Sazuna/UAT_keywords huggingface dataset:
Errors When Constraining Hot Blackbody Parameters with Optical Photometry. Measuring blackbody parameters for objects hotter than a few 104 K with optical data alone is common in many astrophysical studies. However this process is prone to large errors because at those temperatures the optical bands are mostly sampling the Rayleigh-Jeans tail of the spectrum. Here we quantify these errors by simulating different blackbodies, sampling them in various bands with realistic measurement errors, and refitting them to blackbodies using two different methods and two different priors. We find that when using only optical data, log-uniform priors perform better than uniform priors. Still, measured temperatures of blackbodies above ~35,000 K can be wrong by ~10,000 K, and only lower limits can be obtained for temperatures of blackbodies hotter than ~50,000 K. Bolometric luminosities estimated from optical-only blackbody fits can be wrong by factors of 3-5. When adding space-based ultraviolet data, these errors shrink significantly. For when such data are not available, we provide plots and tables of the distributions of true temperatures that can result in various measured temperatures. It is important to take these distributions into account as systematic uncertainties when fitting hot blackbodies with optical data alone.

Keywords: Optical astronomy, Ultraviolet astronomy, Astronomical methods
Strategies for Determining the Cascade Rate in MHD Turbulence: Isotropy, Anisotropy, and Spacecraft Sampling. Exact laws for evaluating cascade rates, tracing back to the Kolmogorov "4/5" law, have been extended to many systems of interest including magnetohydrodynamics (MHD), and compressible flows of the magnetofluid and ordinary fluid types. It is understood that implementations may be limited by the quantity of available data and by the lack of turbulence symmetry. Assessment of the accuracy and feasibility of such third-order (or Yaglom) relations is most effectively accomplished by examining the von Kármán-Howarth equation in increment form, a framework from which the third-order laws are derived as asymptotic approximations. Using this approach, we examine the context of third-order laws for incompressible MHD in some detail. The simplest versions rely on the assumption of isotropy and the presence of a well-defined inertial range, while related procedures generalize the same idea to arbitrary rotational symmetries. Conditions for obtaining correct and accurate values of the dissipation rate from these laws based on several sampling and fitting strategies are investigated using results from simulations. The questions we address are of particular relevance to sampling of solar wind turbulence by one or more spacecraft.

Keywords: Space plasmas, Magnetohydrodynamics, Plasma physics, Interplanetary turbulence, Magnetohydrodynamical simulations
On the Mass Ratio Distribution of Black Hole Mergers in Triple Systems. Observations have shown that the majority of massive stars, the progenitors of black holes (BHs), have on average more than one stellar companion. In triple systems, wide inner binaries can be driven to a merger by a third body due to long-term secular interactions, most notably by the eccentric Lidov-Kozai effect. In this study, we explore the properties of BH mergers in triple systems and compare their population properties to those of binaries produced in isolation and assembled in dense star clusters. Using the same stellar physics and identical assumptions for the initial populations of binaries and triples, we show that stellar triples yield a significantly flatter mass ratio distribution from q = 1 down to q ~ 0.3 than either binary stars or dense stellar clusters, similar to the population properties inferred from the most recent catalog of gravitational-wave events, though we do not claim that all the observed events can be accounted for with triples. While hierarchical mergers in clusters can also produce asymmetric mass ratios, the unique spins of such mergers can be used to distinguish them from those produced from stellar triples. All three channels occupy distinct regions in the total mass-mass ratio space, which may allow them to be disentangled as more BH mergers are detected by LIGO, Virgo, and KAGRA.

Keywords: Trinary stars, Gravitational waves, Black holes
Multi-messenger Observations of Binary Neutron Star Mergers in the O4 Run. We present realistic expectations for the number and properties of neutron star binary mergers to be detected as multi-messenger sources during the upcoming fourth observing run (O4) of the LIGO-Virgo-KAGRA gravitational-wave (GW) detectors, with the aim of providing guidance for the optimization of observing strategies. Our predictions are based on a population synthesis mode, which includes the GW signal-to-noise ratio, the kilonova (KN) optical and near-infrared light curves, the relativistic jet gamma-ray burst (GRB) prompt emission peak photon flux, and the afterglow light curves in radio, optical, and X-rays. Within our assumptions, the rate of GW events to be confidently detected during O4 is ${7.7}_{-5.7}^{+11.9}$ yr-1 (calendar year), 78% of which will produce a KN, and a lower 52% will also produce a relativistic jet. The typical depth of current optical electromagnetic search and follow-up strategies is still sufficient to detect most of the KNæ in O4, but only for the first night or two. The prospects for detecting relativistic jet emission are not promising. While closer events (within z ≲ 0.02) will likely still have a detectable cocoon shock breakout, most events will have their GRB emission (both prompt and afterglow) missed unless seen under a small viewing angle. This reduces the fraction of events with detectable jets to 2% (prompt emission, serendipitous) and 10% (afterglow, deep radio monitoring), corresponding to detection rates of ${0.17}_{-0.13}^{+0.26}$ and ${0.78}_{-0.58}^{+1.21}$ yr-1, respectively. When considering a GW subthreshold search triggered by a GRB detection, our predicted rate of joint GW+GRB prompt emission detections increases up to a more promising ${0.75}_{-0.55}^{+1.16}$ yr-1.

Keywords: Gravitational wave astronomy, Neutron stars, Gravitational waves, Transient sources
KIC 3440495: A Rapidly Rotating δ Scuti-γ Doradus Hybrid Pulsator in a Binary System. In this paper, we study the pulsation properties of KIC 3440495 using Kepler and TESS data. A Fourier analysis of the light curve reveals 24 pulsation modes as well as 29 frequencies associated with rotation. The rotation frequency is derived to be f rot = 2.322909(2) day-1, and the rotational modulation is determined to be caused by starspots. A large frequency separation of Δν = 54.5 μHz is found by using a Fourier transform, the autocorrelation function, a histogram of frequency differences, and an échelle diagram. We use the large separation to estimate the refined stellar parameters of the star to be v = [239, 279] km s-1, M = [1.5, 1.65] M ⊙, R equator = [2.03, 2.30] R ⊙, R polar = [1.72, 1.78] R ⊙, and ω = [0.61, 0.77]. The phase modulations of the pulsating frequencies show a long-term trend which may be attributed to an orbital effect of a binary system; hence, the star may be a fast rotating pulsator in a binary system. KIC 3440495 has an amplitude spectrum similar to Altair, and is identified as a potential sister of Altair. Based on studies of Altair, KIC 3330495 is presumably a young star at a similar evolutionary stage.

Keywords: Starspots, Stellar rotation, Stellar pulsations
Mapping the Thermal Condensation of Diffuse H I in the North Celestial Pole Loop. The North Celestial Pole Loop (NCPL) provides a unique laboratory for studying the early stages of star formation, in particular the condensation of the neutral interstellar medium (ISM). Understanding the physical properties that control the evolution of its contents is key to uncovering the origin of the NCPL. Archival data from the NCPL region of the GHIGLS 21 cm line survey (9.'4) are used to map its multiphase content with ROHSA, a Gaussian decomposition tool that includes spatial regularization. Column density and mass fraction maps of each phase were extracted along with their uncertainties. Archival data from the DHIGLS 21 cm (1') survey are used to further probe the multiphase content of the NCPL. We have identified four spatially (and dynamically) coherent components in the NCPL, one of which is a remarkably well-defined arch moving at about 14 km s-1 away from us that could be a relic of the large-scale organized dynamical process at the origin of the phase transition. The cold and lukewarm phases together dominate the mass content of the neutral gas along the loop. Using absorption measurements, we find that the cold phase exhibits slightly supersonic turbulence.

Keywords: Interstellar phases, Cold neutral medium, Interstellar medium, H I line emission
The Relation between the Optical Fe II Emission and the Dimensionless Accretion Rate for Active Galactic Nuclei. It was suggested that the prominent feature of the optical Fe II emission has a connection with the accretion process in active galactic nuclei (AGN). For a large sample of 4037 quasars (z &lt; 0.8) with measured H β line dispersion (σ Hβ ) selected from the Sloan Digital Sky Survey (SDSS) and 120 compiled reverberation-mapped (RM) AGN, we use σ Hβ  and the extended R BLR(Hβ)-L 5100 relation to calculate supermassive black holes masses (M BH) from the single-epoch spectra for the SDSS subsample, and σ Hβ  from the mean spectra for the RM subsample. We find a strong correlation between the relative optical Fe II strength R Fe and the dimensionless accretion rate $\dot{{\mathscr{M}}}$ for the SDSS subsample with the Spearman correlation coefficient r  s  of 0.727, which is consistent with that derived from the mean spectra for the RM subsample. The magnitude of velocity shift of the optical Fe II emission has a strong anticorrelation with $\dot{{\mathscr{M}}}$ , whenever there is inflow or outflow. These strong correlations show that the optical Fe II emission has an intimate connection with the accretion process. Assuming that the difference of M BH is due to the variable virial factor f for adopting FWHM H β  as the velocity tracer, we find that there is a relation between f and FWHM H β , $\mathrm{log}f=-(0.41\pm 0.002){\mathrm{logFWHM}}_{H\beta }+(1.719\pm 0.009)$ for the single-epoch spectrum. The relation between $\mathrm{log}f$ and σ Hβ  is not too strong, suggesting that σ Hβ  does not seem to depend much on the broad-line region inclination and a constant σ-based f is suitable for σ Hβ  as the velocity tracer.

Keywords: Supermassive black holes, Reverberation mapping, Active galactic nuclei, Quasars
HIFLOW: Generating Diverse HI Maps and Inferring Cosmology while Marginalizing over Astrophysics Using Normalizing Flows. A wealth of cosmological and astrophysical information is expected from many ongoing and upcoming large-scale surveys. It is crucial to prepare for these surveys now and develop tools that can efficiently extract most information. We present HIFLOW: a fast generative model of the neutral hydrogen (HI) maps that is conditioned only on cosmology (Ω m  and σ 8) and designed using a class of normalizing flow models, the masked autoregressive flow. HIFLOW is trained on the state-of-the-art simulations from the Cosmology and Astrophysics with MachinE Learning Simulations (CAMELS) project. HIFLOW has the ability to generate realistic diverse maps without explicitly incorporating the expected two-dimensional maps structure into the flow as an inductive bias. We find that HIFLOW is able to reproduce the CAMELS average and standard deviation HI power spectrum within a factor of ≲2, scoring a very high R 2 &gt; 90%. By inverting the flow, HIFLOW provides a tractable high-dimensional likelihood for efficient parameter inference. We show that the conditional HIFLOW on cosmology is successfully able to marginalize over astrophysics at the field level, regardless of the stellar and AGN feedback strengths. This new tool represents a first step toward a more powerful parameter inference, maximizing the scientific return of future HI surveys, and opening a new avenue to minimize the loss of complex information due to data compression down to summary statistics.

Keywords: Early universe, Bayesian statistics, Cosmological parameters, Intergalactic medium, Reionization
Total Solar Irradiance during the Last Five Centuries. The total solar irradiance (TSI) varies on timescales of minutes to centuries. On short timescales it varies due to the superposition of intensity fluctuations produced by turbulent convection and acoustic oscillations. On longer timescales, it changes due to photospheric magnetic activity, mainly because of the facular brightenings and dimmings caused by sunspots. While modern TSI variations have been monitored from space since the 1970s, TSI variations over much longer periods can only be estimated either using historical observations of magnetic features, possibly supported by flux transport models, or from the measurements of the cosmogenic isotope (e.g., 14C or 10Be) concentrations in tree rings and ice cores. The reconstruction of the TSI in the last few centuries, particularly in the 17th/18th centuries during the Maunder minimum, is of primary importance for studying climatic effects. To separate the temporal components of the irradiance variations, specifically the magnetic cycle from secular variability, we decomposed the signals associated with historical observations of magnetic features and the solar modulation potential Φ by applying an empirical mode decomposition algorithm. Thus, the reconstruction is empirical and does not require any feature contrast or field transport model. The assessed difference between the mean value during the Maunder minimum and the present value is ≃2.5 W m-2. Moreover it shows, in the first half of the last century, a growth of ≃1.5 W m-2, which stops around the middle of the century to remain constant for the next 50 years, apart from the modulation due to the solar cycle.

Keywords: Solar cycle, Solar photosphere, Solar faculae, Solar activity, Solar-terrestrial interactions, Active solar chromosphere
Changes in the Na D<SUB>1</SUB> Absorption Components of η Carinae Provide Clues on the Location of the Dissipating Central Occulter. The Na D absorption doublet in the spectrum of η Carinae is complex, with multiple absorption features associated with the Great Eruption (1840s), the Lesser Eruption (1890s), and the interstellar clouds. The velocity profile is further complicated by the P Cygni profile originating in the system's stellar winds and blending with the He I λ5876 profile. The Na D profile contains a multitude of absorption components, including those at velocities of -145 km s-1, -168 km s-1, and +87 km s-1, which we concentrate on in this analysis. Ground-based spectra recorded from 2008 to 2021 show significant variability of the -145 km s-1 absorption throughout long-term observations. In the high-ionization phases of η Carinae prior to the 2020 periastron passage, this feature disappeared completely but briefly reappeared across the 2020 periastron, along with a second absorption at -168 km s-1. Over the past few decades, η Carinae has been gradually brightening, which is shown to be caused by a dissipating occulter. The decreasing absorption of the -145 km s-1 component, coupled with similar trends seen in absorptions of ultraviolet resonant lines, indicate that this central occulter was possibly a large clump associated with the Little Homunculus or another clump between the Little Homunculus and the star. We also report on a foreground absorption component at +87 km s-1. Comparison of Na D absorption in the spectra of nearby systems demonstrates that this redshifted component likely originates in an extended foreground structure consistent with a previous ultraviolet spectral survey in the Carina Nebula.

Keywords: Ejecta, Binary stars, Massive stars, Luminous blue variable stars, Circumstellar matter
Investigating the Asymmetry of Magnetic Field Profiles of "Simple" Magnetic Ejecta through an Expansion-modified Flux Rope Model. Magnetic clouds (MCs) are most often fitted with flux rope models that are static and have symmetric magnetic field profiles. However, spacecraft measurements near 1 au show that MCs usually expand when propagating away from the Sun and that their magnetic field profiles are asymmetric. Both effects are expected to be related, since expansion has been shown to result in a shift of the peak of the magnetic field toward the front of the MC. In this study, we investigate the effects of expansion on the asymmetry of the total magnetic field strength profile of MCs. We restrict our study to the simplest events, i.e., those that are crossed close to the nose of the MC. From a list of 25 such "simple" events, we compare the fitting results of a specific expanding Lundquist model with those of a classical force-free circular cross-sectional static Lundquist model. We quantify the goodness of the fits by the χ 2 of the total magnetic field and identify three types of MCs: (i) those with little expansion, which are well fitted by both models; (ii) those with moderate expansion, which are well fitted by the expanding model, but not by the static model; and (iii) those with expansion, whose asymmetry of the magnetic field cannot be explained. We find that the assumption of self-similar expansion cannot explain the measured asymmetry in the magnetic field profiles of some of these magnetic ejecta (MEs). We discuss our results in terms of our understanding of the magnetic fields of the MEs and their evolution from the Sun to Earth.

Keywords: Solar wind, Interplanetary magnetic fields
The Sun's Mean Line-of-sight Field. In this paper, I regard the Sun-as-a-star magnetic field (i.e., the mean field) as a filter for the spherical harmonic components of the photospheric field, and then calculate the transmission coefficients of this filter. The coefficients for each harmonic, Y  l   m , are listed in three tables according to their dependence on B 0, the observer's latitude in the star's polar coordinate system. These coefficients are used to interpret the 46 yr sequence of daily mean-field measurements at the Wilcox Solar Observatory. I find that the nonaxisymmetric part of the field originates in the ${Y}_{1}^{1}$ , ${Y}_{2}^{2}$ , and a combination of the ${Y}_{3}^{3}$ and ${Y}_{3}^{1}$ harmonic components. The axisymmetric part of the field originates in ${Y}_{2}^{0}$ plus a B 0-dependent combination of the ${Y}_{1}^{0}$ and ${Y}_{3}^{0}$ components. The power spectrum of the field has peaks at frequencies corresponding to the ~27 day synodic equatorial rotation period and its second and third harmonics. Each of these peaks has fine structure on its low-frequency side, indicating magnetic patterns that rotate slowly under the influence of differential rotation and meridional flow. The sidebands of the fundamental mode resolve into peaks corresponding to periods of ~28.5 and ~30 days, which tend to occur at the start of sunspot maximum, whereas the ~27 day period tends to occur toward the end of sunspot maximum. We might expect similar rotational sidebands to occur in magnetic observations of other Sun-like stars and to be a useful complement to asteroseismology studies of convection and magnetic fields in those stars.

Keywords: Solar cycle, Stellar magnetic fields, Solar rotation, Solar magnetic fields
Molecular Clouds as Gravitational Instabilities in Rotating Disks: A Modified Stability Criterion. Molecular gas disks are generally Toomre stable (Q  T  &gt; 1) and yet clearly gravitationally unstable to structure formation as evidenced by the existence of molecular clouds and ongoing star formation. This paper adopts a 3D perspective to obtain a general picture of instabilities in flattened rotating disks, using the 3D dispersion relation to describe how disks evolve when perturbed over their vertical extents. By explicitly adding a vertical perturbation to an unperturbed equilibrium disk, stability is shown to vary with height above the midplane. Near z = 0, where the equilibrium density is roughly constant, instability takes on a Jeans-like quality, occurring on scales larger than the Jeans length and subject to a threshold Q  M  = κ 2/(4π G ρ) = 1 or roughly Q  T  ≈ 2. Far from the midplane, on the other hand, stability is pervasive, and the threshold for the total disk (out to z = ±∞) to be stabilized is lowered to Q  T  = 1 as a consequence. In this new framework, gas disks are able to fragment through partial 3D instability even where total 2D instability is suppressed. The growth rates of the fragments formed via 3D instability are comparable to, or faster than, Toomre instabilities. The rich structure in molecular disks on the scale of tens of parsecs can thus be viewed as a natural consequence of their 3D nature and their exposure to a variety of vertical perturbations acting on roughly a disk scale height, i.e., due to their situation within the more extended galaxy potential, participation in the disk-halo flow, and exposure to star formation feedback.

Keywords: Giant molecular clouds, Interstellar medium, Galaxy dynamics, Disk galaxies
Search for Coincident Gravitational-wave and Fast Radio Burst Events from 4-OGC and the First CHIME/FRB Catalog. Advanced LIGO and Virgo have reported 90 confident gravitational-wave (GW) observations from compact-binary coalescences from their three observation runs. In addition, numerous subthreshold GW candidates have been identified. Binary neutron star (BNS) mergers can produce GWs and short-gamma-ray bursts, as confirmed by GW170817/GRB 170817A. There may be electromagnetic counterparts recorded in archival observations associated with subthreshold GW candidates. The CHIME/FRB Collaboration has reported the first large sample of fast radio bursts (FRBs), millisecond radio transients detected up to cosmological distances; a fraction of these may be associated with BNS mergers. This work searches for coincident GWs and FRBs from BNS mergers using candidates from the fourth Open Gravitational-wave Catalog and the first CHIME/FRB catalog. We use a ranking statistic for GW/FRB association that combines the GW detection statistic with the odds of temporal and spatial association. We analyze GW candidates and nonrepeating FRBs from 2019 April 1 to 2019 July 1, when both the Advanced LIGO/Virgo GW detectors and the CHIME radio telescope were observing. The most significant coincident candidate has a false alarm rate of 0.29 per observation time, which is consistent with a null observation. The null results imply, at most, ${ \mathcal O }(0.01) \% $ - ${ \mathcal O }(1) \% $ of FRBs are produced promptly from the BNS mergers.

Keywords: Gravitational wave astronomy, Radio bursts, High energy astrophysics