the Automated Planet Finder as survey support and observed meaningful constraints on system parameters, due to its more uniform phase coverage. Finally, we compared our measured masses to those predicted by commonly used mass–radius relations and investigated evidence of systematic bias.
Uncovering the Ghostly Remains of an Extremely Diffuse Satellite in the Remote Halo of NGC 253*
Authors: Okamoto Sakurako , Ferguson Annette M. N. , Arimoto Nobuo , Ogami Itsuki , Žemaitis Rokas , Chiba Masashi , Irwin Mike J. , Jang In Sung , Koda Jin , Komiyama Yutaka , Lee Myung Gyoon , Lee Jeong Hwan , Rich Michael R. , Tanaka Masayuki , Tanaka Mikito 
Published: May 2024

Abstract
We present the discovery of NGC253-SNFC-dw1, a new satellite galaxy in the remote stellar halo of the Sculptor Group spiral, NGC 253. The system was revealed using deep, resolved star photometry obtained as part of the Subaru Near-Field Cosmology Survey that uses the Hyper Suprime-Cam on the Subaru Telescope. Although rather luminous (M

V
= −11.7 ± 0.2) and massive (M
* ∼ 1.25 × 107
M
⊙), the system is one of the most diffuse satellites yet known, with a half-light radius of R

h
= 3.37 ± 0.36 kpc and an average surface brightness of ∼30.1 mag arcmin−2 within the R

h
. The color–magnitude diagram shows a dominant, old (∼10 Gyr), and metal-poor ([M/H] = −1.5 ± 0.1 dex) stellar population, as well as several candidate thermally pulsing asymptotic giant branch stars. The distribution of red giant branch stars is asymmetrical and displays two elongated tidal extensions pointing toward NGC 253, suggestive of a highly disrupted system being observed at apocenter. NGC253-SNFC-dw1 has a size comparable to that of the puzzling Local Group dwarfs Andromeda XIX and Antlia 2 but is 2 magnitudes brighter. While unambiguous evidence of tidal disruption in these systems has not yet been demonstrated, the morphology of NGC253-SNFC-dw1 clearly shows that this is a natural path to produce such diffuse and extended galaxies. The surprising discovery of this system in a previously well-searched region of the sky emphasizes the importance of surface-brightness limiting depth in satellite searches.
The Interplay between the Initial Mass Function and Star Formation Efficiency through Radiative Feedback at High Stellar Surface Densities
Authors: Menon Shyam H. , Lancaster Lachlan , Burkhart Blakesley , Somerville Rachel S. , Dekel Avishai , Krumholz Mark R. 
Published: May 2024

Abstract
The observed rest-UV luminosity function at cosmic dawn (z ∼ 8–14) measured by JWST revealed an excess of UV-luminous galaxies relative to many prelaunch theoretical predictions. A high star formation efficiency (SFE) and a top-heavy initial mass function (IMF) are among the mechanisms proposed for explaining this excess. Although a top-heavy IMF has been proposed for its ability to increase the light-to-mass ratio (ΨUV), the resulting enhanced radiative pressure from young stars could decrease the SFE, potentially driving galaxy luminosities back down. In this Letter, we use idealized radiation hydrodynamic simulations of star cluster formation to explore the effects of a top-heavy IMF on the SFE of clouds typical of the high-pressure conditions found at these redshifts. We find that the SFE in star clusters with solar-neighborhood-like dust abundance decreases with increasingly top-heavy IMFs—by ∼20% for an increase of a factor of 4 in ΨUV and by 50% for a factor of ∼10 in ΨUV. However, we find that an expected decrease in the dust-to-gas ratio (∼0.01 × solar) at these redshifts can completely compensate for the enhanced light output. This leads to a (cloud-scale; ∼10 pc) SFE that is ≳70% even for a factor of 10 increase in ΨUV, implying that highly efficient star formation is unavoidable for high surface density and low-metallicity conditions. Our results suggest that a top-heavy IMF, if present, likely coexists with efficient star formation in these galaxies.
Gamma-Ray Bursts as Distance Indicators by a Statistical Learning Approach
Authors: Dainotti Maria Giovanna , Narendra Aditya , Pollo Agnieszka , Petrosian Vahé , Bogdan Malgorzata , Iwasaki Kazunari , Prochaska Jason Xavier , Rinaldi Enrico , Zhou David 
Published: May 2024

Abstract
Gamma-ray bursts (GRBs) can be probes of the early Universe, but currently, only 26% of GRBs observed by the Neil Gehrels Swift Observatory have known redshifts (z) due to observational limitations. To address this, we estimated the GRB redshift (distance) via a supervised statistical learning model that uses optical afterglow observed by Swift and ground-based telescopes. The inferred redshifts are strongly correlated (a Pearson coefficient of 0.93) with the observed redshifts, thus proving the reliability of this method. The inferred and observed redshifts allow us to estimate the number of GRBs occurring at a given redshift (GRB rate) to be 8.47–9 yr−1 Gpc−1 for 1.9 < z < 2.3. Since GRBs come from the collapse of massive stars, we compared this rate with the star formation rate, highlighting a discrepancy of a factor of 3 at z < 1.