Sazuna/UAT_keywords huggingface dataset:
XRISM Reveals a Remnant Torus in the Low-luminosity AGN M81*. Up to 40% of galaxies in the local Universe host a low-luminosity active galactic nucleus (LLAGN), making it vital to understand this mode of black hole accretion. However, the presence or absence of Seyfert-like geometries—an accretion disk close to the black hole, an optical broad-line region, and a molecular torus—remains uncertain owing to the low flux levels of sources within this class. Herein we present an analysis of an XRISM/Resolve spectrum of M81*, the LLAGN in the heart of the nearby spiral galaxy M81. A weak, neutral Fe K emission line is detected and resolved into Kα,1 and Kα,2 components. It shows a negligible velocity shift and weak broadening (FWHM =460‑160+260kms‑1 ) that corresponds to an inner emission radius of r ≥ 2.7 × 104 GM c‑2 for likely inclinations. The Fe Kα line likely traces a torus. The upper limit on additional splitting of the Fe Kα line components translates to a limit on the local magnetic field of B ≤ 3.5 × 108 G, assuming Zeeman splitting. The spectra also reveal ionized plasma(s) through He-like Fe XXV and H-like Fe XXVI emission lines. These can be fit equally well assuming photoionization and collisional excitation. The H-like Fe XXVI line is better described when a second component is included with a redshift of v = 1600 km s‑1, but this addition is of marginal statistical significance. We discuss these results in the context of radiatively inefficient accretion flow models, magnetically arrested disks, and possible links to the Fermi bubbles in the Milky Way.

Keywords: Low-luminosity active galactic nuclei, Black holes
Localizing Dynamically Formed Black Hole Binaries in Milky Way Globular Clusters with LISA. The dynamical formation of binary black holes (BBHs) in globular clusters (GCs) may contribute significantly to the observed gravitational-wave (GW) merger rate. Furthermore, the Laser Interferometer Space Antenna (LISA) may detect many BBH sources from GCs at mHz frequencies, enabling the characterization of such systems within the Milky Way and nearby Universe. In this work, we use Monte Carlo N-body simulations to construct a realistic sample of Galactic clusters, thus estimating the population, detectability, and parameter measurement accuracy of BBHs hosted within them. In particular, we show that the GW signal from 0.7 ± 0.7, 2.0 ± 1.7, 3.6 ± 2.3, and 13.4 ± 4.7 BBHs in Milky Way GCs can exceed the signal-to-noise ratio (SNR) threshold of SNR = 30, 5, 3, and 1 for a 10 yr LISA observation, with ∼50% of detectable sources exhibiting high eccentricities (e ≳ 0.9). Moreover, the Fisher matrix and Bayesian analyses of the GW signals indicate that these systems typically feature highly resolved orbital frequencies (δforb/forb ∼ 10‑7 to 10‑5) and eccentricities (δe/e ∼ 10‑3 to 0.1), as well as a measurable total mass when SNR exceeds ∼20. Notably, we show that high-SNR BBHs can be confidently localized to specific Milky Way GCs with a sky localization accuracy of δΩ ∼ 1 deg2, and we address the large uncertainties in their distance measurement (δR ∼ 0.3–20 kpc). The detection and localization of even a single BBH in a Galactic GC would allow accurate tracking of its long-term orbital evolution, enable a direct test of the role of GCs in BBH formation, and provide a unique probe into the evolutionary history of Galactic clusters.

Keywords: Gravitational waves, Gravitational wave sources
Retention of Surface Water on Tidally Locked Rocky Planets in the Venus Zone around M Dwarfs. Terrestrial planets within the Venus zone surrounding M-dwarf stars can retain surface ice caps on the perpetual dark side if atmospheric heat transport is inefficient, as suggested by previous global climate simulations. This condition is proposed to play a role in the potential regional habitability of these planets. However, the amount of surface ice may be limited by considering the water condensed from the steam atmosphere in a runaway greenhouse state, and the physical mechanism for triggering the condensation process is not clear. Here, we use a two-column moist radiative–convective–subsiding model to investigate the water condensation process on tidally locked planets from the runaway greenhouse state. We find that the water condensation process is characterized by two distinct equilibrium states under the same incoming stellar flux. The initiation of condensation corresponds to a warm, unstable state exhibiting positive Planck feedback, whereas the termination phase corresponds to a cold, stable state exhibiting negative Planck feedback. We further show that the surface water mass in the collapsed state decreases with the incoming stellar flux, background surface pressure, and optical thickness of noncondensable greenhouse gases, with a global equivalent depth of less than ∼20 cm. Our two-column approach provides a straightforward way to understand the water evolution on Venus zone planets around M dwarfs.

Keywords: Extrasolar rocky planets, Water vapor, Exoplanet atmospheres, Surface ices, Land-atmosphere interactions
Model-independent H<SUB>0</SUB> within FLRW: Joint Constraints from GWTC-3 Standard Sirens and Strong Lensing Time Delays. We use 47 gravitational-wave (GW) standard sirens from the third Gravitational-Wave Transient Catalog to calibrate distances in the strong gravitational lensing (SGL) system RXJ1131-1231 and constrain the Hubble constant (H0) via the distance sum rule, without assuming a specific cosmological model. For ΩK = 0, we obtain  H0=73.22−5.43+5.95  km s−1 Mpc−1 and  H0=70.40−5.60+8.03  km s−1 Mpc−1 by breaking the mass-sheet transform using lens galaxy's mass model and stellar kinematics, respectively. Allowing ΩK to vary increases the central value of H0 and reduces its precision. We find that GW dark sirens have significant potential for calibrating SGL systems, due to their relatively higher redshifts. By combining 42 binary black holes and RXJ1131-1231, we obtain an H0 constraint with a precision approximately 40% better than the measurement from GW170817 using the Hubble law. This suggests that high-precision, model-independent H0 measurements can be achieved with this method as the redshift range of GW dark sirens expands, even without the need for GW bright sirens.

Keywords: Cosmology, Strong gravitational lensing, Gravitational waves, Hubble constant
Exploring the Link between Fast Radio Burst and Binary Neutron Star Origins with Spaceborne Gravitational Wave Observations. The origin of repeating fast radio bursts (rFRBs) is an open question, with observations suggesting that at least some are associated with old stellar populations. It has been proposed that some rFRBs may be produced by interactions of the binary neutron star (BNS) magnetospheres decades to centuries before the coalescence. These systems would also emit centi-Hertz gravitational waves during this period, which can be detectable by spaceborne gravitational wave detectors. We explore the prospects of using current and future spaceborne gravitational wave detectors, such as TianQin, LISA, and DECIGO, to test this fast radio burst (FRB) formation hypothesis. Focusing on nearby galaxies like M81, which hosts an rFRB source in a globular cluster, we calculate the detection capabilities for BNS systems. Our analysis reveals that while missions like TianQin and LISA face limitations in horizon distance, changing the detector pointing direction could significantly enhance detection probabilities. Considering that the chance of a Milky Way–like galaxy coincidentally containing a BNS within 100 yr before merger is only 3 × 10‑5–5 × 10‑3, if a signal is detected originating from M81, we can establish the link between FRBs and BNSs with a significance level of at least 2.81σ. For TianQin and LISA, Bayes factors for rFRB–BNS associations range from 4 × 106 to 7 × 108 under ideal assumptions of uniform event distribution, dropping to 5 × 102–105 when accounting for the fact that the events are confined in galaxies. Next-generation detectors such as DECIGO offer enhanced capabilities compared to TianQin and LISA and should easily detect these systems in M81 and beyond. DECIGO can boost the Bayes factor by up to 4 orders of magnitude (1010–1012 ideally and 104–106 realistically). Our work highlights the critical role of spaceborne gravitational wave missions in unraveling FRB origins.

Keywords: Gravitational wave detectors, Gravitational wave sources, Gravitational wave astronomy, Gravitational waves, Radio transient sources
Gravitational-wave Parameter Estimation in Non-Gaussian Noise Using Score-based Likelihood Characterization. Gravitational-wave (GW) parameter estimation typically assumes that instrumental noise is Gaussian and stationary. Obvious departures from this idealization are typically handled on a case-by-case basis, e.g., through bespoke procedures to "clean" non-Gaussian noise transients (glitches), as was famously the case for the GW170817 neutron-star binary. Although effective, this data manipulation can bias key astrophysical inferences, such as binary precession, and compound unpredictably when combining multiple observations. Alternative bias-free methods, like joint noise-signal inference, remain too computationally expensive for large-scale execution. Here we take a different approach: rather than explicitly modeling individual non-Gaussianities to then apply the traditional GW likelihood, we seek to learn the true distribution of instrumental noise without presuming Gaussianity and stationarity in the first place. Assuming only noise additivity, we employ score-based diffusion models to learn an empirical noise distribution directly from detector data and then combine it with a deterministic waveform model to provide an unbiased estimate of the likelihood function. We validate the method by performing inference on a subset of GW parameters from 400 mock observations, containing real LIGO noise from either the Livingston or Hanford detectors. We show that the proposed method can recover the true parameters even in the presence of loud glitches, and that the inference is unbiased over a population of signals without applying any cleaning to the data. This work provides a promising avenue for extracting unbiased source properties in future GW observations over the coming decade.

Keywords: Gravitational wave detectors, Bayesian statistics, Neural networks, Posterior distribution, Non-Gaussianity, Gravitational waves, LIGO
Formation of Chromospheric Fan-shaped Jets through Magnetic Reconnection. Recurrent chromospheric fan-shaped jets highlight the highly dynamic nature of the solar atmosphere. They have been named as "light walls" or "peacock jets" in high-resolution observations. In this study, we examined the underlying mechanisms responsible for the generation of recurrent chromospheric fan-shaped jets utilizing data from the Goode Solar Telescope at Big Bear Solar Observatory, along with data from the Atmospheric Imaging Assembly (AIA) and the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory. These jets appear as dark elongated structures in Hα wing images, persist for over an hour, and are located in the intergranular lanes between a pair of same-polarity sunspots. Our analysis reveals that magnetic flux cancellation at the jet base plays a crucial role in their formation. HMI line-of-sight magnetograms show a gradual decrease in opposite-polarity fluxes spanning the sequence of jets in Hα‑0.8 Å images, suggesting that recurrent magnetic reconnection, likely driven by recurrent miniature flux-rope eruptions that are built up and triggered by flux cancellation, powers these jets. Additionally, magnetic field extrapolations reveal a 3D magnetic null-point topology at the jet formation site ∼1.25 Mm height. Furthermore, we observed strong brightening in the AIA 304 Å channel above the neutral line. Based on our observations and extrapolation results, we propose that these recurrent chromospheric fan-shaped jets align with the minifilament eruption model previously proposed for coronal jets. Though our study focuses on fan-shaped jets in between same-polarity sunspots, a similar mechanism might be responsible for light-bridge-associated fan-shaped jets.

Keywords: Solar atmosphere, Solar magnetic reconnection, Solar spicules, Solar magnetic fields, Solar filament eruptions, Solar chromosphere, Active solar chromosphere
A Massive Black Hole 0.8 kpc from the Host Nucleus Revealed by the Offset Tidal Disruption Event AT2024tvd. Tidal disruption events (TDEs) that are spatially offset from the nuclei of their host galaxies offer a new probe of massive black hole (MBH) wanderers, binaries, triples, and recoiling MBHs. Here we present AT2024tvd, the first off-nuclear TDE identified through optical sky surveys. High-resolution imaging with the Hubble Space Telescope shows that AT2024tvd is 0 .″ 914 ± 0 .″ 010 offset from the apparent center of its host galaxy, corresponding to a projected distance of 0.808 ± 0.009 kpc at z = 0.045. Chandra and Very Large Array observations support the same conclusion for the TDE's X-ray and radio emission. AT2024tvd exhibits typical properties of nuclear TDEs, including a persistent hot UV/optical component that peaks at Lbb ∼ 6 × 1043 erg s−1, broad hydrogen lines in its optical spectra, and delayed brightening of luminous (LX,peak ∼ 3 × 1043 erg s−1), highly variable soft X-ray emission. The MBH mass of AT2024tvd is 106±1 M⊙, at least 10 times lower than its host galaxy's central black hole mass (≳108 M⊙). The MBH in AT2024tvd has two possible origins: a wandering MBH from the lower-mass galaxy in a minor merger during the dynamical friction phase or a recoiling MBH ejected by triple interactions. Combining AT2024tvd with two previously known off-nuclear TDEs discovered in X-rays (3XMM J2150 and EP240222a), which likely involve intermediate-mass black holes in satellite galaxies, we find that the parent galaxies of all three events are very massive (∼1010.9 M⊙). This result aligns with expectations from cosmological simulations that the number of offset MBHs scales linearly with the host halo mass.

Keywords: Supermassive black holes, Tidal disruption, X-ray transient sources, Time domain astronomy, Galaxy mergers
Statistical Trends in JWST Transiting Exoplanet Atmospheres. Our brains are hardwired for pattern recognition as correlations are useful for predicting and understanding nature. As more exoplanet atmospheres are being characterized with JWST, we are starting to unveil their properties on a population level. Here we present a framework for comparing exoplanet transmission spectroscopy from 3 to 5 μm with four bands: L (2.9–3.7 μm), SO2 (3.95–4.1 μm), CO2 (4.25–4.4 μm), and CO (4.5–4.9 μm). Together, the four bands cover the major carbon-, oxygen-, nitrogen-, and sulfur-bearing molecules including H2O, CH4, NH3, H2S, SO2, CO2, and CO. Among the eight high-precision gas giant exoplanet planet spectra we collect, we find strong correlations between the SO2 – L index and planet mass (r = ‑0.41 ± 0.09) and temperature (r = ‑0.64 ± 0.08), indicating SO2 preferably exists (SO2 – L &gt; ‑0.5) among low-mass (∼ &lt;0.3 M J) and cooler (∼ &lt;1200 K) targets. We also observe strong temperature dependency for both CO2 – L and CO – L indices. Under equilibrium chemistry and isothermal thermal structure assumptions, we find that the planet sample favors supersolar metallicity and a low C/O ratio (&lt;0.7). In addition, the presence of a mass–metallicity correlation is favored over uniform metallicity with the eight planets. We further introduce the SO2 – L versus CO2 – L diagram, similar to the color–magnitude diagram for stars and brown dwarfs. All reported trends here will be testable and will be further quantified with existing and future JWST observations within the next few years.

Keywords: Exoplanet atmospheres
Uncertainties in the Inference of Internal Structure: The Case of TRAPPIST-1 f. We use the TRAPPIST-1 system as a model observation of Earth-like planets. The densities of these planets being 1%─10% less than the Earth suggest that the outer planets may host significant hydrospheres. We explore the uncertainty in water mass fraction (wmf) from observed mass and radius. We investigate the interior structure of TRAPPIST-1 f (T1-f) using the open-source solver MAGRATHEA and varying assumptions in the interior model. We find that T1-f likely has a wmf of 16.2% ± 9.9% when considering all possible core mass fractions, and requires 6.9% ± 2.0% water at an Earth-like mantle-to-core ratio. We quantify uncertainties from observational precision, model assumptions, and experimental and theoretical data on the bulk modulus of planet-building materials. We show that observational uncertainties are smaller than model assumptions of mantle mineralogy and core composition but larger than hydrosphere, temperature, and equation-of-state assumptions/uncertainties. Our findings show that while precise mass and radius measurements are crucial, uncertainties in planetary models can often outweigh those from observations, emphasizing the importance of refining both theoretical models and experimental data to better understand exoplanet interiors.

Keywords: Extrasolar rocky planets, Hydrosphere, Exoplanets, Exoplanet structure, Planetary interior
Tracking the Jet-like Corona of Black Hole Swift J1727.8‑1613 during a Flare State through Type-C Quasiperiodic Oscillations. Type-C quasiperiodic oscillations (QPOs) in black hole X-ray transients typically manifest in the low-hard and hard-intermediate states. This study presents a detailed spectral and temporal analysis of the black hole candidate Swift J1727.8‑1613 using NICER observations from 2023 August and September, with a focus on the first flare period. We detected Type-C QPOs whose centroid frequency increased from 0.33 Hz to 2.63 Hz. An additional increase in frequency was observed when the outburst entered a flare period. The time-averaged spectra, along with the rms and phase-lag spectra of the QPOs, were jointly fitted using the time-dependent Comptonization model vkompthdk to examine the geometry of the corona during this flare. Correlations between spectral and temporal properties suggest that the detected type-C QPOs are primarily modulated by Lense–Thirring precession. Leveraging simultaneous radio observations that indicate discrete jet ejections, we propose a scenario to describe the coevolution of the disk–corona–jet during a flare (∼3 days). This scenario is partially supported for the first time by polarization data in the soft gamma-ray band from the IBIS instrument on board the International Gamma-Ray Astrophysics Laboratory. A phenomenological analysis of the corona scenario was also conducted.

Keywords: X-ray astronomy, X-ray binary stars, Accretion, Stellar mass black holes
Further Investigations into Emission Components of PSR B0950+08 and Correlations between Them with Single Pulses. With the phase-to-phase cross-correlation method, we analyzed the single pulses of PSR B0950+08 obtained at the Five-hundred-meter Aperture Spherical radio Telescope. The correlation map produced with the single pulses reveals a modulation of the correlation coefficients, which are between the intensities at different phases of the single pulses. The modulation varies by a period of two phase bins with 2048 bins over the whole pulse phase. Such a modulation is related to the microstructures of the single pulses and may ultimately imply that the Lorentz factors of the charged particles in the pulsar magnetosphere are highly similar along the line of sight trajectory. The modulation rule reverses after a constant phase separation of  191.°43 . It also reverses around the peak phase of the mean pulse profile, implying that the Lorentz factors are different from the normal value around the reversal phase. According to the analyses with the correlation map, we propose that the bridge emission between the main pulse (MP) and its preceding interpulse (IP) is the overlap of the MP and the IP. For the "weak emission" trailing the MP, it is identified as an independent profile component. There are strong emissions from the IP but no giant pulse from the MP during this observation. The correlation between the IPs and the MPs is mainly dominated by the positive correlations between the subcomponents of the IP and one subcomponent of the MP, according to our analyses.

Keywords: Radio pulsars, Pulsars
Constraints on the Galaxy Formation Models during the Epoch of Reionization with High-redshift Observations. We use high-resolution N-body dark matter simulations and L-GALAXIES semianalytical galaxy formation models to explore the high-z galaxy properties and estimate the budget of ionizing photons. The parameters within L-GALAXIES are obtained using a Markov Chain Monte Carlo (MCMC) method with high-z galaxy observations from JWST and other telescopes. We consider two versions of L-GALAXIES, with and without dust correction on galaxy UV luminosities. With the best-fit parameters, both L-GALAXIES 2015 and L-GALAXIES 2020 reproduce well observations of UV luminosity functions, stellar mass functions, star formation rate densities, and ionizing photon emission efficiency. With the assumption of an escape fraction of 20%, all models produce more ionizing photons than the number of hydrogen atoms in the Universe at z &gt; 6. The inclusion of dust correction within MCMC results in higher star formation efficiency, which predicts ∼50% more ionizing photons, with better consistency between the predicted stellar mass functions and observations.

Keywords: Reionization
Revisiting the X-Ray Polarization of the Shell of Cassiopeia A Using Spectropolarimetric Analysis. X-ray synchrotron radiation is expected to be highly polarized. Thanks to the Imaging X-ray Polarimetry Explorer (IXPE), it is now possible to evaluate the degree of X-ray polarization in sources such as supernova remnants (SNRs). Jointly using IXPE data and high-resolution Chandra observations, we perform a spatially resolved spectropolarimetric analysis of SNR Cassiopeia A (Cas A). We focus on the 3–6 keV energy band on regions near the shell dominated by nonthermal synchrotron emission. By combining IXPE's polarization sensitivity with Chandra's higher spatial and spectral resolution, we constrain the local polarization degree (PD) and polarization angle across the remnant. Our analysis reveals PD values ranging locally from 10% to 26%, showing significant regional variations that underscore the complex magnetic field morphology of Cas A. The polarization vectors indicate a predominantly radial magnetic field, consistent with previous studies. Thanks to the improved modeling of thermal contamination using Chandra data, we retrieve higher PD values compared to earlier IXPE analysis and more significant detections with respect to the standard IXPEOBSSIM analysis. Finally, we also estimate the degree of magnetic turbulence η from the measured photon index and PD, under the assumption of an isotropic fluctuating field across the shell of Cas A.

Keywords: Supernova remnants, Spectropolarimetry, Interstellar medium
The Atacama Cosmology Telescope: Systematic Transient Search of Single Observation Maps. We conduct a systematic search for astrophysical transients using data from the Atacama Cosmology Telescope. The data were taken from 2017 to 2022 in three frequency bands spanning 77 to 277 GHz. In this paper, we present a pipeline for transient detection using single-observation maps where each pixel of a map contains one observation with an integration time of approximately 4 minutes. We detect 34 transient events at 27 unique locations. All but two of the transients are associated with Galactic stars and exhibit a wide range of properties. We also detect an event coincident with the classical nova YZ Ret and one event consistent with a flaring active galactic nucleus. We notably do not detect any reverse shock emission from gamma-ray bursts, a nondetection that may be in tension with current models.

Keywords: Asteroids, Millimeter astronomy, Transient sources, Active galactic nuclei, Stellar flares, Transient detection, Classical novae