Sazuna/UAT_keywords huggingface dataset:
Choosing Suitable Noise Models for Nanohertz Gravitational-wave Astrophysics. Accurately estimating the parameters of the nanohertz gravitational-wave background is essential for understanding its origin. The background is typically modeled with a power-law spectrum, parameterized with an amplitude A, which describes its intensity, and a spectral index γ, which describes how the background varies with frequency. Different collaborations have produced varied estimates of γ, some in tension with the value of γ = 13/3 expected for circular, gravitational-wave-driven binary black holes. However, estimates of A and γ can be affected by systematic errors and misspecified noise models. We investigate how systematic errors—which may plausibly be present in pulsar timing analyses—can shift inferences about A, γ. We demonstrate that conservatively incorporating noise sources into the model that are not actually present in the data does not produce bias inferences in practice. This addresses concerns that an overly complex noise model might lead to bias from a needlessly conservative prior. Our results highlight the importance of using comprehensive noise models in pulsar timing analyses to ensure accurate and reliable parameter estimation of the gravitational-wave background.

Keywords: Astronomy data analysis, Gravitational waves
BASS. LIII. The Eddington Ratio as the Primary Regulator of the Fraction of X-Ray Emission in Active Galactic Nuclei. Active galactic nuclei (AGN) emit radiation via accretion across the entire energy spectrum. While the standard disk and corona model can somewhat describe this emission, it fails to predict specific features such as the soft X-ray excess, the short-term optical/UV variability, and the observed UV/X-ray correlation in AGN. In this context, the fraction of AGN emission in different bands (i.e., bolometric corrections) can be useful to better understand the accretion physics of AGN. Past studies have shown that the X-ray bolometric corrections are strongly dependent on the physical properties of AGN, such as their luminosities and Eddington ratios. However, since these two parameters depend on each other, it has been unclear which is the main driver of the X-ray bolometric corrections. We present here results from a large study of hard-X-ray-selected (14–195 keV) nearby (z &lt; 0.1) AGN. Based on our systematic analysis of the simultaneous optical-to-X-ray spectral energy distributions of 236 unobscured AGN, we found that the primary parameter controlling the X-ray bolometric corrections is the Eddington ratio. Our results show that, while the X-ray bolometric correction increases with the bolometric luminosity for sources with intermediate Eddington ratios (0.01–1), this dependence vanishes for sources with lower Eddington ratios (&lt;0.01). This could be used as evidence for a change in the accretion physics of AGN at low Eddington ratios.

Keywords: High energy astrophysics, Active galaxies, Galaxy nuclei, X-ray active galactic nuclei, Active galactic nuclei
Quasiperiodic Variation during a Fast X-Ray Outburst of a High-mass X-Ray Binary MAXI J0709-159/LY CMa Observed by NICER. We report on a quasiperiodic variation at ∼1 Hz during a fast X-ray outburst of a high-mass X-ray binary MAXI J0709‑159/LY CMa observed by the Neutron star Interior Composition ExploreR (NICER). The new X-ray transient MAXI J0709‑159 was discovered on 2022 January 25. Due to the transient X-ray behavior characterized by the short (a few hours) outburst duration, rapid (≲1 s) variability with spectral change, and large luminosity swing from 1032 erg s‑1 to 1037 erg s‑1, the object was considered to likely be a supergiant X-ray binary with a neutron star (NS) categorized as a supergiant fast X-ray transient. Follow-up NICER and NuSTAR observations confirmed that the position of the new X-ray object is consistent with a Be star, LY CMa, which has also been identified as a B supergiant. We analyzed the NICER data obtained from 3 hr to 6 days after the discovery. The light curve reveals that the X-ray activity continued for ∼7 hr in sparse short flares, each lasting ≲100 s, and the luminosity instantaneously reached up to ∼1 × 1038 erg s‑1. The light-curve and spectral features reasonably agree with those expected from accretion of a clumpy stellar wind onto a magnetized NS. The variability power spectrum during the brightest flare shows a broad peak at 1.1 Hz resembling a quasiperiodic oscillation (QPO). If the QPO is attributed to the Keplerian orbital frequency at the inner edge of a transient accretion disk truncated by the NS magnetosphere, the NS surface magnetic field is estimated to be ∼1012 G.

Keywords: Neutron stars, X-ray transient sources, High mass x-ray binary stars
Counting Mass with Gaia: Mass Density of Stars and Stellar Remnants in the Solar Neighborhood. In the light of new full-sky surveys, many attempts to create a consistent Galactic model were made. The main interest is to estimate the still poorly understood dark matter content. However, the results vary depending on methodology, assumptions, and baryonic distribution used. To understand this discrepancy, we take the first step by estimating the model-free local mass density of stars and stellar remnants. We use a complete sample from the Gaia Catalogue of Nearby Stars within 100 pc from the Sun, together with the data on the sample of the white dwarfs and the recent estimate of the neutron star concentration in the solar neighborhood. After correction for unresolved binary stars and accounting for missing low-mass stars, we find that the local mass density of stars and stellar remnants in the solar neighborhood is  ρ100=0.040−0.006+0.012M⊙pc−3  with a Kroupa initial mass function (IMF) and  ρ100=0.037−0.006+0.012M⊙pc−3  with a Chabrier IMF.

Keywords: Milky Way disk, Binary stars, Dark matter
First X-Ray Polarimetric View of a Low-luminosity Active Galactic Nucleus: The Case of NGC 2110. Low-luminosity active galactic nuclei (LLAGN) provide a unique view of Comptonization and nonthermal emission from accreting black holes in the low accretion rate regime. However, to decipher the exact nature of the Comptonizing corona in LLAGN, its geometry and emission mechanism must be understood beyond the limits of spectro-timing techniques. Spectropolarimetry offers the potential to break the degeneracies between different coronal emission models. Compton-thin LLAGN provide an opportunity for such spectropolarimetric exploration in the 2–8 keV energy range using the Imaging X-Ray Polarimetry Explorer (IXPE). In this work, we carry out a spectropolarimetric analysis of the first IXPE observation, in synergy with a contemporaneous Nuclear Spectroscopic Telescope Array observation, of an LLAGN: NGC 2110. Using 554.4 ks of IXPE data from 2024 October, we constrain the 99% upper limit on the polarization degree (PD) to be less than 8.3% assuming the corresponding polarization angle (PA) to be aligned with the radio jet, and less than 3.6% if in the perpendicular direction. In the absence of a significant PD detection, the PA remains formally unconstrained, yet the polarization significance contours appear to be aligned with the radio jet, tentatively supporting models in which the corona is radially extended in the plane of the disk. We also carry out detailed Monte Carlo simulations using MONK and STOKES codes to test different coronal models against our results and compare the polarization properties between NGC 2110 and brighter Seyferts.

Keywords: X-ray astronomy, Supermassive black holes, Astrophysical black holes, Low-luminosity active galactic nuclei, Active galactic nuclei, X-ray active galactic nuclei, Polarimetry, Astronomical simulations
Chandra X-Ray Observatory Study of the X-Ray Emission of PKS 0023−26 and Comparison with Recent ALMA Results. We present a deep high-resolution Chandra X-ray Observatory study of the powerful compact radio source PKS 0023−26 associated with a quasar at redshift 0.322. Earlier studies of the optical environment suggested that the source could be located in a galaxy cluster or a group. However, we report a nondetection of hot gas on large scales (out to ∼60 kpc radius) and place an upper limit on the X-ray luminosity of &lt;3 × 1042 erg s−1, consistent only with the presence of a poor, low-temperature (kT &lt; 0.5 keV) galaxy group. X-ray spectral analysis of the central circular region, r &lt; 7 kpc, shows, in addition to the mildly absorbed active galactic nucleus, a thermal emission component with a temperature of  kT=0.9−0.37+0.19  keV. We discuss the origin of this hot component as a result of interaction between the evolving radio source and the interstellar medium (ISM). Our high-angular-resolution X-ray image traces the distribution of hot gas, which is closely aligned with and extends beyond the radio source, and also in the direction perpendicular to the axis of the radio source. The X-rays are enhanced in the northern radio lobe and at the location of the peak of the CO(3─2)/CO(2─1) line emission, suggesting that the interactions between the jet and cold medium result in the X-ray radiation that excites CO. The shock driven by the jet into the ISM is supersonic with a Mach number of  M∼1.75 ─2, creating the cocoon of hot X-rays that surrounds the radio source. This result agrees with observations of shocks in other radio galaxies and points to the prevalent impact of jets on the ISM.

Keywords: Active galaxies, X-ray active galactic nuclei
Transient Blurring of the Scintillation Arc of Pulsar B1737+13. For many pulsars, the scattering structures responsible for scintillation are typically dominated by a single, thin screen along the line of sight, which persists for years or decades. In recent years, an increasing number of doubly lensed events have been observed, where a secondary lens crosses the line of sight. This causes additional or distorted scintillation arcs over timescales ranging from days to months. In this work, we report such a transient event for pulsar B1737+13 and propose a possible lensing geometry including the distance to both lenses and the orientation of the main screen. Using phase retrieval techniques to separate the two lenses in the wavefield, we report the curvature and rate of motion of features associated with the secondary lens as it passed through the line of sight. By fitting the annual variation of the curvature, we report a possible distance and orientation for the main screen. The distance of the secondary lens is found by mapping the secondary feature onto the sky and tracking its position over time for different distances. We validate this method using B0834+06, for which the screen solutions are known through VLBI, and successfully recover the correct solution for the secondary feature. With the identified lensing geometry, we are able to estimate the size of the secondary lens, 1–3 au. Although this is an appropriate size for a structure that could cause an extreme scattering event, we do not have conclusive evidence for or against that possibility.

Keywords: Pulsars, Supernova remnants, Interstellar medium, Interstellar scintillation, Interstellar scattering, Shocks, Magnetohydrodynamical simulations
A Target Search for Fast Radio Bursts Associated with Two Fast Blue Optical Transients: AT2018cow and CSS161010. Fast blue optical transients (FBOTs) are luminous, rapidly evolving events with blue spectra, possibly powered by newborn magnetars and linked to fast radio bursts (FRBs). Given this potential connection, we conducted deep radio observations of two nearby FBOTs (AT2018cow and CSS161010) using the Five-hundred-meter Aperture Spherical radio Telescope, but detected no FRB-like signals. Our observations establish the most stringent upper limits on millisecond radio transients from FBOTs, reaching ∼10 mJy flux density. Assuming a log-normal luminosity function analogous to the repeating FRB 121102, we constrain the burst rate from potential magnetars in FBOTs to &lt; 0.01 hr‑1. The short ejecta escape timescale (∼2.6 yr) compared to our observation epochs (4‑6 yr post-explosion) suggests that nondetection may not be attributed to FBOT's ejecta absorption. These findings impose useful constraints on the FRB activity emanating from newborn magnetars within FBOTs. They indicate that if there is a burst phase, it is either characterized by weaker bursts, occurs less frequently compared to those in known repeating FRB sources, or takes place beyond the time frame of our current observations. To gain deeper insights into the birth-related activity of magnetars, it is of importance to conduct timely and sustained FRB searches in FBOTs that emerge in the future.

Keywords: Magnetars, Transient sources, Radio transient sources
The X-Ray Link between High Eddington Ratio Dust-obscured Galaxies (DOGs) and Hot DOGs. Dust-obscured galaxies (DOGs) with extremely red optical-to-infrared colors are often associated with intense starburst and active galactic nucleus (AGN) activity. Studying DOGs can provide insights into the processes that drive the growth of galaxies and their central supermassive black holes. However, the general DOG population is heterogeneous, spanning a wide range of evolutionary stages, and has X-ray obscuring column densities (NH) covering low to high levels. In this work, we focus on seven high Eddington ratio DOGs ( logλEdd≳−0.5 ) to examine their X-ray obscuration properties using new and archival X-ray observations. We confirm that these systems are generally heavily obscured, with six out of seven having NH ≳ 1023 cm−2 and three out of seven having NH ≳ 1024 cm−2. Based on the observed similarity with the rare Hot DOG population, we argue that both high-λEdd DOGs and Hot DOGs likely trace the postmerger phase, during which AGNs are enshrouded by large columns of dust-rich material.

Keywords: AGN host galaxies, Active galactic nuclei, Galaxy evolution
Development of 1D Non-ideal MHD Simulation Code Towards understanding Long-term Evolution of Protoplanetary Disk. We developed a one-dimensional magnetohydrodynamic (MHD) simulation code to investigate the long-term evolution of protoplanetary disks with low computational cost. In this simulation code, the physical processes necessary for protostellar formation and protoplanetary disk evolution, such as magnetic braking, nonideal MHD effects, and angular momentum transport due to viscosity, are implemented. Using this simulation code, we performed the simulations of the long-term evolution of protoplanetary disks starting from the molecular cloud. Our simulation results suggest that the disk size and mass are a few tens of astronomical units and ∼0.01 M⊙ at 105 yr after protostellar formation. These values were relatively consistent with observations. The disk evolves through magnetic braking, and its radial profiles are consistent with the analytical solutions of previous studies. Our simulation code will be an important tool for studying the long-term evolution of protoplanetary disks.

Keywords: Protostars, Magnetohydrodynamics, Protoplanetary disks
Tracing the Formation History of Intrahalo Light with Horizon Run 5. We investigate the formation history of intrahalo light (IHL) using the high-resolution (∼1 kpc), large-scale (∼1 Gpc) cosmological hydrodynamical simulation Horizon Run 5 (HR5). IHL particles are identified by carefully considering both their binding energies and positions with respect to the tidal radii of individual galaxies. By analyzing more than 1200 galaxy groups and clusters with ≳1013 M⊙ and tracing their individual IHL particles back in time, we classify the origin of each IHL particle at each epoch, based on the status of the originating galaxy, into one of three categories: brightest halo galaxy (BHG) formation/merger, satellite galaxy stripping, and preprocessing. Our study reveals that IHL production through BHG formation/merger is the predominant production channel, contributing over 60% of the total IHL mass across all redshifts. The second most significant IHL production channel is preprocessing, providing more than 20% in the final HR5 snapshot. Stripping is negligible at z &gt; 4 but becomes gradually more important as the halos mature at z &lt; 4. Finally, we verify that the IHL production through the disruption of dwarf galaxies and in situ formation is negligible, contributing less than ∼3% and ∼0.5% to the total IHL production, respectively.

Keywords: Galaxy clusters, Hydrodynamical simulations, Galaxy interactions, Galaxy groups
Connecting Solar Orbiter and L1 Measurements of Mesoscale Solar Wind Structures to Their Coronal Source Using the ADAPT-WSA Model. Much of the dynamics of the ambient solar wind (SW) manifests at mesoscales—scales larger than kinetic but smaller than global structures. Mesoscale structures often form at the Sun, survive to 1 au, and are geoeffective. Identifying their origins, release, and acceleration mechanisms is critical to advancing heliophysics. We investigate a 6 day interval (2022 March 4 00:00:00 UT─2022 March 9 23:59:59 UT) in which Solar Orbiter (SO) was radially aligned with Earth. We characterize mesoscale structures observed in SO Heavy Ion Sensor (HIS) Fe/O and O7+/O6+ in situ measurements, and confirm their survival to L1. A subset of these structures are periodic, suggesting that they formed at the Sun. We use the ADAPT-WSA model to connect in situ measurements to their remotely observed sources at the Sun. We characterize the SW sources using model-determined proxies for SW formation (e.g., the S-web). We compare Fe/O observed at SO/HIS, with S/O abundances derived by the Spectral Imaging of the Coronal Environment (SO/SPICE), at the WSA-determined SW sources. We find (1) SO and ACE/Wind observe similar many-hour structures, linking mesoscale structures from their source to two well-separated locations in situ for the first time. (2) Observed periodicities are consistent with those observed in prior studies of mesoscale structures throughout the inner heliosphere. (3) SW originating from only one of the four SPICE rasters can be interpreted as plasma originating from open fields. The SW from the other three require a different interpretation, and we suggest interchange reconnection as the most natural solution.

Keywords: Solar corona
Mass and Metal Flows in Isolated IllustrisTNG Halos. The circumgalactic medium (CGM) is a reservoir of metals and star-forming fuel. Most baryons in the Universe are in the CGM or the intergalactic medium (IGM). The baryon cycle—how mass and metals reach the CGM from the inner regions of the galaxy and how gas from the CGM replenishes star-forming activity in the inner regions—is an essential question in galaxy evolution. In this paper, we study the flow of mass and metals in a stacked sample of 2770 isolated halos from the IllustrisTNG100 cosmological hydrodynamic simulation. The mean gas flow as a function of radius and angle is similar across a large galactic mass range when accounting for different feedback modes. Although both star formation and black holes cause powerful outflows, the flows from star formation are more angularly restricted. Black hole feedback dominates mass flow throughout the halo, while star formation feedback mainly affects the inner region. When scaling by virial radius (Rv), large dynamical changes occur at 0.2Rv for most halos, suggesting a characteristic size for the inner galaxy. Despite kinetic-mode feedback from black holes being the primary quenching mechanism in IllustrisTNG, a small population of high-mass kinetic-mode disks are able to form stars.

Keywords: Galaxy formation, Galaxy infall, Galaxy dynamics, Galaxy structure, Galaxy kinematics, Galaxy evolution, Star formation, Circumgalactic medium, Radio active galactic nuclei, Galaxy quenching, Galaxy accretion, Galaxy processes
A Parameter-masked Mock Data Challenge for Beyond-two-point Galaxy Clustering Statistics. The past few years have seen the emergence of a wide array of novel techniques for analyzing high-precision data from upcoming galaxy surveys, which aim to extend the statistical analysis of galaxy clustering data beyond the linear regime and the canonical two-point (2pt) statistics. We test and benchmark some of these new techniques in a community data challenge named "Beyond-2pt," initiated during the Aspen 2022 Summer Program "Large-Scale Structure Cosmology beyond 2-Point Statistics," whose first round of results we present here. The challenge data set consists of high-precision mock galaxy catalogs for clustering in real space, in redshift space, and on a light cone. Participants in the challenge have developed end-to-end pipelines to analyze mock catalogs and extract unknown ("masked") cosmological parameters of the underlying ΛCDM models with their methods. The methods represented are density-split clustering, nearest neighbor statistics, BACCO power spectrum emulator, void statistics, LEFTfield field-level inference using effective field theory (EFT), and joint power spectrum and bispectrum analyses using both EFT and simulation-based inference. In this work, we review the results of the challenge, focusing on problems solved, lessons learned, and future research needed to perfect the emerging beyond-2pt approaches. The unbiased parameter recovery demonstrated in this challenge by multiple statistics and the associated modeling and inference frameworks supports the credibility of cosmology constraints from these methods. The challenge data set is publicly available, and we welcome future submissions from methods that are not yet represented.

Keywords: Astrostatistics techniques, Large-scale structure of the universe
Plasma Instability in Front of Ejected Energetic Electrons and Type III Solar Radio Bursts. Type III radio bursts are signatures of the fluxes of near-relativistic electrons ejected during solar flares. These bursts are frequently observed by spacecraft such as the Parker Solar Probe. It has been traditionally believed that these electron beams generate Langmuir waves through the two-stream instability, which are then converted into electromagnetic waves. In this study, we revise that model, by examining how the electron distribution becomes truncated due to the "time-of-flight" effect, as the beam travels through a randomly inhomogeneous and gently varying solar wind plasma. Rather than the two-stream instability, this truncation destabilizes the distribution and leads to the generation of Langmuir waves via a linear instability; we confine our analysis to this linear regime and do not take into account the backreaction of the generated Langmuir waves on the electron distribution, which is nonlinear. The instability grows until slower electrons arrive and dampen the waves. Our qualitative analysis shows that the resulting wave intensity growth and decay closely match the intensity–time profile of observed type III radio bursts at the fundamental frequency, supporting this modified theory.

Keywords: Solar coronal radio emission, Solar wind
Solar Flares as Electron Accelerators: Toward a Resolution of the Acceleration Efficiency Issue. A major open issue concerning the active Sun is the effectiveness with which magnetic reconnection accelerates electrons in flares. A paper published by Nature in 2022 used microwave observations to conclude that the Sun is an almost ideal accelerator, energizing nearly all electrons within a coronal volume to nonthermal energies. Shortly thereafter, a paper published in Astrophysical Journal Letters used hard X-ray measurements of the same event to reach the contradictory conclusion that less than 1% of the available electrons were accelerated. Here we address this controversy by using spatially resolved observations of hard X-ray emission and a spectral inversion method to determine the evolution of the electron spectrum throughout a set of flares. We use the spatial variation of the electron spectrum to deduce the density of the medium where electrons propagate and, from this and the total intensity of the flare, the ratio of accelerated to ambient electron densities. Results show that this ratio never exceeds 1% or so in all the events analyzed.

Keywords: Solar flares, Astronomy data analysis, X-ray telescopes, Spectroscopy, Solar x-ray flares