Sazuna/UAT_keywords huggingface dataset:
Compton-thick AGN in the NuSTAR Era. VIII. A joint NuSTAR-XMM-Newton Monitoring of the Changing-look Compton-thick AGN NGC 1358. We present the multi-epoch monitoring with NuSTAR and XMM-Newton of NGC 1358, a nearby Seyfert 2 galaxy whose properties made it a promising candidate X-ray changing-look active galactic nucleus (AGN), i.e., a source whose column density could transition from its 2017 Compton-thick (having LOS hydrogen column density N H,LOS &gt; 1024 cm-2) state to a Compton-thin (N H,LOS &lt; 1024 cm-2) one. The multi-epoch X-ray monitoring confirmed the presence of significant N H,LOS variability over timescales of weeks to years, and allowed us to confirm the changing-look nature of NGC 1358, which has most recently been observed in a Compton-thin status. Multi-epoch monitoring with NuSTAR and XMM-Newton is demonstrated to be highly effective in simultaneously constraining three otherwise highly degenerate parameters: the torus average column density and covering factor, and the inclination angle between the torus axis and the observer. We find a tentative anticorrelation between column density and luminosity, which can be understood under the framework of chaotic cold accretion clouds driving recursive AGN feedback. The monitoring campaign of NGC 1358 has proven the efficiency of our newly developed method to select candidate N H,LOS-variable, heavily obscured AGN, which we plan to soon extend to a larger sample to better characterize the properties of the obscuring material surrounding accreting supermassive black holes, as well as to constrain AGN feeding models.

Keywords: Accretion, X-ray active galactic nuclei, Active galactic nuclei, Astrophysical black holes
Compact and Variable Radio Emission from an Active Galaxy with Supersoft X-Ray Emission. RX J1301.9+2747 is a unique active galaxy with a supersoft X-ray spectrum that lacks significant emission at energies above 2 keV. In addition, it is one of few galaxies displaying quasiperiodic X-ray eruptions that recur on a timescale of 13-20 ks. We present multiepoch radio observations of RX J1301.9+2747 using GMRT, Very Large Array (VLA), and Very Long Baseline Array (VLBA). The VLBA imaging at 1.6 GHz reveals a compact radio emission unresolved at a scale of &lt;0.7 pc, with a brightness temperature of T b &gt; 5 × 107 K. The radio emission is variable by more than a factor of 2.5 over a few days, based on the data taken from VLA monitoring campaigns. The short-term radio variability suggests that the radio emitting region has a size as small as 8 × 10-4 pc, resulting in an even higher brightness temperature of T b ~ 1012 K. A similar limit on the source size can be obtained if the observed flux variability is not intrinsic and caused by the interstellar scintillation effect. The overall radio spectrum is steep with a time-averaged spectral index α = -0.78 ± 0.03 between 0.89 and 14 GHz. These observational properties rule out a thermal or star formation origin of the radio emission, and appear to be consistent with the scenario of episodic jet ejections driven by a magnetohydrodynamic process. Simultaneous radio and X-ray monitoring observations down to a cadence of hours are required to test whether the compact and variable radio emission is correlated with the quasiperiodic X-ray eruptions.

Keywords: Accretion, Relativistic jets, Active galactic nuclei, Radio jets
Limits on X-Ray Polarization at the Core of Centaurus A as Observed with the Imaging X-Ray Polarimetry Explorer. We present measurements of the polarization of X-rays in the 2-8 keV band from the nucleus of the radio galaxy Centaurus A (Cen A), using a 100 ks observation from the Imaging X-ray Polarimetry Explorer (IXPE). Nearly simultaneous observations of Cen A were also taken with the Swift, NuSTAR, and INTEGRAL observatories. No statistically significant degree of polarization is detected with IXPE. These observations have a minimum detectable polarization at 99% confidence (MDP99) of 6.5% using a weighted, spectral model-independent calculation in the 2-8 keV band. The polarization angle ψ is consequently unconstrained. Spectral fitting across three orders of magnitude in X-ray energy (0.3-400 keV) demonstrates that the SED of Cen A is well described by a simple power law with moderate intrinsic absorption (N H ~ 1023 cm-2) and a Fe Kα emission line, although a second unabsorbed power law is required to account for the observed spectrum at energies below 2 keV. This spectrum suggests that the reprocessing material responsible for this emission line is optically thin and distant from the central black hole. Our upper limits on the X-ray polarization are consistent with the predictions of Compton scattering, although the specific seed photon population responsible for the production of the X-rays cannot be identified. The low polarization degree, variability in the core emission, and the relative lack of variability in the Fe Kα emission line support a picture where electrons are accelerated in a region of highly disordered magnetic fields surrounding the innermost jet.

Keywords: X-ray quasars, Radio galaxies, Polarimetry
Compressed Sensing Based RFI Mitigation and Restoration for Pulsar Signals. In pulsar signal processing, two primary difficulties are (1) radio-frequency interference (RFI) mitigation and (2) information loss due to preprocessing and mitigation itself. Linear mitigation methods have a difficulty in RFI modeling, and accommodate a limited range of RFI morphologies. Thresholding methods suffer from manual factors and adaptability. There is also a distinct lack of methods dedicated to information loss. In this paper, a novel method "CS-Pulsar" is proposed. It carries out compressed sensing (CS) on time-frequency signals to accomplish RFI mitigation and signal restoration simultaneously. Curvelets allow an optimal sparse representation for multichannel pulsar signals containing the time-of-arrival dispersion relationship. CS-Pulsar mitigation is implemented using a regularized least-squares framework that does not require the statistics of RFI to be known beforehand. CS-Pulsar implements channel restoration, and useful signal contents are retrieved from the measurement error by a morphological component analysis aided by the root-mean-square envelope. These two steps allow CS-Pulsar to provide key signal details for special astrophysical purposes. Experiments of signal restoration for pulsar data from the Nanshan 26 m radio telescope reveal the advantage of CS-Pulsar. The method successfully removes false peaks due to on-pulse RFI in multipeaked pulsar profiles. CS-Pulsar also increases the timing accuracy and signal-to-noise ratio proving its feasibilities and prospects in astrophysical measurements.

Keywords: Astronomical techniques, Astronomy data modeling, Wavelet analysis, Radio pulsars
The Long-stable Hard State of XTE J1752-223 and the Disk Truncation Dilemma. The degree to which the thin accretion disks of black hole X-ray binaries are truncated during hard spectral states remains a contentious open question in black hole astrophysics. During its singular observed outburst in 2009-2010, the black hole X-ray binary XTE J1752-223 spent ~1 month in a long-stable hard spectral state at a luminosity of ~0.02-0.1 L Edd. It was observed with 56 RXTE pointings during this period, with simultaneous Swift-XRT daily coverage during the first 10 days of the RXTE observations. While reflection modeling has been extensively explored in the analysis of these data, there is disagreement surrounding the geometry of the accretion disk and corona implied by the reflection features. We reexamine the combined, high signal-to-noise, simultaneous Swift and RXTE observations, and perform extensive reflection modeling with the latest relxill suite of reflection models, including newer high disk density models. We show that reflection modeling requires that the disk be within ~5 R ISCO during the hard spectral state, while weaker constraints from the thermal disk emission imply higher truncation (R in = 6-80 R ISCO). We also explore more complex coronal continuum models, allowing for two Comptonization components instead of one, and show that the reflection features still require only a mildly truncated disk. Finally we present a full comparison of our results to previous constraints found from analyses of the same data set.

Keywords: Accretion, Black hole physics, Radiative processes, Atomic physics
Bridging Optical and Far-infrared Emission-line Diagrams of Galaxies from Local to the Epoch of Reionization: Characteristic High [O III] 88 μm/SFR at z &gt; 6. We present photoionization modeling of galaxy populations at z ∼ 0, 2, and &gt;6 to bridge optical and far-infrared (FIR) emission-line diagrams. We collect galaxies with measurements of optical and/or FIR ([O III] 88 μm and [C II] 158 μm) emission-line fluxes and plot them on the [O III]λ5007/Hβ-[N II]λ6585/Hα (BPT) and L([O III]88)/SFR-L([C II]158)/SFR diagrams, where SFR is the star formation rate and L([O III]88) and L([C II]158) are the FIR line luminosities. We aim to explain the galaxy distributions on the two diagrams with photoionization models that employ three nebular parameters: the ionization parameter U, hydrogen density nH, and gaseous metallicity Zgas. Our models successfully reproduce the nebular parameters of local galaxies, and then predict the distributions of the z ∼ 0, 2, and &gt;6 galaxies in the diagrams. The predicted distributions illustrate the redshift evolution on all the diagrams; e.g., [O III]/Hβ and [O III]88/[C II]158 ratios continuously decrease from z &gt; 6 to 0. Specifically, the z &gt; 6 galaxies exhibit ∼0.5 dex higher U than low-redshift galaxies at a given Zgas and show predicted flat distributions on the BPT diagram at log[O III]/Hβ = 0.5-0.8. We find that some of the z &gt; 6 galaxies exhibit high L([O III]88)/SFR ratios. To explain these high ratios, our photoionization models require a low stellar-to-gaseous-metallicity ratio or bursty/increasing star formation history at z &gt; 6. JWST will test the predictions and scenarios for the z &gt; 6 galaxies proposed by our photoionization modeling.

Keywords: Optical astronomy, Photodissociation regions, Far infrared astronomy, H II regions, Galaxy evolution, High-redshift galaxies
Reconstructing the Assembly of Massive Galaxies. I. The Importance of the Progenitor Effect in the Observed Properties of Quiescent Galaxies at z ≈ 2. We study the relationship between the morphology and star formation history (SFH) of 361 quiescent galaxies (QGs) at redshift &lt;z obs&gt; ≈ 2, with stellar mass $\mathrm{log}{M}_{* }\geqslant 10.3$ , selected with the UVJ technique. Taking advantage of panchromatic photometry covering the rest-frame UV-to-NIR spectral range ( ≈40 bands), we reconstruct the nonparametric SFH of the galaxies with the fully Bayesian SED fitting code PROSPECTOR. We find that the half-light radius R  e , observed at z obs, depends on the formation redshift of the galaxies, z form, and that this relationship depends on M *. At $\mathrm{log}{M}_{* }\lt 11$ , the relationship is consistent with ${R}_{e}\propto {\left(1+{z}_{\mathrm{form}}\right)}^{-1}$ , in line with the expectation that the galaxies' central density depends on the cosmic density at the time of their formation, i.e., the "progenitor effect." At $\mathrm{log}{M}_{* }\gt 11$ , the relationship between R  e  and z form flattens, suggesting that mergers become increasingly important for the size growth of more massive galaxies after they quenched. We also find that the relationship between z form and galaxy compactness similarly depends on M *. While no clear trend is observed for QGs with $\mathrm{log}{M}_{* }\gt 11$ , lower-mass QGs that formed earlier, i.e., with larger z form, have larger central stellar-mass surface densities, both within the R  e  (Σ e ) and central 1 kpc (Σ1 kpc), and also larger M 1 kpc/M *, the fractional mass within the central 1 kpc. These trends between z form and compactness, however, essentially disappear if the progenitor effect is removed by normalizing the stellar density with the cosmic density at z form. Our findings highlight the importance of reconstructing the SFH of galaxies before attempting to infer their intrinsic structural evolution.

Keywords: Quenched galaxies, Apparent magnitude, Galaxy structure, Galaxy evolution, High-redshift galaxies
Metal Lines Associated with the Lyα Forest from eBOSS Data. We investigate the metal species associated with the Lyα forest in eBOSS quasar spectra. Metal absorption lines are revealed in stacked spectra from cross-correlating the selected Lyα absorbers in the forest and the flux fluctuation field. Up to 13 metal species are identified as being associated with relatively strong Lyα absorbers (those with flux fluctuations - 1.0 &lt; δ Lyα  &lt; - 0.6 and with a neutral hydrogen column density of ~ 1015-16 cm-2) over the absorber redshift range of 2 &lt; z abs &lt; 4. The column densities of these species decrease toward higher redshift and for weaker Lyα absorbers. From modeling the column densities of various species, we find that the column density pattern suggests contributions from multiple gas components, both in the circumgalactic medium (CGM) and the intergalactic medium (IGM). While the low-ionization species (e.g., C II, Si II, and Mg II) can be explained by high-density, cool gas (T ~ 104 K) from the CGM, the high-ionization species may reside in low-density or high-temperature gas in the IGM. The measurements provide inputs for modeling the metal contamination in the Lyα forest baryon acoustic oscillation measurements. Comparisons with metal absorptions in high-resolution quasar spectra and hydrodynamic galaxy formation simulations can further elucidate the physical conditions of these Lyα absorbers.

Keywords: Lyman alpha forest, Metal line absorbers, Intergalactic medium
Confirming the Existence of Twin Stars in a NICER Way. We demonstrate that future radius measurements of the NICER mission have the potential to reveal the existence of a strong phase transition in dense neutron star matter by confirming the existence of so-called twin stars, compact star configurations with the same mass but different radii. The latest radius constraints from NICER for the pulsars J0740+6620 as well as J0030+0451 are discussed using relativistic mean field equations of state with varying stiffness, connected with a first-order phase transition to quark matter. We show that twin star solutions are compatible with the new radius constraint but are located at radii below the present constraints from NICER, serving as a smoking gun for a strong phase transition in neutron star matter. This scenario is realized if a strong phase transition takes place in neutron stars of the first branch with masses above 2 M ⊙.

Keywords: Nuclear astrophysics, Neutron star cores, Compact objects, Pulsars
Discovery of a 584.65 Hz Burst Oscillation in the Low-mass X-Ray Binary 4U 1730-22. Type-I X-ray burst oscillations are powered by thermonuclear energy released on the neutron star (NS) surface in low-mass X-ray binaries (LMXBs), where the burst oscillation frequencies are close to the NS spin rates. In this work, we report the detection of oscillation at 584.65 Hz during the cooling tail of type-I X-ray bursts observed from the accreting NS LMXB 4U 1730-22 on 2022 March 20, by the Neutron star Interior Composition Explorer telescope. The oscillation signal showed a strong Leahy power, P m ~ 54.04, around 584.65 Hz, which has single-trial and multiple-trial confidence levels of 7.05σ and 4.73σ, respectively. The folded pulse profile of the oscillation in the 0.2-10 keV band showed a sinusoidal shape with the fractional rms amplitude of (8.0 ± 1.1)%. We found the oscillation frequency showed insignificant upward drifting, i.e., less than 0.3 Hz, during the cooling tail, similar to the behavior appearing in accreting millisecond X-ray pulsars (AMXP), and indicate the source could be an AMXP spinning at 1.71 ms.

Keywords: Neutron stars, Low-mass x-ray binary stars, X-ray sources, X-ray bursts
Cosmological Simulations of the Intergalactic Medium Evolution. III. SPH Simulations. We have developed a new numerical algorithm to study the joint evolution of galaxies and the intergalactic medium (IGM) in a cosmological context, with the specific goal of studying the deposition and dispersion of metals in the IGM. This algorithm combines a standard gasdynamical algorithm to simulate the evolution of the IGM, a semi-analytical model to describe the evolution of galaxies, and prescriptions for galaxy formation, accretion, mergers, and tidal disruption. The main goal in designing this algorithm was performance. In its current version, the algorithm can simulate the evolution of cosmological volumes containing thousands of galaxies in a few days, using between 12 and 32 processors. This algorithm is particularly suited for parameter surveys (both numerical parameters and physical parameters) since a large number of simulations can be completed in a fairly short amount of time. Furthermore, the algorithm provides a platform for the development and testing of new treatments of subgrid physics, which could then be implemented into other algorithms. In this paper, we describe the algorithm and present, for illustration, two simulations of the evolution of a (20 Mpc)3 cosmological volume containing ~1200 galaxies at z = 0.

Keywords: Intergalactic abundances, Galaxy evolution, Intergalactic medium
Timing Properties of the X-Ray Accreting Pulsar 1A 0535+262 Studied with Insight-HXMT. We report results on the timing analysis of the 2020 giant outburst of 1A 0535+262, using broadband data from Insight-HXMT. The analysis of the pulse profile evolution from the subcritical-luminosity to the supercritical-luminosity regime is presented for the first time. We found that the observed pulse profile exhibits a complex dependence on both energy and luminosity. A dip structure at the energy of the cyclotron resonant scattering features is found for the first time in the pulse fraction-energy relation of 1A 0535+262, when the outburst evolves in a luminosity range from 4.8 × 1037 to 1.0 × 1038 erg s-1. The observed structure is luminosity dependent and appears around the source critical luminosity (~6.7 × 1037 erg s-1).

Keywords: X-ray astronomy, X-ray binary stars, Pulsars
Black Hole-Black Hole Total Merger Mass and the Origin of LIGO/Virgo Sources. The LIGO-Virgo-KAGRA (LVK) Collaboration has reported nearly 100 black hole (BH)-BH mergers. LVK provides estimates of rates, masses, effective spins, and redshifts for these mergers. Yet the formation channel(s) of the mergers remains uncertain. One way to search for a formation site is to contrast the properties of detected BH-BH mergers with different models of BH-BH merger formation. Our study is designed to investigate the usefulness of the total BH-BH merger mass and its evolution with redshift in establishing the origin of gravitational-wave sources. We find that the average intrinsic BH-BH total merger mass shows exceptionally different behaviors for the models that we adopt for our analysis. In the local universe (z = 0), the average merger mass changes from ${\overline{M}}_{\mathrm{tot},\mathrm{int}}\sim 25\,{M}_{\odot }$ for the common envelope binary evolution and open cluster formation channels, to ${\overline{M}}_{\mathrm{tot},\mathrm{int}}\sim 30\,{M}_{\odot }$ for the stable Roche lobe overflow binary channel, to ${\overline{M}}_{\mathrm{tot},\mathrm{int}}\sim 45\,{M}_{\odot }$ for the globular cluster channel. These differences are even more pronounced at larger redshifts. However, these differences are diminished when considering the LVK O3 detector sensitivity. A comparison with the LVK O3 data shows that none of our adopted models can match the data, despite the large errors on BH-BH masses and redshifts. We emphasize that our conclusions are derived from a small set of six models that are subject to numerous known uncertainties. We also note that BH-BH mergers may originate from a mix of several channels, and that other (than those adopted here) BH-BH formation channels may exist.

Keywords: Black hole physics
A Comprehensive Analysis of the Gravitational Wave Events with the Stacked Hilbert-Huang Transform: From Compact Binary Coalescence to Supernova. We analyze the gravitational wave signals with a model-independent time-frequency analysis, which is improved from the Hilbert-Huang transform (HHT) and optimized for characterizing the frequency variability on the time-frequency map. Instead of the regular HHT algorithm, i.e., obtaining intrinsic mode functions with ensemble empirical mode decomposition and yielding the instantaneous frequencies, we propose an alternative algorithm that operates the ensemble mean on the time-frequency map. We systematically analyze the known gravitational wave events of the compact binary coalescence observed in the first gravitational-wave transient catalog, and in the simulated gravitational wave signals from core-collapse supernovae (CCSNe) with our method. The time-frequency maps of the binary black hole coalescence cases show much more detail compared to those wavelet spectra. Moreover, the oscillation in the instantaneous frequency caused by mode-mixing could be reduced with our algorithm. For the CCSNe data, the oscillation from the proto-neutron star and the radiation from the standing accretion shock instability can be precisely determined with the HHT in great detail. More importantly, the initial stage of different modes of oscillations can be clearly separated. These results provide new hints for further establishment of the detecting algorithm and new probes to investigate the underlying physical mechanisms.

Keywords: Gravitational wave astronomy, Neutron stars, Black holes, Core-collapse supernovae
CARAMEL-GAS: A Step toward Fast Empirical Models of the Broad-line-emitting Gas. Fast empirical models of the broad emission line region (BLR) are a powerful tool to interpret velocity-resolved reverberation mapping (RM) data, estimate the mass of the supermassive black holes, and gain insight into its geometry and kinematics. Much of the effort so far has been devoted to describing the emissivity of one emission line at a time. We present here an alternative approach aimed at describing the underlying BLR gas distribution, by exploiting simple numerical recipes to connect it with emissivity. This approach is a step toward describing multiple emission lines originating from the same gas and allows us to clarify some issues related to the interpretation of RM data. We illustrate this approach-implemented in the code CARAMEL-GAS-using three data sets covering the Hβ emission line (Mrk 50, Mrk 1511, Arp 151) that have been modeled using the emissivity-based version of the code. As expected, we find differences in the parameters describing the BLR gas and emissivity distribution, but the emissivity-weighted lag measurements and all other model parameters including black hole mass and overall BLR morphology and kinematics are consistent with the previous measurements. We also model the Hα emission line for Arp 151 using both the gas- and emissivity-based BLR models. We find ionization stratification in the BLR with Hα arising at larger radii than Hβ, while all other model parameters are consistent within the uncertainties.

Keywords: Supermassive black holes, Photoionization, Astronomy data modeling, Reverberation mapping