Sazuna/UAT_keywords huggingface dataset:
A Closer Look at the Origin of LINER Emission in Later-type Galaxies and Its Connection to Evolved Stars with a Machine Learning Classification Scheme. Identifying the dominant ionizing sources in galaxies is essential for understanding their formation and evolution. Traditionally, spectra are classified based on their dominant ionizing source using strong emission lines and Baldwin, Phillips, &amp; Terlevich (BPT) diagrams. The ionizing source is traditionally determined by the emission line ratios using the BPT diagrams. Low-ionization nuclear emission-line regions (LINERs) are a class of ionizing mechanisms that is observationally identified but with a poorly understood origin, unlike the case of star-forming regions and active galactic nuclei (AGN). LINERs, typically found in early-type galaxies, are often associated with low-luminosity AGN activity but may also be powered by aging stellar populations, particularly post-asymptotic giant branch (p-AGB) stars. In this study, we employ a machine-learning-based encoder, SPENDER, to analyze the full MaNGA integral field unit spectra and identify key spectral features of LINERs. By examining the continuum and line emission of these spaxels, our approach aims to uncover hidden patterns and better understand the dominant ionizing sources. We show in this work that the neural-network-based encoder was able identify LINER sources from the stellar continuum alone. The characteristics of the stellar population underlying LINER regions are consistent with evolved low-mass stars, implying that the source driving LINER emission is probably p-AGB stars rather than AGN activity.

Keywords: LINER galaxies, Galaxy classification systems, Emission line galaxies
μ-GLANCE: A Novel Technique to Detect Chromatically and Achromatically Lensed Gravitational-wave Signals. Gravitational microlensing in the wave-optics (WO) regime occurs when the Schwarzschild radius of a lensing object is comparable to or smaller than the wavelength of incoming gravitational waves (GWs), producing chromatic amplitude and phase modulations. In contrast, geometric-optics effects happen when wavelength is much smaller than the lensing object, leading to frequency-independent amplifications and phase shifts. GWs can undergo both effects of lensing owing to interactions with objects of different scales. To detect and characterize the WO features from a lensed GW, we have developed a novel method, μ-GLANCE (Micro-Gravitational Lensing Authenticator using Non-modeled Cross-correlation Exploration). In this technique, we calculate the cross-correlation between the residuals from different detectors. We assign a false-alarm rate to each potential WO microlensed candidate from a statistical viewpoint, depending on how many times the noise cross-correlation matches the strength of the residual cross-correlation of the candidate over a certain period of time. We show that for an event with a matched-filtering signal-to-noise ratio close to 30, a residual due to WO lensing with an amplitude about 10% of magnification μ ≈ 3.2 will start to show deviation from the noise distribution at more than a 68% confidence interval with the LIGO-Virgo-KAGRA sensitivity for the fourth observation run. This method provides the first technique to detect geometric-optics and WO effects from a WO microlensed GW without assuming any specific lensing model, and its application to the current and future GW data can identify events with both chromatic and achromatic lensed scenarios.

Keywords: Gravitational microlensing, Gravitational lensing, Gravitational waves
Constraining Extra Mixing During the Main Sequence: Whatever Depletes Lithium Does Not Touch Beryllium. Measurements of lithium (Li) abundances in solar-type stars have shown that standard models of stellar evolution are incapable of explaining the observed depletion as a function of stellar age. Beryllium (Be) is one of the lightest elements that can be measured in stellar photospheres and can be burned at relatively low temperatures. Studying its abundances as a function of stellar age can provide important constraints to stellar mixing models because the level of depletion as a function of time will indicate how deep the photospheric material must be dredged to explain the observed abundances. In an effort to provide the most stringent constraints for nonstandard stellar mixing models, we observed a sample of solar twins and concomitantly analyzed their Li and Be abundances. Unlike what is typically observed for Li, we found that Be does not decrease as a function of stellar age along the main sequence, constraining models that predict the burning of both materials. Based on our data, models that invoke convective overshoot and convective settling are preferred over typical rotationally induced mixing models, as the later burn Be in excess while the former do not. Previous works also proposed mixing due to gravity waves as a possible explanation for observed abundances, which can fit our data as well. Furthermore, based on our solar twins, Be depletion likely happens within the first ∼1 Gyr. We also confirm previous findings of an increase in Be abundance as a function of metallicity, indicative of galactic production via cosmic-ray spallation. *Based on observations collected at the European Southern Observatory under ESO programme 111.24VX.

Keywords: High resolution spectroscopy, Solar atmosphere, Solar analogs, Stellar abundances, Stellar evolution
Gas Transfer between the Inner 3 kpc Disk and the Galactic Central Molecular Zone. We uncovered a more tilted molecular gas structure with highly negative velocities located near the dust lane. Our observations show that the approaching gas flows from the overshoot process are captured by the gravitational potential of the bar and then flow toward the Galactic central molecular zone (CMZ) through the bar channel. The recycled gas from the overshoot effect, in conjunction with freshly accreted gas from the inner 3 kpc disk, accumulates significantly near the   and   regions by adopting a bar length of ∼3.2–3.4 kpc. Importantly, within these regions, there are frequent collisions and substantial angular momentum exchanges between gas flows with different trajectories. In this scenario, the dissipation processes arising from interactions between colliding flows, together with the varying torques induced by the nonaxisymmetric bar, effectively transfer the angular momentum of viscous gas outward, thereby driving the molecular gas to settle into the CMZ within about three orbital periods. A long-term gas inflow with an average rate of ≳1.1 M⊙ yr‑1, coupled with intense transient accretion events that exceed the average rate by several times due to the overshoot effect, significantly regulates the gas distribution, physical properties, and dynamical evolution of the CMZ. These new findings provide robust observational evidence for elucidating the intricate dynamics of molecular gas flows toward the CMZ. Our observations suggest that gas dynamics have a significant impact on the secular evolution of both the Milky Way and the extragalactic gas-rich galaxies.

Keywords: Galaxy structure, Milky Way dynamics, Molecular clouds, Galaxy kinematics, Interstellar medium, Milky Way Galaxy
Jet-mode Feedback in NGC 5972: Insights from Resolved MUSE, GMRT, and VLA Observations. NGC 5972, a Voorwerp galaxy, features a helical-shaped extended emission-line region (EELR) with a radius &gt;10 kpc and an S-shaped radio structure spanning about 470 kpc. We use the Very Large Telescope, Multi Unit Spectroscopic Explorer, Giant Metrewave Radio Telescope, and Very Large Array (VLA) to study the stellar and ionized gas kinematics and how the radio jet influences the gas in the galaxy. Our sensitive radio observations detect the southern jet for the first time, roughly coinciding with the southern EELR. The VLA images show a continuous inner jet connected to the outer east─west lobe, confirming the jet origin of the radio emission. Our kinematic analysis shows spatial correlations between the radio jet and the outflowing gas, supporting the jet-driven feedback mechanism. More interestingly, we observe enhanced velocity dispersion in the perpendicular direction along with a shell-like structure. Our Baldwin─Phillips─Telervich analysis shows that the [O III] emission overlapping with the radio jet is consistent with the shock+precursor model, whereas in the perpendicular region, a pure shock model fits well with the observations, indicating jet-induced shocks. Radio observations indicate episodic AGN activity characterized by surface brightness and spectral index discontinuities. Overall, based on our findings, we propose a jet-driven feedback mechanism as one of the key factors in the formation of the EELR in NGC 5972. Future high-resolution radio observations will be crucial to further investigate the origin of the EELR and quantify the extent to which the jet influences its formation and evolution.

Keywords: AGN host galaxies, High resolution spectroscopy, Radio jets
Improving Pulsar Timing Precision with Single Pulse Fluence Clustering. Traditional pulsar timing techniques involve averaging large numbers of single pulses to obtain a high signal-to-noise ratio (S/N) profile, which is cross-correlated with a template to measure a time of arrival (TOA). However, the morphology of individual single pulses varies greatly due to pulse jitter, and pulses of different fluence contribute differently to the S/N of the pulse average. Our study proposes a method that accounts for these variations by identifying a range of "states" and timing each separately. We selected two 1 hr observations of PSR J2145‑0750, each in a different frequency band, with the Green Bank Telescope. We normalized the pulse amplitudes using the dynamic spectrum to account for scintillation effects and probed different excision algorithms to reduce radio-frequency interference. We then measured four pulse parameters (amplitude, position, width, and energy) to classify the single pulses using automated clustering algorithms. For each cluster, we calculated an average pulse profile and template and used both to obtain a TOA and TOA error. Finally, we computed the weighted average TOA and TOA error, the latter as a metric of the total timing precision for the epoch. The TOA is shifted relative to the one obtained without clustering, and we can estimate the shift with this weighting using the same data. For the 820 and 1400 MHz bands, we obtained TOA uncertainties of 0.057 and 0.46 μs, compared to 0.066 and 0.74 μs when no clustering is applied. We conclude that tailoring this method could help improve the timing precision for certain bright pulsars in NANOGrav's data set.

Keywords: Pulsar timing method, Millisecond pulsars, Gravitational waves, Compact objects, Radio astronomy
Thirty-two New Bright ZZ Ceti Stars from TESS: Adding Cycles 4 and 5. Analyzing all 120 s and 20 s light curves obtained by the TESS satellite up to Sector 69—the end of the fifth year of observations—for all known white dwarfs and white dwarf candidates up to G = 17.5 mag, we report the discovery of 32 new pulsating DA white dwarf stars. For all objects, we obtained the period spectra and performed a seismological analysis using full evolutionary models to estimate the structural parameters, such as effective temperature, stellar mass, and hydrogen envelope mass. The median stellar mass for the pulsators from asteroseismology is 0.609 M⊙, in agreement with the median value of photometric and spectroscopic determinations, 0.602 M⊙, excluding the low and extremely low mass objects. Finally, we found rotational-splitting multiplets for nine stars, which led to rotation periods between 4 hr and 1 day.

Keywords: Surveys, Stellar oscillations, White dwarf stars
Reversals of Toroidal Magnetic Field in Local Shearing Box Simulations of Accretion Disk with a Hot Corona. The presence of a hot corona above the accretion disk can have important consequences for the evolution of magnetic fields and the Shakura–Sunyaev viscosity parameter α in such a strongly coupled system. In this work, we have performed three-dimensional magnetohydrodynamical shearing-box numerical simulations of an accretion disk with a hot corona above the cool disk. Such a two-layer, piecewise isothermal system is vertically stratified under linear gravity, and initial conditions here include a strong azimuthal magnetic field with a ratio between the thermal and magnetic pressures being of order unity in the disk region. Instabilities in this magnetized system lead to the generation of turbulence, which, in turn, governs the further evolution of magnetic fields in a self-sustaining manner. Remarkably, the mean toroidal magnetic field undergoes a complete reversal in time by changing its sign, and it is predominantly confined within the disk. This is a rather unique class of evolution of the magnetic field that has not been reported earlier. Solutions of mean magnetic fields here are thus qualitatively different from the vertically migrating dynamo waves that are commonly seen in previous works, which model a single layer of an isothermal gas. Effective α is found to have values between 0.01 and 0.03. We have also make a comparison between models with Smagorinsky and explicit schemes for the kinematic viscosity (ν). In some cases with an explicit ν, we find a burst-like temporal behavior in α.

Keywords: Stellar accretion disks, Magnetic fields, Compact objects
Spatially Resolved Kinematics of Post-starburst Galaxies. Star-forming galaxies can reach quiescence via rapid transition through merger-triggered starbursts that consequently affect both their kinematics and star formation rates. In this work, we analyze the spatially resolved kinematics of 89 post-starburst galaxies (PSBs) with data from the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey and place them in context with star-forming galaxies (SFGs) and early-type galaxies (ETGs) to study the impact of merger history on galaxy kinematics. We measure the specific angular momentum to characterize them as slow or fast rotators. We find that the MaNGA PSB sample has ~6% slow rotators, which is less than the ~14% slow rotators in the ATLAS3D ETG sample and ~20% slow rotators in the MaNGA ETGs, and more than the ~3.5% slow rotators in the MaNGA SFGs. This implies that for PSBs to evolve into ETGs, they must still lose some angular momentum. While ETGs with higher stellar mass tend to be slow rotators, PSBs do not follow this trend. We find significant correlations between specific angular momentum and mass-weighted age for the SFG and ETG samples, but do not see any significant trends within the short PSB phase. These results indicate that significant evolution in angular momentum must continue to take place as the galaxy ages after the PSB phase. For PSBs to evolve directly into ETGs, they must undergo dry mergers to shed excess angular momentum without causing further epochs of star formation.

Keywords: E+A galaxies, Galaxy kinematics, Galaxy evolution, Galaxy quenching, Post-starburst galaxies
The Spin Measurement of the Black Hole SLX 1746-331 Using Insight-HXMT Observations. We present an X-ray spectral analysis of a black hole X-ray binary, SLX 1746-331, during the 2023 outburst using five Insight-HXMT observations. We jointly use the reflection model relxillcp and the general relativistic thermal thin disk model kerrbb to fit the spectra from 2 to 100 keV. By jointly fitting the five spectra, we constrain the black hole mass to be M = 5.8 ± 0.3M⊙ and the dimensionless spin parameter to be   (90% statistical confidence). The reflection model shows that SLX 1746-331 is a high-inclination system with the inclination angle  , and the accretion disk has a density  . In addition, with the different reflection model relxilllp, which assumes a lamppost geometry corona, we still obtain similar results.

Keywords: Stellar accretion disks, Black hole physics, X-ray binary stars
Detecting the 21 cm Signal from the Cosmic Dark Ages. The cosmic "dark ages" is the period between the last scattering of the cosmic microwave background and the appearance of the first luminous sources, spanning redshifts 1100 ≳ z ≳ 30. The only way to observe this period is by examining the 21 cm hyperfine transition line of neutral hydrogen H I, which—given the high redshifts (and hence long wavelengths)—must be observed from outside Earth's ionosphere. Given the faintness of the signal, concepts for a radio array on the lunar far side (where large collecting areas can be deployed and radio frequency interference is minimal) have been proposed, like FarView or FARSIDE, but designs are still in the preliminary stages. This paper studies multiple aspects of array design to determine the impact of different design decisions on sensitivity to the dark ages 21 cm power spectrum. We do so by using the sensitivity package 21cmSense to model and simulate various array configurations. We present a fiducial design based on a modification of the FarView concept, which consists of a collecting area of ∼2.5 km2 with 82,944 tightly packed dual-polarization dipoles grouped into 5184 correlated elements, or subarrays, delivering a &gt;10σ detection of the z = 30 signal with a 5 yr lifetime. We find that, beyond mere collecting area, the most important factor in achieving this sensitivity is the presence of very short baselines that can only be realized with small, closely packed antennas.

Keywords: Cosmology, Observational cosmology, Radio astronomy
StAGE: Stellar Archaeology-driven Galaxy Evolution. We build a semiempirical framework of galaxy evolution (dubbed StAGE) firmly grounded on stellar archaeology. The latter provides data-driven prescriptions that, on a population statistical ground, allow us to define the age and the star formation history for the progenitors of quiescent galaxies (QGs). We exploit StAGE to compute the cosmic star formation rate (SFR) density contributed by the progenitors of local QGs, and show it to remarkably agree with that estimated for high-z dusty star-forming galaxies which are faint/dark in the near-infrared (NIR), so pointing toward a direct progenitor-descendant connection among these galaxy populations. Furthermore, we argue that by appropriately correcting the observed stellar mass density by the contribution of such NIR-dark progenitors, StAGE recovers a SFR density which is consistent with direct determinations from UV/IR/radio surveys, so substantially alleviating a longstanding tension. Relatedly, we also show how StAGE can provide the average mass and metal assembly history of QGs, and their redshift-dependent statistics. Focusing on the supermassive black holes (BHs) hosted by massive QGs, we exploit StAGE to reconstruct the average BH mass assembly history, the cosmic BH accretion rate density as a function of redshift, and the evolution of the Magorrian-like relationship between the relic stellar and BH masses. All in all, StAGE may constitute a valuable tool to understand via a data-driven, easily expandable, and computationally low-cost approach the coevolution of QGs and of their hosted supermassive BHs across cosmic times.

Keywords: Galaxy evolution, Stellar evolution
Discovery of a New Flaring Class in GRS 1915+105 Using AstroSat. The highly variable black hole X-ray binary GRS 1915+105 has shown many flaring classes when the source oscillates between the high soft state (HS) and the hard intermediate state with a transition time of less than 10 s. The X-ray flux is anticorrelated with the hardness ratio (HR2) during these X-ray flaring classes. We have analyzed Astrosat/Large Area X-ray Proportional Counter and Soft X-ray Telescope data and report here a new X-ray flaring class named η class when the source oscillates between two HS states (the power-law index is always greater than 4) with transition time around 50 s. The X-ray flux is correlated with the hardness ratio. This class is quasi-regular, and we have detected high-frequency quasiperiodic oscillations around 70 Hz during this new flaring class. The accretion rate changes by a factor of 3 over the burst cycle. We report here the results of our extensive study of spectral and timing characteristics of this new class.

Keywords: X-ray astronomy, Black hole physics, X-ray observatories, High energy astrophysics
High-frequency Fast Radio Burst Search of Nearby Star-forming Galaxies M77 and M82. The astrophysical origins of fast radio bursts (FRBs) are still unknown, but magnetars are a strong candidate for producing at least some FRBs. To investigate the magnetar progenitor model, we conducted a deep search of M77 and M82, two nearby galaxies with high star formation rates that could potentially harbor large magnetar populations. Using one of the 34 m dishes in the Deep Space Network, we observed the two galaxies at 8.4 GHz for about 100 hr each. At this observing frequency, we are unaffected by the potentially extreme temporal broadening caused by multipath scattering in the turbulent inner regions of the galaxies. We do not detect any FRBs from either galaxy above a fluence detection threshold of  , which corresponds to an isotropic energy equivalent of   for M77 and   for M82. Based on the nondetections, we set a 95% upper limit to the 8.4 GHz burst rate of R95 = 273 yr‑1 and R95 = 233 yr‑1 for M77 and M82, respectively. By estimating the magnetar population in each galaxy, we set an upper limit to the burst rate per magnetar of  . Unlike previous searches of these galaxies at frequencies of ν ≲ 1.5 GHz, our results give a scattering-independent limit to the burst rate.

Keywords: Radio bursts, High time resolution astrophysics, Radio transient sources
Revisiting the Group-dominant Elliptical NGC 5044 in the Radio Band: Continuum Emission and Detection of H I Absorption. We present new MeerKAT L-band (continuum and H I) and upgraded Giant Metrewave Radio Telescope (300–850 MHz) observations of the archetypal cool-core group-dominant early-type galaxy NGC 5044. Our new continuum images reveal diffuse, steep spectrum ( ) radio emission extending about 25 kpc around the unresolved radio core. The observed radio emission overlaps the known X-ray cavities but is not confined to them. We also find the first direct evidence of neutral atomic gas in NGC 5044, in the form of a 3.8σ significant two-component H I absorption line seen against the emission of the active nucleus. The peak velocities are well correlated with the previously reported CO(2–1) absorption, but the H I lines are moderately broader, spanning velocities from 265 to 305 km s‑1. We do not detect H I emission but place an upper limit of MH I&lt; 5.4 × 107 M⊙in the central 15″ (2.2 kpc) of the galaxy. This is significantly less than the estimated molecular gas content and implies a molecular-to-atomic mass ratio of &gt;∼1.7:1, consistent with these gas phases forming through cooling from the hot intra-group medium. We also constrain the spin temperature to Tspin ≤ 950 K, indicating that the detected H I is in the cold neutral phase.

Keywords: Radio continuum emission, Cooling flows, Early-type galaxies