adsabs/SciX_UAT_keywords huggingface dataset:
On the Correlation between Hot Jupiters and Stellar Clustering: High-eccentricity Migration Induced by Stellar Flybys

A recent observational study suggests that the occurrence of hot Jupiters (HJs) around solar-type stars is correlated with stellar clustering. We study a new scenario for HJ formation, called "Flyby Induced High-e Migration," that may help explain this correlation. In this scenario, stellar flybys excite the eccentricity and inclination of an outer companion (giant planet, brown dwarf, or low-mass star) at large distance (10-300 au), which then triggers high-e migration of an inner cold Jupiter (at a few astronomical units) through the combined effects of von Zeipel-Lidov-Kozai (ZLK) eccentricity oscillation and tidal dissipation. Using semianalytical calculations of the effective ZLK inclination window, together with numerical simulations of stellar flybys, we obtain the analytic estimate for the HJ occurrence rate in this formation scenario. We find that this "flyby induced high-e migration" could account for a significant fraction of the observed HJ population, although the result depends on several uncertain parameters, including the density and lifetime of birth stellar clusters, and the occurrence rate of the "cold Jupiter + outer companion" systems.

Keywords: hot jupiters; exoplanet dynamics
Empirical Models of the Hβ Broad Emission Line Gas Density Field

We present the second iteration of the CARAMEL-GAS code, an empirical model of the broad-line region (BLR) gas density field. Building on the initial development and testing of CARAMEL-GAS, we expand the meaning of the model parameter α, which initially represented only the power-law index of the dependency of emissivity on radial distance. In this work, we test a more generalized radial power-law index, α, that also includes a description of the effective emitting size(s) of the BLR structure as a function of radial distance. We select a sample of 10 active galactic nuclei (AGN) from three different Lick AGN Monitoring Project campaigns to further validate the CARAMEL-GAS code and test the generalized radial power-law index, α. Our results confirm that the CARAMEL-GAS results are in general agreement with the published results determined using the original CARAMEL code, further demonstrating that our forward modeling method is robust. We find that a positive radial power-law index is generally favored and propose three possible scenarios: (i) the BLR structure has increasing effective emitting size(s) at larger radial distances from the central source, (ii) emission is concentrated at the outer edges of the BLR, and (iii) stronger theoretical assumptions are needed to break the degeneracies inherent to the interpretation of reverberation mapping data in terms of underlying gas properties.

Keywords: active galactic nuclei; active galaxies; supermassive black holes
Multifrequency VLBI Observations of the M84 Inner Jet/Counterjet

Observational studies of the innermost regions of the edge-on jets in nearby active galactic nuclei (AGN) are crucial to understanding their kinematics and morphology. For the inner jet of the nearby low-luminosity AGN in M84, we present new high-sensitivity observations with very long baseline Interferometry since 2019, as well as archival Very Long Baseline Array observations in 2014. We find that the compact core in M84 has an inverted-to-flat spectrum from 1.5-88 GHz. Based on the turnover frequency of 4.2 ± 0.2 GHz in the spectrum, we estimated a magnetic field strength of 1 ~ 10 mG and an electron number density of ~105 cm-3 in the core region. Three inner jet components within ~3 mas of the core are identified and traced in the images at 22 GHz, whose apparent speeds are 0.11 c, 0.27 c, and 0.32 c, respectively. We calculate the viewing angle of ${58}_{-18}^{{+17}^\circ} $ for the inner jet based on the proper motion and the flux ratio of jet to counterjet. A propagating sinusoidal model with a wavelength of ~3.4 mas is used to fit the helical morphology of the jet extended to 20 mas (~2.2 × 104 Schwarzschild radii).

Keywords: relativistic jets; low-luminosity active galactic nuclei; very long baseline interferometry
The Impact of Ambipolar Diffusion on the Rossby Wave Instability in a Protoplanetary Disk

Recent observational and simulation studies have revealed that ambipolar diffusion is an important phenomenon in the outer regions of a protoplanetary disk (PPD). However, numerous simulation studies have found that ambipolar diffusion suppresses the turbulence caused by the magnetorotational instability (MRI) in these regions of a PPD. The aim of this study is to investigate the impact of ambipolar diffusion on the Rossby wave instability (RWI) at large radii of a PPD. To accomplish this, we examine the occurrence of the RWI in a PPD threaded by the magnetic field in the presence of ambipolar diffusion. Additionally, we scale the ambipolar diffusivity with respect to both the toroidal magnetic field and an important parameter known as the Elsässer number. We obtain the growth rate of unstable RWI modes in the outer regions of a PPD using linear perturbation analysis. In our nonaxisymmetric perturbation analysis, we find that the amplitude of the toroidal field oscillates in various modes for small values of the Elsässer numbers. For small Elsässer numbers, the growth rate of unstable modes associated with the RWI decreases. In other words, ambipolar diffusion suppresses the perturbation caused by the RWI. This effect is similar to the effect of ambipolar diffusion on the MRI. In contrast to the MRI, where there is a range around 1 for the Elsässer numbers, the existence of ambipolar diffusion supports the occurrence of RWI. Finally, we compare our findings with those of simulation studies to emphasize the importance of RWI in the outer regions of a PPD.

Keywords: magnetic fields; protoplanetary disks
Exploring the Link between the X-Ray Power Spectra and Energy Spectra of Active Galactic Nuclei

Active galactic nuclei (AGN) are generally considered the scaled-up counterparts of X-ray binaries (XRBs). It is known that the power spectral density (PSD) of the X-ray emission of XRBs shows significant evolution with spectral state. It is not clear whether AGN follow a similar evolutionary trend, however, though their X-ray emission and the PSD are both variable. In this work, we study a sample of nine AGN with multiple long observations with XMM-Newton, which exhibit significant X-ray spectral variation. We perform Bayesian PSD analysis to measure the PSD shape and variation. We find that a large change in the X-ray energy spectrum (mainly the change in flux state) is often accompanied by a large change in the PSD shape. The emergence of a high-frequency break in the PSD also depends on the spectral state. Among the four sources with significant high-frequency PSD breaks detected, three show the break only in the high-flux state, while the remaining one shows it only in the low-flux state. Moreover, the X-ray rms variability in different spectral states of an AGN is found to vary by as much as 1.0 dex. These results suggest that the different variability properties observed are likely caused by different physical processes dominating different spectral states. Our results also indicate that the intrinsic PSD variation can introduce a significant fraction of the dispersion as reported for the correlations between various X-ray variability properties and the black hole mass.

Keywords: active galactic nuclei; active galaxies; x-ray active galactic nuclei
A Steep Decline in the Galaxy Space Density beyond Redshift 9 in the CANUCS UV Luminosity Function

We present a new sample of 158 galaxies at redshift z > 7.5 selected from deep James Webb Space Telescope (JWST) NIRCam imaging of five widely separated sight lines in the CANUCS survey. Two-thirds of the pointings and 80% of the galaxies are covered by 12–14 NIRCam filters, including seven to nine medium bands, providing accurate photometric redshifts and robustness against low-redshift interlopers. A sample of 28 galaxies at z > 7.5 with spectroscopic redshifts shows a low systematic offset and scatter in the difference between photometric and spectroscopic redshifts. We derive the galaxy UV luminosity function at redshifts 8–12, finding a slightly higher normalization than previously seen with the Hubble Space Telescope at redshifts 8–10. We observe a steeper decline in the galaxy space density from z = 8 to 12 than found by most JWST Cycle 1 studies. In particular, we find only eight galaxies at z > 10 and none at z > 12.5, with no z > 10 galaxies brighter than F277W AB = 28 or M UV = ‑20 in our unmasked, delensed survey area of 53.4 arcmin2. We attribute the lack of bright z > 10 galaxies in CANUCS compared to GLASS and CEERS to intrinsic variance in the galaxy density along different sight lines. The evolution in the CANUCS luminosity function between z = 8 and 12 is comparable to that predicted by simulations that assume a standard star formation efficiency without invoking any special adjustments.

Keywords: high-redshift galaxies
Exploring the Mass Segregation Effect of X-Ray Sources in Globular Clusters. IV. Evidence of Black Hole Burning in ω Centauri

Using X-ray sources as sensitive probes of stellar dynamical interactions in globular clusters (GCs), we study the mass segregation and binary burning processes in ω Cen. We show that the mass segregation of X-ray sources is quenched in ω Cen, while the X-ray source abundance of ω Cen is much smaller than other GCs, and the binary hardness ratio (defined as ${L}_{{\rm{X}}}/({L}_{K}{f}_{b})$ , with fb being the binary fraction, ${L}_{{\rm{X}}}$ and LK being the cumulative X-ray and K-band luminosity of GCs, respectively) of ω Cen is located far below the ${L}_{{\rm{X}}}/({L}_{K}{f}_{b})\mbox{--}{\sigma }_{c}$ correlation line of the dynamically normal GCs. This evidence suggests that the binary burning processes are highly suppressed in ω Cen, and other heating mechanisms, very likely a black hole subsystem (BHS), are essential in the dynamical evolution of ω Cen. Through the black hole burning processes (i.e., dynamical hardening of the BH binaries), the BHS is dominating the energy production of ω Cen, which also makes ω Cen a promising factory of gravitational-wave sources in the Galaxy.

Keywords: globular star clusters; binary stars; x-ray binary stars; stellar mass black holes; gravitational wave sources; stellar dynamics; intermediate-mass black holes
Reassessing the Evidence for Time Variability in the Atmosphere of the Exoplanet HAT-P-7 bf

We reassess the claimed detection of variability in the atmosphere of the hot Jupiter HAT-P-7 b, reported by Armstrong et al. Although astronomers expect hot Jupiters to have changing atmospheres, variability is challenging to detect. We looked for time variation in the phase curves of HAT-P-7 b in Kepler data using similar methods to Armstrong et al., and identified apparently significant variations similar to what they found. Numerous tests show the variations to be mostly robust to different analysis strategies. However, when we injected unchanging phase-curve signals into the light curves of other stars and searched for variability, we often saw similar levels of variations as in the HAT-P-7 light curve. Fourier analysis of the HAT-P-7 light curve revealed background red noise from stellar supergranulation on timescales similar to the planet's orbital period. Tests of simulated light curves with the same level of noise as HAT-P-7's supergranulation show that this effect alone can cause the amplitude and phase-offset variability we detect for HAT-P-7 b. Therefore, the apparent variations in HAT-P-7 b's atmosphere could instead be caused by nonplanetary sources, most likely photometric variability due to supergranulation on the host star.

Keywords: exoplanet atmospheres; exoplanet atmospheric variability; exoplanet astronomy
Two New Black Widow Millisecond Pulsars in M28

We report the discovery of two Black Widow millisecond pulsars in the globular cluster (GC) M28 with the MeerKAT telescope. PSR J1824-2452M (M28M) is a 4.78 ms pulsar in a 5.82 hr orbit, and PSR J1824-2452N (M28N) is a 3.35 ms pulsar in a 4.76 hr orbit. Both pulsars have dispersion measures near 119.30 pc cm-3 and have low-mass companion stars (~0.01-0.03 M ⊙) that do not cause strong radio eclipses or orbital variations. Including these systems, there are now five known black widow pulsars in M28. The pulsar searches were conducted as a part of an initial phase of MeerKAT's GC census (within the TRAPUM Large Survey Project). These faint discoveries demonstrate the advantages of MeerKAT's survey sensitivity over previous searches, and we expect to find additional pulsars in continued searches of this cluster.

Keywords: millisecond pulsars; radio pulsars; radio astronomy; globular star clusters
The Vulcan Mission to Io: Lessons Learned during the 2022 JPL Planetary Science Summer School

A mission to Jupiter's moon Io, the most volcanically active body in the solar system, was suggested as a priority for the New Frontiers program in the 2013 Planetary Science Decadal Survey. We present a New Frontiers–class mission concept, Vulcan, that was designed as an educational exercise through the Jet Propulsion Laboratory's 2022 Planetary Science Summer School. Vulcan would leverage an instrument suite consisting of wide- and narrow-angle cameras, a thermal infrared spectrometer, two fluxgate magnetometers, and ion and electron electrostatic analyzers to conduct the most thorough investigation of Io to date. Using 78 flybys over a 2 yr primary science mission, Vulcan would characterize the effects of tidal forces on the differentiation state, crustal structure, and volcanism of Io and investigate potential interactions between Io's volcanoes, surface features, and atmosphere. Although Vulcan was developed as an academic exercise, we show that a New Frontiers–class mission to Io could achieve transformative science in both geophysics and plasma physics, unifying typically disparate subfields of planetary science. A dedicated mission to Io, in combination with the Europa Clipper and Jupiter Icy Moons Explorer missions, would address fundamental questions raised by the 2023 Planetary Science Decadal Survey and could complete our understanding of the spectrum of planetary habitability. Lessons learned from Vulcan could be applied to a New Frontiers 5 Io mission concept in the near future.

Keywords: io; planetary probes; space probes; galilean satellites; tidal interaction; planetary geology
Kepler-80 Revisited: Assessing the Participation of a Newly Discovered Planet in the Resonant Chain

In this paper, we consider the chain of resonances in the Kepler-80 system and evaluate the impact that the additional member of the resonant chain discovered by Shallue & Vanderburg has on the dynamics of the system and the physical parameters that can be recovered by a fit to the transit timing variations (TTVs). Ultimately, we calculate the mass of Kepler-80 g to be 0.8 ± 0.3M ⊕ when assuming all planets have zero eccentricity, and 1.0 ± 0.3 M ⊕ when relaxing that assumption. We show that the outer five planets are in successive three-body mean-motion resonances (MMRs). We assess the current state of two-body MMRs in the system and find that the planets do not appear to be in two-body MMRs. We find that while the existence of the additional member of the resonant chain does not significantly alter the character of the Kepler-80 three-body MMRs, it can alter the physical parameters derived from the TTVs, suggesting caution should be applied when drawing conclusions from TTVs for potentially incomplete systems. We also compare our results to those of MacDonald et al., who perform a similar analysis on the same system with a different method. Although the results of this work and MacDonald et al. show that different fit methodologies and underlying assumptions can result in different measured orbital parameters, the most secure conclusion is that which holds true across all lines of analysis: Kepler-80 contains a chain of planets in three-body MMRs but not in two-body MMRs.

Keywords: exoplanet dynamics; exoplanet systems; exoplanet astronomy
Massive Galaxy Mergers Have Distinctive Global H I Profiles

The global 21 cm H I emission-line profile of a galaxy encodes valuable information on the spatial distribution and kinematics of the neutral atomic gas. Galaxy interactions significantly influence the H I disk and imprint observable features on the integrated H I line profile. In this work, we study the neutral atomic gas properties of galaxy mergers selected from the Great Observatories All-sky LIRG Survey. The H I spectra come from new observations with the Five-hundred-meter Aperture Spherical Telescope and from a collection of archival data. We quantify the H I profile of the mergers with a newly developed method that uses the curve of growth of the line profile. Using a control sample of non-merger galaxies carefully selected to match the stellar mass of the merger sample, we show that mergers have a larger proportion of single-peaked H I profiles, as well as a greater tendency for the H I central velocity to deviate from the systemic optical velocity of the galaxy. By contrast, the H I profiles of mergers are not significantly more asymmetric than those of non-mergers.

Keywords: galaxy interactions; galaxy evolution; galaxy mergers; h i line emission
Sparse Identification of Variable Star Dynamics

Variable stars play a crucial role as standard candles and provide valuable insights into stellar physics. They can be modeled either through fully fledged hydrodynamical simulations or analytically as systems of coupled differential equations describing the evolution of relevant physical quantities. Typically, such equations are arrived at by simplified physical assumptions concerning the conservation laws governing stellar interiors. Here we apply a data-driven technique-sparse identification of nonlinear dynamics (SINDy)-to automatically learn governing equations from observed light curves. We apply SINDy to 3100 light curves of three different variable types from the Catalina Sky Survey. The success rate depends systematically on variable type, with possible implications for variable star classification; however, it does not obviously depend on amplitude or period. Successful models can be reduced to the generalized Lienard equation $\ddot{x}+(a+{bx}+c\dot{x})\dot{x}+x=0$ . Members of the Lienard class of ordinary differential equations, such as the well-studied van der Pol oscillator, already saw some application to variable star modeling. For a, b = 0 the equation can be solved exactly, and it admits both periodic and nonperiodic solutions. We find a condition on the coefficients of the general equation for the presence of a limit cycle, which is also observed numerically in several instances.

Keywords: rr lyrae variable stars; rrab variable stars; rrc variable stars; pulsating variable stars; delta scuti variable stars
The H I Structure of the Local Volume Dwarf Galaxy Pisces A

Dedicated H I surveys have recently led to a growing category of low-mass galaxies found in the Local Volume. We present synthesis imaging of one such galaxy, Pisces A, a low-mass dwarf originally confirmed via optical imaging and spectroscopy of neutral hydrogen (H I) sources in the Galactic Arecibo L-band Feed Array H I survey. Using H I observations taken with the Karl G. Jansky Very Large Array, we characterize the kinematic structure of the gas and connect it to the galaxy&'s environment and evolutionary history. While the galaxy shows overall ordered rotation, a number of kinematic features indicate a disturbed gas morphology. These features are suggestive of a tumultuous recent history and represent $\sim 3.5$ % of the total baryonic mass. We find a total baryon fraction ${f}_{\mathrm{bary}}=0.13$ if we include these features. We also quantify the cosmic environment of Pisces A, finding an apparent alignment of the disturbed gas with nearby, large-scale filamentary structure at the edge of the Local Void. We consider several scenarios for the origin of the disturbed gas, including gas stripping via ram pressure or galaxy-galaxy interactions, as well as accretion and ram pressure compression. Though we cannot rule out a past interaction with a companion, our observations best support the suggestion that the neutral gas morphology and recent star formation in Pisces A are a direct result of its interactions with the intergalactic medium.

Keywords: dwarf galaxies; galaxies; radio galaxies
Global Mapping of HCl on Mars by IRTF/iSHELL

Hydrogen chloride (HCl)—a key marker of the chlorine cycle on Mars—has been recently discovered in the Martian atmosphere by the ExoMars/TGO mission. In-orbit data indicate that this molecule appears in the atmosphere only in a limited time period and specifically in the southern summer season. A snapshot global mapping of HCl is indispensable to examine its sources and sinks, but such observations are not currently possible from any orbiters. Here, we present the first spatially resolved map of HCl obtained with the ground-based NASA InfraRed Telescope Facility. We find clear features of HCl, demonstrating that HCl is present close to the surface. HCl is detected in the equatorial region for the first time, revealing that HCl is widely distributed on Mars. However, the spatial distribution of HCl is not uniform, and it is enhanced in the southern polar region. Interestingly, this nonuniform spatial distribution of HCl column abundance is strikingly similar to that of water vapor column abundance. This highlights the important role of water vapor in the evolution of HCl through the atmosphere, as previously noted, and suggests its potential involvement in the atmospheric chlorine source processes.

Keywords: planetary atmospheres
Propagation of Torsional Alfvén Pulses in Zero-beta Flux Tubes

In this study, we investigate analytically the generation of mass flux due to a torsional Alfvén pulse. We derive that the presence of torsional Alfvén waves, which have been observed in, e.g., photospheric magnetic bright points (MBPs), can result in vertical plasma motions. The formation of this mass flux may even be a viable contribution to the generation of chromospheric mass transport, playing potential roles in the form of localized lower solar atmospheric jets. This relationship is studied using a flux tube model, with the waves introduced at the lower boundary of the tube as a magnetic shear perturbation. Due to the nature of MBPs we simplify the model by using the zero-beta approximation for the plasma inside the tube. The analytical results are demonstrated by an example of the type of Alfvén wave perturbation that one might expect to observe, and comparison is made with properties of spicules known from observations. We find that field-aligned plasma flux is formed nonlinearly as a result of the Lorentz force generated by the perturbations, and could be consistent with jet formation, although the current model is not intended to determine the entire evolution of a jet. Critical discussion of the model follows, including suggestions for improvements and for high-resolution proposed observations in order to constrain the driving magnetic and velocity shear.

Keywords: solar spicules; solar chromosphere; magnetohydrodynamics; alfven waves; solar magnetic bright points; solar magnetic fields; solar physics