Sazuna/UAT_keywords huggingface dataset:
Detecting Exoplanets beyond the Local Supercluster through Gravitational Waves with B-DECIGO and DECIGO. The first detection of a gravitational-wave (GW) signal in 2015 has opened a new observational window to probe the Universe. This probe can not only reveal previously inaccessible binaries, black holes, and other compact objects, but also can detect exoplanets through their imprint on GW signals, thereby significantly extending current exoplanet surveys. To date, nearly 6000 exoplanets have been confirmed, yet most of them reside either in the solar neighbourhood or along the sightline toward the Galactic bulge, reflecting the range limits of traditional electromagnetic techniques. In this work, we adopt the method proposed in N. Tamanini &amp; C. Danielski to investigate frequency modulations in GW signals from early-stage binary neutron stars induced by circumbinary planets (CBPs) and find that CBPs can be detected by the future space-borne detector Deci-hertz Interferometer Gravitational-wave Observatory (DECIGO). For a binary neutron star system with the masses of two components, both being 1.4 M⊙, DECIGO could detect CBPs with masses dozens of times that of Jupiter out to distances of ∼1 Gpc, well beyond the Local Supercluster, offering an unprecedented opportunity to study planetary formation and evolution for the post-main-sequence stage.

Keywords: Exoplanet detection methods, Gravitational wave detectors, Binary stars, Gravitational waves
Investigation on the Predictive Potentiality of Photospheric Magnetic Parameters for Distinguishing Confined from Eruptive Solar Flares. A question often arises as to why some solar flares are confined in the lower corona while others, termed eruptive flares, are associated with coronal mass ejections. Here, we intend to rank the importance of preflare magnetic parameters of active regions in their potentiality to predict whether an imminent flare will be eruptive or confined. We compiled a dataset comprising 277 solar flares of GOES-class M1.0 and above, taking place within 45∘ from the disk center between 2010 and 2023, involving 94 active regions. Among the 277 flares, 135 are confined and 142 are eruptive. Our statistical analysis reveals that the magnetic parameters that are most relevant to the flare category are total unsigned magnetic flux Φ, mean magnetic shear angle Θ along the polarity inversion line (PIL), photospheric free magnetic energy Ef, and centroid distance d between opposite polarities. These four parameters are not independent of each other but, in combination, might be promising in distinguishing confined from eruptive flares. For a subset of 77 flares with high-gradient PILs, the area of high free energy regions (AHi) becomes the most effective parameter related to the flare type, with confined flares possessing larger AHi than eruptive ones. Our results corroborate the general concept that the eruptive behavior of solar flares is regulated by an interplay between the constraining overlying flux, which is often dominant in both Φ and Ef and related to d, and the current-carrying core flux, which is related to Θ.

Keywords: Solar active region magnetic fields, Solar flares, Solar coronal mass ejections
First Eccentric Inspiral─Merger─Ringdown Analysis of Neutron Star─Black Hole Mergers. The gravitational wave event GW200105 was the first confident neutron star─black hole (NSBH) merger identified by the LIGO─Virgo─KAGRA collaboration. A recent analysis with an eccentric precessing waveform model that describes the inspiral phase of the l = 2 and m = {0, ±2} modes has identified this event as the first NSBH merger with strong evidence of orbital eccentricity. In this paper we perform the first analysis of this event with an aligned-spin eccentric waveform model that describes the full inspiral, merger, and ringdown, includes subdominant harmonics, and is partially calibrated to numerical relativity simulations. This analysis confirms the results and finds evidence in favor of eccentricity even with a log-uniform prior in eccentricity. We also analyze the NSBH events GW200115 and GW230529, completing the analysis of all NSBHs with IMRPHENOMTEHM, and find that these signal are consistent with vanishing eccentricity. Finally, we briefly discuss computational challenges when performing the analysis with time-domain eccentric waveform models.

Keywords: Neutron stars, Gravitational wave detectors, Bayesian statistics, Posterior distribution, Elliptical orbits, Stellar mass black holes, Gravitational wave sources, Gravitational wave astronomy, Gravitational waves, Eccentricity
Testing the Nature of GW200105 by Probing the Frequency Evolution of Eccentricity. GW200105 is a compact binary coalescence event, consisting of a neutron star and a black hole, observed in LIGO─Virgo─KAGRA's third observing run. Recent reanalyses of the event using state-of-the-art waveform models have claimed observation of signatures of an eccentric orbit. It has nevertheless been pointed out in the literature that certain physical or modified gravity effects could mimic eccentricity by producing a spurious nonzero eccentricity value, at a given reference frequency, when recovered with an eccentric waveform model. We recently developed a waveform-model-independent eccentricity evolution consistency test (EECT) to identify such mimickers, by comparing the measured frequency evolution of eccentricity, e(f), with that expected from general relativity (GR). In this paper, we apply EECT to GW200105 and find that it satisfies EECT within 68% confidence. Our analysis therefore lends complementary support in favor of the eccentricity hypothesis, while also providing a novel test of the consistency of e(f) with GR.

Keywords: Gravitational waves, Gravitational wave sources
Stability of Adiabatic Processes and Evolution of Pickup Ion Dimensionality. In adiabatic processes, such as in many space plasmas, particles flow with no heat entering or exiting their system, while, more generally, the difference between polytropic and adiabatic indices provides a measure of any heating. In this paper, we investigate the thermodynamics of polytropic processes and the relationship between heating and the difference between polytropic and adiabatic indices, extended to account for variable kinetic degrees of freedom. Then, we examine the stability of fluctuating adiabatic process. We show that fluctuations of the adiabatic index cannot be effectively damped to restore equality between polytropic and adiabatic indices, unless the variability of degrees of freedom introduces another source of entropy and heating. We find that the convergence of the stability of the pickup ion (PUI) adiabatic index is very slow, and thus PUIs are rarely adiabatic; in contrast, solar wind protons at ∼1 au are nearly adiabatic. Moreover, we develop the relationship between heat transfer and variable dimensionality. We use this to characterize the evolution of the PUI distribution in the heliosphere. While the initial pickup and final thermalization phases are instantaneous and asymptotically reached, we characterize their duration by the time needed for the dimensionality to change by ∼0.1, and derive the time scales of the phases of PUI evolution: (i) pickup phase is the shorter, ∼1 hr; (ii) isotropization phase takes ∼1 day, (iii) cooling phase is much longer, ∼10 days; and (iv) thermalization phase, ∼1.5 yr. Finally, using observations from Voyager, we verify this model of the evolution of the PUI dimensionality.

Keywords: Space plasmas, Polytropes, Heliosphere, Pickup ions
Combining Solar Imagery and In Situ Data for Prediction of Geomagnetic Storms. In this work, we propose the use of the Most Extreme Space Weather Events (MESWE) dataset, which combines 12 solar corona and solar wind parameters to predict the disturbance storm time (Dst) index 4 or 8 hr ahead by deep learning models. The dataset focuses on periods of extreme solar activity in the past 30 yr that triggered great and severe geomagnetic storms, as measured by geomagnetic indices. Using the MESWE dataset and leveraging the gated recurrent units type of recurrent neural network, we obtain a significantly reduced persistence effect compared to models trained with conventional methodologies in the Dst index forecasting community. The performance of the models is compared quantitatively by using the dynamic time warping method. In addition, we introduce a methodology to reduce the risk of the split of the validation test set that can lead to misleading performance assessments. The methodology of combining imagery and in situ data and the results presented in this work are directly aligned with the objectives of the European Space Agency Vigil mission.

Keywords: Solar activity, Space weather, Geomagnetic fields, Neural networks
Continued Radio Observations of the Persistent Radio Source Associated with FRB 20190520B Provide Insights into Its Origin. Follow-up studies of persistent emission from fast radio burst (FRB) sources are critical for understanding their elusive emission mechanisms and the nature of their progenitors. This work presents new observations of the persistent radio source (PRS) associated with FRB 20190520B. We observe a gradual decay in the PRS brightness, which is punctuated by periods of brightening and dimming at both 1.5 and 3 GHz. Furthermore, our low-frequency (&lt;1 GHz) observations—the first for this source—reveal evidence of a spectral break, which can be attributed to absorption processes. Interpreted within the framework of the magnetar wind nebula model, our data constrain the age of the magnetar progenitor to  52−10+16  yr, broadly consistent with previous work. Assuming the observed 1.5 GHz variability is driven by scintillation, we discuss the constraints on the size of the persistent source. The observations presented here challenge the predictions of the previously published best-fit hypernebula model for this source.

Keywords: Radio bursts, Radio sources, Transient sources, Radio transient sources
Active Galactic Nucleus-driven Biconical Outflows as the Origin of the Double-peaked [O III] Doublet in SDSS J134733.36+121724.27. In this manuscript, we recheck the spectroscopic properties of SDSS J134733.36+121724.27 (4C+12.50), confirming the presence of the double-peaked [O III]λλ4959, 5007 Å doublet and a broad Hα. The former likely results from active galactic nucleus (AGN)-driven biconical outflows, while the absence of a broad Hβ supports a classification of the source as a Type-1.9 AGN. We analyze its high-quality Sloan Digital Sky Survey (SDSS) optical spectrum after robustly subtracting host galaxy and AGN continuum contributions through a simple stellar population fitting method employing 39 templates and a power-law continuum. Each narrow line of the [O III]λλ4959, 5007 Å doublet is better described by two Gaussian components (blueshifted and redshifted) than by a single Gaussian, as confirmed by the F-test. Broad components are included for both Hα and Hβ, but only Hα reveals a significant detection, further supported by a comparison between the SDSS spectrum and that previously reported. These results support that the object is highly consistent with a Type-1.9 AGN classification, and the double-peaked [O III] profiles are most likely produced by AGN-driven biconical outflows rather than by a rotating narrow-line region or a dual AGN merger system. Additional observations are still needed to strengthen these conclusions.

Keywords: Supermassive black holes, Active galactic nuclei, Emission line galaxies
Stellar Loci. IX. Estimation of Stellar Parameters from CSST-like Photometry. The China Space Station Telescope (CSST) will conduct a deep and wide imaging survey in the near-ultraviolet, u, g, r, i, z, and y bands. In this work, using theoretical data synthesized from the BOSZ spectra of R. C. Bohlin et al., along with observational data constructed from different sources, we present two methods for estimating stellar parameters from CSST-like photometry. One approach is to estimate metallicity [M/H] and surface gravity log g simultaneously by using the metallicity- and log g-dependent stellar loci. Tests with theoretical data (without photometric errors) result in precisions of 0.088 dex and 0.083 dex for [M/H] and log g, respectively. With 0.01 mag photometric errors, precision is degraded by about a factor of 2, due to degeneracy in [M/H] and log g. Tests with observational data, although with larger photometric errors, result in precisions of 0.10 dex and 0.39 dex for [Fe/H] and log g, respectively, thanks to the strong correlation between stellar colors and log g in real data. The other approach is the giant-dwarf loci method to obtain classifications and metallicity estimates. With the same observational data, it achieves a better [Fe/H] precision of 0.084 dex, due to the stronger constraints imposed on log g. The method also performs well in distinguishing giants from dwarfs, particularly for red or metal-poor giants. This work demonstrates the clear potential of the CSST data, paving the way for stellar-parameter estimates for many billions of stars.

Keywords: Fundamental parameters of stars, Surface gravity, Metallicity, Astronomy data analysis
A Late-time Radio Survey of Type Ia-CSM Supernovae with the Very Large Array. Type Ia-CSM supernovae (SNe) are a rare and peculiar subclass of thermonuclear SNe characterized by emission lines of hydrogen or helium, indicative of high-density circumstellar medium (CSM). Their implied mass-loss rates of ∼10−4─10−1 M⊙ yr−1 (assuming ∼100 km s−1 winds) from optical observations are generally in excess of values observed in realistic SN Ia progenitors. In this paper, we present an independent study of CSM densities around a sample of 29 archival Ia-CSM SNe using radio observations with the Karl G. Jansky Very Large Array at 6 GHz. Motivated by the late (∼2 yr) radio detection of the Ia-CSM SN 2020eyj, we observed old (&gt;1 yr) SNe, when we are more likely to see the emergent synchrotron emission that may have been suppressed earlier by free─free absorption by the CSM. We do not detect radio emission down to 3σ limits of ∼35 μJy in our sample. The only radio-detected candidate in our sample, SN 2022esa, was likely misclassified as a Ia-CSM with early spectra, and appears more consistent with a peculiar Ic based on later epochs. Assuming wind-like CSM with temperatures between 2 × 104 K and 105 K, and a magnetic field-to-shock energy fraction ϵB = 0.01 − 0.1, the radio upper limits rule out mass-loss rates between ∼10−4 and 10−2 M⊙ yr−1 (100 km s−1)−1. This is somewhat in tension with the estimates from optical observations, and may indicate that more complex CSM geometries and/or lower values of ϵB may be present.

Keywords: Circumstellar matter, White dwarf stars, Type Ia supernovae, Radio astronomy
Supernova-induced Binary-interaction-powered Supernovae: A Model for SN2022jli. We present 3D hydrodynamical modelling of supernova (SN)-induced binary-interaction-powered SNe; a scenario proposed for the peculiar type Ic SN SN2022jli. In this scenario, SN ejecta of a stripped-envelope star impact a close-by stellar companion, temporarily inflating the envelope. The expanded envelope engulfs the neutron star (NS), causing strong mass accretion at super-Eddington rates. Feedback from the accretion powers the SN light curve with periodic undulations. Our simulations capture key features of SN2022jli, both the overall decline and the superimposed undulations of the light curve. Based on our parameter study, we find that (i) the accretion feedback should be sufficiently geometrically confined and (ii) the eccentricity of the post-SN binary orbit should be 0.8 ≲ e ≲ 0.9 to sustain a high accretion rate and match the low undulation amplitude (∆L/L ∼ 0.1) of SN2022jli. Different combinations of parameters could account for other SNe like SN2022mop, SN2009ip and SN2015ap, which have varying undulation periods and amplitudes. We also discuss possible explanations for other key features of SN2022jli such as the γ-ray detection at ∼200 days and the rapid optical drop at ∼250 days. Finally, we speculate on the future evolution of the system and its relation to existing NS binaries.

Keywords: Type Ic supernovae, Core-collapse supernovae, Close binary stars, Transient sources, Gamma-ray transient sources, Supernovae
Jipole: A Differentiable ipole-based Code for Radiative Transfer in Curved Spacetimes. Recent imaging of supermassive black holes by the Event Horizon Telescope has relied on exhaustive parameter-space searches, matching observations to large, precomputed libraries of theoretical models. As observational data become increasingly precise, the limitations of this computationally expensive approach grow more acute, creating a pressing need for more efficient methods. In this work, we present Jipole, an automatically differentiable (AD), ipole-based code for radiative transfer in curved spacetimes, designed to compute image gradients with respect to underlying model parameters. These gradients quantify how parameter changes—such as the black hole's spin or the observer's inclination—affect the image, enabling more efficient parameter estimation and reducing the number of required images. We validate Jipole against ipole in two analytical tests and then compare pixelwise intensity derivatives from AD with those from finite-difference methods. We then demonstrate the utility of these gradients by performing parameter recovery for an analytical model in three increasingly complex cases for the injected image: ideal, blurred, and blurred with added noise. In most cases, high-accuracy fits are obtained in only a few optimization steps, failing only in cases with extremely low signal-to-noise ratios. These results highlight the potential of AD-based methods to accelerate robust, high-fidelity model-data comparisons in current and future black hole imaging efforts.

Keywords: Black hole physics, Plasma astrophysics, High energy astrophysics
Ionization Rate of Interstellar Neutral Helium from New Horizons/SWAP Observations. Interstellar neutral (ISN) atoms enable studies of the physical conditions in the local interstellar medium surrounding the heliosphere. ISN helium, which is the most abundant species at 1 au, is directly observed by space missions, such as Interstellar Boundary Explorer (IBEX). However, some of these atoms are ionized by solar UV radiation before reaching 1 au, producing pickup ions (PUIs). A recent analysis of IBEX data suggests that the helium photoionization rates predicted by models are underestimated by up to 40%. The Solar Wind Around Pluto (SWAP) instrument on board New Horizons enables the study of PUIs, giving complementary insight into the other side of the ionization process. Our goal is to verify this increased helium ionization by determining the ionization rate of ISN helium in the heliosphere based on SWAP observations of helium PUIs. For this purpose, we analyze SWAP data collected between 2012 and 2022, at distances 22─54 au from the Sun. We develop a new method for fitting model distribution functions to the observational data using the maximum likelihood method. Our approach accounts for the spacecraft's rotation and the SWAP response function, which depends on both energy and inflow direction. We estimate SWAP's efficiency for helium relative to that for hydrogen, and determine the ISN helium ionization rate. We find that the photoionization rate obtained from the SWAP observations is ∼43% larger than the rates predicted by models, confirming the IBEX results.

Keywords: Space plasmas, Photoionization, Heliosphere, Interstellar atomic gas, Solar wind, Pickup ions, Interstellar medium wind, Space vehicles
The Head-on Collision of a Neutron Star with a White Dwarf. We have computed the physical processes involved in a head-on collision between a neutron star (NS) and a white dwarf (WD). The outcomes of such collisions vary depending on the mass and type of the WD. We have separately examined the dynamical processes for collisions between NSs and helium WDs (He-WDs), carbon─oxygen WDs (CO-WDs), and oxygen─neon WDs (ONe-WDs). We aim to investigate whether the collision can trigger a thermonuclear explosion of the WD, and if not, whether the NS can remain bound within the WD to form a Thorne─Żytkow-like object (TZlO). For a thermonuclear explosion to occur, at least two conditions must be satisfied: (i) the collision-induced temperature must reach the ignition threshold of the relevant nuclear reactions, and (ii) the burning material must remain in a degenerate state. For different types of WDs, there exist parameter ranges where both conditions are fulfilled, implying that NS─WD collisions can indeed induce thermonuclear explosions, leading to sub-Chandrasekhar Type Ia supernovae or other exotic optical transients powered by thermonuclear explosion. On the other hand, the formation of a TZlO requires that the WD material exerts sufficient drag on the NS to prevent its escape, while the interaction must not trigger a thermonuclear explosion of the WD. Our results indicate that such conditions can be realized in the case of low-mass CO-WDs and low-mass ONe-WDs, provided that the viscous coefficient is sufficiently large.

Keywords: Neutron stars, Collision physics, White dwarf stars, Supernovae
Diversity of Low-mass Planet Atmospheres in the C─H─O─N─S─Cl System with Interior Dissolution, Nonideality, and Condensation: Application to TRAPPIST-1e and Sub-Neptunes. A quantitative understanding of the nature and composition of low-mass rocky (exo)planet atmospheres during their evolution is needed to interpret observations. The magma ocean stage of terrestrial and sub-Neptune planets permits mass exchange between their interiors and atmospheres, during which the mass and speciation of the atmosphere is dictated by the planet's volatile budget, chemical equilibria, and gas/fluid solubility in molten rock. As the atmosphere cools, it is modified by gas-phase reactions and condensation. We combine these processes into an open-source Python package built using JAX called Atmodeller, and perform calculations for planet sizes and conditions analogous to TRAPPIST-1e and K2-18b. For TRAPPIST-1e-like planets, our simulations indicate that CO-dominated atmospheres are prevalent during the magma ocean stage, which, upon isochemical cooling, predominantly evolve into CO2-rich atmospheres of a few hundred bar at 280 K. Around 40% of our simulations predict the coexistence of liquid water, graphite, α-sulfur, and ammonium chloride—key ingredients for surface habitability. For sub-Neptune gas dwarfs, pressures are sufficiently high (∼GPa) that gas fugacities deviate from ideality, thereby drastically enhancing solubilities. This buffers the total atmospheric pressure to lower values than for the ideal case. These effects conspire to produce CH4-rich sub-Neptune atmospheres for total pressures exceeding ∼3.5 GPa, provided H/C is ∼100× solar and fO2 moderately reducing (3 log10 units below the iron─wüstite buffer). Otherwise, molecular hydrogen remains the predominant species at lower total pressures and/or higher H/C. For all planets at high temperature, solubility enriches C/H in the atmosphere relative to the initial composition.

Keywords: Extrasolar rocky planets, Planetary interior, Planetary atmospheres, Planet formation