adsabs/SciX_UAT_keywords huggingface dataset:
Light-curve Evolution due to Secular Dynamics and the Vanishing Transits of KOI 120.01

Non-Keplerian dynamics of planetary orbits manifest in the transit light curve as variations of different types. In addition to transit timing variations, the shape of the transits contains additional information on variations in the geometry of the orbit. This study presents an analytic approach to light-curve fitting: dynamical variations in the orbital elements are transformed to a light curve using an analytic function with a restricted set of fitting parameters. Our method requires no N-body integration, resulting in a smaller number of degrees of freedom and a faster calculation. The approach described here is for the case of secular perturbations. By assuming that the orbital motion is dominated by nodal and apsidal precessions, analytic expressions for the light-curve transit parameters are derived as a function of the orbital variations. Detecting and characterizing such dynamical scenarios provides information regarding the possible existence of nontransiting companions, or the nonspherical mass distribution of the host star. The variations may imply forces out of the orbital plane, and thus probe mutual inclinations among components of the system. The derived models successfully reproduce the vanishing transit signals of KOI 120.01, and suggest a possible interesting scenario of a planet orbiting one member of a close-in binary system undergoing unusually rapid nodal regression. The model parameters are degenerate, so we provide relevant information for follow-up observations, which are suggested in order to place further constraints on this unique Kepler object.

Keywords: celestial mechanics; exoplanet systems; close binary stars
Measurement of Interstellar Magnetization by Synchrotron Polarization Variance

Since synchrotron polarization fluctuations are related to the fundamental properties of the magnetic field, we propose the polarization intensity variance to measure the Galactic interstellar medium (ISM) magnetization. We confirm the method's applicability by comparing it with the polarization angle dispersion and its reliability by measuring the underlying Alfvénic Mach number of magnetohydrodynamic turbulence. With the finding of the power-law relation of ${ \mathcal A }\propto {M}_{{\rm{A}}}^{2}$ between polarization intensity variance ${ \mathcal A }$ and Alfvénic Mach number M A, we apply the new technique to the Canadian Galactic Plane Survey data, achieving the Alfvénic Mach number of the Galactic ISM. Our results show that the low-latitude Galactic ISM is dominated by sub-Alfénic turbulence, with M A approximately between 0.5 and 1.0.

Keywords: interplanetary turbulence; radiative magnetohydrodynamics; interstellar medium; interstellar emissions
Evidence for Mixing between ICM and Stripped ISM by the Analysis of the Gas Metallicity in the Tails of Jellyfish Galaxies

Hydrodynamical simulations show that the ram pressure stripping in galaxy clusters fosters a strong interaction between stripped interstellar medium (ISM) and the surrounding medium, with the possibility of intracluster medium (ICM) cooling into cold gas clouds. Exploiting the MUSE observation of three jellyfish galaxies from the GAs Stripping Phenomena in galaxies with MUSE (GASP) survey, we explore the gas metallicity of star-forming clumps in their gas tails. We find that the oxygen abundance of the stripped gas decreases as a function of the distance from the parent galaxy disk; the observed metallicity profiles indicate that more than 40% of the most metal-poor stripped clouds are constituted by cooled ICM, in qualitative agreement with simulations that predict mixing between the metal-rich ISM and the metal-poor ICM.

Keywords: galaxy clusters; intracluster medium; ram pressure stripped tails; interstellar abundances
Disk Tearing: Implications for Black Hole Accretion and AGN Variability

Accretion disks around black holes power some of the most luminous objects in the universe. Disks that are misaligned to the black hole spin can become warped over time by Lense-Thirring precession. Recent work has shown that strongly warped disks can become unstable, causing the disk to break into discrete rings producing a more dynamic and variable accretion flow. In a companion paper, we present numerical simulations of this instability and the resulting dynamics. In this paper, we discuss the implications of this dynamics for accreting black hole systems, with particular focus on the variability of active galactic nuclei (AGN). We discuss the timescales on which variability might manifest, as well as the impact of the observer orientation with respect to the black hole spin axis. When the disk warp is unstable near the inner edge of the disk, we find quasi-periodic behavior of the inner disk, which may explain the recent quasi-periodic eruptions observed in, for example, the Seyfert 2 galaxy GSN 069 and in the galactic nucleus of RX J1301.9+2747. These eruptions are thought to be similar to the "heartbeat" modes observed in some X-ray binaries (e.g., GRS 1915+105 and IGR J17091-3624). When the instability manifests at larger radii in the disk, we find that the central accretion rate can vary on timescales that may be commensurate with, e.g., changing-look AGN. We therefore suggest that some of the variability properties of accreting black hole systems may be explained by the disk being significantly warped, leading to disk tearing.

Keywords: accretion; circumstellar disks; relativistic disks; stellar accretion disks; hydrodynamics; hydrodynamical simulations; black hole physics
Elucidating the Formation of Ethynylbutatrienylidene (HCCCHCCC; X1A') in the Taurus Molecular Cloud (TMC-1) via the Gas-phase Reaction of Tricarbon (C3) with the Propargyl Radical (C3H3)

The recent astronomical detection of ethynylbutatrienylidene (HCCCHCCC)-a high-energy isomer of triacetylene (HCCCCCCH) and hexapentaenylidene (H2CCCCCC)-in TMC-1 puzzled the laboratory astrophysics community since proposed reaction pathways could not synthesize the ethynylbutatrienylidene (HCCCHCCC) under cold molecular cloud conditions. Exploiting a retrosynthesis coupled with electronic structure calculations and astrochemical modeling, we reveal that observed fractional abundance of ethynylbutatrienylidene (HCCCHCCC) of 1.3 ± 0.2 × 10-11 can be quantitatively replicated though the barrierless and exoergic reaction of tricarbon (C3) with the resonantly stabilized propargyl radical (C3H3) after a few 105 yr-typical ages of cold molecular clouds. Our study provides persuasive evidence that previously assumed "dead" reactants such as tricarbon (C3) and the propargyl radical (C3H3) provide fundamental molecular building blocks in molecular mass growth processes leading to exotic, high-energy isomers of hydrocarbons: ethynylbutatrienylidene (HCCCHCCC).

Keywords: astrochemistry; interstellar dust; laboratory astrophysics
Energetics of Shock-triggered Supersubstorms (SML < -2500 nT)

The solar wind energy input and dissipation in the magnetospheric-ionospheric systems of 17 supersubstorms (SSSs: SML < -2500 nT) triggered by interplanetary shocks during solar cycles 23 and 24 are studied in detail. The SSS events had durations ranging from ~42 minutes to ~6 hr, and SML intensities ranging from -2522 nT to -4143 nT. Shock compression greatly strengthens the upstream interplanetary magnetic field southward component (B s), and thus, through magnetic reconnection at the Earth's dayside magnetopause, greatly enhances the solar wind energy input into the magnetosphere and ionosphere during the SSS events studied. The additional solar wind magnetic reconnection energy input supplements the ~1.5 hr precursor (growth-phase) energy input and both supply the necessary energy for the high-intensity, long-duration SSS events. Some of the solar wind energy is immediately deposited in the magnetosphere/ionosphere system, and some is stored in the magnetosphere/magnetotail system. During the SSS events, the major part of the solar wind input energy is dissipated into Joule heating (~30%), with substantially less energy dissipation in auroral precipitation (~3%) and ring current energy (~2%). The remainder of the solar wind energy input is probably lost down the magnetotail. It is found that during the SSS events, the dayside Joule heating is comparable to that of the nightside Joule heating, giving a picture of the global energy dissipation in the magnetospheric/ionospheric system, not simply a nightside-sector substorm effect. Several cases are shown where an SSS is the only substorm that occurs during a magnetic storm, essentially equating the two phenomena for these cases.

Keywords: space weather; interplanetary magnetic fields; interplanetary shocks
The Luminosity Function of Red Supergiants in M31

The mass-loss rates of red supergiant stars (RSGs) are poorly constrained by direct measurements, and yet the subsequent evolution of these stars depends critically on how much mass is lost during the RSG phase. In 2012 the Geneva evolutionary group updated their mass-loss prescription for RSGs with the result that a 20 M⊙ star now loses 10 times more mass during the RSG phase than in the older models. Thus, higher-mass RSGs evolve back through a second yellow supergiant phase rather than exploding as Type II-P supernovae, in accord with recent observations (the so-called "RSG Problem"). Still, even much larger mass-loss rates during the RSG phase cannot be ruled out by direct measurements of their current dust-production rates, as such mass loss is episodic. Here, we test the models by deriving a luminosity function for RSGs in the nearby spiral galaxy, M31, which is sensitive to the total mass loss during the RSG phase. We carefully separate RSGs from asymptotic giant branch stars in the color-magnitude diagram following the recent method exploited by Yang and collaborators in their Small Magellanic Cloud studies. Comparing our resulting luminosity function with that predicted by the evolutionary models shows that the new prescription for RSG mass loss does an excellent job of matching the observations, and we can readily rule out significantly larger values.

Keywords: massive stars; red supergiant stars; stellar mass loss; andromeda galaxy; luminosity function
Haze Formation in Warm H2-rich Exoplanet Atmospheres

New observing capabilities coming online over the next few years will provide opportunities for characterization of exoplanet atmospheres. However, clouds/hazes could be present in the atmospheres of many exoplanets, muting the amplitude of spectral features. We use laboratory simulations to explore photochemical haze formation in H2-rich exoplanet atmospheres at 800 K with metallicity either 100 or 1000 times solar. We find that haze particles are produced in both simulated atmospheres with small particle size (20-140 nm) and relatively low production rate (2.4 × 10-5 to 9.7 × 10-5 mg cm-3 hr-1), but the particle size and production rate is dependent on the initial gas mixtures and the energy sources used in the simulation experiments. The gas phase mass spectra show that complex chemical processes happen in these atmospheres and generate new gas products that can further react to form larger molecules and solid haze particles. Two H2-rich atmospheres with similar C/O ratios (∼0.5) yield different haze particle size, haze production rate, and gas products, suggesting that both the elemental abundances and their bonding environments in an atmosphere can significantly affect the photochemistry. There is no methane (CH4) in our initial gas mixtures, although CH4 is often believed to be required to generate organic hazes. However, haze production rates from our experiments with different initial gas mixtures indicate that CH4 is neither required to generate organic hazes nor necessary to promote the organic haze formation. The variety and relative yield of the gas products indicate that CO and N2 enrich chemical reactions in H2-rich atmospheres.

Keywords: exoplanet atmospheres; planetary atmospheres; laboratory astrophysics
Stellar Feedback on the Earliest Stage of Massive Star Formation

We report SOFIA/GREAT observations of high-J CO lines and [C II] observations of the super star cluster candidate H72.97-69.39 in the Large Magellanic Cloud (LMC), which is in its very early formation stage. We use our observations to determine if shocks are heating the gas or if photon-dominated regions (PDRs) are being heated by local far-UV radiation. We use a PDR model and a shock model to determine whether the CO and [C II] lines arise from PDRs or shocks. We can reproduce the observed high-J CO and [C II] emission with a clumpy PDR model with the following properties: a density of 104.7 cm-3, a mass of 104 M⊙, and UV radiation of 103.5 in units of Draine field. Comparison with the ALMA beam-filling factor suggests a higher density within the uncertainty of the fit. We find the lower-limit [C II]/total infrared (TIR) ratio (ɛ) traced by [C II]/TIR to be 0.026%, lower than other known young star-forming regions in the LMC. Our shock models may explain the CO (16-15) and CO (11-10) emission lines with shock velocity of 8-11 km s-1, pre-shock density of 104-105 cm-3, and GUV = 0 in units of Draine field. However, the [C II] line emission cannot be explained by a shock model, thus it is originating in a different gas component. Observations of [O ] 63 μm predicted to be 1.1 × 10-13 W m-2 by PDR models and 7.8 × 10-15 W m-2 by shock models will help distinguish between the PDR and shock scenarios.

Keywords: star formation; young stellar objects; protostars; photodissociation regions; shocks
Compact Binary Merger Rate in Dark-matter Spikes

Today, the existence of supermassive black holes (SMBHs) in the center of galactic halos is almost confirmed. An extremely dense region referred to as dark-matter spike is expected to form around central SMBHs as they grow and evolve adiabatically. In this work, we calculate the merger rate of compact binaries in dark-matter spikes while considering halo models with spherical and ellipsoidal collapses. Our findings exhibit that ellipsoidal-collapse dark-matter halo models can potentially yield the enhancement of the merger rate of compact binaries. Finally, our results confirm that the merger rate of primordial black hole binaries is consistent with the results estimated by the LIGO-Virgo detectors, while such results cannot be realized for binary neutron stars and primordial black hole-neutron star binaries.

Keywords: dark matter; primordial black holes; neutron stars; supermassive black holes; gravitational waves
Chandra Observations of Abell 2261 Brightest Cluster Galaxy, a Candidate Host to a Recoiling Black Hole

We use Chandra X-ray observations to look for evidence of a recoiling black hole from the brightest cluster galaxy in Abell 2261 (A2261-BCG). A2261-BCG is a strong candidate for a recoiling black hole because of its large, flat stellar core, revealed by Hubble Space Telescope imaging observations. We took 100 ks observations with Chandra and combined it with 35 ks of archival observations to look for low-level accretion onto a black hole of expected mass $M\sim {10}^{10}\,{M}_{\odot }$ that could possibly be located in one of four off-center stellar knots near the galaxy's center or else in the optical center of the galaxy or in the location of radio emission. We found no X-ray emission arising from a point source in excess of the cluster gas and can place limits on the accretion of any black hole in the central region to a 2-7 keV flux below $4.3\times {10}^{-16}\ \mathrm{erg}\ {{\rm{s}}}^{-1}\ {\mathrm{cm}}^{-2}$ , corresponding to a bolometric Eddington fraction of about 10-6. Thus there is either no 1010 ${M}_{\odot }$ black hole in the core of A2261-BCG, or it is accreting at a low level. We also discuss the morphology of the X-ray emitting gas in the cluster and how its asymmetry is consistent with a large dynamic event.

Keywords: supermassive black holes; low-luminosity active galactic nuclei; x-ray active galactic nuclei; brightest cluster galaxies; x-ray astronomy; black hole physics; gravitational waves; galaxy clusters; abell clusters; intracluster medium
Modeling the Chromosphere and Transition Region of Planet-hosting Star GJ 436

Ahead of upcoming space missions intending to conduct observations of low-mass stars in the ultraviolet (UV) spectral region it becomes imperative to simultaneously conduct atmospheric modeling from the UV to the visible (VIS) and near-infrared (NIR). Investigations on extended spectral regions will help to improve the overall understanding of the diversity of spectral lines arising from very different atmospheric temperature regions. Here we investigate atmosphere models with a chromosphere and transition region for the M2.5V star GJ 436, which hosts a close-in Hot Neptune. The atmosphere models are guided by observed spectral features from the UV to the VIS/NIR originating in the chromosphere and transition region of GJ 436. High-resolution observations from the Hubble Space Telescope and Calar Alto high-Resolution search for M dwarfs with Exo-earths with Near-infrared and optical Echelle Spectrographs (CARMENES) are used to obtain an appropriate model spectrum for the investigated M dwarf. We use a large set of atomic species considered in nonlocal thermodynamic equilibrium conditions within our PHOENIX model computations to approximate the physics within the low-density atmospheric regions. In order to obtain an overall match for the nonsimultaneous observations, it is necessary to apply a linear combination of two model spectra, where one of them better reproduces the UV lines while the other better represents the lines from the VIS/NIR range. This is needed to adequately handle different activity states across the observations.

Keywords: stellar activity; stellar chromospheres; m dwarf stars; stellar atmospheres; ultraviolet spectroscopy
Ionization Distributions in Outflows of Active Galaxies: Universal Trends and Prospect of Future XRISM Observations

The physics behind the ionization structure of outflows from black holes is yet to be fully understood. Using archival observations with the Chandra/HETG gratings over the past two decades, we measured an absorption measure distribution for a sample of outflows in nine active galactic nuclei (AGNs), namely the dependence of outflow column density, N H, on the ionization parameter, ξ. The slope of $\mathrm{log}$ N H versus $\mathrm{log}\xi $ is found to be between 0.00 and 0.72. We find an anticorrelation between the log of total column density of the outflow and the log of AGN luminosity, and none with the black hole mass and accretion efficiency. A major improvement in the diagnostics of AGN outflows will potentially occur with the launch of the XRISM/Resolve spectrometer. We study the ability of Resolve to reveal the outflow ionization structure by constructing the absorption measure distribution from simulated Resolve spectra, utilizing its superior resolution and effective area. Resolve constrains the column density as well as HETG, but with much shorter observations.

Keywords: x-ray active galactic nuclei; seyfert galaxies
First Detection of Hydroxyl Radical Emission from an Exoplanet Atmosphere: High-dispersion Characterization of WASP-33b Using Subaru/IRD

We report the first detection of a hydroxyl radical (OH) emission signature in the planetary atmosphere outside the solar system, in this case, in the dayside of WASP-33b. We analyze high-resolution near-infrared emission spectra of WASP-33b taken using the InfraRed Doppler spectrograph on the 8.2 m Subaru telescope. The telluric and stellar lines are removed using a detrending algorithm, SYSREM. The residuals are then cross-correlated with OH and H2O planetary spectrum templates produced using several different line lists. We check and confirm the accuracy of OH line lists by cross-correlating with the spectrum of GJ 436. As a result, we detect the emission signature of OH at Kp of ${230.9}_{-7.4}^{+6.9}$ km s-1 and vsys of -0.3 ${}_{-5.6}^{+5.3}$ km s-1 with a signal-to-noise ratio (S/N) of 5.4 and a significance of 5.5σ. Additionally, we marginally detect H2O emission in the H-band with an S/N of 4.0 and a significance of 5.2σ using the POKAZATEL line list. However, no significant signal is detected using the HITEMP 2010, which might be due to differences in line positions and strengths, as well as the incompleteness of the line lists. Nonetheless, this marginal detection is consistent with the prediction that H2O is mostly thermally dissociated in the upper atmosphere of the ultra-hot Jupiters. Therefore, along with CO, OH is expected to be one of the most abundant O-bearing molecules in the dayside atmosphere of ultra-hot Jupiters and should be considered when studying their atmospheres. * Based on data collected at the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan.

Keywords: exoplanet atmospheres; exoplanet atmospheric composition; high resolution spectroscopy
Magnetic Reconnection between Loops Accelerated By a Nearby Filament Eruption

Magnetic reconnection modulated by nonlocal disturbances in the solar atmosphere has been investigated theoretically, but rarely observed. In this study, employing Hα and extreme ultraviolet (EUV) images and line-of-sight magnetograms, we report the acceleration of reconnection by an adjacent filament eruption. In Hα images, four groups of chromospheric fibrils are observed to form a saddle-like structure. Among them, two groups of fibrils converge and reconnect. Two newly reconnected fibrils then form and retract away from the reconnection region. In EUV images, similar structures and evolution of coronal loops are identified. The current sheet forms repeatedly at the interface of reconnecting loops, with a width and length of 1-2 and 5.3-7.2 Mm and a reconnection rate of 0.18-0.3. It appears in the EUV low-temperature channels, with an average differential emission measure (DEM) weighed temperature and EM of 2 MK and 2.5 × 1027 cm-5. Plasmoids appear in the current sheet and propagate along it, and then further along the reconnection loops. The filament, located to the southeast of the reconnection region, erupts and pushes away the loops covering the reconnection region. Thereafter, the current sheet has a width and length of 2 and 3.5 Mm and a reconnection rate of 0.57. It becomes much brighter and appears in the EUV high-temperature channels, with an average DEM-weighed temperature and EM of 5.5 MK and 1.7 × 1028 cm-5. In the current sheet, more hotter plasmoids form. More thermal and kinetic energy is hence converted. These results suggest that the reconnection is significantly accelerated by the propagating disturbance caused by the nearby filament eruption.

Keywords: solar magnetic reconnection; plasma physics; solar corona; solar ultraviolet emission; solar magnetic fields
Collisional Growth Efficiency of Dust Aggregates and Its Independence of the Strength of Interparticle Rolling Friction

The pairwise collisional growth of dust aggregates consisting of submicron-sized grains is the first step of planet formation, and understanding the collisional behavior of dust aggregates is therefore essential. It is known that the main energy dissipation mechanisms are the tangential frictions between particles in contact, namely, rolling, sliding, and twisting. However, there is great uncertainty for the strength of rolling friction, and the dependence of the collisional growth condition on the strength of rolling friction was poorly understood. Here we performed numerical simulations of collisions between two equal-mass porous aggregates with various collision velocities and impact parameters, and we also changed the strength of rolling friction systematically. We found that the threshold of the collision velocity for the fragmentation of dust aggregates is nearly independent of the strength of rolling friction. This is because the total amount of the energy dissipation by the tangential frictions is nearly constant even though the strength of rolling friction is varied.

Keywords: protoplanetary disks; circumstellar disks; planet formation; planetesimals