Sazuna/UAT_keywords huggingface dataset:
Constraining the Number Density of the Accretion Disk Wind in Hercules X-1 Using Its Ionization Response to X-Ray Pulsations. X-ray binaries are known to launch powerful accretion disk winds that can have a significant impact on the binary systems and their surroundings. To quantify the impact and determine the launching mechanisms of these outflows, we need to measure the wind plasma number density, an important ingredient in the theoretical disk wind models. While X-ray spectroscopy is a crucial tool for understanding the wind properties, such as their velocity and ionization, in nearly all cases, we lack the signal-to-noise ratio to constrain the plasma number density, weakening the constraints on the outflow location and mass outflow rate. We present a new approach to determining this number density in the X-ray binary Hercules X-1, by measuring the speed of the wind ionization response to the time-variable illuminating continuum. Hercules X-1 is powered by a highly magnetized neutron star, pulsating with a period of 1.24 s. We show that the wind number density in Hercules X-1 is sufficiently high to respond to these pulsations by modeling the ionization response with the time-dependent photoionization model TPHO. We then perform a pulse-resolved analysis of the best-quality XMM-Newton observation of Hercules X-1 and directly detect the wind response, confirming that the wind density is at least 1012 cm−3. Finally, we simulate XRISM observations of Hercules X-1 and show that they will allow us to accurately measure the number density at different locations within the outflow. With XRISM, we will rule out ∼3 orders of magnitude in density parameter space, constraining the wind mass outflow rate, energetics, and its launching mechanism.

Keywords: Accretion, Neutron stars, Compact objects
Cyclical Period Changes in Cataclysmic Variables: A Statistical Study. We report the results of a statistical study of cyclical period changes in cataclysmic variables (CVs). Assuming the third-body hypothesis as the cause of period changes, we estimate the third-body mass, m 3, and its separation from the binary, a 3, for 21 CVs showing cyclical period changes from well-sampled observed-minus-calculated diagrams covering more than a decade of observations. The inferred a 3 values are independent of the binary orbital period, P orb, whereas the m 3 values increase with P orb by 1 order of magnitude from the shortest period (oldest) to the longest period (youngest) systems, implying significant mass loss from the third body with time. A model for the time evolution of the triple system is not able to simultaneously explain the observed behavior of the m 3(P orb) and a 3(P orb) distributions because the combined mass loss from the binary and the third body demands an increase in orbital separation by factors ∼140 as the binary evolves toward shorter P orb's, in clear disagreement with the observed distribution. We conclude that the third-body hypothesis is statistically inconsistent and cannot be used to explain cyclical period changes observed in CVs. On the other hand, the diagram of the amplitude of the period change versus the CV donor-star mass is consistent both with the alternative hypothesis that the observed cyclical period changes are a consequence of magnetic activity in the solar-type donor star, and with the standard evolutionary scenario for CVs.

Keywords: Eclipses, Exoplanets, Stellar evolutionary models, Interacting binary stars, Cataclysmic variable stars, Variable star period change
Do All the Quasars and High-excitation Radio Galaxies (HERGs) in the 3CRR Catalog Contain a Magnetically Arrested Disk (MAD)?. Based on the magnetization, an accretion disk with a large-scale magnetic field can be separated into either standard and normal evolution or magnetically arrested disk (MAD), which are difficult to identify from observations. It is still unclear whether all the radio-loud active galactic nuclei (RLAGNs) with a thin disk and strong radio emissions contain a MAD. We investigate this issue by utilizing the 3CRR catalog. We compile a sample of 35 quasars and 14 high-excitation radio galaxies powered by a thin accretion disk. In order to consistently compare with the MAD sample given by Li et al., the optical-UV emissions of our sample are all detected by the Hubble Space Telescope. It is found that the average X-ray luminosity (L X) of our sample is about 5.0 times higher than that of radio-quiet active galactic nuclei with matching optical-UV luminosity (L UV), in general accord with the factor of 4.5 times in MAD sample within the uncertainty. The relationship between radio (5 GHz) and X-ray (2 keV) luminosities in the 3CRR sources is also found to be consistent with the MAD sample. Furthermore, the jet efficiencies of 3CRR sources are consistent with those from the GRMHD simulations of MAD. Therefore, we suggest that probably all the quasars and at least a fraction of high-excitation radio galaxies in the 3CRR catalog, and perhaps all the RLAGNs with strong radio emissions contain a MAD.

Keywords: Radio active galactic nuclei, Galaxy accretion disks, Magnetic fields, Quasars
On the Formation and Detectability of H<SUB>2</SUB>CNCN and Its Progenitors. New highly exothermic formation pathways incorporating both thermodynamic and kinetic control for the newly astronomically detected H2CNCN molecule are paired with extremely accurate quantum chemical rovibrational spectroscopic computations. The reactions between astronomically known CH2CN/CH2CCH + HNCN follow effectively identical pathways and proceed through stable intermediates and over deeply submerged transition states to form H2CNCN and HCN/HCCH coproducts. Similarly, the reaction between CH2CN and NCN‑ can also form H2CNCN, although this pathway first requires the initial formation of NCN‑, which is currently undetected in space, via HNCN + CN‑. This two-step mechanism uses the highly abundant CN‑ as the catalyst. Incredibly accurate quantum chemical spectroscopic data are reported for all reactants and products of these reactions, with errors between experimental values and the computations herein on the order of 0.1% or less. Anharmonic vibrational frequencies and intensities are also reported in order to guide experimental and observational searches for these molecules that have mostly been detected in the radio but may now be detectable via JWST.

Keywords: Infrared spectroscopy, Rotational spectroscopy, Ion-neutral reactions, Interstellar medium, Molecular reactions
Phase-resolved Deadtime of the Crab Pulsar Using IXPE Data. After receiving an X-ray photon, an X-ray detector is not operational for a duration known as deadtime. It is detector specific and its effect on the data depends upon the luminosity of the source. It reduces the observed photon count rate in comparison to the expected one. In periodic sources such as the Crab pulsar, it can distort the folded light curve (FLC). An undistorted FLC of the Crab pulsar is required in combination with its polarization properties for studying its X-ray emission mechanism. This work derives a simple formula for the distortion of the FLC of a pulsar caused by the detector deadtime, and validates it using Crab pulsar data from the X-ray observatories Neutron Star Interior Composition Explorer and Nuclear Spectroscopic Telescope Array, which have very small and relatively large detector deadtimes respectively. Then it derives a method for correcting the distorted FLC of the Crab pulsar in Imaging X-ray Polarimeter Explorer data, which have intermediate detector deadtime. The formula is verified after addressing several technical issues. This work ends with a discussion of why an undistorted FLC is important for studying the formation of cusps in the FLC of the Crab pulsar.

Keywords: X-ray stars
Al<SUB>2</SUB>O Photochemistry. The chemistry within the interstellar medium (ISM) is notably influenced by the interplay between kinetics and photochemical processes, which play significant roles in both the formation and destruction of molecular species. This study focuses on theoretical investigations of Al2O photochemistry, aiming to elucidate the mechanisms underlying the production of AlO and Al in the VY-CMa star. Utilizing advanced theoretical methodologies, we explore the lowest electronic states with singlet and triplet spin multiplicities in linear Al2O. We investigated the photostability of Al2O in the near UV‒Vis region, revealing the low likelihood of photodissociation and photoconversion while suggesting the plausibility of fluorescence and phosphorescence phenomena. Calculations also identify three prominent peaks in the UV range at 261.5, 206.2, and 199 nm. Finally, Al2O is predicted to be photostable and cannot be the parent molecule of the diatomic AlO or even the astrochemical reservoir of atomic aluminum. These results contribute to improving the astronomical models in simulating aluminum chemistry in the ISM.

Keywords: Interstellar absorption, Interstellar medium
Transverse Oscillations and Kelvin–Helmholtz Instability in Curved Arcade Loops with Siphon Flows. The effect of plasma flow in curved arcade loops on transverse waves and oscillations is examined analytically. The model under study is a semicircular magnetic slab with finite transverse extensions and a mass flow inside, in the zero-β plasma approximation. It is found that in the quasi-perpendicular propagation limit, the model supports two fast surface modes: one with higher (FSW+) and another with lower (FSW‑) frequency. For a weak flow, the frequency of the FSW+ (FSW‑) increases (decreases) as the flow speed grows in both propagating and quasi-standing wave regimes. We show that the FSW+ and FSW‑ are subjected to the Kelvin–Helmholtz (KH) instability, and the threshold flow is greater (less than) the internal Alfvén speed for the FSW+ (FSW‑). The presence of plasma flow results in modifying the period ratio P 1/2P 2 of the fundamental harmonic to the first overtone with P 1/2P 2 less (more) than 1 for the FSW+ (FSW‑), and this effect degenerates in the straight waveguide limit. The sub-Alfvénic flow can prohibit resonant absorption of kink modes when the frequencies of the FSW+ and FSW‑ become out of the Alfvén continuum. It is also shown that in the static case and for a weak flow case, the FSW+ (FSW‑) is interpreted as a vertically (horizontally) polarized kink mode, while for moderate flow, both modes have oblique polarization. We apply the developed theory to interpret the observational cases of kink oscillations in coronal loops with signatures of a siphon flow and the onset of KH instability induced by the blowout jet along a loop-shaped magnetic structure.

Keywords: Solar coronal loops
Investigation of Phase Shift and Travel Time of Acoustic Waves in the Lower Solar Atmosphere Using Multiheight Velocities. We report and discuss the phase shift and phase travel time of low-frequency (ν &lt; 5.0 mHz) acoustic waves estimated within the photosphere and photosphere–chromosphere interface regions, utilizing multiheight velocities in the quiet Sun. The bisector method has been employed to estimate seven height velocities in the photosphere within the Fe I 6173 Å line scan, while nine height velocities are estimated from the chromospheric Ca II 8542 Å line scan observations obtained from the narrowband imager instrument installed on the Multi-Application Solar Telescope operational at the Udaipur Solar Observatory, India. Utilizing a fast Fourier transform at each pixel over the full field of view, phase shift and coherence have been estimated. The frequency and height-dependent phase shift integrated over the regions having an absolute line-of-sight magnetic field of less than 10 G indicates the nonevanescent nature of low-frequency acoustic waves within the photosphere and photosphere–chromosphere interface regions. Phase travel time estimated within the photosphere shows nonzero values, aligning with previous simulations and observations. Further, we report that the nonevanescent nature persists beyond the photosphere, encompassing the photospheric–chromospheric height range. We discuss possible factors contributing to the nonevanescent nature of low-frequency acoustic waves. Additionally, our observations reveal a downward propagation of high-frequency acoustic waves indicating refraction from higher layers in the solar atmosphere. This study contributes valuable insights into the understanding of the complex dynamics of acoustic waves within different lower solar atmospheric layers, shedding light on the nonevanescent nature and downward propagation of the acoustic waves.

Keywords: Solar photosphere, Helioseismology, Quiet sun, Solar oscillations, Solar chromosphere
Cold Filaments Formed in Hot Wake Flows Uplifted by Active Galactic Nucleus Bubbles in Galaxy Clusters. Multiwavelength observations indicate that the intracluster medium in some galaxy clusters contains cold filaments, while their formation mechanism remains debated. Using hydrodynamic simulations, we show that cold filaments could naturally condense out of the hot gaseous wake flows uplifted by jet-inflated active galactic nucleus (AGN) bubbles. Consistent with observations, the simulated filaments extend to tens of kiloparsecs from the cluster center, with a representative mass of 108–109 M ⊙ for a typical AGN outburst energy of 1060 erg. They show smooth velocity gradients, stretching typically from inner inflows to outer outflows with velocity dispersions of several hundred kilometers per second. The properties of cold filaments are affected substantially by the jet properties. Compared to kinetic-energy-dominated jets, it is easier for thermal-energy-dominated jets to produce long cold filaments with large masses, as observed. AGN jets with an early turn-on time, a low jet base, or a very high power tend to overheat the cluster center and produce short cold filaments that take a relatively long time to condense out.

Keywords: Galaxy clusters, Hydrodynamical simulations, Radio jets, Active galactic nuclei, Intracluster medium, Astrophysical fluid dynamics
Molecular Hydrogen Formation via Vibrational Excitation of Partially Superhydrogenated Pyrenes. While polycyclic aromatic hydrocarbons (PAHs) are now accepted to be abundant in interstellar space, the abundance and influence of superhydrogenated PAHs (HPAHs) in the interstellar medium (ISM) are still under investigation. HPAHs may act as catalysts for or reactants in small-molecule formation via hydrogen abstraction reactions, H2 evaporation, and carbon skeleton fragmentation. Here, we present a gas-phase infrared (IR) action spectroscopy study of the HPAH 4, 5, 9, 10-tetrahydropyrene (THP; C16H14), performed at the Free Electron Lasers for Infrared eXperiments facility. IR action spectroscopy was performed on the THP cation, protonated THP, and their fragments produced by collision-induced dissociation in the range from 600 to 1800 cm‑1. Calculated IR spectra, at the density functional theory level, agree with experimental IR spectra to a high degree and were utilized to determine molecular structures of the HPAH fragments. Molecular dynamics simulations compared with experimental mass spectra reveal favorable HPAH fragmentation pathways. Molecular hydrogen (H2) is observed to be a primary fragment of [THP+H]+ with superhydrogenated duo groups. This contrasts the notion that HPAHs typically undergo carbon skeleton fragmentation leading to C x H y  formation. These observations show that lowered symmetry and duo or trio aliphatic groups on HPAHs uniquely change their IR spectra, stability, and fragmentation patterns. As a result, these species may contribute to H2 formation in the ISM.

Keywords: Molecular gas, Reaction catalysts, Polycyclic aromatic hydrocarbons, Molecular clouds, Photodissociation regions, Astrochemistry, Dense interstellar clouds, Molecular physics, Dark interstellar clouds, Diffuse interstellar clouds
Timing and Scintillation Studies of Pulsars in Globular Cluster M3 (NGC 5272) with FAST. We present the phase-connected timing solutions of all five pulsars in globular cluster M3 (NGC 5272), namely PSRs M3A to F (PSRs J1342+2822A to F), with the exception of PSR M3C, from FAST archival data. In these timing solutions, those of PSRs M3E and F are obtained for the first time. We find that PSRs M3E and F have low-mass companions and are in circular orbits with periods of 7.1 and 3.0 days, respectively. For PSR M3C, we have not detected its signal in all 41 observations. We found no X-ray counterparts for these pulsars in archival Chandra images in the band of 0.2–20 keV. From the autocorrelation function analysis of M3A and M3B's dynamic spectra, the scintillation timescale ranges from 7.0 ± 0.3 to 60.0 ± 0.6 minutes, and the scintillation bandwidth ranges from 4.6 ± 0.2 to 57.1 ± 1.1 MHz. The measured scintillation bandwidths from the dynamic spectra indicate strong scintillation, and the scattering medium is anisotropic. From the secondary spectra, we captured a scintillation arc only for PSR M3B with a curvature of 649 ± 23 m‑1 mHz‑2.

Keywords: Globular star clusters, Binary pulsars, Interstellar scintillation, Millisecond pulsars
Revealing the Production Mechanism of High-energy Neutrinos from NGC 1068. The detection of high-energy neutrino signals from the nearby Seyfert galaxy NGC 1068 provides us with an opportunity to study nonthermal processes near the center of supermassive black holes. Using the IceCube and latest Fermi-LAT data, we present general multimessenger constraints on the energetics of cosmic rays and the size of neutrino emission regions. In the photohadronic scenario, the required cosmic-ray luminosity should be larger than ∼1%‑10% of the Eddington luminosity and the emission radius should be ≲15R S in low-β plasma and ≲3R S in high-β plasma. The leptonic scenario overshoots the NuSTAR or Fermi-LAT data for any emission radii we consider, and the required gamma-ray luminosity is much larger than the Eddington luminosity. The beta-decay scenario also violates not only the energetics requirement but also gamma-ray constraints, especially when the Bethe–Heitler and photomeson production processes are consistently considered. Our results rule out the leptonic and beta-decay scenarios in a nearly model-independent manner and support hadronic mechanisms in magnetically powered coronae if NGC 1068 is a source of high-energy neutrinos.

Keywords: Supermassive black holes, Neutrino astronomy, Active galaxies, Galaxy jets, Non-thermal radiation sources, Gamma-ray astronomy, Particle astrophysics
Deeper, Sharper, Faster: Application of Efficient Transformer to Galaxy Image Restoration. The Transformer architecture has revolutionized the field of deep learning over the past several years in diverse areas, including natural language processing, code generation, image recognition, and time-series forecasting. We propose to apply Zamir et al.'s efficient transformer to perform deconvolution and denoising to enhance astronomical images. We conducted experiments using pairs of high-quality images and their degraded versions, and our deep learning model demonstrates exceptional restoration of photometric, structural, and morphological information. When compared with the ground-truth James Webb Space Telescope images, the enhanced versions of our Hubble Space Telescope–quality images reduce the scatter of isophotal photometry, Sérsic index, and half-light radius by factors of 4.4, 3.6, and 4.7, respectively, with Pearson correlation coefficients approaching unity. The performance is observed to degrade when input images exhibit correlated noise, point-like sources, and artifacts. We anticipate that this deep learning model will prove valuable for a number of scientific applications, including precision photometry, morphological analysis, and shear calibration.

Keywords: Neural networks, Galaxy structure, Galaxy physics, Galaxy photometry, Astronomy image processing
Solar Rotation and Activity for Cycle 24 from SDO/AIA Observations. Differential rotation plays a crucial role in the dynamics of the Sun. We study the solar rotation and its correlation with solar activity by applying a modified machine learning algorithm to identify and track coronal bright points (CBPs) from the Solar Dynamics Observatory/Atmospheric Imaging Assembly observations at 193 Å during cycle 24. For more than 321,440 CBPs, the sidereal and meridional velocities are computed. We find the occurring height of CBPs to be about 5627 km above the photosphere. We obtain a rotational map for the corona by tracking CBPs at the formation height of Fe XII (193 Å) emissions. The equatorial rotation (14.°40 to 14.°54 day‑1) and latitudinal gradient of rotation (‑3.°0 to ‑2.°64 day‑1) show very slightly positive and negative trends with solar activity (sunspots and flares), respectively. For cycle 24, our investigations show that the northern hemisphere has more differential rotation than the southern hemisphere, confirmed by the asymmetry of the midlatitude rotation parameter. The asymmetry (ranked) of the latitudinal gradient of the rotation parameter is concordant with the sunspot numbers for 7 yr within the 9 yr of the cycle; however, for only 3 yr, it is concordant with the flare index. The minimum horizontal Reynolds stress changes from about ‑2500 m2 s‑2 (corresponding to high activity) in 2012 and 2014 to ‑100 m2 s‑2 (corresponding to low activity) in 2019 over 5° to 35° latitudes within cycle 24. We conclude that the negative horizontal Reynolds stress (momentum transfer toward the Sun's equator) is a helpful indication of solar activity.

Keywords: Sunspots, Solar differential rotation, Solar rotation, Solar corona
The Complex Star Formation History of the Halo of NGC 5128 (Cen A). NGC 5128 (Cen A) is the nearest giant elliptical galaxy and one of the brightest extragalactic radio sources in the sky, boasting a prominent dust lane and jets emanating from its nuclear supermassive black hole. In this paper, we construct the star formation history (SFH) of two small fields in the halo of NGC 5128: a northeastern field (Field 1) at a projected distance of ∼18.8 kpc from the center, and a southern field (Field 2) ∼9.9 kpc from the center. Our method is based on identifying long-period variable (LPV) stars that trace their sibling stellar population and hence historical star formation due to their high luminosity and strong variability; we identified 395 LPV stars in Field 1 and 671 LPV stars in Field 2. Even though the two fields are ∼28 kpc apart on opposite sides from the center, they show similar SFHs. In Field 1, the star formation rate (SFR) increased significantly around t ∼ 800 Myr and t ∼ 3.8 Gyr and in Field 2, the SFR increased considerably around t ∼ 800 Myr, t ∼ 3.8 Gyr, and t ∼ 6.3 Gyr, where t is the lookback time. The increase in SFR ∼800 Myr ago agrees with previous suggestions that the galaxy experienced a merger around that time. The SFH reconstructed from LPV stars supports a scenario in which multiple episodes of nuclear activity lead to episodic jet-induced star formation. While there is no catalog of LPV stars for the central part of NGC 5128, applying our method to the outer regions (for the first time in a galaxy outside the Local Group) has enabled us to put constraints on the complex evolution of this cornerstone galaxy.

Keywords: Late stellar evolution, Galaxy jets, Asymptotic giant branch stars, Star formation, Galaxy evolution