adsabs/SciX_UAT_keywords huggingface dataset:
ASASSN-14ko is a Periodic Nuclear Transient in ESO 253-G003

We present the discovery that ASASSN-14ko is a periodically flaring active galactic nucleus at the center of the galaxy ESO 253-G003. At the time of its discovery by the All-Sky Automated Survey for Supernovae (ASAS-SN), it was classified as a supernova close to the nucleus. The subsequent 6 yr of V- and g-band ASAS-SN observations revealed that ASASSN-14ko has nuclear flares occurring at regular intervals. The 17 observed outbursts show evidence of a decreasing period over time, with a mean period of P0 = 114.2 ± 0.4 days and a period derivative of $\dot{P}=-0.0017\pm 0.0003$ <!-- --> . The most recent outburst in 2020 May, which took place as predicted, exhibited spectroscopic changes during the rise and had a UV bright, blackbody spectral energy distribution similar to tidal disruption events (TDEs). The X-ray flux decreased by a factor of 4 at the beginning of the outburst and then returned to its quiescent flux after ∼8 days. The Transiting Exoplanet Survey Satellite observed an outburst during Sectors 4-6, revealing a rise time of 5.60 ± 0.05 days in the optical and a decline that is best fit with an exponential model. We discuss several possible scenarios to explain ASASSN-14ko's periodic outbursts, but currently favor a repeated partial TDE. The next outbursts should peak in the optical on UT 2020 September 7.4±1.1 and UT 2020 December 26.5±1.4.

Keywords: black hole physics; galaxies; seyfert galaxies; galaxy accretion disks
Dynamical Evolution of White Dwarfs in Triples in the Era of Gaia

The Gaia mission has detected many white dwarfs (WDs) in binary and triple configurations, and while observations suggest that triple-stellar systems are common in our Galaxy, not much attention was devoted to WDs in triples. For stability reasons, these triples must have hierarchical configurations, i.e., two stars are on a tight orbit (the inner binary), with the third companion on a wider orbit about the inner binary. In such a system, the two orbits torque each other via the eccentric Kozai-Lidov mechanism, which can alter the orbital configuration of the inner binary. We simulate thousands of triple-stellar systems for over 10 Gyr, tracking gravitational interactions, tides, general relativity, and stellar evolution up to their WD fate. As demonstrated here, three-body dynamics coupled with stellar evolution is a critical channel to form tight WD binaries or merge a WD binary. Among these triples, we explore their manifestations as cataclysmic variables, Type Ia supernovae, and gravitational-wave events. The simulated systems are then compared to a sample of WD triples selected from the Gaia catalog. We find that including the effect of mass-loss-induced kicks is crucial for producing a distribution of the inner binary-tertiary separations that is consistent with Gaia observations. Lastly, we leverage this consistency to estimate that, at minimum, 30% of solar-type stars in the local 200 pc were born in triples.

Keywords: astrodynamics; three-body problem; stellar evolution; theoretical models; white dwarf stars; binary stars; common envelope evolution; trinary stars; gravitational wave sources; cataclysmic variable stars
Studying Magnetic Fields and Dust in M17 Using Polarized Thermal Dust Emission Observed by SOFIA/HAWC+

We report on the highest spatial resolution measurement to date of magnetic fields (B-fields) in M17 using thermal dust polarization measurements taken by SOFIA/HAWC+ centered at a wavelength of 154 μm. Using the Davis-Chandrasekhar-Fermi method, in which the polarization angle dispersion calculated using the structure function technique is the quantity directly observed by SOFIA/HAWC+, we found the presence of strong B-fields of 980 ± 230 and 1665 ± 885 μG in the lower-density M17-N and higher-density M17-S regions, respectively. The B-field morphology in M17-N possibly mimics the fields in gravitationally collapsing molecular cores, while in M17-S the fields run perpendicular to the density structure. M17-S also displays a pillar feature and an asymmetric large-scale hourglass-shaped field. We use the mean B-field strengths to determine Alfvénic Mach numbers for both regions, finding that B-fields dominate over turbulence. We calculate the mass-to-flux ratio, λ, finding λ = 0.07 for M17-N and 0.28 for M17-S. These subcritical λ values are consistent with the lack of massive stars formed in M17. To study dust physics, we analyze the relationship between dust polarization fraction, p, emission intensity, I, gas column density, N(H2), polarization angle dispersion function, S, and dust temperature, T d. p decreases with intensity as I -α with α = 0.51. p tends to first increase with T d, but then decreases at higher T d. The latter feature, seen in M17-N at high T d when N(H2) and S decrease, is evidence of the radiative torque disruption effect.

Keywords: interstellar magnetic fields; astrophysical magnetism; magnetic fields; star forming regions; stellar winds; star formation; interstellar dust; interstellar dust processes
GalWeight Application: A Publicly Available Catalog of Dynamical Parameters of 1800 Galaxy Clusters from SDSS-DR13, (GalWCat19)

Utilizing the SDSS-DR13 spectroscopic data set, we create a new publicly available catalog of 1800 galaxy clusters (GalWeight cluster catalog, GalWCat19) and a corresponding catalog of 34,471 identified member galaxies. The clusters are identified from overdensities in redshift phase space. The GalWeight technique introduced by Abdullah et al. is then applied to identify cluster members. The completeness of the cluster catalog (GalWCat19) and the procedure followed to determine cluster mass are tested on the Bolshoi N-body simulations. The 1800 GalWCat19 clusters range in redshift between 0.01 and 0.2 and have masses in the range of (0.4-14) × 1014 h -1 M ⊙. The cluster catalog provides a large number of cluster parameters, including sky position, redshift, membership, velocity dispersion, and mass at overdensities Δ = 500, 200, 100, and 5.5. The 34,471 member galaxies are identified within the radius at which the density is 200 times the critical density of the universe. The galaxy catalog provides the coordinates of each galaxy and the ID of the cluster that the galaxy belongs to. The cluster velocity dispersion scales with mass as {log}({σ }200) = {log}(946+/- 52 {km} {{{s}}}-1) + (0.349 ± 0.142){log}≤ft[h(z){M}200/{10}15{M}⊙ \right], with a scatter of δ logσ = 0.06 ± 0.04. The catalogs are publicly available at https://mohamed-elhashash-94.webself.net/galwcat/.

Keywords: observational cosmology; galaxy clusters; galaxy dynamics; catalogs
External Enrichment of Mini Halos by the First Supernovae

Recent high-resolution simulations of early structure formation have shown that externally enriched halos may form some of the first metal-enriched stars. This study utilizes a 1 comoving Mpc3 high-resolution simulation to study the enrichment process of metal-enriched halos down to z = 9.3. Our simulation uniquely tracks the metals ejected from Population III stars, and we use this information to identify the origin of metals within metal-enriched halos. These halos show a wide range of metallicities, but we find that the source of metals for ≳50% of metal-enriched halos is supernova explosions of Population III stars occurring outside their virial radii. The results presented here indicate that external enrichment by metal-free stars dominates the enrichment process of halos with virial mass below 106 M⊙ down to z = 9.3. Despite the prevalence of external enrichment in low-mass halos, Population II stars forming due to external enrichment are rare because of the small contribution of low-mass halos to the global star formation rate combined with low metallicities toward the center of these halos resulting from metal ejecta from external sources mixing from the outside in. The enriched stars that do form through this process have absolute metallicities below 10-3 Z⊙. We also find that the fraction of externally enriched halos increases with time: ∼90% of halos that are externally enriched have Mvir < 106 M⊙, and that pair-instability supernovae contribute the most to the enrichment of the intergalactic medium as a whole and are thus are the predominant supernova type contributing to the external enrichment of halos.

Keywords: primordial galaxies
The Formation of Saturn's and Jupiter's Electron Radiation Belts by Magnetospheric Electric Fields

The existence of planetary radiation belts with relativistic electron components means that powerful acceleration mechanisms are operating within their volume. Mechanisms that bring charged particles planetward toward stronger magnetic fields can cause their heating. On the basis that electron fluxes in Saturn's radiation belts are enhanced over discrete energy intervals, previous studies have suggested that rapid inward plasma flows may be controlling the production of their most energetic electrons. However, rapid plasma inflows languish in the planet's inner magnetosphere, and they are not spatially appealing as a mechanism to form the belts. Here we show that slow, global-scale flows resulting from transient noon-to-midnight electric fields successfully explain the discretized flux spectra at quasi- and fully relativistic energies, and that they are ultimately responsible for the bulk of the highest energy electrons trapped at Saturn. This finding is surprising, given that plasma flows at Saturn are dominated by the planetary rotation; these weak electric field perturbations were previously considered impactful only over a very narrow electron energy range where the magnetic drifts of electrons cancel out with corotation. We also find quantitative evidence that ultrarelativistic electrons in Jupiter's radiation belts are accelerated by the same mechanism. Given that similar processes at Earth drive a less efficient electron transport compared to Saturn and Jupiter, the conclusion is emerging that global-scale electric fields can provide powerful relativistic electron acceleration, especially at strongly magnetized and fast-rotating astrophysical objects.

Keywords: planetary magnetospheres; solar system gas giant planets; jupiter; saturn
HSTPROMO Internal Proper-motion Kinematics of Dwarf Spheroidal Galaxies. I. Velocity Anisotropy and Dark Matter Cusp Slope of Draco

We analyze four epochs of Hubble Space Telescope imaging over 18 yr for the Draco dwarf spheroidal galaxy. We measure precise proper motions for hundreds of stars and combine these with existing line-of-sight (LOS) velocities. This provides the first radially resolved 3D velocity dispersion profiles for any dwarf galaxy. These constrain the intrinsic velocity anisotropy and resolve the mass–anisotropy degeneracy. We solve the Jeans equations in oblate axisymmetric geometry to infer the mass profile. We find the velocity dispersion to be radially anisotropic along the symmetry axis and tangentially anisotropic in the equatorial plane, with a globally averaged value , (where 1 – in 3D). The logarithmic dark matter (DM) density slope over the observed radial range, Γdark, is , consistent with the inner cusp predicted in ΛCDM cosmology. As expected given Draco's low mass and ancient star formation history, it does not appear to have been dissolved by baryonic processes. We rule out cores larger than 487, 717, and 942 pc at 1σ, 2σ, and 3σ confidence, respectively, thus imposing important constraints on the self-interacting DM cross section. Spherical models yield biased estimates for both the velocity anisotropy and the inferred slope. The circular velocity at our outermost data point (900 pc) is . We infer a dynamical distance of kpc and show that Draco has a modest LOS rotation, with . Our results provide a new stringent test of the so-called "cusp–core" problem that can be readily extended to other dwarfs.

Keywords: dark matter; dwarf spheroidal galaxies; astronomy data analysis; proper motions; stellar kinematics; stellar dynamics; galaxy dynamics; galaxy structure
Long-term Variability of Non-radial Pulsations in SXP 4.78

OGLE I-band observations for [M2002] SMC 20671, the optical counterpart of SXP 4.78, were searched for periodicities with P > 0.5 days. Three sets of photometric signals were detected, which are attributed to non-radial pulsations of the Be star. All signals show considerable variability in power over the 16 seasons studied. The most likely periods of the NRPs are 0.5826, 0.6164, and 0.6424 days.

Keywords: be stars; x-ray binary stars
A Diversity of Wave-driven Presupernova Outbursts

Many core-collapse supernova (SN) progenitors show indications of enhanced pre-SN mass loss and outbursts, some of which could be powered by wave energy transport within the progenitor star. Depending on the star's structure, convectively excited waves driven by late-stage nuclear burning can carry substantial energy from the core to the envelope, where the wave energy is dissipated as heat. We examine the process of wave energy transport in single-star SNe progenitors with masses between 11 and 50 M⊙. Using MESA stellar evolution simulations, we evolve stars until core collapse and calculate the wave power produced and transmitted to the stars' envelopes. These models improve upon prior efforts by incorporating a more realistic wave spectrum and nonlinear damping effects, reducing our wave-heating estimates by ∼1 order of magnitude compared to prior work. We find that waves excited during oxygen/neon burning typically transmit ∼1046-1047 erg of energy at 0.1-10 yr before core collapse in typical (M < 30 M⊙) SN progenitors. High-mass progenitors can often transmit ∼1047-1048 erg of energy during oxygen/neon burning, but this tends to occur later, at about 0.01-0.1 yr before core collapse. Pre-SN outbursts may be most pronounced in low-mass SN progenitors (M ≲ 12 M⊙) undergoing semidegenerate neon ignition and in high-mass progenitors (M ≳ 30 M⊙) exhibiting convective shell mergers.

Keywords: circumstellar matter; massive stars; stellar mass loss; stellar oscillations; supernovae
SIMPLE: Simple Intensity Map Producer for Line Emission

We present the Simple Intensity Map Producer for Line Emission (SIMPLE), a public code for quickly simulating mock line-intensity maps, and an analytical framework for modeling intensity maps including observational effects. SIMPLE can be applied to any spectral line sourced by galaxies. The SIMPLE code is based on lognormal mock catalogs of galaxies including positions and velocities and assigns luminosities following the luminosity function. After applying a selection function to distinguish between detected and undetected galaxies, the code generates an intensity map, which can be modified with anisotropic smoothing, noise, a mask, and sky subtraction, and it calculates the power spectrum multipoles. We show that the intensity auto-power spectrum and the galaxy-intensity cross-power spectrum agree well with the analytical estimates in real space. We derive and show that the sky subtraction suppresses the intensity autopower spectrum and the cross-power spectrum on scales larger than the size of an individual observation. As an example application, we make forecasts for the sensitivity of an intensity mapping experiment similar to the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX) to the cross-power spectrum of Lyα-emitting galaxies and the Lyα intensity. We predict that HETDEX will measure the galaxy-intensity cross-power spectrum with a high signal-to-noise ratio on scales of 0.04 h Mpc-1 < k < 1 h Mpc-1.

Keywords: observational cosmology; large-scale structure of the universe; lyman-alpha galaxies
The Implications of High Black Hole Spins for the Origin of Binary Black Hole Mergers

The LIGO-Virgo collaboration has reported 50 black hole-black hole (BH-BH) mergers and 8 candidates recovered from digging deeper into the detector noise. The majority of these mergers have low effective spins pointing toward low BH spins and efficient angular momentum (AM) transport in massive stars as proposed by several models (e.g., the Tayler-Spruit dynamo). However, out of these 58 mergers, 7 are consistent with having high effective-spin parameter (χ eff > 0.3). Additionally, two events seem to have high effective spins sourced from the spin of the primary (more massive) BH. These particular observations could be used to discriminate between the isolated binary and dynamical formation channels. It might seem that high BH spins point to a dynamical origin if AM in stars is efficient and forms low-spinning BHs. In such a case dynamical formation is required to produce second and third generations of BH-BH mergers with typically high spinning BHs. Here we show, however, that isolated binary BH-BH formation naturally reproduces such highly spinning BHs. Our models start with efficient AM in massive stars that is needed to reproduce the majority of BH-BH mergers with low effective spins. Later, some of the binaries are subject to a tidal spin-up allowing the formation of a moderate fraction (~10%) of BH-BH mergers with high effective spins (χ eff ≳ 0.4-0.5). In addition, isolated binary evolution can produce a small fraction of BH-BH mergers with almost maximally spinning primary BHs. Therefore, the formation scenario of these atypical BH-BH mergers remains to be found.

Keywords: black holes; compact objects; massive stars
Circumstellar Medium Constraints on the Environment of Two Nearby Type Ia Supernovae: SN 2017cbv and SN 2020nlb

We present deep Chandra X-ray observations of two nearby Type Ia supernovae, SN 2017cbv and SN 2020nlb, which reveal no X-ray emission down to a luminosity LX ≲ 5.3 × 1037 and ≲ 5.4 × 1037 erg s-1 (0.3-10 keV), respectively, at ~16-18 days after the explosion. With these limits, we constrain the pre-explosion mass-loss rate of the progenitor system to be $\dot{M}$ < 7.2 × 10-9 and < 9.7 × 10-9 M⊙ yr-1 for each (at a wind velocity vw = 100 km s-1 and a radius of R ≈ 1016 cm), assuming any X-ray emission would originate from inverse Compton emission from optical photons upscattered by the supernova shock. If the supernova environment was a constant-density medium, we would find a number density limit of nCSM < 36 and < 65 cm-3, respectively. These X-ray limits rule out all plausible symbiotic progenitor systems, as well as large swathes of parameter space associated with the single degenerate scenario, such as mass loss at the outer Lagrange point and accretion winds. We also present late-time optical spectroscopy of SN 2020nlb, and set strong limits on any swept up hydrogen (LHα < 2.7 × 1037 erg s-1) and helium (LHe,λ6678 < 2.7 × 1037 erg s-1) from a nondegenerate companion, corresponding to MH ≲ 0.7-2 × 10-3 M⊙ and MHe ≲ 4 × 10-3 M⊙. Radio observations of SN 2020nlb at 14.6 days after explosion also yield a non-detection, ruling out most plausible symbiotic progenitor systems. While we have doubled the sample of normal Type Ia supernovae with deep X-ray limits, more observations are needed to sample the full range of luminosities and subtypes of these explosions, and set statistical constraints on their circumbinary environments.

Keywords: type ia supernovae; circumstellar matter
Spectroscopic Study of Four Metal-poor Carbon Stars from the Hamburg/ESO Survey: On Confirming the Low-mass Nature of Their Companions

Elemental abundances of extrinsic carbon stars provide insight into the poorly understood origin and evolution of elements in the early Galaxy. In this work, we present the results of a detailed spectroscopic analysis of four potential carbon star candidates from the Hamburg/ESO Survey (HES): HE 0457-1805, HE 0920-0506, HE 1241-0337, and HE 1327-2116. This analysis is based on the high-resolution spectra obtained with Mercator/HERMES (R ~ 86,000) and SUBARU/HDS (R ~ 50,000). Although the abundances of a few elements, such as Fe, C, and O, are available from medium-resolution spectra, we present the first ever detailed high-resolution spectroscopic analysis for these objects. The objects HE 0457-1805 and HE 1241-0337 are found to be CEMP-s stars, HE 0920-0506 a CH star, and HE 1327-2116 a CEMP-r/s star. The object HE 0457-1805 is a confirmed binary, whereas the binary status of the other objects is unknown. The locations of program stars on the diagram of absolute carbon abundance A(C) versus [Fe/H] point at their binary nature. We have examined various elemental abundance ratios of the program stars and confirmed the low-mass nature of their former AGB companions. We have shown that the i-process models could successfully reproduce the observed abundance pattern in HE 1327-2116. The analysis performed for HE 0457-1805, HE 0920-0506, and HE 1241-0337 based on the FRUITY parametric models confirmed that the surface chemical compositions of these three objects are influenced by pollution from low-mass AGB companions. * Based on data collected using Mercator/HERMES, SUBARU/HDS.

Keywords: chemical abundances; chemically peculiar stars; carbon stars
Non-detection of Radio Pulsations in the High-mass X-Ray Binary V0332+53 During Quiescence

Following recent discoveries of ultra-long-period radio-loud neutron stars located beyond death line models in the pulsar period-period derivative diagram, we performed a radio pulsation search in the high-mass X-ray binary V0332+53 during quiescence. Although the period and magnetic field of the neutron star in this binary make it the most promising high-mass X-ray binary to explore for this purpose, the GBT observations do not reveal radio pulsations. Here, We present the duty-cycle-dependent flux density limits on the presence of any pulsations and briefly discuss its possible origins: the intrinsic absence or faintness of pulsations, the presence of low-level residual accretion, or eclipses and/or pulse scattering due to the presence of a massive binary companion.

Keywords: high mass x-ray binary stars; pulsars; radio pulsars; radio astronomy
AstroDLLC: Efficiently Reducing Storage and Transmission Costs for Massive Solar Observation Data via Deep Learning-based Lossless Compression

Effective data compression technology is essential for addressing data storage and transmission needs, especially given the escalating volume and complexity of data generated by contemporary astronomy. In this study, we propose utilizing deep learning-based lossless compression techniques to improve compression efficiency. We begin with a qualitative and quantitative analysis of the temporal and spatial redundancy in solar observation data. Based on this analysis, we introduce a novel deep learning-based framework called AstroDLLC for the lossless compression of astronomical solar images. AstroDLLC first segments high-resolution images into blocks to ensure that deep learning model training does not rely on high-computation power devices. It then addresses the non-normality of the partitioned data through simple reversible computational methods. Finally, it utilizes Bit-swap to train deep learning models that capture redundant features across multiple image frames, thereby enhancing compression efficiency. Comprehensive evaluations using data from the New Vacuum Solar Telescope reveal that AstroDLLC achieves a maximum compression ratio of 3.00 per image, surpassing Gzip, RICE, and other lossless technologies. The performance of AstroDLLC underscores its potential to address data compression challenges in astronomy.

Keywords: astronomical methods; astronomy software; astronomy data analysis; computational methods; gpu computing