Sazuna/UAT_keywords huggingface dataset:
Spectral Analysis of Cygnus X-3 Using Simultaneous AstroSat and Insight-HXMT Observations. We present the results from a spectral analysis of Cygnus X-3 using simultaneous data from AstroSat and Insight-HXMT during its soft state. A pure reflection spectrum, including emission lines of iron, silicon, and sulfur, provides a good fit to the spectral data. An orbital phase-resolved analysis shows no significant spectral parameter variations, except for the normalization. Leveraging IXPE polarization results, we model using a funnel-shaped geometry and estimate the scattered flux and observed polarization for various funnel parameters and observer inclinations. We consider two scenarios: reflection from the funnel walls and scattering by gas within the funnel. Our results reconfirm previous findings, showing that reflection can produce a high polarization degree (PD) of 23%, but not a low PD of 12%. Conversely, scattering can produce a PD of 10%–12%, but not as high as 23% for a fixed observer inclination of 30∘. The scattering results align with previous findings without absorption, but with absorption, PD drops significantly with increasing funnel opening angle. Thus, we can identify common funnel parameters that can produce the different observed PDs in the soft and hard states. The intrinsic luminosity of the source was estimated by comparing the results from a plane disk and the funnel model, which was found to be ∼7 × 1040 erg s‑1 for 12% PD (scattering) and ∼5 × 1041 erg s‑1 for 23% PD (reflection). However, for the reflection model, the luminosity may decrease to ∼ 1040 erg s‑1 when the 23% PD observed is taken as a lower limit.

Keywords: High mass x-ray binary stars, High energy astrophysics
Nature of Ultralong Period Radio Transients: Could They Be Strange Dwarf Pulsars?. Ultralong period radio transients (ULPTs), with periods of thousands of seconds, challenge conventional pulsar models. We propose that these isolated sources are strange dwarf (SD) pulsars—compact objects with a strange quark matter core surrounded by a normal matter crust. We develop a theoretical framework for SD pulsars and apply it to four known isolated ULPTs: GLEAM-X J162759.5–523504.3, GPM J1839–10, ASKAP J1832–0911 (DART J1832–0911), and ASKAP J193505.1+214841.0 (ASKAP J1935+2148). Our analysis shows that SD pulsars naturally explain both the ultralong periods and coherent radio emission of these sources, which occupy a distinctive region in the magnetic field–period diagram. We find that these objects have surface magnetic fields ranging from 106 to 1010 G, with a consistent lower bound near 106 G that suggests a fundamental threshold for pair production in these magnetospheres. Their radio emission efficiencies (ηrad,rot ≈ 10‑4–10‑2) align with those of normal pulsars despite their extreme periods. ASKAP J1935+2148 represents a boundary case, positioned below the theoretical death line but still radio active, offering crucial insights into emission mechanisms at extreme periods. The observed X-ray properties of ASKAP J1832–0911, including its two-component spectrum and synchronous X-ray/radio variability, strongly support the SD pulsar model. This framework provides a unified explanation for ULPTs and has significant implications for understanding exotic dense matter in compact objects.

Keywords: Neutron stars, Radio transient sources, Compact objects, Pulsars
Fermi-LAT Discovery of a Gamma-Ray Outburst from the Peculiar Compact Steep Spectrum Radiogalaxy 3C 216. 3C 216 is an extragalactic radio source classified as a compact steep spectrum (CSS) object, associated with the source 4FGL J0910.0+4257 detected by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope. The source exhibits extended radio structures as well as an inner relativistic jet. In general, jets accelerated by active galactic nuclei (AGNs) are efficient sources of nonthermal radiation, spanning from the radio band to X-ray and gamma-ray energies. Due to relativistic beaming, much of this radiation, particularly in the high-energy domain, is concentrated within a narrow cone aligned with the jet's direction. Consequently, high-energy emission is more easily detected in blazars, where the jet is closely aligned with the line of sight of the observer. Beginning in 2022 November, Fermi-LAT observed increased gamma-ray activity from 3C 216, culminating in a strong outburst in 2023 May. This event was followed up by observations from the Neil Gehrels Swift Observatory telescope. In this work, we perform a careful analysis of the multifrequency data (gamma ray, X-ray, UV, optical) collected during this observational campaign. We find that the spectral energy distribution (SED) of the flaring source evolves in a coherent way, supporting a common origin for the multifrequency emission. These results suggest that the SED observed during the outburst was dominated by a single emission zone, where synchrotron self-Compton (SSC) processes played a primary role. Since single-zone SSC models have typically fewer free parameters than multizone alternatives, they are a powerful probe of the physical conditions of the high-energy emitting regions. Therefore, observing SSC radiation even in CSS sources improves our understanding of the production of high-energy radiation in AGN jets.

Keywords: Gamma-ray sources, Radio sources, High energy astrophysics
The Cosmic Evolution of Fast Radio Bursts Inferred from the CHIME/FRB Baseband Catalog 1. Redshift and luminosity distributions are essential for understanding the cosmic evolution of extragalactic objects and phenomena, such as galaxies, gamma-ray bursts, and fast radio bursts (FRBs). For FRBs, these distributions are primarily estimated using the fluence and the dispersion measure (DM). Calibrating their joint distribution has been challenging due to a lack of accurate fluences in the intensity data of the CHIME/FRB survey. Using the baseband update of CHIME/FRB Catalog 1, we calibrate the 2D fluence–DM distribution for the first time. We find the energy distribution is described well by a Schechter function with a power-law slope of  ‑1.94‑0.12+0.14 . Testing two types of redshift evolution models suggests a likely combination of young and old formation channels.  31‑21+31 % of FRB sources may track star formation, or correspondingly, FRB sources may have delay times of  1.94‑1.31+1.54  Gyr. A pure star formation tracking population is excluded by only one model at &gt;2σ confidence. An updated cosmic star formation rate density evolution up to redshift 14 is constrained by compiling results from several JWST studies. The furthest FRB detection with planned radio facilities is expected to be at z ≈ 5. A radio telescope operating at 200 MHz with a system-equivalent flux density of ≤0.07 Jy (equivalent to a detection threshold of 1 mJy ms) and instantaneous sky coverage of ≳400 deg2 should be able to detect  630‑485+730  FRBs yr‑1 at z ≳ 6 and  53‑43+83  FRBs yr‑1 at z ≳ 8, which is sufficient to differentiate between reionization histories.

Keywords: Luminosity function, Extragalactic radio sources, Radio bursts, Radio transient sources
Active Galactic Nuclei and Host Galaxies in COSMOS-Web. II. First Look At the Kiloparsec-scale Dual and Offset AGN Population. Kiloparsec-scale dual and offset active galactic nuclei (AGNs) are signposts of accreting supermassive black holes (SMBHs) triggered during late-stage galaxy mergers, offering crucial insights into the coevolution of SMBHs and galaxies. However, robustly confirmed systems at high redshift (e.g., z &gt; 1) are scarce and biased toward the most luminous and unobscured systems. In this study, we systematically search for kiloparsec-scale (projected separation &lt;15 kpc) dual and offset AGNs around 571 moderate-luminosity, X-ray-selected AGNs, including the obscured population, utilizing deep Hubble Space Telescope Advanced Camera for Surveys/F814W and multiband JWST NIRCam imaging from the COSMOS-Web survey. We identify 59 dual and 30 offset AGN candidates in late-stage major mergers based on spatially resolved spectral energy distribution analyses. This translates to ∼28 and ∼10 bona fide dual and offset AGNs, using a probabilistic pair-counting scheme to minimize chance superpositions. Notably, the fraction of dual and offset AGNs among moderate-luminosity (Lbol ∼ 1043−1046 erg s−1) obscured AGNs is nearly 2 orders of magnitude higher than that of the most luminous, unobscured quasar pairs. We find tentative evidence for an increasing pair fraction among AGNs with redshift (from a few percent at z ∼ 0.5 to  ∼22.9−17.7+27.5%  at z ∼ 4.5) and a higher occurrence rate of dual over offset AGNs. There is no pileup of dual/offset AGNs below ∼2kpc separations. These results generally align with predictions from the ASTRID and Horizon-AGN cosmological simulations, when matching sample selection criteria, implying a high probability of both black holes being active simultaneously in late-stage major mergers.

Keywords: AGN host galaxies, Double quasars, Active galactic nuclei, Galaxy evolution, Galaxy mergers
Rapid Spatiotemporal Evolution of Vertical Electric Currents during an X-class Flare. In this paper, we present a detailed analysis of the spatiotemporal evolution of photospheric vertical electric currents (VECs) during an X1.1 flare (SOL2013-11-10T05:08). The VEC on the solar surface is calculated using the 135 s high-temporal-resolution vector magnetograms obtained from the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory. In the region, a highly sheared magnetic channel that is also a polarity inversion line (PIL) divides the region into two parts. The spatial configuration of VEC ribbons is always conjugate footprints, and it takes the form of a sigmoid along two sides of the PIL at the beginning of the flare. The temporal evolution of the VECs shows a rapid enhancement associated with the impulsive phase of the flare, and mean horizontal fields in this region show similar temporal behavior. The most prominent enhancement of VECs not only shows up along the two sides of the enhancement Bh but also spreads outward along the PILs. The VECs in positive and negative fields have an initial separation motion and are followed by an apparent approaching motion. In contrast, the flaring loops and white-light flare ribbons have an initial contraction and later expansion motion. Our results show that the rapid change of magnetic fields related to flares has a predominant role in affecting the spatiotemporal evolution of VECs.

Keywords: Solar photosphere, Solar flares, Solar magnetic reconnection
The Formation of Double Hot Jupiter Systems through von Zeipel–Lidov–Kozai Migration. The von Zeipel–Lidov–Kozai (ZLK) mechanism with tidal friction has been demonstrated as a promising avenue to generate hot Jupiters in stellar binary systems. Previous population studies of hot Jupiter formation have largely examined this mechanism in systems comprised of three bodies: two stars and one planet. However, because stars in a binary system form in similar environments with comparable metallicities, the formation of a single hot Jupiter in such a system may imply that the conditions are more likely met for the companion star as well. We investigate the ZLK mechanism with tidal friction as a potential mechanism to produce double hot Jupiter systems in stellar binaries. Using N-body simulations, we characterize the evolution of two cold Jupiters, each orbiting one star in a binary system, undergoing mirrored ZLK migration. We then examine the robustness of this mechanism to asymmetries in stellar masses, planet masses, and planet orbital inclinations relative to the binary plane. We predict that, under the assumptions that (1) most hot Jupiters in binary star systems form through ZLK migration of primordially formed cold Jupiters and (2) if one star in the binary system forms a cold Jupiter, the second does as well. A comprehensive search could identify double hot Jupiters in up to ∼9% of the close- to moderate-separation (a* ≤ 2000 au) binary systems that already host a known hot Jupiter. We also argue that a blind search for ZLK-migrated double hot Jupiters should prioritize twin stellar binaries with pericenter approaches of a few hundred astronomical units.

Keywords: Exoplanet dynamics, Binary stars, Hot Jupiters, Exoplanets, Exoplanet systems, Orbital evolution, Exoplanet evolution, Exoplanet tides, Star-planet interactions
Can the Neutrinos from TXS 0506+056 Have a Coronal Origin?. The blazar TXS 0506+056 has been the first astrophysical source associated with high-energy astrophysical neutrinos, and it has emerged as the second-most-prominent hotspot in the neutrino sky over 10 yr of observations. Although neutrino production in blazars has traditionally been attributed to processes in the powerful relativistic jet, the observation of a significant neutrino flux from NGC 1068—presumably coming from the active galactic nucleus (AGN) corona—suggests that neutrinos can also be produced in the cores of AGN. This raises the question whether neutrino production in TXS 0506+056 is also associated with the core region. We study this scenario, focusing on the hypothesis that this blazar is a masquerading BL Lac object, a high-excitation quasar with hidden broad emission lines and a standard accretion disk. We show that magnetic reconnection is an acceleration process necessary to reach tens of PeV proton energies, and we use observationally motivated estimates of the X-ray luminosity of the coronal region to predict the emission of secondaries and compare them to the observed multiwavelength and neutrino spectra of the source. We find that the coronal neutrino emission from TXS 0506+056 is too low to describe the IceCube observed neutrinos from this AGN, which in turn suggests that the blazar jet remains the preferred location for neutrino production.

Keywords: High energy astrophysics, Neutrino astronomy, Plasma astrophysics, Non-thermal radiation sources, Active galactic nuclei
The Frequency-dependent Modulation Features of PSR J1948+3540. Using observations from the Giant Metrewave Radio Telescope and FAST, we conducted multiwavelength studies on PSR J1948+3540 and analyzed its intensity modulation characteristics in detail. We found that the intensity modulation of this pulsar exhibits broad low-frequency modulation features. The modulation frequency/period is time dependent, but the dominant modulation component varies with the observing frequency. Specifically, at low frequencies, the modulation is dominated by the first half of the middle component, while at high frequencies, it is dominated by the second half of the middle component. Spectral analysis revealed that the intensities of the leading and trailing components vary with the observing frequency, but the middle component does not change significantly. In addition, the polarization analyses reveal that the peak of the radiation intensity is located in the latter half of the middle component, whereas the linear polarization is dominant in the former half. However, due to the low degree of linear polarization, the change of the dominant modulation component with the observed frequency is not caused by the variation in linear polarization. The phenomenon of the dominant modulation component varying with observing frequency has not been reported before and remains difficult to understand within the current theoretical framework.

Keywords: Radio pulsars, Pulsars
The Soft X-Ray Aspect of Gamma-Ray Bursts in the Einstein Probe Era. The Einstein Probe (EP) satellite, dedicated to time-domain high-energy astrophysics and multimessenger astronomy, was recently launched and successfully put into operation. The Wide-field X-ray Telescope (WXT; 0.5–4 keV) on board has identified multiple gamma-ray burst (GRB) events, with an average duration of several hundred seconds. This duration is several times longer than the average duration of long gamma-ray bursts (LGRBs) detected by the Neil Gehrels Swift Observatory, which typically stands at several tens of seconds. Additionally, EP has detected some unknown X-ray transients whose connection to GRBs is uncertain, due to the absence of gamma-ray counterparts and efficient follow-up observation at multiple wavelengths. Several main factors could account for the longer time, including the Doppler effect of off-axis viewing, the spectral lag effect of the synchrotron spectrum of cooling electrons, and some unknown prolonged intrinsic X-ray activities. Our studies indicate that EP GRBs may primarily consist of off-axis-viewed bursts, forming a unique population among the GRB zoo, yet the intrinsic origin for the specific bursts could not be excluded. By analyzing the statistical properties of the historical LGRB samples, we explored observable properties of on-axis and off-axis LGRBs in the soft X-ray band. The predicted characteristics of off-axis-viewed GRBs, including the duration, the energy fluence, the low-energy spectral index, and the slopes of the Amati and Yonetoku relations, could be tested with a larger sample of GRB events detected by EP in the future.

Keywords: Gamma-ray bursts, Non-thermal radiation sources, High energy astrophysics
Inclusion of Isomers/Astromers in s-process Nucleosynthesis: The Pivotal Case of <SUP>85</SUP>Kr. 85Kr is an s-process branch point nucleus: the competition between neutron capture and β decay influences the production of nearby nuclides. Its evolution is complicated by the existence of a long-lived isomer that β-decays on a much shorter timescale than the ground state. We calculate the effective thermal transition rates between the ground and isomeric states along with estimates of their thermal β-decay rates in a suite of nucleosynthesis computations to assess the consequences of this isomer on isotopic abundances. A central finding in this study is that the s-process flow with the isomer included under astrophysical conditions relevant for the s-process creates a shift in abundance yield of the important radioactivity 87Rb by a factor of ∼2.4 relative to the case when the 85Kr is taken to be internally equilibrated when neutron exposures approach the main branch limit. On the other hand, the 88Sr/86Sr ratio is little affected because the bulk of the flow through 85Kr is still via beta decay, whether the isomer is taken into account or not.

Keywords: S-process, Stellar nucleosynthesis, Nuclear astrophysics
An Unusual Change in the Radio Jets of GRS 1915+105. We compare Very Large Array observations of GRS 1915+105 made in 1994 and 2023, with nearly three decades of difference. The source has experienced intriguing major changes. The position angle of the bipolar ejecta in the plane of the sky has increased counterclockwise by 24°. The inclination angle of the flow with respect to the line of sight has increased by 17°. The observations of 2023 also show the temporal quasi-sinusoidal radio oscillations reported for several previous epochs. However, the 2023 oscillations are faster than ever before, with a period of about 8 minutes as opposed to the periods in the range of 20–40 minutes observed in previous epochs. Analysis of GRS 1915+105 images over the years suggests that the observed changes took place within a year or less. Our analysis indicates that during 2023, the plane of the accretion disk with an accretion rate enhanced by a factor of ∼4.3 was aligned with the line of sight, which may explain the deep X-ray obscured state and the high mid-infrared luminosity observed with JWST in that epoch. More recent 2024 observations show that the position angle of the ejecta has returned to its historic values. Future monitoring of the time evolution of the source may clarify the cause of these remarkable changes.

Keywords: Relativistic jets
Impact of Thermonuclear Reaction Rate Uncertainties on the Identification of Presolar Grains from Classical Novae. Approximately 30%–40% of classical novae generate dust between 20 and 100 days following the eruption. However, there has yet to be a definitive identification of presolar stardust grains originating from classical novae. While multiple studies have suggested a nova origin for specific grains, aligning simultaneously all measured isotopic ratios of a specific grain with those predicted from simulations remains challenging. Using Monte Carlo simulations, this work investigates how uncertainties in thermonuclear reaction rates influence the isotopic ratios predicted in simulations of classical novae, specifically impacting the identification of presolar grains. In particular, we address two questions: (i) What is the impact of uncertainties in reaction rates on the range of isotopic ratios predicted by classical nova simulations? (ii) Which reaction rate uncertainties most significantly influence the predicted abundance ratios in presolar grains? Our results show that current reaction rate uncertainties affect the isotopic ratios of 12C/13C, 14N/15N, 16O/17O, 16O/18O, 24Mg/25Mg, 24Mg/26Mg, 26Al/27Al, and 28Si/29Si by less than 20% in either carbon–oxygen or oxygen–neon (ONe) novae, especially when considering the mixing of matter throughout the entire envelope. However, the isotopic ratios of 28Si/30Si, 32S/33S, and 32S/34S in ONe novae are exceptions: their variability greatly exceeds a factor of 2 due to the uncertainties in the reaction rates of 30P(p,γ)31S, 33S(p,γ)34Cl, and 34S(p,γ)35Cl, respectively. These results highlight the significant influence of specific reaction rates on the predicted abundance ratios and underscore the necessity for accurate nuclear measurements to reduce these uncertainties.

Keywords: Classical novae
Leptohadronic Multimessenger Modeling of Two High-redshift (z &gt; 1) Neutrino Emission Blazar Candidates. The blazars are one of the leading candidate sources of high-energy neutrinos. Recently, two blazars have been found to be temporally and spatially correlated with some IceCube high-energy neutrino events. The two blazars, GB6 J2113+1121 and NVSS J171822+423948, are flat spectrum radio quasars (FSRQs) with redshifts greater than unity. In particular, NVSS J171822+423948 has a redshift of 2.7, which provides an important probe for studying the radiation processes of jets from active galactic nuclei in the early Universe. To better understand the physical origin of the IceCube neutrinos, we adopt the one-zone leptohadronic model to fit the multimessenger emission of GB6 J2113+1121 and NVSS J171822+423948 during their γ-ray flaring periods and then calculate the high-energy neutrino detection probability. The chance of detecting a single muon neutrino from these two sources is found to be ∼2% and 0.8%, respectively. Although such detection rates are not high mainly because of their high redshifts, our investigation strongly suggests that these sources are efficient PeV neutrino emitters. Our results also indicate that electromagnetic cascades produced by hadronic processes contribute significantly to X-ray and γ-ray emissions. However, high-energy γ-rays can be severely absorbed by the soft photon field from the broad-line region, which weakens the correlation between γ-rays and neutrinos, while suggesting a stronger connection between X-rays and neutrinos. We predict that IceCube will continue to detect neutrinos from FSRQs with redshifts greater than 1 in the future.

Keywords: Gamma-ray astronomy, Neutrino astronomy, Galaxy jets