adsabs/SciX_UAT_keywords huggingface dataset:
Architectures of Exoplanetary Systems. III. Eccentricity and Mutual Inclination Distributions of AMD-stable Planetary Systems

The angular momentum deficit (AMD) of a planetary system is a measure of its orbital excitation and a predictor of long-term stability. We adopt the AMD-stability criterion to constrain the orbital architectures for exoplanetary systems. Previously, He et al. showed through forward modeling (SysSim) that the observed multiplicity distribution can be well reproduced by two populations consisting of a low and a high mutual inclination component. Here, we show that a broad distribution of mutual inclinations arising from systems at the AMD-stability limit can also match the observed Kepler population. We show that distributing a planetary system's maximum AMD among its planets results in a multiplicity-dependent distribution of eccentricities and mutual inclinations. Systems with intrinsically more planets have lower median eccentricities and mutual inclinations, and this trend is well described by power-law functions of the intrinsic planet multiplicity (n): ${\tilde{\mu }}_{e,n}\propto {n}^{-{1.74}_{-0.07}^{+0.11}}$ and ${\tilde{\mu }}_{i,n}\propto {n}^{-{1.73}_{-0.08}^{+0.09}}$ , where ${\tilde{\mu }}_{e,n}$ and ${\tilde{\mu }}_{i,n}$ are the medians of the eccentricity and inclination distributions. We also find that intrinsic single planets have higher eccentricities (σe,1 ∼ 0.25) than multiplanet systems and that the trends with multiplicity appear in the observed distributions of period-normalized transit duration ratios. We show that the observed preferences for planet-size orderings and uniform spacings are more extreme than what can be produced by the detection biases of the Kepler mission alone. Finally, we find that for systems with detected transiting planets between 5 and 10 days, there is another planet with a greater radial velocity signal ≃53% of the time.

Keywords: exoplanet systems; exoplanet detection methods; exoplanet catalogs; exoplanets; extrasolar rocky planets; astrostatistics distributions; computational methods; radial velocity; planet hosting stars; exoplanet dynamics; planetary system formation
High-energy Neutrino and Gamma-Ray Emission from Tidal Disruption Events

Tidal disruption events (TDE) have been considered as cosmic-ray and neutrino sources for a decade. We suggest two classes of new scenarios for high-energy multi-messenger emission from TDEs that do not have to harbor powerful jets. First, we investigate high-energy neutrino and gamma-ray production in the core region of a supermassive black hole. In particular, we show that ∼1-100 TeV neutrinos and MeV gamma rays can efficiently be produced in hot coronae around an accretion disk. We also study the consequences of particle acceleration in radiatively inefficient accretion flows (RIAFs). Second, we consider possible cosmic-ray acceleration by sub-relativistic disk-driven winds or interactions between tidal streams, and show that subsequent hadronuclear and photohadronic interactions inside the TDE debris lead to GeV-PeV neutrinos and sub-GeV cascade gamma rays. We demonstrate that these models should be accompanied by soft gamma rays or hard X-rays as well as optical/UV emission, which can be used for future observational tests. Although this work aims to present models of non-jetted high-energy emission, we discuss the implications of the TDE AT2019dsg that might coincide with the high-energy neutrino IceCube-191001A, by considering the corona, RIAF, hidden sub-relativistic wind, and hidden jet models. It is not yet possible to be conclusive about their physical association and the expected number of neutrinos is typically much less than unity. We find that the most optimistic cases of the corona and hidden wind models could be consistent with the observation of IceCube-191001A, whereas jet models are unlikely to explain the multi-messenger observations.

Keywords: particle astrophysics; cosmological neutrinos; high energy astrophysics; black holes; tidal disruption; gamma-ray transient sources; high-energy cosmic radiation
Implications of Increased Central Mass Surface Densities for the Quenching of Low-mass Galaxies

We use the Cosmic Assembly Deep Near-infrared Extragalactic Legacy Survey data to study the relationship between quenching and the stellar mass surface density within the central radius of 1 kpc (Σ1) of low-mass galaxies (stellar mass M* ≲ 109.5 M⊙) at 0.5 ≤ z < 1.5. Our sample is mass complete down to ~109 M⊙ at 0.5 ≤ z < 1.0. We compare the mean Σ1 of star-forming galaxies (SFGs) and quenched galaxies (QGs) at the same redshift and M*. We find that low-mass QGs have a higher Σ1 than low-mass SFGs, similar to galaxies above 1010 M⊙. The difference of Σ1 between QGs and SFGs increases slightly with M* at M* ≲ 1010 M⊙ and decreases with M* at M* ≳ 1010 M⊙. The turnover mass is consistent with the mass where quenching mechanisms transition from internal to environmental quenching. At 0.5 ≤ z < 1.0, we find that Σ1 of galaxies increases by about 0.25 dex in the green valley (i.e., the transition region from star forming to fully quenched), regardless of their M*. Using the observed specific star formation rate gradient in the literature as a constraint, we estimate that the quenching timescale (i.e., time spent in the transition) of low-mass galaxies is a few (~4) Gyr at 0.5 ≤ z < 1.0. The mechanisms responsible for quenching need to gradually quench star formation in an outside-in way, i.e., preferentially ceasing star formation in outskirts of galaxies while maintaining their central star formation to increase Σ1. An interesting and intriguing result is the similarity of the growth of Σ1 in the green valley between low-mass and massive galaxies, which suggests that the role of internal processes in quenching low-mass galaxies is a question worthy of further investigation.

Keywords: galaxy formation; galaxy evolution; galaxy quenching; galaxy structure; galaxy physics; dwarf galaxies; quenched galaxies; galaxy environments; extragalactic astronomy
A 350 MHz Green Bank Telescope Survey of Unassociated Fermi LAT Sources: Discovery and Timing of 10 Millisecond Pulsars

We have searched for radio pulsations toward 49 Fermi Large Area Telescope (LAT) 1FGL Catalog γ-ray sources using the Green Bank Telescope at 350 MHz. We detected 18 millisecond pulsars (MSPs) in blind searches of the data; 10 of these were discoveries unique to our survey. 16 are binaries, with eight having short orbital periods P B < 1 day. No radio pulsations from young pulsars were detected, although three targets are coincident with apparently radio-quiet γ-ray pulsars discovered in LAT data. Here, we give an overview of the survey and present radio and γ-ray timing results for the 10 MSPs discovered. These include the only isolated MSP discovered in our survey and six short-P B binary MSPs. Of these, three have very-low-mass companions (M c ≪ 0.1 M ⊙) and hence belong to the class of black widow pulsars. Two have more massive, nondegenerate companions with extensive radio eclipses and orbitally modulated X-ray emission consistent with the redback class. Significant γ-ray pulsations have been detected from nine of the discoveries. This survey and similar efforts suggest that the majority of Galactic γ-ray sources at high Galactic latitudes are either MSPs or relatively nearby nonrecycled pulsars, with the latter having on average a much smaller radio/γ-ray beaming ratio as compared to MSPs. It also confirms that past surveys suffered from an observational bias against finding short-P B MSP systems.

Keywords: millisecond pulsars; pulsars; binary pulsars; radio pulsars; gamma-rays
Localized Amplification of Magnetic Field in the Solar Photosphere Associated with a Rapid Moving Pore

In the Sun, the flows of hot plasma drive a dynamo that generates a global magnetic field as well as smaller-scale local fields. The existence of a magnetic field in turn affects the motion of plasma so that complex dynamic characteristics can be observed. In this Letter, we give an analysis on the localized amplification of magnetic fields in front of a moving pore. Moving with the pore, the formation of semicircular penumbra-like structures and enhancement of horizontal fields can be observed simultaneously. The increasing horizontal magnetic fields in a penumbra-like area probably did not come from the pore, since the penumbra-like structures were not connected to the pore and a magnetic gap existed. The possibility of flux emergence can also be safely excluded. We further report that horizontal magnetic fields in the front of a moving pore are amplified in accordance with the MHD induction equation after necessary yet reasonable simplification. All characteristics show that the flows driven by the moving pore can lead to the amplification of the magnetic fields around its front. The observations are from the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory.

Keywords: solar magnetic fields; solar photosphere; sunspot flow; penumbra; solar dynamo; sunspots; solar active regions; solar active region velocity fields
Applying Random Forest Classification to Ultracool Dwarf Discovery in Deep Surveys. II. Color Classification with PanSTARRS, 2MASS, UKIDSS, and WISE Photometry

We evaluate color-based classifiers in a synthesis of Pan-STARRS, 2MASS, UKIDSS, and AllWISE catalogs to identify ultracool dwarfs (UCDs). Using the Best et al. compilation of UCDs and a sample of background sources as our training set, we constructed a two-tier random forest model to segregate UCDs from non-UCDs and sort them into spectral subgroups. We also developed a regressor model to infer numerical classifications. Our classifier models achieved accuracies of 97%-99%, while our regressor model achieved a classification accuracy of 0.64 subtypes for classifications M5-T8. We applied these models to a 7 deg2 region with overlapping survey data and identified 336 UCD candidates, of which 26 are previously identified UCDs and 17 are extragalactic sources.

Keywords: brown dwarfs; l dwarfs; t dwarfs; m dwarf stars; surveys; random forests
SDSS-IV MaNGA: Cannibalism Caught in the Act-On the Frequency of Occurrence of Multiple Cores in Brightest Cluster Galaxies

Although it is generally accepted that massive galaxies form in a two-phased fashion, beginning with a rapid mass buildup through intense starburst activities followed by primarily dry mergers that mainly deposit stellar mass at outskirts, the late time stellar mass growth of brightest cluster galaxies (BCGs), the most massive galaxies in the universe, is still not well understood. Several independent measurements have indicated a slower mass growth rate than predictions from theoretical models. We attempt to resolve the discrepancy by measuring the frequency of BCGs with multiple cores, which serve as a proxy of the merger rates in the central region and facilitate a more direct comparison with theoretical predictions. Using 79 BCGs at z = 0.06-0.15 with integral field spectroscopic data from the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) project, we obtain a multiple-core fraction of 0.11 ± 0.04 at z ≈ 0.1 within an 18 kpc radius from the center, which is comparable to the value of 0.08 ± 0.04 derived from mock observations of 218 simulated BCGs from the cosmological hydrodynamical simulation IllustrisTNG. We find that most cores that appear close to the BCGs from imaging data turn out to be physically associated systems. Anchoring on the similarity in the multiple-core frequency between the MaNGA and IllustrisTNG, we discuss the mass growth rate of BCGs over the past 4.5 Gyr.

Keywords: galaxy formation; galaxy clusters; elliptical galaxies; galaxy mergers
Binary Intermediate-mass Black Hole Mergers in Globular Clusters

We consider the formation of binary intermediate black holes (BIMBHs) in globular clusters (GC), which could happen either in situ or due to the mergers between clusters. We simulate the evolution of the BIMBH orbit (and its subsequent merger) due to stellar ejections. We also take into account the evaporation of GCs due to the tidal field of the host galaxy and two-body relaxation. Our results show that if at least 10-3 of all GCs become BIMBH hosts and the BIMBH masses are ∼1% of the GC mass, at least one of the inspiraling (or merging) BIMBHs will be detected by LISA during its 4 yr mission lifetime. Most of the detected BIMBHs come (1) from heavy GCs (≳3 × 105 ${M}_{\odot }$), as lower-mass GCs end up being disrupted before their BIMBHs have time to merge, and (2) from redshifts 1 < z < 3, assuming that most GCs form around z ∼ 4 and given that the merger timescale for most BIMBHs is ∼1 Gyr. If the BIMBH to GC mass ratio is lower (∼10-3) but the fraction of BIMBH hosts among GCs is higher (≳10-2), some of their mergers will also be detected by LIGO, Virgo, and KAGRA and the proposed Einstein Telescope.

Keywords: black holes; gravitational waves; globular star clusters; intermediate-mass black holes
Properties of Dense Molecular Gas along the Major Axis of M82

Dense gas is important for galaxy evolution and star formation. Optically thin dense-gas tracers, such as isotopologues of HCN, HCO+, etc., are very helpful in diagnosing the excitation conditions of dense molecular gas. However, previous studies of optically thin dense-gas tracers mostly focused on the average properties of galaxies as a whole, due to limited sensitivity and angular resolution. M82, a nearby prototype starburst galaxy, offers a unique case for spatially resolved studies with single-dish telescopes. With the IRAM 30 m telescope, we observed the J = 1 → 0 transition of H13CN, HC15N, H13CO+, HN13C, H15NC, and SiO J = 2 → 1, HC3N J = 10 → 9, and H2CO J = 2 → 1 toward five positions along the major axis of M82. The intensity ratios of I(HCN)/I(H13CN) and I(HCO+)/I(H13CO+) show a significant spatial variation along the major axis, with lower values in the central region than those on the disk, indicating higher optical depths in the central region. The optical depths of HCO+ lines are found to be systematically higher than those of HCN lines at all positions. Furthermore, we find that the 14N/15N ratios have an increasing gradient from the center to the outer disk.

Keywords: starburst galaxies; interstellar medium; star formation
On the Anticorrelation between Duration and Redshift in Gamma-Ray Bursts

For gamma-ray bursts (GRBs) with durations greater than two seconds (so-called long GRBs), the intrinsic prompt gamma-ray emission appears, on average, to last longer for bursts at lower redshifts. We explore the nature of this duration-redshift anticorrelation, describing systems and conditions in which this cosmological evolution could arise. In particular, we explore its dependence on the metallicity of a massive star progenitor, because we can securely count on the average stellar metallicity to increase with decreasing redshift. Although stars with higher metallicity/lower redshift lose mass and angular momentum through line-driven winds, in some cases these stars are able to form more extended accretion disks when they collapse, potentially leading to longer-duration GRBs. We also examine how this duration-redshift trend may show up in interacting binary models composed of a massive star and compact object companion, recently suggested to be the progenitors of radio-bright GRBs. Under certain conditions, mass loss and equation-of-state effects from massive stars with higher metallicity and lower redshift can decrease the binary separation. This can then lead to spin-up of the massive star and allow for a longer-duration GRB upon the massive star's collapse. Finally, the duration-redshift trend may also be supported by a relatively larger population of small-separation binaries born in situ at low redshift.

Keywords: gamma-ray bursts; close binary stars; massive stars
Models of Millimeter and Radio Emission from Interacting Supernovae

This work utilizes established models of synchrotron-powered light curves for core-collapse supernovae in dense circumstellar environments, namely, type IIn and Ibn, to demonstrate the potential for detecting millimeter emission from these events. The progenitor types of these supernovae are still an open question, but using the synchrotron light curves as probes for the circumstellar environments could shed light on the mass-loss histories of the progenitors and discern between different theories. Observations in millimeter bands are particularly fruitful, as they probe regions at smaller radii and higher ambient densities, where centimeter emission tends to be self-absorbed. In our application of these light curves, we explore a diversity of progenitor types and mass-loss profiles to understand their effects on the light-curve shapes. Additionally, we fit model parameters to the 8 GHz light curve of type IIn supernova 2006jd and then create millimeter light curves using these parameters to show the possibility of detecting an early millimeter peak from such an event. We predict that next generation millimeter surveys will possess the capability to detect nearby and extreme events. However, there is a pressing need for millimeter follow-up of optically discovered interacting supernovae to more completely sample the true population.

Keywords: core-collapse supernovae; millimeter astronomy
Investigating the Atmospheric Mass Loss of the Kepler-105 Planets Straddling the Radius Gap

An intriguing pattern among exoplanets is the lack of detected planets between approximately 1.5 R ⊕ and 2.0 R ⊕. One proposed explanation for this "radius gap" is the photoevaporation of planetary atmospheres, a theory that can be tested by studying individual planetary systems. Kepler-105 is an ideal system for such testing due to the ordering and sizes of its planets. Kepler-105 is a Sun-like star that hosts two planets straddling the radius gap in a rare architecture with the larger planet closer to the host star (R b = 2.53 ± 0.07 R ⊕, P b = 5.41 days, R c = 1.44 ± 0.04 R ⊕, P c = 7.13 days). If photoevaporation sculpted the atmospheres of these planets, then Kepler-105b would need to be much more massive than Kepler-105c to retain its atmosphere, given its closer proximity to the host star. To test this hypothesis, we simultaneously analyzed radial velocities and transit-timing variations of the Kepler-105 system, measuring disparate masses of M b = 10.8 ± 2.3 M ⊕ (ρ b = 3.68 ± 0.84 g cm‑3) and M c = 5.6 ± 1.2 M ⊕ (ρ c = 10.4 ± 2.39 g cm‑3). Based on these masses, the difference in gas envelope content of the Kepler-105 planets could be entirely due to photoevaporation (in 76% of scenarios), although other mechanisms like core-powered mass loss could have played a role for some planet albedos.

Keywords: exoplanet atmospheres; exoplanet formation; exoplanet evolution; radial velocity; transit timing variation method; exoplanets
Automated Chemical Reaction Network Generation and Its Application to Exoplanet Atmospheres

With the advent of JWST and the spectroscopic characterization of exoplanet atmospheres in unprecedented detail, there is a demand for more complete pictures of chemical and photochemical reactions and their impacts on atmospheric composition. Traditionally, building reaction networks for (exo)planetary atmospheres involves manually tracking relevant species and reactions, a time-consuming and error-prone process. This approach's applicability is also often limited to specific conditions, making it less versatile for different planetary types (i.e., photochemical networks for Jupiters may not be directly applicable to water-rich exoplanets). We introduce an automated approach using a computer-aided chemical reaction network generator, combined with a 1D photochemical kinetic-transport model, offering significant advantages. This approach automatically selects reaction rates through a rate-based iterative algorithm and multiple refinement steps, enhancing model reliability. Also, this approach allows for the efficient simulation of diverse chemical environments, from hydrogen to water, carbon dioxide, and nitrogen-dominated atmospheres. Using WASP-39b and WASP-80b as examples, we demonstrate our approach's effectiveness, showing good agreement with recent JWST data. Our WASP-39b model aligns with prior studies and JWST observations, capturing photochemically produced sulfur dioxide. The WASP-80b model reveals an atmosphere influenced by deep-interior thermochemistry and vertical mixing, consistent with JWST NIRCam observations. Furthermore, our model identifies a novel initial step for the N2–NH3–HCN pathway that enhances the efficiency of the conversion in high-temperature/high-pressure environments. This automated chemical network generation offers a novel, efficient, and precise framework for studying exoplanetary atmospheres, marking a significant advancement over traditional modeling techniques.

Keywords: exoplanet atmospheres; exoplanet atmospheric composition; planetary atmospheres; theoretical models; astrochemistry
Pre-main-sequence Brackett Emitters in the APOGEE DR17 Catalog: Line Strengths and Physical Properties of Accretion Columns

Very young (t ≲ 10 Myr) stars possess strong magnetic fields that channel ionized gas from the interiors of their circumstellar disks to the surface of the star. Upon impacting the stellar surface, the shocked gas recombines and emits hydrogen spectral lines. To characterize the density and temperature of the gas within these accretion streams, we measure equivalent widths of Brackett (Br) 11-20 emission lines detected in 1101 APOGEE spectra of 326 likely pre-main-sequence accretors. For sources with multiple observations, we measure median epoch-to-epoch line strength variations of 10% in Br11 and 20% in Br20. We also fit the measured line ratios to predictions of radiative transfer models by Kwan & Fischer. We find characteristic best-fit electron densities of n e = 1011-1012 cm-3, and excitation temperatures that are inversely correlated with electron density (from T ~ 5000 K for n e ~ 1012 cm-3 to T ~ 12,500 K at n e ~ 1011 cm-3). These physical parameters are in good agreement with predictions from modeling of accretion streams that account for the hydrodynamics and radiative transfer within the accretion stream. We also present a supplementary catalog of line measurements from 9733 spectra of 4255 Brackett emission-line sources in the APOGEE Data Release 17 data set.

Keywords: accretion; stellar accretion; pre-main sequence stars; be stars; classical t tauri stars; emission line stars