Sazuna/UAT_keywords huggingface dataset:
Is There a Retrograde Accretion Disk around 4U 1626─67? Tracking Torque Reversals with a State-space Model. X-ray timing studies of the persistent, Galactic, accretion-powered pulsar 4U 1626−67 reveal torque reversals, during which the pulse frequency ν(t) alternates between multiyear episodes of secular acceleration and deceleration, separated by transitions lasting ≲150 days. Here an unscented Kalman filter is applied to track the ν(t) fluctuations observed in 22.7 yr (3340 samples) of publicly available Compton Gamma-Ray Observatory and Fermi Gamma-Ray Space Telescope data to test the canonical picture of magnetocentrifugal accretion for consistency with prograde─prograde and retrograde─prograde accretion disk configurations on either side of the 2008 torque reversal. It is found that the retrograde─prograde model is preferred, with a log Bayes factor equal to 0.44 and a maximum a posteriori log likelihood ratio equal to 2.5. The mass accretion rate Q(t) and magnetocentrifugal fastness ω(t) transition smoothly between episodes of deceleration and acceleration: Q(t) shifts by ≤0.34 dex across the reversal, and one measures ω(t) ≍ 0.25 and ω(t) ≍ 0.30 during deceleration and acceleration, respectively. The angular acceleration  Ω̇(t)  satisfies  −9≲Ω̇(t)/(10−12rads−2)≲−5  and  2≲Ω̇(t)/(10−12rads−2)≲9  before and after the 2008 reversal, respectively, compared to  Ω̇≍−3.0×10−12rads−2  before reversal and  Ω̇≍2.5×10−12rads−2  after reversal, as inferred from previous long-term X-ray timing and spectral analysis of 4U 1626−67.

Keywords: Neutron stars, Magnetic fields, High energy astrophysics, Pulsars
Precision Determination of Scintillation Screen Parameters from Annual Modulation Measurement of Pulsar Scintillation Arc Curvature with the FAST Telescope. Pulsar scintillation observations have revealed ubiquitous discrete scintillation screens in the interstellar medium. A major obstacle in identifying the nature of these screens is the uncertainty in their distances, which prevents precise correlation with known structures in the Milky Way. We used the Five-hundred-meter Aperture Spherical radio Telescope to observe PSR B1237+25, PSR 1842+14, and PSR 2021+51. We detected 10 scintillation arcs in PSR B1237+25, 1 in PSR 1842+14, and at least 6 in PSR 2021+51. By modeling the annual modulation of these scintillation arcs, we constrained the distances of the scintillation screens, as well as the anisotropic scattering directions and the projected velocities in those directions. The scintillation screens are distributed throughout the entire paths between Earth and the pulsars. Among these, the distance to the main scintillation screen toward PSR B1237+25 is  267−28+32  pc, the scintillation screen toward PSR B1842+14 is at a distance of  240−120+210  pc, and the main scintillation screen toward PSR B2021+51 is located at  887−132+167  pc. Several screens in our sample appear at distances coinciding with the Local Bubble boundary, particularly the brightest scintillation arc toward PSR B1237+25. We provide a substantial sample of scintillation screen measurements, revealing the rich plasma density fluctuation structures present in the Milky Way.

Keywords: Pulsars, Radio pulsars, Interstellar medium, Interstellar scintillation
TiNy Titans H I: Discovering Satellites via H I Gas in an Isolated, Compact Group of Dwarf Galaxies. We report on the H I content of an isolated, compact group of six dwarf galaxies at a distance of 145 Mpc. The distribution and kinematics of the H I, including multiple gaseous bridges, indicate the group is a gravitationally bound system. The H I maps further reveal two newly discovered dwarf satellites easily identified by their gas but only barely visible in optical images. The four dwarf group members previously identified in the Sloan Digital Sky Survey have 9.06 &lt; log(M*/M⊙) &lt; 9.43 and 9.42 &lt; log(MH I/M⊙) &lt; 9.73. The two newly discovered dwarf satellites have log(M*/M⊙) = 6.10 with log(MH I/M⊙) = 8.71 and log(M*/M⊙) = 7.07 with log(MH I/M⊙) = 9.18. New Gemini optical spectra link the H I detections and their optical counterparts. The group's 3D velocity dispersion (188 km s−1), mass-to-light ratio (M/LB ∼ 44), dynamical-to-baryonic mass ratio (Mdyn/Mbar ∼ 21), size (69 kpc), and gas fraction (0.56) are all consistent with the compact dwarf groups in the TNG50 simulation. The group has a top-heavy satellite mass function that is inconsistent with predictions for LMC-sized hosts and may instead be two or more groups coming together. A Voronoi tessellation reveals the group resides in a tendril outside the intersection of two filaments. These intermediate-density environments within the large-scale structure provide the conditions needed for groups of star-forming, gas-rich dwarf galaxies to form and eventually merge. Our results further show that it is possible to uncover fainter dwarf satellites around dwarf galaxy hosts via H I maps.

Keywords: Galaxy mergers, Dwarf galaxies, Galaxy groups, H I line emission
Detection of Millimeter-wavelength Flares from Two Accreting White Dwarf Systems in the SPT-3G Galactic Plane Survey. Blind discoveries of millimeter-wave transient events in nontargeted surveys, as opposed to follow-up or pointed observations, have only become possible in the past decade using cosmic microwave background surveys. Here we present the first results from the SPT-3G Galactic Plane Survey—the first dedicated high-sensitivity, wide-field, time-domain, millimeter-wave survey of the Galactic Plane, conducted with the South Pole Telescope (SPT) using the SPT-3G camera. The survey field covers approximately 100 deg2 near the Galactic center. In 2023 and 2024, this survey consisted of roughly 1500 individual 20 minute observations in three bands centered at 95, 150, and 220 GHz, with plans for more observations in the coming years. We report the detection of two transient events exceeding a 5σ threshold in both the 95 and 150 GHz bands in the first 2 yr of SPT-3G Galactic Plane Survey data. Both events are unpolarized and exhibit durations of approximately 1 day, with peak flux densities at 150 GHz of at least 50 mJy. The peak isotropic luminosities at 150 GHz are on the order of 1031 erg s−1. Both events are associated with previously identified accreting white dwarfs. Magnetic reconnection in the accretion disk is a likely explanation for the observed millimeter flares. In the future, we plan to expand the transient search in the Galactic Plane by lowering the detection threshold, enabling single-band detections, analyzing lightcurves on a range of timescales, and including additional data from future observations.

Keywords: Galactic center, Millimeter astronomy, Surveys, White dwarf stars, Transient sources
Hubble Constant Measurement from Quasiperiodic Eruptions as Electromagnetic Counterparts to Extreme Mass Ratio Inspirals. Gravitational waves (GWs) accompanied by electromagnetic counterparts, known as bright sirens, provide a novel methodology to measure the Hubble constant (H0). However, the rarity of such multimessenger events limits the precision of the H0 constraint. Recently, the newly discovered class of nuclear transient, quasiperiodic eruptions (QPEs), shows intriguing evidence of a stellar-mass companion captured by a supermassive black hole in an extreme/intermediate mass ratio inspiral, which is the most promising source of space-based GW detectors, such as LISA. Here, we model the secular orbital evolution of known QPE systems using two frameworks: a stripping scenario in which periodic mass transfer at periapsis drives the evolution, and an orbiter─disk collision scenario in which the companion interacts with a misaligned accretion disk, modulated by coupled orbiter─disk precession. For each framework, we assess detectability by LISA, together with the resulting constraints on H0. Our principal findings are (i) in the stripping scenario, no currently known QPE reaches detectability within a four-year LISA mission; (ii) in the orbiter─disk scenario, two sources—eRO-QPE2 and eRO-QPE4—are detectable with signal-to-noise ratios ≃8.5─28.8 and constrain H0 with a fractional uncertainty of 6.7%─14.9%. QPE systems remain uncertain on the decade-long secular evolution. Therefore, they motivate continued time-domain monitoring of QPE candidates.

Keywords: Hubble constant, X-ray transient sources, Gravitational waves, X-ray sources
COSI Short Gamma-Ray Burst Localization Using BGO Shield Data. The Compton Spectrometer and Imager (COSI) is a NASA satellite mission under development designed to survey the entire sky at 0.2─5 MeV with a wide-field gamma-ray telescope. Its main instrument is a germanium detector array surrounded on the sides and bottom by bismuth germanium oxide scintillator active shields (the "Anticoincidence Subsystem" (ACS)) to reduce and monitor background and for detecting transients. COSI will have an onboard trigger algorithm to detect gamma-ray bursts (GRBs) in the ACS and send data to the ground for further analysis. In this paper, we present three localization methods that we evaluated for the localization of short GRBs (sGRBs) using the ACS light curves. The first method is the χ2 fit already used by the Fermi Gamma-ray Burst Monitor, which calculates the best fit between look-up tables and the GRB data. The second method is a maximum likelihood estimation fit implemented in bc-tools for the BurstCube mission that performs a fit between the instrument response function and the GRB data. The last method is based on deep learning techniques and consists of a neural network developed for the COSI mission and trained to perform a regression of the sGRB position, taking as input the count rates of each ACS panel. The localization errors obtained by analyzing simulated sGRBs with the three methods are consistent. Despite the theoretical similarity between the approaches, their consistency in results is noteworthy, as they differ substantially in their implementations and optimization processes. The bc-tools obtain the best localization accuracy.

Keywords: Gamma-ray bursts, High energy astrophysics, Neural networks
The JWST Weather Report from the Nearest Brown Dwarfs. III. Heterogeneous Clouds and Thermochemical Instabilities as Possible Drivers of WISE 1049AB's Spectroscopic Variability. We present a new analysis of the spectroscopic variability of WISE J104915.57−531906.1AB (WISE 1049AB, L7.5+T0.5), observed using the NIRSpec instrument on board the James Webb Space Telescope (GO 2965; PI: Biller). We explore the variability of the dominant molecular bands present in their 0.6─5.3 μm spectra (H2O, CH4, and CO), finding that the B component exhibits a higher maximum deviation than the A component in all the wavelength ranges tested. The light curves reveal wavelength-dependent (atmospheric depth) and possibly chemistry-dependent variability. In particular, for the A component, the variability in the light curves at the wavelengths traced by the CH4 and CO molecular absorption features is higher than that for of H2O, even when both trace similar pressure levels. We conclude that clouds alone are unlikely to explain the increased variability of CO and CH4 with respect to H2O, suggesting that an additional physical mechanism is needed to explain the observed variability. This mechanism is probably due to thermochemical instabilities. Finally, we provide visual representations of the 3D atmospheric maps reconstructed for both components using the molecular band contributions at different pressure levels and the fits of planetary-scale waves.

Keywords: Brown dwarfs, Atmospheric clouds, Planetary atmospheres, Atmospheric dynamics, Atmospheric variability
First in Situ Estimates of the Sheath Resistance for the PSP/FIELD Antenna: Employing an Electron Shot Noise Model. Quasi-thermal noise is an important diagnostic tool for measuring electron density and temperature in space plasmas, with its low-frequency range being dominated by electron shot noise. However, previous missions have shown that conventional shot noise models often yield poor fits in the low frequency  (f&lt;fp) , limiting the accurate characterization of electron parameters. To address this issue, we introduce an effective sheath resistance into the previous model, thereby establishing a calibrated shot noise model that improves measurements of electron parameters in the inner heliosphere. Methodologically, we applied the steep-descent and Levenberg─Marquardt method algorithm to determine the electron density and temperature above the plasma frequency; we then isolate the pure shot noise by subtracting other noise sources; and finally, we derive the antenna impedance using measurements below the plasma frequency ( fp ). Based on Parker Solar Probe (PSP) observations during PSP Encounter 4 ∼ 8 (with unbiased antennas operating in the dipole regime), we obtain an effective antenna capacitance of  8.30±0.21pF  and an effective resistance in the range of 0.5 ∼ 4 MΩ, with their radial of the capacitances and resistances of  r−0.072±0.001  and  r2.57±0.02 , respectively.

Keywords: Discrete radio sources, Space plasmas, Solar wind, Radio spectroscopy
Coupled Planetary Interior and Tidal Evolution. We present a new planetary structure/thermal evolution model, designed for use in problems that couple orbital dynamics with planetary structure. We first benchmark our structural/thermal evolution calculations against the MESA stellar evolution code, finding excellent agreement across a wide range of planet mass, equilibrium temperature, entropy, and extra heating deposited at various depths in the planet. We then apply our method to study the tidal migration histories of Neptunes in the recently identified "ridge" (periods ∼3─6 days), a feature that has been suggested to be populated via high-eccentricity migration (HEM) of more distant Neptunes. We find that it is difficult to form a circularized Neptune in the ridge without instigating runaway tidal inflation and likely atmospheric destruction; low-eccentricity Neptunes in the ridge can only be emplaced by HEM if they are metal-rich and exhibit finely tuned tidal quality factors. If follow-up observations confirm that low-eccentricity Neptunes in the ridge did arrive via HEM and are not strongly enriched in metals, our calculations indicate that their tidal heating mechanism must operate in the upper reaches of the planet to avoid runaway inflation. Gravity modes excited in upper radiative layers are a possible candidate mechanism, while friction in the core or turbulent dissipation in convective zones could be ruled out.

Keywords: Exoplanet dynamics, Exoplanet migration, Exoplanet evolution, Exoplanet tides, Exoplanet atmospheric structure
Shedding Light on Desert Dwellers. The "sub-Jovian desert" (2 ≲ Rp ≲ 10 R⊕, periods ≲3 days) is sparsely populated but no longer empty. Recent surveys have revealed that planets residing in the desert are dense (ρ ≳ 1 g cm−3), massive (∼10−50 M⊕), and orbit metal-rich stars that are indistinguishable from those hosting hot Jupiters. However, their origins remain mysterious. In this work, we adopt and test the hypothesis that tidal destruction of hot Jupiters can populate the sub-Jovian desert with stripped remnant planets. We first show that stars hosting desert dwellers exhibit Galactic kinematics indicative of an older population descended from those hosting hot Jupiters. We highlight that tidally driven Roche-lobe overflow (RLO) can indeed populate the desert with planets similar to those observed, but only if angular momentum transfer during RLO is inefficient ("lossy" RLO). The entire width of the sub-Jovian desert can be backfilled with the remnants of hot Jupiters that possessed their empirically inferred spread in entropy. In this picture, current desert dwellers such as LTT 9779 b should be tidally decaying at an observationally testable rate of ∼0.5 ms yr−1. Our theory also predicts that desert dweller host stars may rotate up to an order of magnitude more rapidly than field stars; rotation period differences may persist ∼ Gyr after RLO. Lossy RLO may also manifest as a burst of IR excess that could outshine the host star for up to ∼103 yr. If these predictions are confirmed by observations, our theory indicates that desert dwellers can be leveraged to study the interiors of giant planets in exquisite detail.

Keywords: Exoplanet dynamics, Roche lobe overflow, Hot Jupiters
Extreme Neutral Outflow in a Non-active Galactic Nucleus Quiescent Galaxy at z ∼ 1.3. We report the discovery of a substantial sodium doublet (Na D λλ5890, 5896)—traced neutral outflow in the quiescent galaxy JADES-GS-206183 at z = 1.317. Its JWST/NIRSpec-Microshutter Array spectrum shows a deep, blueshifted Na D absorption, revealing a neutral outflow with  vout=828−49+79kms−1  and a mass outflow rate of  log(Ṁout/M⊙yr−1)=2.40−0.16+0.11 . This outflow rate exceeds that of any neutral outflows identified beyond z ∼ 1 by the same line and is comparable with those in local galaxies with intensive star formation (SF) or luminous active galactic nuclei (AGN). JADES-GS-206183 is also a peculiar quiescent galaxy with a spiral+bar morphology, high dust attenuation (AV = 2.27 ± 0.23 mag). Paschen α (Paα) emission from the FRESCO NIRCam grism confirms its low star formation rate (SFRPaα = 10.78 ± 0.55 M⊙ yr−1), placing it 0.5 dex below the main sequence ( log(sSFRyr−1)=−10.2 ). Despite the systematics introduced by different SF history priors, the spectral energy distribution modeling, combining Hubble Space Telescope-to-NIRCam photometry with the Very Large Telescope/MUSE spectrum, suggests that JADES-GS-206183 experienced an older episode of SF 0.5─2 Gyr ago and a possible rejuvenation within the recent ∼10 Myr. Moreover, rest-frame optical lines indicate that the current AGN activity of JADES-GS-206183, if present, is also weak. Even though we tentatively detect a broad component of the Hα line, it likely traces an ionized outflow rather than an AGN. The results demonstrate that the Na D outflow in JADES-GS-206183 is highly unlikely to be driven by current SF or nuclear activity. Instead, it may represent a long-lasting fossil outflow from past AGN activity, potentially cotriggered with the early phase of rejuvenation.

Keywords: Galactic winds, Galaxy quenching, Star formation, Galaxy evolution
Prompt Searches for Very-high-energy γ-Ray Counterparts to IceCube Astrophysical Neutrino Alerts. The search for sources of high-energy astrophysical neutrinos can be significantly advanced through a multimessenger approach, which seeks to detect the γ-rays that accompany neutrinos as they are produced at their sources. Multimessenger observations have so far provided the first evidence for a neutrino source, illustrated by the joint detection of the flaring blazar TXS 0506+056 in high-energy (E &gt; 1 GeV) and very-high-energy (VHE; E &gt; 100 GeV) γ-rays in coincidence with the high-energy neutrino IceCube-170922A, identified by IceCube. Imaging atmospheric Cherenkov telescopes (IACTs), namely FACT, H.E.S.S., MAGIC, and VERITAS, continue to conduct extensive neutrino target-of-opportunity follow-up programs. These programs have two components: follow-up observations of single astrophysical neutrino candidate events (such as IceCube-170922A), and observation of known γ-ray sources after the identification of a cluster of neutrino events by IceCube. Here we present a comprehensive analysis of follow-up observations of high-energy neutrino events observed by the four IACTs between 2017 September (after the IceCube-170922A event) and 2021 January. Our study found no associations between γ-ray sources and the observed neutrino events. We provide a detailed overview of each neutrino event and its potential counterparts. Furthermore, a joint analysis of all IACT data is included, yielding combined upper limits on the VHE γ-ray flux.

Keywords: High energy astrophysics, Cosmological neutrinos, Gamma-rays, Particle astrophysics
Estimation of Jupiter's Dynamical Parameters Based on Juno Two-way Doppler Tracking Data. With the continued acquisition of high-precision tracking data by the Juno spacecraft, significant progress has been made in accurately determining Jupiter's dynamical parameters. In this study, we utilize the orbit determination and gravity field recovery software SPOT, developed by Wuhan University, to process all available two-way Doppler tracking data of Juno's perijove passes between 2016 and 2024. Incorporating 19 additional perijoves (PJ39─PJ68) beyond the 26 arcs used in the previous study, a joint estimation of Jupiter's 40 degree zonal gravity harmonics, four tesseral degree-2 terms, spin-axis orientation parameters, and tidal Love number is determined. The results indicate that, compared with previously published Juno-based gravity field solutions, the accuracy of coefficients J2─J5 has improved by more than a factor of 2, while the J13─J36 terms exhibit an average improvement of about 30%. A stochastic force was introduced to absorb unmodeled small perturbations near perijoves, but its rapidly varying orientation does not point to an identifiable physical origin. The uncertainty of Jupiter's spin-axis rotation parameter is improved to about 1 × 10─7 rad, indicating no significant deviation between the principal axis of inertia and the rotation axis. The estimated accuracy of the static tidal Love numbers is improved by roughly a factor of 2 compared with earlier Juno-based tidal analyses. Due to limitations in orbital geometry, the satellite-dependent tidal Love numbers cannot be determined with sufficient accuracy to reveal potential dynamical tidal effects. This work provides improved dynamical parameters for constraining Jupiter's interior structure.

Keywords: Gravitational fields, Tides, Orbit determination, Jupiter
Galaxy and Mass Assembly (GAMA). The Properties of Quasar Host Galaxies: Star Formation Histories and Stellar Populations. We investigated the star formation history and stellar populations of a sample of 205 Type I quasar host galaxies (0.1 &lt; z &lt; 0.35) and compared them with normal (nonactive) galaxies of the same mass and redshift within the volume of the Galaxy and Mass Assembly redshift survey. We find that quasar host galaxies tend to be star-forming galaxies (∼80%) lying on the star-forming main sequence; the fraction of quasar host galaxies that are quiescent (∼20%) is lower than the fraction of quiescent galaxies in the comparison sample of normal galaxies (54%). We find that the mean star formation rate (SFR) of quasar host galaxies has increased over the past 100 Myr by a factor of 2─3, but these galaxies were star-forming at all times previously. Our data are more consistent with quasar activity originating together with an increase in the SFR of otherwise normal galaxies, similar to episodic star formation in normal spirals. We argue that this indicates that secular processes and minor mergers may be the favored triggers of nuclear activity in the local Universe.

Keywords: AGN host galaxies, Supermassive black holes, Quasars, Galactic and extragalactic astronomy, Star formation, Spectral energy distribution, Extragalactic astronomy, Galaxies