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JWST Transit Spectra. I. Exploring Potential Biases and Opportunities in Retrievals of Tidally Locked Hot Jupiters with Clouds and Hazes

The atmospheres on tidally locked planets likely exhibit large differences between their day- and night-sides. In this paper, we illustrate how the combined effects of aerosols and day-night temperature gradients shape transit spectra of tidally locked exoplanets and evaluate the implications for retrievals of atmospheric properties. We have developed a new code, Multi-dimensional Exoplanet TransIt Spectra (METIS), which can compute transit spectra for arbitrary longitude-latitude-altitude grids of temperature and pressure. Using METIS, we pair flexible treatments of clouds and hazes with simple parameterized day-night temperature gradients to compute transit spectra and perform retrieval experiments across a wide array of possible exoplanet atmospheric properties. Our key findings are that: (1) the presence of aerosols can increase the effects of day-night temperature gradients on transit spectra; (2) ignoring day-night temperature gradients when attempting to perform Bayesian parameter estimation will return biased results, even when aerosols are present; (3) when a day-night temperature gradient is accounted for in the retrieval, some spectra contain sufficient information to constrain temperatures and the width of the transition from day to night. The presence of clouds and hazes can actually tighten such constraints, but also weaken constraints on metallicity and reference pressure. These last findings are predicated on the assumptions made in parameterizing the day-night atmospheric structure and the assumption of thermochemical equilibrium. Our results imply that this may be a promising avenue to pursue and represent a step toward the larger goal of developing models and theory of adequate complexity to match the superior-quality data that will soon be available.

Keywords: exoplanet atmospheres; transmission spectroscopy; hot jupiters
Comparison of Ion–Proton Differential Speed between Interplanetary Coronal Mass Ejections and Solar Wind near 1 au

The elemental abundance of interplanetary coronal mass ejections (ICMEs) and solar wind near 1 au is often adopted to represent the abundance in the corresponding coronal sources. However, the absolute abundance of heavy ions (relative to hydrogen) near 1 au might be different from the coronal abundance due to the ion–proton differential speed (V ip ). To illustrate the V ip characteristics and explore whether it influences the absolute abundance analysis for ICMEs and solar wind, we perform a statistical study on the V ip for He2+, C5+, O6+, and Fe10+ in both ICMEs and solar wind based on measurements of Advanced Composition Explorer. The results show that the V ip is negligible within ICMEs and slow solar wind (< 400 km s‑1), while obvious in the intermediate (400–600 km s‑1) and fast wind (> 600 km s‑1). Previous studies showed that the V ip in ICMEs keeps negligible during propagation from 0.3 to 5 au, but in solar wind it increases with the decreasing heliocentric distance. Therefore, it might be questionable to infer the absolute abundance of coronal sources through in situ abundance near 1 au for solar wind. Fortunately, the ion–oxygen (O6+) differential speed (V io ) is negligible for He2+, C5+, and Fe10+ within both ICMEs and solar wind, and previous studies suggested that the V io does not vary significantly with the heliocentric distance. This indicates that various heavy ions always flow at the same bulk speed and their relative abundance (relative to oxygen) near 1 au can represent the coronal abundance for both ICMEs and solar wind.

Keywords: solar coronal mass ejections; solar wind; solar abundances; solar cycle
Cosmic Evolution of Stellar-mass Black Hole Merger Rate in Active Galactic Nuclei

Binary black hole mergers encode information about their environment and the astrophysical processes that led to their formation. Measuring the redshift dependence of their merger rate will help probe the formation and evolution of galaxies and the evolution of the star formation rate. Here we compute the cosmic evolution of the merger rate for stellar-mass binaries in the disks of active galactic nuclei (AGNs). We focus on recent evolution out to redshift z = 2, covering the accessible range of current Earth-based gravitational-wave observatories. On this scale, the AGN population density is the main contributor to redshift dependence. We find that the AGN-assisted merger rate varies by less than a factor of two in the range 0 < z ≤ 2, comparable to the expected level of evolution for globular clusters, but much smaller than the order-of-magnitude evolution for field binaries.

Keywords: gravitational wave astronomy; active galactic nuclei
Simultaneous Evolution of the Virial Parameter and Star Formation Rate in Molecular Clumps Undergoing Global Hierarchical Collapse

We compare dense clumps and cores in a numerical simulation of molecular clouds (MCs) undergoing global hierarchical collapse (GHC) to observations in two MCs at different evolutionary stages, the Pipe and the G14.225 clouds, to test the ability of the GHC scenario to follow the early evolution of the energy budget and star formation activity of these structures. In the simulation, we select a region that contains cores of sizes and densities similar to the Pipe cores and find that it evolves through accretion, developing substructure similar to that of the G14.225 cloud after ∼1.6 Myr. Within this region, we follow the evolution of the Larson ratio ${ \mathcal L }\equiv {\sigma }_{{\rm{v}}}/{R}^{1/2}$ , where ${\sigma }_{{\rm{v}}}$ is the velocity dispersion and R is the size; the virial parameter α; and the star formation activity of the cores/clumps. In the simulation, we find that as the region evolves, (i) its clumps have ${ \mathcal L }$ and α values first consistent with those of the Pipe substructures and later with those of G14.225; (ii) the individual cores first exhibit a decrease in α followed by an increase when star formation begins; (iii) collectively, the ensemble of cores/clumps reproduces the observed trend of lower α for higher-mass objects; and (iv) the star formation rate and star formation efficiency increase monotonically. We suggest that this evolution is due to the simultaneous loss of externally driven compressive kinetic energy and increase of the self-gravity-driven motions. We conclude that the GHC scenario provides a realistic description of the evolution of the energy budget of the clouds&' substructure at early times, which occurs simultaneously with an evolution of the star formation activity.

Keywords: interstellar medium; molecular clouds; collapsing clouds; scaling relations
Algorithmic Pulsar Timer for Binaries

Pulsar timing is a powerful tool that, by accounting for every rotation of a pulsar, precisely measures the spin frequency, spin frequency derivatives, astrometric position, binary parameters when applicable, properties of the interstellar medium, and potentially general relativistic effects. Typically, this process demands fairly stringent scheduling requirements for monitoring observations as well as deep domain knowledge to "phase connect" the timing data. We present an algorithm that automates the pulsar-timing process for binary pulsars, whose timing solutions have an additional level of complexity, although the algorithm works for isolated pulsars as well. Using the statistical F-test and the quadratic dependence of the reduced χ 2 near a minimum, the global rotation count of a pulsar can be determined efficiently and systematically. We have used our algorithm to establish timing solutions for two newly discovered binary pulsars, PSRs J1748‑2446aq and J1748‑2446at, in the globular cluster Terzan 5, using ∼70 Green Bank Telescope observations from the last 13 yr.

Keywords: binary pulsars; pulsars; millisecond pulsars; radio pulsars; pulsar timing method; algorithms
The GRETOBAPE Gas-phase Reaction Network: The Importance of Being Exothermic

The gas-phase reaction networks are the backbone of astrochemical models. However, due to their complexity and nonlinear impact on the astrochemical modeling, they can be the first source of error in the simulations if incorrect reactions are present. Over time, following the increasing number of species detected, astrochemists have added new reactions, based on laboratory experiments and quantum mechanics (QM) computations, as well as reactions inferred by chemical intuition and the similarity principle. However, sometimes no verification of their feasibility in the interstellar conditions, namely their exothermicity, was performed. In this work, we present a new gas-phase reaction network, GRETOBAPE, based on the KIDA2014 network and updated with several reactions, cleaned from endothermic reactions not explicitly recognized as such. To this end, we characterized all the species in the GRETOBAPE network with accurate QM calculations. We found that ~5% of the reactions in the original network are endothermic, although most of them are reported as barrierless. The reaction network of Si-bearing species is the most impacted by the endothermicity cleaning process. We also produced a cleaned reduced network, GRETOBAPE-RED, to be used to simulate astrochemical situations where only C-, O-, N-, and S-bearing species with less than six atoms are needed. Finally, the new GRETOBAPE network, its reduced version, and the database with all the molecular properties are made publicly available. The species property database can be used in the future to test the feasibility of possibly new reactions.

Keywords: astrochemistry; interstellar molecules; chemical reaction network models
A Survey for New Stars and Brown Dwarfs in the Ophiuchus Star-forming Complex

We have performed a survey for new members of the Ophiuchus cloud complex using high-precision astrometry from the second data release of Gaia, proper motions measured with multi-epoch images from the Spitzer Space Telescope, and color-magnitude diagrams constructed with photometry from various sources. Through spectroscopy of candidates selected with those data, we have identified 155 new young stars. Based on available measurements of kinematics, we classify 102, 47, and 6 of those stars as members of Ophiuchus, Upper Sco, and other populations in Sco-Cen, respectively. We have also assessed the membership of all other stars in the vicinity of Ophiuchus that have spectroscopic evidence of youth from previous studies, arriving at a catalog of 373 adopted members of the cloud complex. For those adopted members, we have compiled mid-infrared photometry from Spitzer and the Wide-field Infrared Survey Explorer and have used mid-infrared colors to identify and classify circumstellar disks. We find that 210 of the members show evidence of disks, including 48 disks that are in advanced stages of evolution. Finally, we have estimated the relative median ages of the populations near the Ophiuchus clouds and the surrounding Upper Sco association using absolute K-band magnitudes (MK) based on Gaia parallaxes. If we adopt an age 10 Myr for Upper Sco, then the relative values of MK imply median ages of ∼2 Myr for L1689 and embedded stars in L1688, 3-4 Myr for low-extinction stars near L1688, and ∼6 Myr for the group containing ρ Oph.

Keywords: pre-main sequence stars; young stellar objects; brown dwarfs; low mass stars
Benzonitrile as a Proxy for Benzene in the Cold ISM: Low-temperature Rate Coefficients for CN + C6H6

The low-temperature reaction between CN and benzene (C6H6) is of significant interest in the astrochemical community due to the recent detection of benzonitrile, the first aromatic molecule identified in the interstellar medium (ISM) using radio astronomy. Benzonitrile is suggested to be a low-temperature proxy for benzene, one of the simplest aromatic molecules, which may be a precursor to polycyclic aromatic hydrocarbons. In order to assess the robustness of benzonitrile as a proxy for benzene, low-temperature kinetics measurements are required to confirm whether the reaction remains rapid at the low gas temperatures found in cold dense clouds. Here, we study the C6H6 + CN reaction in the temperature range 15-295 K, using the well-established CRESU technique (a French acronym standing for Reaction Kinetics in Uniform Supersonic Flow) combined with pulsed-laser photolysis-laser-induced fluorescence. We obtain rate coefficients, k(T), in the range (3.6-5.4) × 10-10 cm3 s-1 with no obvious temperature dependence between 15 and 295 K, confirming that the CN + C6H6 reaction remains rapid at temperatures relevant to the cold ISM.

Keywords: reaction rates; astrochemistry; interstellar molecules; interstellar medium; interdisciplinary astronomy; polycyclic aromatic hydrocarbons; dense interstellar clouds; interstellar clouds
Design and Performance Analysis of a Highly Efficient Polychromatic Full Stokes Polarization Modulator for the CRISP Imaging Spectrometer

We present the design and performance of a polychromatic polarization modulator for the CRisp Imaging SpectroPolarimeter (CRISP) Fabry-Perot tunable narrow-band imaging spectropolarimer at the Swedish 1 m Solar Telescope (SST). We discuss the design process in depth, compare two possible modulator designs through a tolerance analysis, and investigate thermal sensitivity of the selected design. The trade-offs and procedures described in this paper are generally applicable in the development of broadband polarization modulators. The modulator was built and has been operational since 2015. Its measured performance is close to optimal between 500 and 900 nm, and differences between the design and as-built modulator are largely understood. We show some example data, and briefly review scientific work that used data from SST/CRISP and this modulator.

Keywords: polarimeters
Benzyne in V4334 Sqr: A Quest for the Ring with SOFIA/EXES

Large aromatic molecules are ubiquitous in both circumstellar and interstellar environments. Detection of small aromatic molecules, such as benzene (C6H6) and benzyne (C6H4), are rare in astrophysical environments. Detection of such species will have major implications for our understanding of the astrochemistry involved in the formation of the molecules necessary for life, including modeling the chemical pathways to the formation of larger hydrocarbon molecules. We conducted a search for the infrared 18 μm spectral signature of benzyne in V4334 Sgr with the Stratospheric Observatory for Infrared Astronomy (SOFIA)/Echelon-Cross-Echelle Spectrograph (EXES) finding no evidence for a feature at the sensitivity of our observations.

Keywords: asymptotic giant branch stars; circumstellar dust; astrochemistry
Shadowing in the Protoplanetary Disk of ZZ Tau IRS with HST

An inner component misaligned from an outer component in a protoplanetary disk can result in the former casting shadows on the latter. We present a new instance of shadowing on the outer disk around a very-low-mass star, ZZ Tau IRS. Through the analysis of near-infrared (NIR) archival data at λ = 1.6 μm acquired with the Wide Field Camera 3 on the Hubble Space Telescope, we identified brightness asymmetries in the top and bottom halves of the highly inclined outer disk, separated by a dark lane. The brighter sides in the top and bottom halves are on the opposite sides, which we attributed to shadows cast by a misaligned inner disk. Radiative transfer modeling of the system with a misaligned angle of 15 deg between the inner and outer disks well reproduced the observations. Additionally, we found an elevated brightness temperature of 12CO (3–2) at r ∼ 30 au on the brighter side in NIR wavelengths in the top half disk, which can be explained by the shadowing effect too. While the origin of the misaligned inner disk remains unclear, future monitoring observations to search for temporal variations in brightness asymmetries will likely provide useful clues.

Keywords: protoplanetary disks; planetary-disk interactions; exoplanet formation; m stars; near infrared astronomy
Ultramassive Black Holes Formed by Triple Quasar Mergers at z 2

The origin of rare and elusive ultramassive black holes (UMBH; with M BH > 1010 M ⊙) is an open question. Using the large volume cosmological hydrodynamic simulation ASTRID, we report on the formation of an extremely massive UMBH with M BH ~ 1011 M ⊙ at z ~ 2. The UMBH is assembled as a result of two successive mergers of massive galaxies each with stellar mass M * > 3 × 1011 M ⊙ that also produces a bright, rare triple quasar system powered by three ~109 M ⊙ black holes. The second merger of supermassive black holes (SMBHs) follows the first after 150 Myr. The merger events lead to sustained Eddington accretion onto the central SMBH, forming a UMBH in the center of a massive compact stellar core with M * > 2 × 1012 M ⊙. The strong feedback of the UMBH quenches the surrounding star formation to <10 M ⊙ yr-1 in the inner 50 h -1 kpc region. There are two more UMBHs with M BH > 5 × 1010 M ⊙ at z > 2 in ASTRID that are also produced by major mergers of galaxies, and their progenitors can be observed as quasar triplets of lower luminosity. The rarely observed quasar multiples can be the cradle of UMBHs at high redshift, and likely end up in the center of the most massive clusters.

Keywords: hydrodynamical simulations; supermassive black holes
Energy-dependent Analyses of the Gamma-Ray Emission from HESS J1857+026 with Fermi-LAT

We report the discovery of the energy-dependent morphology of the GeV gamma-ray emission from HESS J1857+026 with more than 13 yr of Fermi Large Area Telescope data. The GeV gamma-ray emission from this region is composed of two extended components. The hard component with an index of 1.74 ± 0.07 in the energy range of 0.5–500 GeV is spatially coincident with HESS J1857+026, and its 68% containment radius varies from ∼0.°44 below 40 GeV to ∼0.°30 above 140 GeV. The hard GeV gamma-ray spectrum and the energy-dependent morphology of HESS J1857+026 make it favor a pulsar wind nebula origin, which is associated with the energetic pulsar PSR J1856+0245. The soft component with an index of 2.70 ± 0.16 and another extended gamma-ray source detected in this region, 4FGL J1857.9+0313e, with an index of 2.55 ± 0.07, are spatially coincident with two molecular clumps in the northeast and southwest of HESS J1857+026, which favors the hadronic process, and the protons could be accelerated by the hypothetical supernova remnant associated with PSR J1856+0245.

Keywords: gamma-ray sources; pulsar wind nebulae; supernova remnants; molecular clouds; gamma-rays
The GLASS-JWST Early Release Science Program. III. Strong-lensing Model of Abell 2744 and Its Infalling Regions

We present a new high-precision, JWST-based, strong-lensing model for the galaxy cluster Abell 2744 at z = 0.3072. By combining the deep, high-resolution JWST imaging from the Grism Lens Amplified Survey from Space-JWST and Ultradeep NIRSpec and NIRCam Observations before the Epoch of Reionization programs and a Director's Discretionary Time program, with newly obtained Very Large Telescope/Multi Unit Spectroscopic Explorer (MUSE) data, we identify 32 multiple images from 11 background sources lensed by two external subclusters at distances of ~160″ from the main cluster. The new MUSE observations enable the first spectroscopic confirmation of a multiple-image system in the external clumps. Moreover, the reanalysis of the spectrophotometric archival and JWST data yields 27 additional multiple images in the main cluster. The new lens model is constrained by 149 multiple images (~66% more than in our previous model) covering an extended redshift range between 1.03 and 9.76. The subhalo mass component of the cluster includes 177 member galaxies down to m F160W = 21, of which 163 are spectroscopically confirmed. Internal velocity dispersions are measured for 85 members. The new lens model is characterized by a remarkably low scatter between the predicted and observed positions of the multiple images (0.″43). This precision is unprecedented given the large multiple-image sample, the complexity of the cluster mass distribution, and the large modeled area. The improved precision and resolution of the cluster total mass distribution provides a robust magnification map over a ~30 arcmin2 area, which is critical for inferring the intrinsic physical properties of the highly magnified, high-z sources. The lens model and the new MUSE redshift catalog are released with this publication.

Keywords: galaxy clusters; strong gravitational lensing; dark matter
Commotion in their Motions: Proper Motion Anomalies of Nearby AGB Stars

Proper motion anomalies (PMa) are often useful for identifying companions, but using this technique for large and luminous stars like Asymptotic Giant Branch (AGB) stars is problematic. We studied nearby AGB stars and their potential companions in a PMa catalog derived from Hipparcos and Gaia DR2 proper motion measurements. We found that companion configurations based on PMa for AGB stars are often implausible, such that the radius of the primary star is larger than the orbit of the putative companion. This may suggest an alternative origin of PMa in AGB stars, possibly surface brightness fluctuations due to their large convective surfaces.

Keywords: asymptotic giant branch stars; proper motions; parallax
DRAFT: A Method for Wave Analyses in Space Plasmas

In this study, we apply a method for wave analyses in space plasmas, to better understand the nature of plasma waves and turbulence. Such a method is based on four-spacecraft measurements of magnetic fields or electric fields; it calculates the phase velocity of each single-frequency wave by using the timing analysis, then divides the wave frequency by the phase velocity to obtain the wavevector, and finally solves the dispersion relation (ω-k relation) by considering all frequency channels, and thus is termed Dispersion RelAtion From Timing (DRAFT). Quantitatively, we define three parameters, match of amplitude (MOA), ratio of half-wavelength to spacecraft separation (λ/2R sc), and correlation coefficient (CC), to judge the reliability of this method. We illustrate the usage of this method and validate the efficiency of the three parameters by analyzing the Magnetospheric Multiscale data. We find that the DRAFT results are generally accurate under conditions MOA > 0.5, λ/2R sc > 1, CC > 0.8. As a support, we compare our method with the previous methods such as Means and singular value decomposition (SVD). We find that if the three criteria (MOA, λ/2R sc, CC) are satisfied, the DRAFT, Means, and SVD are consistent in resolving the wave normal angle. Such a comparison robustly validates the reliability and rationality of the DRAFT method. Using DRAFT, we successfully solve the dispersion relation of an Alfvén wave in Earth's magnetosheath and obtain its three-dimensional K -spectrum. Our method should be useful to study the low-frequency waves and weak turbulence in space plasmas.

Keywords: space plasmas; alfven waves; astronomy data analysis; astronomical techniques