Sazuna/UAT_keywords huggingface dataset:
Ultrafast Compact Binary Mergers. The duration of orbital decay induced by gravitational waves (GWs) is often the bottleneck of the evolutionary phases going from star formation to a merger. We show here that kicks imparted to the newly born compact object during the second collapse generically result in a GW merger time distribution behaving like   ${dN}/d\mathrm{log}t\propto {t}^{2/7}$   at short durations, leading to ultrafast mergers. Namely, a nonnegligible fraction of neutron star binaries, formed in this way, will merge on a timescale as short as 10 Myr, and a small fraction will merge even on a timescale less than 10 kyr. The results can be applied to different types of compact binaries. We discuss here the implications for binary neutron star mergers. These include unique short gamma-ray bursts (GRBs), eccentric and misaligned mergers, r-process enrichment in the very early Universe and in highly star-forming regions, and possible radio precursors. Interestingly, we conclude that among the few hundred short GRBs detected so far, a few must have formed via this ultrafast channel.

Keywords: Neutron stars, Gamma-ray bursts, Core-collapse supernovae, Compact binary stars, Chemical abundances, Gravitational waves
Large-scale Structures in COSMOS2020: Evolution of Star Formation Activity in Different Environments at 0.4 &lt; z &lt; 4. To study the role of environment in galaxy evolution, we reconstruct the underlying density field of galaxies based on COSMOS2020 (The Farmer catalog) and provide the density catalog for a magnitude-limited (K  s  &lt; 24.5) sample of ∼210,000 galaxies at 0.4 &lt; z &lt; 5 within the COSMOS field. The environmental densities are calculated using a weighted kernel density estimation approach with the choice of a von Mises─Fisher kernel, an analog of the Gaussian kernel for periodic data. Additionally, we make corrections for the edge effect and masked regions in the field. We utilize physical properties extracted by LePhare to investigate the connection between star formation activity and the environmental density of galaxies in six mass-complete subsamples at different cosmic epochs within 0.4 &lt; z &lt; 4. Our findings confirm a strong anticorrelation between star formation rate (SFR)/specific SFR (sSFR) and environmental density out to z ∼ 1.1. At 1.1 &lt; z &lt; 2, there is no significant correlation between SFR/sSFR and density. At 2 &lt; z &lt; 4, we observe a reversal of the SFR/sSFR─density relation such that both SFR and sSFR increase by a factor of ∼10 with increasing density contrast, δ, from −0.4 to 5. This observed reversal at higher redshifts supports the scenario where an increased availability of gas supply, along with tidal interactions and a generally higher star formation efficiency in dense environments, could potentially enhance star formation activity in galaxies located in rich environments at z &gt; 2.

Keywords: Galaxy environments, Galaxy quenching, Galaxy evolution, Large-scale structure of the universe
Distinguishing ΛCDM from Evolving Dark Energy with Om Two-point Statistics: Implications from the Space-borne Gravitational-wave Detector. The Omh 2(z  i , z  j ) two-point diagnostics was proposed as a litmus test of the ΛCDM model, and measurements of the cosmic expansion rate H(z) have been extensively used to perform this test. The results obtained so far suggested a tension between observations and predictions of the ΛCDM model. However, the data set of H(z) direct measurements from cosmic chronometers and baryon acoustic oscillations was quite limited. This motivated us to study the performance of this test on a larger sample obtained in an alternative way. In this paper, we propose that gravitational-wave (GW) standard sirens could provide large samples of H(z) measurements in the redshift range of 0 &lt; z &lt; 5, based on the measurements of the dipole anisotropy of luminosity distance arising from the matter inhomogeneities of the large-scale structure and the local motion of the observer. We discuss the effectiveness of our method in the context of the space-borne DECi-herz Interferometer Gravitational-wave Observatory, based on a comprehensive H(z) simulated data set from binary neutron star merger systems. Our results indicate that in the GW domain, the Omh 2(z  i , z  j ) two-point diagnostics could effectively distinguish whether ΛCDM is the best description of our Universe. We also discuss the potential of our methodology in determining possible evidence for dark energy evolution, focusing on its performance on the constant and redshift-dependent dark energy equation of state.

Keywords: Cosmological parameters, Dark energy
Reconnaissance with JWST of the J-region Asymptotic Giant Branch in Distance Ladder Galaxies: From Irregular Luminosity Functions to Approximation of the Hubble Constant. We study stars in the J-regions of the asymptotic giant branch (JAGB) of near-infrared color–magnitude diagrams in the maser host NGC 4258 and four hosts of six Type Ia supernovae (SNe Ia): NGC 1448, NGC 1559, NGC 5584, and NGC 5643. These clumps of stars are readily apparent near 1.0 &lt; F150W ‑ F277W &lt; 1.5 and m F150W = 22–25 mag with James Webb Space Telescope NIRCam photometry. Various methods have been proposed to assign an apparent reference magnitude to this recently proposed standard candle, including the mode, median, sigma-clipped mean, or a modeled luminosity function parameter. We test the consistency of these by measuring intrahost variations, finding differences of up to ∼0.2 mag that significantly exceed statistical uncertainties. Brightness differences appear intrinsic, and are further amplified by the nonuniform shape of the JAGB luminosity function, also apparent in the LMC and SMC. We follow a "many methods" approach to measure consistently JAGB magnitudes and distance moduli to the SN Ia host sample calibrated by NGC 4258. We find broad agreement with distance moduli measured from Cepheids, tip of the red giant branch, and Miras. However, the SN host mean distance modulus estimated via the JAGB method necessary to estimate H 0 differs by ∼0.19 mag among the above definitions, the result of different levels of luminosity function asymmetry. The methods yield a full range of 71‑78 km s‑1 Mpc‑1, i.e., a fiducial result of H 0 = 74.7 ± 2.1(stat) ± 2.3(sys, ±3.1 if combined in quadrature) km s‑1 Mpc‑1, with systematic errors limited by the differences in methods. Future work may seek to standardize and refine this promising tool further, making it more competitive with established distance indicators.

Keywords: Luminosity function, Observational cosmology, Standard candles, Carbon stars, Distance indicators, Hubble constant, Asymptotic giant branch stars, James Webb Space Telescope, Stellar distance, Galaxies
Shock Cooling and Breakout Emission for Optical Flares Associated with Gravitational-wave Events. The astrophysical origin of stellar-mass black hole (BH) mergers discovered through gravitational waves (GWs) is widely debated. Mergers in the disks of active galactic nuclei (AGNs) represent promising environments for at least a fraction of these events, with possible observational clues in the GW data. An additional clue to unveil AGN merger environments is provided by possible electromagnetic emission from postmerger accreting BHs. Associated with BH mergers in AGN disks, emission from shocks emerging around jets launched by accreting merger remnants is expected. Here we compute the properties of the emission produced during breakout and the subsequent adiabatic expansion phase of the shocks, and we then apply this model to optical flares suggested to be possibly associated with GW events. We find that the majority of the reported flares can be explained by breakout and shock cooling emission. If the optical flares are produced by shock cooling emission, they would display moderate color evolution, possibly color variations among different events, and a positive correlation between delay time and flare duration and would be preceded by breakout emission in X-rays. If the breakout emission dominates the observed lightcurve, we predict the color to be distributed in a narrow range in the optical band and the delay time from GW to electromagnetic emission to be longer than ∼2 days. Hence, further explorations of delay time distributions, flare color evolution, and associated X-ray emission will be useful to test the proposed emission model for the observed flares.

Keywords: Jets, Transient sources, Gravitational wave sources, Active galactic nuclei, Astrophysical black holes
Spatial Relationship between CMEs and Prominence Eruptions during SC 24 and SC 25. During their propagation, coronal mass ejections (CMEs) and prominences sometimes display a nonradial motion. During the years after the solar minimum, the CME central position angle tended to be offset closer to the equator compared to that of the associated prominence eruptions (PE). No such effect was observed during solar maximum. The purpose of this paper is to investigate the latitudinal offsets of CMEs with respect to their source regions. We study 256 events from SC 24 and SC 25, listed in the Coordinate Data Analysis Workshop Data Center. We analyzed the CMES radial offset from the associated PEs by comparing their latitudes in the plane of the sky. This work is an extension of the previous work by Gopalswamy et al., but with an independent data set. We have confirmed the systematic equatorward offset of CME from the solar source region for the rising phase of Solar Cycle 25. Our analysis of the relation between CME linear speed and PE-CME latitudinal offset indicated that the velocities of the deflected CMEs are mainly in the range of 200 and 800 km s‑1. In this study, we compared the nonradial offsets for the rising and decay phases of SC 24 and our analysis has shown that during the decay phase more events deflected toward the pole can be observed. The observed variation is attributed to the presence of a substantial number of low-latitude coronal holes during the decay phase and to the influence from nearby active regions.

Keywords: Solar prominences, Solar coronal mass ejections
Constraints on the Origins of the Galactic Neutrino Flux Detected by IceCube. Galactic and extragalactic objects in the Universe are sources of high-energy neutrinos that may contribute to the astrophysical neutrino signal seen by IceCube. Recently, a study done using cascade-like events seen by IceCube reported neutrino emission from the Galactic plane with &gt;4σ significance. In this work, we put a lower limit on the number of Galactic sources required to explain this emission. To achieve this, we use a simulation package created to simulate point sources in the Galaxy along with the neutrino and gamma-ray flux emissions originating from them. Along with using past IceCube discovery potential curves, we also account for Eddington bias effects due to Poisson fluctuations in the number of detected neutrino events. We present a toy Monte Carlo simulation to show that there must be at least eight sources, each with luminosity less than 1.6 × 1035 erg s‑1, responsible for the Galactic neutrino emission. Our results constrain the number of individual point-like emission regions, which apply both to discrete astrophysical sources and to individual points of diffuse emission.

Keywords: Neutrino astronomy, Milky Way Galaxy, High energy astrophysics, Astronomical simulations
Is It Possible to Detect Coronal Mass Ejections on Solar-type Stars through Extreme-ultraviolet Spectral Observations?. Stellar coronal mass ejections (CMEs) from host stars are an important factor that affects the habitability of exoplanets. Although their solar counterparts have been well observed for decades, it is still very difficult to find solid evidence of stellar CMEs. Using the spectral line profile asymmetry caused by the Doppler shift of erupting plasma, several stellar CME candidates have been identified from spectral lines formed at chromospheric or transition region temperatures of the stars. However, a successful detection of stellar CME signals based on the profile asymmetries of coronal lines is still lacking. It is unclear whether we can detect such signals. Here we construct an analytical model for CMEs on solar-type stars and derive an expression of stellar extreme-ultraviolet (EUV) line profiles during CME eruptions. For different instrumental parameters, exposure times, CME propagation directions, and stellar activity levels, we synthesized the corresponding line profiles of Fe IX λ171.07 and Fe XV λ284.16. Further investigations provide constraints on the instrumental requirements for successful detection and characterization of stellar CMEs. Our results show that it is possible to detect stellar CME signals and infer their velocities based on spectral profile asymmetries using an EUV spectrometer with a moderate spectral resolution and signal-to-noise ratio. Our work provides important references for the design of future EUV spectrometers for stellar CME detection and the development of observation strategies.

Keywords: G dwarf stars, Stellar coronae, Spectroscopy, Stellar coronal mass ejections
The Star Formation History in Local Group Galaxies. I. Ten Dwarf Galaxies. The star formation histories (SFHs) of galaxies provide valuable insights into galaxy evolution and stellar physics. Understanding the SFHs enables the study of chemical enrichment of galaxies, star formation triggered by interactions, and the behavior of various stellar populations. This work investigates the SFHs of ten dwarf galaxies in the Local Group (LG), which spans a wide range of types, masses, luminosities, and metallicities. The analysis is based on our new sample of the member stars in the LG after removing foreground dwarf stars by using information from the near-infrared color–color diagram and Gaia astrometry. The sample includes the most complete and pure red supergiants and asymptotic giant branch stars to gain valuable insights into the recent SFHs of the galaxies. A fitting method based on the color–magnitude diagram (CMD) is introduced to measure the SFH. The Padova isochrones are used to generate initial model CMDs, accounting for photometric errors and completeness through star-field simulations to match the completeness and error distributions of the observed CMDs. Subsequently, the SFHs, distance modulus, and metallicity of the ten dwarf galaxies are determined by fitting the CMDs. The results indicate that the star formation rates of dwarf irregulars show a gradual increase, while those of dwarf ellipticals exhibit a gradual decrease from the past to the present. Furthermore, this work shows that the star formation activity in dwarf ellipticals persisted up to 30 Myr ago. A significant increasing feature in the SFH of NGC 6822 reveals star formation activity triggered by an interaction event.

Keywords: Local Group, Red supergiant stars, Massive stars, Dwarf galaxies, Stellar evolutionary models, Star formation
High-cadence Timing of Binary Pulsars with CHIME. We performed near-daily observations of the binary pulsars PSR J0218+4232, PSR J1518+4904, and PSR J2023+2853 with the Canadian Hydrogen Intensity Mapping Experiment (CHIME). For the first time, we detected the Shapiro time delay in all three pulsar binary systems, using only 2–4 yr of CHIME/Pulsar timing data. We measured the pulsar masses to be   ${1.49}_{-0.20}^{+0.23}$   M ⊙,   ${1.470}_{-0.034}^{+0.030}$   M ⊙, and   ${1.50}_{-0.38}^{+0.49}$   M ⊙, respectively. The companion mass to PSR J0218+4232 was found to be   ${0.179}_{-0.016}^{+0.018}$   M ⊙. We constrained the mass of the neutron star companion of PSR J1518+4904 to be   ${1.248}_{-0.029}^{+0.035}$   M ⊙, using the observed apsidal motion as a constraint on the mass estimation. The binary companion to PSR J2023+2853 was found to have a mass of   ${0.93}_{-0.14}^{+0.17}$   M ⊙; in the context of the near-circular orbit, this mass estimate suggests that the companion to PSR J2023+2853 is likely a high-mass white dwarf. By comparing the timing model obtained for PSR J0218+4232 with previous observations, we found a significant change in the observed orbital period of the system of   $\dot{{P}_{{\rm{b}}}}=0.14(2)\times {10}^{-12}$  ; we determined that this variation arises from "Shklovskii acceleration" due to the relative motion of the binary system, and used this measurement to estimate a distance of d = (6.7 ± 1.0) kpc to PSR J0218+4232. This work demonstrates the capability of high-cadence observations, enabled by the CHIME/Pulsar system, to detect and refine general-relativistic effects of binary pulsars over short observing timescales.

Keywords: Observational astronomy, Interferometers, Pulsars
Solar Eruptions in Nested Magnetic Flux Systems. The magnetic topology of erupting regions on the Sun is a key factor in the energy buildup and release, and the subsequent evolution of flares and coronal mass ejections (CMEs). The presence/absence of null points and separatrices dictates whether and where current sheets form and magnetic reconnection occurs. Numerical simulations show that energy buildup and release via reconnection in the simplest configuration with a null, the embedded bipole, is a universal mechanism for solar eruptions. Here we demonstrate that a magnetic topology with nested bipoles and two nulls can account for more complex dynamics, such as failed eruptions and CME–jet interactions. We investigate the stalled eruption of a nested configuration on 2013 July 13 in NOAA Active Region 11791, in which a small bipole is embedded within a large transequatorial pseudo-streamer containing a null. In the studied event, the inner active region erupted, ejecting a small flux rope behind a shock accompanied by a flare; the flux rope then reconnected with pseudo-streamer flux and, rather than escaping intact, mainly distorted the pseudo-streamer null into a current sheet. EUV and coronagraph images revealed a weak shock and a faint collimated outflow from the pseudo-streamer. We analyzed Solar Dynamics Observatory and Solar TErrestrial RElations Observatory observations and compared the inferred magnetic evolution and dynamics with three-dimensional magnetohydrodynamics simulations of a simplified representation of this nested fan-spine system. The results suggest that the difference between breakout reconnection at the inner null and at the outer null naturally accounts for the observed weak jet and stalled ejection. We discuss the general implications of our results for failed eruptions.

Keywords: Solar activity, Solar magnetic fields, Solar coronal mass ejections, Solar magnetic reconnection
An Angular Diameter Measurement of β UMa via Stellar Intensity Interferometry with the VERITAS Observatory. We use the Very Energetic Radiation Imaging telescope Array System (VERITAS) imaging air Cherenkov telescope array to obtain the first measured angular diameter of β UMa at visual wavelengths using stellar intensity interferometry (SII) and independently constrain the limb-darkened angular diameter. The age of the Ursa Major moving group has been assessed from the ages of its members, including nuclear member Merak (β UMa), an A1-type subgiant, by comparing effective temperature and luminosity constraints to model stellar evolution tracks. Previous interferometric limb-darkened angular-diameter measurements of β UMa in the near-infrared (Center for High Angular Resolution Astronomy (CHARA) Array, 1.149 ± 0.014 mas) and mid-infrared (Keck Nuller, 1.08 ± 0.07 mas), together with the measured parallax and bolometric flux, have constrained the effective temperature. This paper presents current VERITAS-SII observation and analysis procedures to derive squared visibilities from correlation functions. We fit the resulting squared visibilities to find a limb-darkened angular diameter of 1.07 ± 0.04 (stat) ± 0.05 (sys) mas, using synthetic visibilities from a stellar atmosphere model that provides a good match to the spectrum of β UMa in the optical wave band. The VERITAS-SII limb-darkened angular diameter yields an effective temperature of 9700 ± 200 ± 200 K, consistent with ultraviolet spectrophotometry, and an age of 390 ± 29 ± 32 Myr, using MESA Isochrones and Stellar Tracks. This age is consistent with 408 ± 6 Myr from the CHARA Array angular diameter.

Keywords: Fundamental parameters of stars, Long baseline interferometry, Astronomy data modeling
Inertial Waves in a Nonlinear Simulation of the Sun's Convection Zone and Radiative Interior. Recent observations of Rossby waves and other more exotic forms of inertial oscillations in the Sun's convection zone have kindled the hope that such waves might be used as a seismic probe of the Sun's interior. Here, we present a 3D numerical simulation in spherical geometry that models the Sun's convection zone and upper radiative interior. This model features a wide variety of inertial oscillations, including both sectoral and tesseral equatorial Rossby waves, retrograde mixed inertial modes, prograde thermal Rossby waves, the recently observed high-frequency retrograde (HFR) vorticity modes, and what may be latitudinal overtones of these HFR modes. With this model, we demonstrate that sectoral and tesseral Rossby waves are ubiquitous within the radiative interior as well as within the convection zone. We suggest that there are two different Rossby-wave families in this simulation that live in different wave cavities: one in the radiative interior and one in the convection zone. Finally, we suggest that many of the retrograde inertial waves that appear in the convection zone, including the HFR modes, are in fact all related, being latitudinal overtones that are mixed modes with the prograde thermal Rossby waves.

Keywords: Internal waves, Solar interior, Solar physics, Solar oscillations, Astrophysical fluid dynamics
Bright Supernova Precursors by Outbursts from Massive Stars with Compact Object Companions. A fraction of core-collapse supernovae (SNe) with signs of interaction with a dense circumstellar matter are preceded by bright precursor emission. While the precursors are likely caused by a mass ejection before core collapse, their mechanism to power energetic bursts—sometimes reaching 1048–1049 erg, which is larger than the binding energies of red supergiant envelopes—is still under debate. Remarkably, such a huge energy deposition should result in an almost complete envelope ejection and hence a strong sign of interaction, but the observed SNe with precursors show in fact typical properties among the interacting SNe. More generally, the observed luminosity of 1040‑1042 erg s‑1 is shown to be challenging for a single SN progenitor. To resolve these tensions, we propose a scenario where the progenitor is in a binary system with a compact object (CO) and an outburst from the star leads to a super-Eddington accretion onto the CO. We show that for sufficiently short separations outbursts with moderate initial kinetic energies of 1046–1047 erg can be energized by the accreting CO so that their radiative output can be consistent with the observed precursors. We discuss the implications of our model in relation to CO binaries detectable with Gaia and gravitational-wave detectors.

Keywords: Circumstellar matter, Eruptive phenomena, Core-collapse supernovae, Stellar mass loss