adsabs/SciX_UAT_keywords huggingface dataset:
Multiwavelength Follow-up of the Hyperluminous Intermediate-mass Black Hole Candidate 3XMM J215022.4-055108

We recently discovered the X-ray/optical outbursting source 3XMM J215022.4-055108. It was best explained as the tidal disruption of a star by an intermediate-mass black hole of mass of a few tens of thousand solar masses in a massive star cluster at the outskirts of a large barred lenticular galaxy at DL = 247 Mpc. However, we could not completely rule out a Galactic cooling neutron star as an alternative explanation for the source. In order to further pin down the nature of the source, we have obtained new multiwavelength observations by XMM-Newton and the Hubble Space Telescope (HST). The optical counterpart to the source in the new HST image is marginally resolved, which rules out the Galactic cooling neutron star explanation for the source and suggests a star cluster of half-light radius ∼27 pc. The new XMM-Newton observation indicates that the luminosity was decaying as expected for a tidal disruption event and that the disk was still in the thermal state with a supersoft X-ray spectrum. Therefore, the new observations confirm the source as one of the best intermediate-mass black hole candidates.

Keywords: stellar accretion disks; black hole physics; x-ray transient sources; ultracompact dwarf galaxies; intermediate-mass black holes; tidal disruption
Serpentinization in the Thermal Evolution of Icy Kuiper Belt Objects in the Early Solar System

Here we present an improved algorithm to model the serpentinization process in planetesimals in the early solar system. Although it is hypothesized that serpentinization-like reactions played an important role in the thermal evolution of planetesimals, few and restricted models are available in this topic. These processes may be important, as the materials involved were abundant in these objects. Our model is based on the model by Góbi & Kereszturi and contains improvements in the consideration of heat capacities and lithospheric pressure and in the calculation of the amount of interfacial water. Comparison of our results with previous calculations shows that there are significant differences in, e.g., the serpentinization time-the time necessary to consume most of the reactants at specific initial conditions-or the amount of heat produced by this process. In a simple application we show that in icy bodies, under some realistic conditions, below the melting point of water ice, serpentinization reaction using interfacial water may be able to proceed and eventually push the local temperature above the melting point to start a "runaway" serpentinization. According to our calculations in objects with radii R ≳ 200 km, serpentinization might have quickly reformed nearly the whole interior of these bodies in the early solar system.

Keywords: planetary interior
RNO 54: A Previously Unappreciated FU Ori Star

We present evidence in support of the hypothesis that the young stellar object RNO 54 is a mature-stage FU Ori type source. The star was first cataloged as a "red nebulous object" in the 1980s but appears to have undergone its outburst prior to the 1890s. Present-day optical and near-infrared spectra are consistent with those of other FU Ori-type stars, both in the details of spectral line presence and shape, and in the overall change in spectral type from an FGK-type in the optical, to the M-type presented in the near-infrared. In addition, the spectral energy distribution of RNO 54 is well-fit by a pure-accretion disk model with parameters: $\dot{M}={10}^{-3.45\pm 0.06}$ M ⊙ yr-1, M * = 0.23 ± 0.06 M ⊙, and R inner = 3.68 ± 0.76 R ⊙, though we believe R inner is likely close to its upper range of 4.5R ⊙ in order to produce a ${T}_{\max }=7000$ K that is consistent with the optical to near-infrared spectra. The resulting L acc is ~265 L ⊙. To find these values, we adopted a source distance d = 1400 pc and extinction A V = 3.9 mag, along with disk inclination i = 50 deg based on the consideration of confidence intervals from our initial disk model, and in agreement with observational constraints. The new appreciation of a well-known source as an FU Ori-type object suggests that other such examples may be lurking in extant samples.

Keywords: eruptive variable stars; fu orionis stars; young stellar objects
The Promise and Limitations of Precision Gravity: Application to the Interior Structure of Uranus and Neptune

We study the constraining power of a high-precision measurement of the gravity field for Uranus and Neptune, as could be delivered by a low-periapse orbiter. Our study is practical, assessing the possible deliverables and limitations of such a mission with respect to the structure of the planets. Our study is also academic, assessing in a general way the relative importance of the low-order gravity, high-order gravity, rotation rate, and moment of inertia (MOI) in constraining planetary structure. We attempt to explore all possible interior density structures of a planet that are consistent with hypothetical gravity data via MCMC sampling of parameterized density profiles. When the gravity field is poorly known, as it is today, uncertainties in the rotation rate on the order of 10 minutes are unimportant, as they are interchangeable with uncertainties in the gravity coefficients. By the same token, when the gravity field is precisely determined, the rotation rate must be known to comparable precision. When gravity and rotation are well known, the MOI becomes well constrained, limiting the usefulness of independent MOI determinations unless they are extraordinarily precise. For Uranus and Neptune, density profiles can be well constrained. However, the nonuniqueness of the relative roles of H/He, watery volatiles, and rock in the deep interior will still persist with high-precision gravity data. Nevertheless, the locations and magnitudes (in pressure space) of any large-scale composition gradient regions can likely be identified, offering a crucially better picture of the interiors of Uranus or Neptune.

Keywords: uranus; neptune; planetary interior
Formation of Massive Star Clusters by Fast H I Gas Collision

Young massive clusters (YMCs) are dense aggregates of young stars, which are essential to galaxy evolution, owing to their ultraviolet radiation, stellar winds, and supernovae. The typical mass and radius of YMCs are M ∼ 104 M⊙ and R ∼ 1 pc, respectively, indicating that many stars are located in a small region. The formation of YMC precursor clouds may be difficult because a very compact massive cloud should be formed before stellar feedback blows off the cloud. Recent observational studies suggest that YMCs can be formed as a consequence of the fast H I gas collision with a velocity of ∼100 km s-1, which is the typical velocity of the galaxy-galaxy interaction. In this study, we examine whether the fast H I gas collision triggers YMC formation using three-dimensional magnetohydrodynamics simulations, which includes the effects of self-gravity, radiative cooling/heating, and chemistry. We demonstrate that massive gravitationally bound gas clumps with M > 104 M⊙ and L ∼ 4 pc are formed in the shock compressed region induced by the fast H I gas collision, in which massive gas clumps can evolve into YMCs. Our results show that the YMC precursors are formed by the global gravitational collapse of molecular clouds, and YMCs can be formed even in low-metal environments, such as the Magellanic Clouds. Additionally, the very massive YMC precursor cloud, with M > 105 M⊙, can be created when we consider the fast collision of H I clouds, which may explain the origin of the very massive stellar cluster R136 system in the Large Magellanic Cloud.

Keywords: young star clusters; star formation
The Comprehensive Archive of Substellar and Planetary Accretion Rates

Accretion rates ( ) of young stars show a strong correlation with object mass (M); however, extension of the relation into the substellar regime is less certain. Here, we present the Comprehensive Archive of Substellar and Planetary Accretion Rates (CASPAR), the largest compilation to date of substellar accretion diagnostics. CASPAR includes: 658 stars, 130 brown dwarfs, and 10 bound planetary mass companions. In this work, we investigate the contribution of methodological systematics to scatter in the relation and compare brown dwarfs to stars. In our analysis, we rederive all quantities using self-consistent models, distances, and empirical line flux to accretion luminosity scaling relations to reduce methodological systematics. This treatment decreases the original 1σ scatter in the relation by ∼17%, suggesting that it makes only a small contribution to the dispersion. The CASPAR rederived values are best fit by from 10 M J to 2 M ⊙, confirming previous results. However, we argue that the brown-dwarf and stellar populations are better described separately and by accounting for both mass and age. Therefore, we derive separate age-dependent relations for these regions and find a steepening in the brown-dwarf slope with age. Within this mass regime, the scatter decreases from 1.36 dex to 0.94 dex, a change of ∼44%. This result highlights the significant role that evolution plays in the overall spread of accretion rates, and suggests that brown dwarfs evolve faster than stars, potentially as a result of different accretion mechanisms.

Keywords: brown dwarfs; stellar accretion; classical t tauri stars; astronomy databases; pre-main sequence stars
The Young Embedded Disk L1527 IRS: Constraints on the Water Snowline and Cosmic-Ray Ionization Rate from HCO+ Observations

The water snowline in circumstellar disks is a crucial component in planet formation, but direct observational constraints on its location remain sparse owing to the difficulty of observing water in both young embedded and mature protoplanetary disks. Chemical imaging provides an alternative route to locate the snowline, and HCO+ isotopologues have been shown to be good tracers in protostellar envelopes and Herbig disks. Here we present ~0.″5 resolution (~35 au radius) Atacama Large Millimeter/submillimeter Array (ALMA) observations of HCO+ J = 4 - 3 and H13CO+ J = 3 - 2 toward the young (Class 0/I) disk L1527 IRS. Using a source-specific physical model with the midplane snowline at 3.4 au and a small chemical network, we are able to reproduce the HCO+ and H13CO+ emission, but for HCO+ only when the cosmic-ray ionization rate is lowered to 10-18 s-1. Even though the observations are not sensitive to the expected HCO+ abundance drop across the snowline, the reduction in HCO+ above the snow surface and the global temperature structure allow us to constrain a snowline location between 1.8 and 4.1 au. Deep observations are required to eliminate the envelope contribution to the emission and to derive more stringent constraints on the snowline location. Locating the snowline in young disks directly with observations of H2O isotopologues may therefore still be an alternative option. With a direct snowline measurement, HCO+ will be able to provide constraints on the ionization rate.

Keywords: interstellar molecules; astrochemistry; protostars
Origin of Spectral Hardening of Secondary Cosmic-Ray Nuclei

We discuss the acceleration and escape of secondary cosmic-ray (CR) nuclei, such as lithium, beryllium, and boron, produced by spallation of primary CR nuclei like carbon, nitrogen, and oxygen accelerated at the shock in supernova remnants (SNRs) surrounded by the interstellar medium (ISM) or a circumstellar medium (CSM). We take into account the energy-dependent escape of CR particles from the SNR shocks, which is supported by gamma-ray observations of SNRs, to calculate the spectra of primary and secondary CR nuclei running away into the ambient medium. We find that if the SNR is surrounded by a CSM with a wind-like density distribution (i.e., nCSM ∝ r-2), the spectra of the escaping secondary nuclei are harder than those of the escaping primary nuclei, while if the SNR is surrounded by a uniform ISM, the spectra of the escaping secondaries are always softer than those of the escaping primaries. Using this result, we show that if there was a past supernova surrounded by a dense wind-like CSM (~2.5 × 10-3 M⊙ yr-1), which happened ~1.6 × 105 yr ago at a distance of ~1.6 kpc, we can simultaneously reproduce the spectral hardening of primary and secondary CRs above ~200 GV that have recently been reported by AMS-02.

Keywords: cosmic ray sources; cosmic ray astronomy; cosmic rays
Metal-THINGS: On the Metallicity and Ionization of ULX Sources in NGC 925

We present an analysis of the optical properties of three Ultra Luminous X-ray (ULX) sources identified in NGC 925. We use Integral field unit data from the George Mitchel spectrograph in the context of the Metal-THINGS survey. The optical properties for ULX-1 and ULX-3 are presented, while the spaxel associated with ULX-2 had a low S/N, which prevented its analysis. We also report the kinematics and dimensions of the optical nebula associated with each ULX using ancillary data from the PUMA Fabry-Perot spectrograph. A BPT analysis demonstrates that most spaxels in NGC 925 are dominated by star-forming regions, including those associated with ULX-1 and ULX-3. Using the resolved gas-phase metallicities, a negative metallicity gradient is found, consistent with previous results for spiral galaxies, while the ionization parameter tends to increase radially throughout the galaxy. Interestingly, ULX-1 shows a very low gas metallicity for its galactocentric distance, identified by two independent methods, while exhibiting a typical ionization. We find that such low gas metallicity is best explained in the context of the high-mass X-ray binary population, where the low-metallicity environment favors active Roche lobe overflows that can drive much higher accretion rates. An alternative scenario invoking accretion of a low-mass galaxy is not supported by the data in this region. Finally, ULX-3 shows both a high metallicity and ionization parameter, which is consistent with the progenitor being a highly accreting neutron star within an evolved stellar population region.

Keywords: emission line galaxies; ionization; chemical abundances; abundance ratios; spectroscopy; x-ray sources
Preferential Heating of Heavy Ions in Shocks

Observations show that postshock temperatures of heavy ions in supernovae collisionless shocks are approximately proportional to their masses. So far there is no convincing explanation of this dependence that would take into account the microphysics of the ion interaction with the electromagnetic fields inside the shock front. Here it is shown that perpendicular temperature increases due to the gyration of heavy ions starts inevitably upon crossing the shock front because of the global change of the magnetic field. An estimate for the downstream temperature as a function of the shock angle and magnetic compression is derived.

Keywords: shocks
Weak-lensing Peak Statistics in Mocks by the Inverse-Gaussianization Method

Recent studies have shown the great power of peak counts in weak-lensing maps. In this work, we apply the inverse-Gaussianization method proposed in Yu et al. to produce weak-lensing convergence maps quickly and investigate the peak statistics, including the peak height counts and peak steepness counts in these mocks. The distributions of peak height and steepness are in good agreement with the simulation results. The difference is ≲20% for these peak statistics in the maps at source redshift zs = 1. Also, the loss of off-diagonal elements in the peak covariance motivates us to consider the super-sample variance in weak-lensing peak statistics. We propose four correction methods to effectively recover the (anti)correlation among different bins by adding different scatters in the mean value of these mocks. Finally, as an example of the application, we adopt the improved inverse-Gaussianization method to quickly generate 40,000 mocks to calculate precision matrices for the power spectrum and peak-statistics joint analysis.

Keywords: weak gravitational lensing; non-gaussianity; cosmology; large-scale structure of the universe
SN 2022jli: A Type Ic Supernova with Periodic Modulation of Its Light Curve and an Unusually Long Rise

We present multiwavelength photometry and spectroscopy of SN 2022jli, an unprecedented Type Ic supernova discovered in the galaxy NGC 157 at a distance of ≈ 23 Mpc. The multiband light curves reveal many remarkable characteristics. Peaking at a magnitude of g = 15.11 ± 0.02, the high-cadence photometry reveals periodic undulations of 12.5 ± 0.2 days superimposed on the 200-day supernova decline. This periodicity is observed in the light curves from nine separate filter and instrument configurations with peak-to-peak amplitudes of ≃ 0.1 mag. This is the first time that repeated periodic oscillations, over many cycles, have been detected in a supernova light curve. SN 2022jli also displays an extreme early excess that fades over ≈25 days, followed by a rise to a peak luminosity of L opt = 1042.1 erg s-1. Although the exact explosion epoch is not constrained by data, the time from explosion to maximum light is ≳ 59 days. The luminosity can be explained by a large ejecta mass (M ej ≈ 12 ± 6 M ⊙) powered by 56Ni, but we find it difficult to quantitatively model the early excess with circumstellar interaction and cooling. Collision between the supernova ejecta and a binary companion is a possible source of this emission. We discuss the origin of the periodic variability in the light curve, including interaction of the SN ejecta with nested shells of circumstellar matter and neutron stars colliding with binary companions.

Keywords: transient sources; supernovae; core-collapse supernovae; type ic supernovae
Serendipitous Discovery of a Physical Binary Quasar at z = 1.76

Binary quasars are extremely rare objects, used to investigate clustering on very small scales at different redshifts. The cases where the two quasar components are gravitationally bound, known as physical binary quasars, can also exhibit enhanced astrophysical activity and therefore are of particular scientific interest. Here we present the serendipitous discovery of a physical pair of quasars with an angular separation of Δθ = (8.76 ± 0.11)″. The redshifts of the two quasars are consistent within the errors and measured as z = (1.76 ± 0.01). Under the motivated assumption that the pair does not arise from a single gravitationally lensed quasar, the resulting projected physical separation was estimated as (76 ± 1) kpc. For both targets we detected Si iv, C iv, C iii], and Mg ii emission lines. However, the two quasars show significantly different optical colors, one being among the most reddened quasars at z > 1.5 and the other with colors consistent with typical quasar colors at the same redshift. Therefore it is ruled out that the sources are a lensed system. This is our second serendipitous discovery of a pair of two quasars with different colors, having a separation ≲10″, which extends the catalog of known small-separation quasar pairs.

Keywords: double quasars; quasars; cosmology; redshifted
Ephemeris Refinement of the Exoplanet Candidate around the White Dwarf WD1856+534

The exoplanet candidate around the white dwarf WD 1856+534 is of special interest for exoplanet atmosphere characterization because of its very cool temperature and potentially large spectral signal in transmission spectroscopy. Here we present ground-based transit follow-up to verify the transit depth and refine the orbital ephemeris allowing for a more accurate scheduling of future transit observations. Our new ephemeris provides transit time predictions with an uncertainty of less than 30 s until the year 2030.

Keywords: exoplanet systems
Ensemble Variability Properties of Active Galactic Nuclei in the SDSS DR17

We present the results from a study of ∼9600 broadline-selected active galactic nuclei (AGNs) with host galaxies detected from the Sloan Digital Sky Survey (SDSS) Data Release 17. We compute ensemble variability statistics based on a comparison of the original SDSS photometric data with spectrophotometric measurements obtained days to decades later in the Sloan g, r, and i bands. Galaxy and AGN templates have been fitted to the SDSS spectra to isolate the AGN component from the host galaxy. The sources have absolute magnitudes in the range ‑24 < M i < ‑18 and lie at redshifts less than z ∼ 0.9. A variability analysis reveals that the anticorrelation between luminosity and variability amplitude continues down to log(Lbol [erg s‑1]) = 43.5, demonstrating that the relationship extends by 4 orders of magnitude in AGN luminosity. To further explore the connection between AGN luminosity and variability, we determine the black hole mass and the accretion rate through measurement of the Hβ line width and the monochromatic luminosity at rest frame 5100 Å. Our results suggest that the accretion rate is the dominant parameter impacting the amplitude of variability and that the anticorrelation between the accretion rate and amplitude extends to rates as low as 1% Eddington. Moreover, we also identify an anticorrelation between the variability amplitude and black hole mass, with the correlation appearing strongest among the AGNs with low accretion rates.

Keywords: active galactic nuclei; low-luminosity active galactic nuclei; supermassive black holes; principal component analysis; extragalactic astronomy; quasars; time domain astronomy; sloan photometry; multivariate analysis; seyfert galaxies
Spatiotemporal Energy Partitioning in a Nonthermally Dominated Two-loop Solar Flare

Solar flares show remarkable variety in the energy partitioning between thermal and nonthermal components. Those with a prominent nonthermal component but only a modest thermal one are particularly well suited for study of the direct effect of the nonthermal electrons on plasma heating. Here, we analyze such a well-observed, impulsive single-spike nonthermal event, a solar flare SOL2013-11-05T035054, where the plasma heating can be entirely attributed to the energy losses of these impulsively accelerated electrons. Evolution of the energy budget of thermal and nonthermal components during the flare is analyzed using X-ray, microwave, and EUV observations and three-dimensional modeling. The results suggest that (I) the flare geometry is consistent with a two-loop morphology and the magnetic energy is likely released due to interaction between these two loops; (II) the released magnetic energy is converted to the nonthermal energy of accelerated electrons only, which is subsequently converted to the thermal energy of the plasma; (III) the energy is partitioned in these two flaring loops in comparable amounts; (IV) one of these flaring loops remained relatively tenuous but rather hot, while the other remained relatively cool but denser than the first. Therefore, this solar flare demonstrates an extreme efficiency of conversion of the free magnetic energy to the nonthermal energy of particle acceleration and the flow of energy into two loops from the nonthermal component to the thermal one with negligible direct heating.

Keywords: solar flares; the sun; solar extreme ultraviolet emission; solar radio emission; solar x-ray emission