adsabs/SciX_UAT_keywords huggingface dataset:
A Search for X-Ray/UV Correlation in the Reflection-dominated Seyfert 1 Galaxy Markarian 1044

Correlated variability between coronal X-rays and disk optical/UV photons provides a very useful diagnostic of the interplay between the different regions around an active galactic nucleus (AGN) and how they interact. AGNs that reveal strong X-ray reflection in their spectra should normally exhibit optical/UV to X-ray correlation consistent with reprocessing-whereas the optical/UV emission lags behind the X-rays. While such correlated delay has been seen in some sources, it has been absent in others. Mrk 1044 is one such source that has been known to reveal strong X-ray reflection in its spectra. In our analysis of three long XMM-Newton and several Swift observations of the source, we found no strong evidence for correlation between its UV and X-ray lightcurves both on short and long timescales. Among other plausible causes for the nondetection, we posit that higher X-ray variability rather than UV and strong general relativistic effects close to the black hole may also be responsible. We also present results from the spectral analysis based on XMM-Newton and NuSTAR observations, which show the strong soft X-ray excess and iron Kα line in the 0.3-50 keV spectrum that can be described by relativistic reflection.

Keywords: high energy astrophysics; seyfert galaxies; active galactic nuclei; x-ray active galactic nuclei
Constraining Screened Modified Gravity with Spaceborne Gravitational-wave Detectors

Screened modified gravity (SMG) is a unified theoretical framework that describes scalar-tensor gravity with a screening mechanism. Based on the gravitational-wave (GW) waveform derived in our previous work, in this article we investigate the potential constraints on SMG theory through GW observation by future spaceborne GW detectors, including the Laser Interferometer Space Antenna (LISA), TianQin, and Taiji. We find that, for the extreme-mass-ratio inspirals (EMRIs) consisting of a massive black hole and a neutron star, if the EMRIs are at the Virgo cluster, the GW signals can be detected by the detectors at quite high significance level, and the screened parameter ɛNS can be constrained at about ${ \mathcal O }({10}^{-5})$ , which is more than one order of magnitude tighter than the potential constraint given by a ground-based Einstein telescope. However, for the EMRIs consisting of a massive black hole and a white dwarf, it is more difficult to detect them than in the previous case. For the specific SMG models, including chameleon, symmetron, and dilaton, we find these constraints are complementary to that from the Cassini experiment, but weaker than those from lunar laser ranging observations and binary pulsars, due to the strong gravitational potentials on the surface of neutron stars. By analyzing the deviation of the GW waveform in SMG from that in general relativity, as anticipated, we find the dominant contribution of the SMG constraint comes from the correction terms in the GW phases, rather than the extra polarization modes or the correction terms in the GW amplitudes.

Keywords: gravitational waves; gravitational wave detectors; non-standard theories of gravity
MUSE Reveals Extended Circumnuclear Outflows in the Seyfert 1 NGC 7469

NGC 7469 is a well-known luminous infrared galaxy, with a circumnuclear star formation ring (∼830 pc radius) surrounding a Seyfert 1 active galactic nucleus (AGN). Nuclear unresolved winds were previously detected in X-rays and ultraviolet, as well as an extended biconical outflow in infrared coronal lines. We search for extended outflows by measuring the kinematics of the Hβ and [O III] λ5007 optical emission lines, in data of the Very Large Telescope/Multi-unit Spectroscopic Explorer integral field spectrograph. We find evidence of two outflow kinematic regimes: one slower regime extending across most of the star formation (SF) ring—possibly driven by the massive SF—and a faster regime (with a maximum velocity of -715 km s-1), only observed in [O III], in the western region between the AGN and the massive star-forming regions of the ring, likely AGN-driven. This work shows a case where combined AGN/SF feedback can be effectively spatially resolved, opening up a promising path toward a deeper understanding of feedback processes in the central kiloparsec of AGN.

Keywords: active galactic nuclei; galactic winds
Stellar Parameterization of LAMOST M Dwarf Stars

The M dwarf stars are the most common stars in the Galaxy, dominating the population of the Galaxy at faint magnitudes. Precise and accurate stellar parameters for M dwarfs are of crucial importance for many studies. However, the atmospheric parameters of M dwarf stars are difficult to determine. In this paper, we present a catalog of the spectroscopic stellar parameters (Teff and [M/H]) of ∼300,000 M dwarf stars observed by both LAMOST and Gaia using the Stellar LAbel Machine (SLAM). We train a SLAM model using LAMOST spectra with APOGEE Data Release 16 labels with 2800 K < Teff < 4500K and -2 dex < [M/H] < 0.5 dex. The SLAM Teff is in agreement to within ∼50 K compared to the previous study determined by APOGEE observations, and the SLAM [M/H] agrees within 0.12 dex compared to the APOGEE observation. We also set up a SLAM model trained by the BT-Settl atmospheric model with random uncertainties (in cross validation) to 60 K and agreeing within ∼90 K compared to previous studies.

Keywords: m dwarf stars; astronomy data analysis; low mass stars; catalogs
R-matrix Electron-impact Excitation Data for the H- and He-like Ions with Z = 6-30

Plasma models built on extensive atomic data are essential to interpreting observed cosmic spectra. H-like Lyman series and He-like triplets observable in the X-ray band are powerful diagnostic lines to measure the physical properties of various types of astrophysical plasmas. Electron-impact excitation is a fundamental atomic process for the formation of H-like and He-like key diagnostic lines. Electron-impact excitation data adopted by the widely used plasma codes (AtomDB, CHIANTI, and SPEX) do not necessarily agree with each other. Here we present a systematic calculation of electron-impact excitation data of H-like and He-like ions with the atomic number Z = 6-30 (i.e., C to Zn). A radiation-damped R-matrix intermediate-coupling frame transformation calculation was performed for each ion with configurations up to n = 6. We compare the present work with the above three plasma codes and the literature to assess the quality of the new data, which are relevant for current and future high-resolution X-ray spectrometers.

Keywords: atomic physics; x-ray astronomy; atomic spectroscopy
Frequency of Tidal Features Correlates with Age and Internal Structure of Early-type Galaxies

Previous studies suggest that compact young early-type galaxies (ETGs) were formed by recent mergers. However, it has not yet been revealed whether tidal features that are direct evidence of recent mergers are detected frequently around compact young ETGs. Here, we investigate how the fraction of ETGs having tidal features (fT) depends on age and internal structure (compactness, color gradient, and dust lanes) of ETGs, using 650 ETGs with Mr ≤ -19.5 in 0.015 ≤ z ≤ 0.055 that are in deep coadded images of the Stripe 82 region of the Sloan Digital Sky Survey. We find that tidal features are more frequent in younger ETGs and more compact ETGs, so that compact young ETGs with ages ≲6 Gyr have high fT of ∼0.7 compared to their less compact or old counterparts with ages ≳ 9 Gyr that have fT ≲ 0.1. Among compact young ETGs, those with blue cores have ∼3 times higher fT than those with red cores. In addition, ETGs with dust lanes have ∼4 times higher fT than those without dust lanes. Our results provide direct evidence that compact young ETGs especially with blue cores and ETGs with dust lanes are involved in recent mergers. Based on our results and several additional assumptions, we roughly estimate the typical visible time of tidal features after a merger, which is ∼3 Gyr in the depth of the Stripe 82 coadded images.

Keywords: early-type galaxies; galaxy mergers; tidal tails; galaxy structure; galaxy properties; galaxy ages; galaxy colors
The ExoTETHyS Package: Tools for Exoplanetary Transits around Host Stars

We present here the first release of the open-source python package ExoTETHyS (stable: https://zenodo.org/badge/latestdoi/169268509, development version: https://github.com/ucl-exoplanets/ExoTETHyS/), which aims to provide a stand-alone set of tools for modeling spectrophotometric observations of transiting exoplanets. In particular, we describe: (1) a new calculator of stellar limb-darkening coefficients that outperforms the existing software by one order of magnitude in terms of light-curve model accuracy, i.e., down to <10 parts per million, and (2) an exact transit light-curve generator based on the entire stellar intensity profile rather than limb-darkening coefficients. New tools will be added in later releases to model various effects in exoplanetary transits and eclipsing binaries. ExoTETHyS is a reference package for high-precision exoplanet atmospheric spectroscopy with the upcoming James Webb Space Telescope and Atmospheric Remote-sensing Infrared Exoplanet Large-survey missions.

Keywords: observational astronomy; spectroscopy; high time resolution astrophysics; exoplanet atmospheres; stellar atmospheres; transit photometry; eclipsing binary stars; exoplanet systems; stellar astronomy; limb darkening
The Atacama Cosmology Telescope: Systematic Transient Search of 3 Day Maps

We conduct a systematic search for transients in 3 yr of data (2017-2019) from the Atacama Cosmology Telescope (ACT). ACT covers 40% of the sky at three bands spanning from 77-277 GHz. Analysis of 3 day mean-subtracted sky maps, which were match filtered for point sources, yielded 29 transient detections. Eight of these transients are due to known asteroids, and three others were previously published. Four of these events occur in areas with poor noise models and thus we cannot be confident they are real transients. We are left with 14 new transient events occurring at 11 unique locations. All of these events are associated with either rotationally variable stars or cool stars. Ten events have flat or falling spectra indicating radiation from synchrotron emission. One event has a rising spectrum indicating a different engine for the flare.

Keywords: transient sources; stellar flares; cosmic microwave background radiation; asteroids
The DECam Local Volume Exploration Survey Data Release 2

We present the second public data release (DR2) from the DECam Local Volume Exploration survey (DELVE). DELVE DR2 combines new DECam observations with archival DECam data from the Dark Energy Survey, the DECam Legacy Survey, and other DECam community programs. DELVE DR2 consists of ~160,000 exposures that cover >21,000 deg2 of the high-Galactic-latitude (∣b∣ > 10°) sky in four broadband optical/near-infrared filters (g, r, i, z). DELVE DR2 provides point-source and automatic aperture photometry for ~2.5 billion astronomical sources with a median 5σ point-source depth of g = 24.3, r = 23.9, i = 23.5, and z = 22.8 mag. A region of ~17,000 deg2 has been imaged in all four filters, providing four-band photometric measurements for ~618 million astronomical sources. DELVE DR2 covers more than 4 times the area of the previous DELVE data release and contains roughly 5 times as many astronomical objects. DELVE DR2 is publicly available via the NOIRLab Astro Data Lab science platform.

Keywords: catalogs; surveys; local group
NICER View of the 2020 Burst Storm and Persistent Emission of SGR 1935+2154

We report on NICER observations of the magnetar SGR 1935+2154, covering its 2020 burst storm and long-term persistent emission evolution up to ∼90 days postoutburst. During the first 1120 s taken on April 28 00:40:58 UTC, we detect over 217 bursts, corresponding to a burst rate of >0.2 bursts s-1. Three hours later, the rate was 0.008 bursts s-1, remaining at a comparatively low level thereafter. The T90 burst duration distribution peaks at 840 ms; the distribution of waiting times to the next burst is fit with a lognormal with an average of 2.1 s. The 1-10 keV burst spectra are well fit by a blackbody, with an average temperature and area of kT = 1.7 keV and R2 = 53 km2. The differential burst fluence distribution over ∼3 orders of magnitude is well modeled with a power-law form dN/dF ∝ F-1.5±0.1. The source persistent emission pulse profile is double-peaked hours after the burst storm. We find that the burst peak arrival times follow a uniform distribution in pulse phase, though the fast radio burst associated with the source aligns in phase with the brighter peak. We measure the source spin-down from heavy-cadence observations covering days 21-39 postoutburst, $\dot{\nu }=-3.72(3)\times {10}^{-12}$ Hz s-1, a factor of 2.7 larger than the value measured after the 2014 outburst. Finally, the persistent emission flux and blackbody temperature decrease rapidly in the early stages of the outburst, reaching quiescence 40 days later, while the size of the emitting area remains unchanged.

Keywords: neutron stars; magnetars; soft gamma-ray repeaters
Intergalactic Heating by Lyα Photons Including Hyperfine Structure Corrections

Lyα photons from the first radiating sources in the universe play a pivotal role in 21 cm radio detections of Cosmic Dawn and the Epoch of Reionization. Comments are provided on the effect of the hyperfine structure of hydrogen on the rate of heating or cooling of the Intergalactic Medium by Lyα photons.

Keywords: cosmology
Massive Young Stellar Objects in the Galactic Center. II. Seeing Through the Ice-rich Envelopes

To study the demographics of interstellar ices in the Central Molecular Zone (CMZ) of the Milky Way, we obtain near-infrared spectra of 109 red point sources using NASA IRTF/SpeX at Maunakea. We select the sample from near- and mid-infrared photometry, including 12 objects in the previous paper of this series, to ensure that these sources trace a large amount of absorption through clouds in each line of sight. We find that most of the sample (100 objects) show CO band-head absorption at 2.3 μm, tagging them as red (super-) giants. Despite the photospheric signature, however, a fraction of the sample with L-band spectra (9/82 = 0.11) exhibit large H2O ice column densities (N > 2 × 1018 cm-2), and six of them also reveal CH3OH ice absorption. As one of such objects is identified as a young stellar object (YSO) in our previous work, these ice-rich sight lines are likely associated with background stars in projection to an extended envelope of a YSO or a dense cloud core. The low frequency of such objects in the early stage of stellar evolution implies a low star-formation rate (≲0.02 M ⊙ yr-1), reinforcing the previous claim on the suppressed star-formation activity in the CMZ. Our data also indicate that the strong "shoulder" CO2 ice absorption at 15.4 μm observed in YSO candidates in the previous paper arises from CH3OH-rich ice grains having a large CO2 concentration [N(CO2)/N(CH3OH) ≈ 1/3].

Keywords: astrochemistry; galactic center; interstellar abundances; protostars; ice formation; young stellar objects
Evolution, Structure, and Topology of Self-generated Turbulent Reconnection Layers

We present a 3D MHD simulation of two merging flux ropes exhibiting self-generated and self-sustaining turbulent reconnection (SGTR) that is fully 3D and fast. The exploration of SGTR is crucial for understanding the relationship between MHD turbulence and magnetic reconnection in astrophysical contexts including the solar corona. We investigate the pathway toward SGTR and apply novel tools to analyze the structure and topology of the reconnection layer. The simulation proceeds from 2.5D Sweet-Parker reconnection to 2.5D nonlinear tearing, followed by a dynamic transition to a final SGTR phase that is globally quasi-stationary. The transition phase is dominated by a kink instability of a large "cat-eye" flux rope and the proliferation of a broad stochastic layer. The reconnection layer has two general characteristic thickness scales, which correlate with the reconnection rate and differ by a factor of approximately six: an inner scale corresponding with current and vorticity densities, turbulent fluctuations, and outflow jets, and an outer scale associated with field line stochasticity. The effective thickness of the reconnection layer is the inner scale of the effective reconnection electric field produced by turbulent fluctuations, not the stochastic thickness. The dynamics within the reconnection layer are closely linked with flux rope structures that are highly topologically complicated. Explorations of the flux rope structures and distinctive intermediate regions between the inner core and stochastic separatrices ("SGTR wings") are potentially key to understanding SGTR. The study concludes with a discussion on the apparent dualism between plasmoid-mediated and stochastic perspectives on SGTR.

Keywords: solar magnetic reconnection; space plasmas; magnetic fields; magnetohydrodynamical simulations; magnetohydrodynamics; solar corona; solar coronal heating; solar magnetic fields; astrophysical fluid dynamics; solar flares
Dynamical Analysis of the Maclaurin Disk with Velocity Dispersion and Its Influence on the Formation of the Bar

We investigate the influence of Toomre's Q parameter on the bar-forming dynamics of the Maclaurin disk using N-body simulations. According to Toomre's criterion, the local velocity dispersion parametrized by Q ≥ 1 is required to suppress the local axisymmetric instability but, in turn, it deviates particle orbits from a nearly circular limit in which particle natural frequencies are calculated. We resolve this by including the effect of velocity dispersion, as the pressure potential, into the effective potential with the gravitational potential. With this formulation, a circular orbit approximation is retrieved. The effective potential hypothesis can describe the Q dependence of angular and epicyclic motions of the processes of the formation of a bar and the established bars reasonably well provided that Q ≥ 1. This indicates the influence of the initial Q imprinted on the entire disk dynamics and not only that Q serves as the indicator of stability. In addition, we perform a stability test for the disk-in-halo systems. With the presence of a halo, disks are more susceptible to the formation of a bar as seen by the elevated critical Q than that for the isolated disk. This is attributed to the differential rotation that builds the unstable non-axisymmetric spiral modes more efficiently, which are the ingredients of the bar instability.

Keywords: galaxy dynamics; galaxy bars; n-body simulations
Close Binary Stars Modeled by Two Prolate Ellipsoids in Synchronous Rotation

The presence of tidal deformations in close binary stars has already been confirmed by astronomical observations. The present paper aims to simply address an astronomy problem, studying the relative movement of close binaries disturbed by their mutual deformation through some basic concepts and tools of celestial mechanics. For this purpose, the tidal effect is modeled by considering that each star is an elongated revolution ellipsoid in such a way that axes of revolution are coincident, and their largest axes point toward each other along the motion. The potential for mutual attraction is then obtained, resulting in a perturbed Keplerian system with perturbation proportional to the inverse of the cubic distance between the stars, thus being a one-degree-of-freedom problem and, therefore, integrable. The effective potential, the integrals of energy and angular momentum, and the Laplace vector are used to obtain qualitative information about the dynamics before integrating it. The motion describes a rosette-like orbit with periodic osculating elements, or a circle when the energy is a local minimum. Finally, an analytical solution is presented in terms of elliptic functions by using a regularizing and linearizing function.

Keywords: binary stars; celestial mechanics; analytical mathematics
Sympathetic Standard and Blowout Coronal Jets Observed in a Polar Coronal Hole

We present the sympathetic eruption of a standard and a blowout coronal jet originating from two adjacent coronal bright points (CBP1 and CBP2) in a polar coronal hole, using soft X-ray and extreme-ultraviolet observations respectively taken by the Hinode and the Solar Dynamics Observatory. In the event, a collimated jet with obvious westward lateral motion first launched from CBP1, during which a small bright point appeared around CBP1's east end, and magnetic flux cancellation was observed within the eruption source region. Based on these characteristics, we interpret the observed jet as a standard jet associated with photospheric magnetic flux cancellation. About 15 minutes later, the westward-moving jet spire interacted with CBP2 and resulted in magnetic reconnection between them, which caused the formation of the second jet above CBP2 and the appearance of a bright loop system in between the two CBPs. In addition, we observed the writhing, kinking, and violent eruption of a small kink structure close to CBP2's west end but inside the jet base, which made the second jet brighter and broader than the first one. These features suggest that the second jet should be a blowout jet triggered by the magnetic reconnection between CBP2 and the spire of the first jet. We conclude that the two successive jets were physically connected to each other rather than a temporal coincidence, and this observation also suggests that coronal jets can be triggered by external eruptions or disturbances, as well as internal magnetic activities or magnetohydrodynamic instabilities.

Keywords: solar x-ray emission; solar flares; solar corona
COLDz: A High Space Density of Massive Dusty Starburst Galaxies ∼1 Billion Years after the Big Bang

We report the detection of CO(J = 2 → 1) emission from three massive dusty starburst galaxies at z > 5 through molecular line scans in the NSF's Karl G. Jansky Very Large Array (VLA) CO Luminosity Density at High Redshift (COLDz) survey. Redshifts for two of the sources, HDF 850.1 (z = 5.183) and AzTEC-3 (z = 5.298), were previously known. We revise a previous redshift estimate for the third source GN10 (z = 5.303), which we have independently confirmed through detections of CO J = 1 → 0, 5 → 4, 6 → 5, and [C II] 158 μm emission with the VLA and the NOrthern Extended Milllimeter Array. We find that two currently independently confirmed CO sources in COLDz are "optically dark", and that three of them are dust-obscured galaxies at z > 5. Given our survey area of ∼60 arcmin2, our results appear to imply a ∼6-55 times higher space density of such distant dusty systems within the first billion years after the Big Bang than previously thought. At least two of these z > 5 galaxies show star formation rate surface densities consistent with so-called "maximum" starbursts, but we find significant differences in CO excitation between them. This result may suggest that different fractions of the massive gas reservoirs are located in the dense, star-forming nuclear regions—consistent with the more extended sizes of the [C II] emission compared to the dust continuum and higher [C II]-to-far-infrared luminosity ratios in those galaxies with lower gas excitation. We thus find substantial variations in the conditions for star formation between z > 5 dusty starbursts, which typically have dust temperatures that are ∼57% ± 25% warmer than starbursts at z = 2-3 due to their enhanced star formation activity.

Keywords: active galaxies; galaxy evolution; starburst galaxies; high-redshift galaxies; infrared excess galaxies; observational cosmology; interstellar line emission; submillimeter astronomy; millimeter astronomy