Sazuna/UAT_keywords huggingface dataset:
3D Numerical Simulations of Magnetar Crustquakes. Crustquakes are frequently invoked as a mechanism to trigger sudden transients in the magnetospheres of magnetars. In this picture, a mechanical failure of the crust excites seismic motions of the magnetar surface that launch force-free waves into the magnetosphere. We first investigate this problem analytically and then perform 3D numerical simulations. Our simulations follow the propagation of high-frequency magnetoelastic waves in the entire crust and include magnetic coupling to the dipolar magnetosphere and liquid core through simplified radiation boundary conditions. We observe seismic waves bouncing between the crust─core interface and the surface with a characteristic frequency ∼1 kHz, which could appear as a modulation of the magnetospheric radiation. Both the starquake and its associated magnetospheric wave emission are strongly damped on a timescale ∼10 ms by magnetic coupling to the liquid core. Since the seismic waves are significantly damped before they can spread laterally around the crust, magnetospheric wave emission occurs primarily near the initial epicenter of the quake. Our simulations suggest that nonaxisymmetric quakes will launch a mixture of Alfvén and fast magnetosonic waves into the magnetosphere. The results will be important for interpreting magnetar bursts and understanding the possible trigger mechanisms of fast radio bursts.

Keywords: Neutron stars, Magnetars, Magnetic fields, Plasma astrophysics
Bright [C II]158 μm Streamers as a Beacon for Giant Galaxy Formation in SPT2349-56 at z = 4.3. Observations of extreme starbursts, often located in the cores of protoclusters, challenge the classical bottom-up galaxy formation paradigm. Giant elliptical galaxies at z = 0 must have assembled rapidly, possibly within few 100 Myr through an extreme growth phase at high-redshift, characterized by elevated star formation rates of several thousand solar masses per year distributed over concurrent, gas-rich mergers. We present a novel view of the z = 4.3 protocluster core SPT2349─56 from sensitive multicycle Atacama Large Millimeter/submillimeter Array dust continuum and [C II]158μm line observations. Distributed across 60 kpc, a highly structured gas reservoir with a line luminosity of L[C II] = 3.0 ± 0.2 × 109 L⊙ and an inferred cold gas mass of Mgas = 8.9 ± 0.7 × 109 M⊙ is found surrounding the central massive galaxy triplet. Like "beads on a string," the newly discovered [C II] streamers fragment into a few kiloparsec-spaced and turbulent clumps that have a similar column density as local Universe spiral galaxy arms at Σgas = 20─60 M⊙ pc−2. For a dust temperature of 30 K, the [C II] emission from the ejected clumps carries ≳3% of the far-IR luminosity, translating into an exceptionally low mass-to-light ratio of α[CII] = 2.95 ± 0.3 M⊙  L⊙−1 , indicative of shock-heated molecular gas. In phase space, about half of the galaxies in the protocluster core populate the same caustic as the [C II] streamers (r/rvir × ∣∆v∣/σvir ≍ 0.1), suggesting angular momentum dissipation via tidal ejection while the brightest cluster galaxy (BCG) is assembling. Our findings provide new evidence for the importance of tidal ejections of [C II]-bright, shocked material following multiple major mergers that might represent a landmark phase in the z ≳ 4 coevolution of BCGs with their hot, metal enriched atmospheres.

Keywords: Submillimeter astronomy, Molecular gas, Galaxy formation, Galaxy mergers, Circumgalactic medium, Brightest cluster galaxies, High-redshift galaxies
A Constrained Linear Model for Continuum Normalization of Stellar Spectra. Inferring stellar parameters and chemical abundances by forward modelling stellar spectra usually requires a spectral synthesis code, or an emulator constructed from a curated training set. In these situations continuum normalization is often implemented as a preprocessing step that is independent of stellar parameters. This leads to results that are biased, or inconsistent across signal-to-noise ratios (S/Ns). A more justified approach is to forward model spectra with all nuisances simultaneously, but in practice this can be an expensive or nonconvex optimization procedure. Here we describe a constrained linear model that can fit stellar absorption, telluric transmission, and the joint continuum-instrument response. Stellar absorption and telluric transmission are each modelled by factorizing a grid of rectified theoretical spectra into two nonnegative matrices with a chosen number of basis components. This model can represent all possible spectra using far fewer parameters than comparable data-driven models. The nonnegativity constraint ensures basis vectors are strictly additive, which limits rectified flux to less than or equal to unity, such that we can distinguish normalized spectra from the joint instrument-continuum response. The model requires no initial guess, and the linearity ensures that inference is convex, stable, and fast. This model allows us to reliably fit nuisances (e.g., tellurics, continuum), and is readily extensible to radial velocity and rotational broadening without any prior knowledge about the fundamental stellar properties. We demonstrate our method by fitting ESO/HARPS high-resolution echelle spectra of BAFGKM-type stars. With repeat observations of α Centauri A, we present results that are best in class: consistent across time to 0.2% at S/N ∼ 100, and to better than 0.5% at S/N ∼ 30.

Keywords: Stellar spectral lines, Astronomy data analysis, Spectroscopy
Light Curves of Time-dependent Accretion Disks in Tidal Disruption Events. Tidal disruption events (TDEs) are believed to be an ideal laboratory for studying the evolution of accretion flow around a supermassive black hole (BH). In general, the mass feeding rate to the BH is suggested to be super-Eddington initially and evolves to be sub-Eddington on timescales of years. In this paper, we carry out calculations of the time-dependent evolution of accretion disks in the standard environment of TDEs, i.e., injecting matter at the circularization radius of the stellar debris in the form of  Ṁinject∝t−5/3 . We find that when  Ṁinject  evolves to a value around the Eddington accretion rate, the radiation pressure instability occurs. We test the influence of the model parameters on the light curves, such as the BH mass MBH, viscosity parameter α, and mass-injecting radius Rout, all of which are found to affect the light curves to some extent. In most cases, we find that the light curves oscillate significantly owing to the radiation pressure instability. As an exception, when α is small or Rout is large, we find that the oscillations are completely suppressed. In this case, the light curve drops steeply and then becomes flat in the late-time evolution, which we apply to explain the observed ultraviolet light curves of ASASSN-15oi and ASASSN-14ae, together with the assumption of a photosphere. Finally, we discuss the potential applications of our time-dependent accretion disk model to explaining multiband light curves of TDEs in the future.

Keywords: Accretion, Black hole physics, Tidal disruption
Evolution of an Alfvén Wave─driven Proton Beam in the Expanding Solar Wind. We investigate the self-consistent formation and long-term evolution of proton beams in the expanding solar wind using an ensemble of one-dimensional hybrid expanding box simulations. Initial conditions are chosen to represent a range of plasma states observed by the Helios spacecraft at 0.3 au, including an amplitude-modulated Alfvén wave that nonlinearly drives a proton beam aligned with the magnetic field. We compare simulation results with solar wind data out to 1.5 au and show that our model reproduces key observed features of proton beams on average, such as the radial evolution of the drift and the relative core-to-beam density ratio. These findings support the theory that the observed evolution of the proton beam drift in the solar wind is determined by kinetic instabilities. More broadly, our results indicate that the interplay between nonlinear Alfvén wave dynamics, expansion effects, and kinetic instabilities plays a fundamental role in solar wind dynamics, with implications for interpreting solar wind heating rate estimates.

Keywords: Space plasmas, Solar physics, Solar wind, Alfven waves
A Relativistic Formula for Radiation Intensity of Multiply Scattered Photons. We derive an analytical solution for the radiation intensity of scattered photons that is valid from the free-streaming phase immediately after photon emission to the diffusive phase after undergoing multiple scatterings. Assuming isotropic and elastic scattering, we utilize the probability density distribution of scattered photons as formulated by Takahashi et al. By applying Lorentz transformation, the radiation intensity in a fluid moving at relativistic speeds can be computed in any inertial frame, enabling the estimation of radiation energy density, radiation flux, and radiation stress tensor. Although this solution is derived assuming simultaneous and isotropic photon emission in the fluid's rest frame, it can also be applied to more general emission conditions. The solution remains valid even when the initial photon distribution is spatially or directionally anisotropic, by appropriately summing the fundamental solutions. The validity of the analytical solution is demonstrated through comparisons with Monte Carlo radiation transport calculations. Future studies will address the applicability of the solution to anisotropic and inelastic scattering, as well as to flows with nonuniform distributions.

Keywords: Relativity, Radiative transfer
Long-term Radio Monitoring of PKS 1127─145: Detection and Physical Interpretation of Quasiperiodic Oscillations. We analyzed over four decades of UMRAO monitoring of PKS 1127─145 at 4.8, 8, and 14.5 GHz to search for quasiperiodic oscillations (QPOs) under red-noise variability. Lomb─Scargle and Weighted Wavelet Z-transform results from 10 day binned light curves were benchmarked against 105 Monte Carlo red-noise realizations. We fit autoregressive moving-average (ARIMA) models to 30 day binned light curves to capture stochastic variability, and then assess periodic components by analyzing the periodograms of the model residuals. A ∼1000 day QPO (rest-frame ∼460 days) is locally significant in both the 8 and 14.5 GHz bands, with the strongest global support at 8 GHz; at 4.8 GHz we find evidence for a ∼3300 day component that is weaker and less reliable owing to the limited number of cycles. The confinement of the shorter period to higher frequencies points to a compact, upstream origin. Plausible mechanisms include orbital motion in a supermassive black hole binary, Lense─Thirring precession of a tilted inner flow, and the motion of a relativistic knot along a preexisting helical jet. In the helical case, VLBI kinematics constrain a Doppler factor δ ≍ 21, sufficient to compress an intrinsic ∼26 yr driver into the observed modulation, thereby connecting central-engine dynamics to the radio QPO.

Keywords: Quasars, Relativistic jets, Astronomy data analysis, Active galactic nuclei, Time series analysis
Functionalization of Benzene Ices by Atomic Oxygen. Small aromatic molecules, including functionalized derivatives of benzene, are known to be present throughout the different stages of star and planet formation. In particular, oxygen-bearing monosubstituted aromatics, likely including phenol, have been identified in the coma of comet 67P. This suggests that, earlier in the star and planet formation evolution, icy grains may act as both reservoirs and sites of functionalization for these small aromatics. We investigate the ice-phase reactivity of singlet oxygen atoms (O(1D)) with benzene, using ozone as a precursor that is readily photodissociated by relatively low energy. Our experiments show that O(1D) efficiently reacts with benzene, forming phenol, benzene oxide, and oxepine as the main products. Phenol formation is temperature-independent, consistent with a barrierless insertion mechanism. In contrast, the formation of benzene oxide/oxepine shows a slight temperature dependence, suggesting that additional reaction pathways involving either ground-state or excited-state oxygen atoms may contribute. In H2O and CO2 ice matrices we find that dilution does not suppress the formation of phenol. We extrapolate an experimental upper limit for the benzene-to-phenol conversion fraction of 27%─44% during the lifetime of an interstellar cloud, assuming O(1D) production rates based on CO2 ice abundances and a cosmic-ray-induced UV field. We compare these estimates with a new analysis of data from the comet 67P, where the C6H6O/C6H6 ratio is 20% ± 6%. This value lies within our estimated range, suggesting that O(1D)-mediated chemistry is a viable pathway for producing oxygenated aromatics in cold astrophysical ices, potentially enriching icy planetesimals with phenol and other biorelevant compounds.

Keywords: Laboratory astrophysics, Ice composition, Astrochemistry
The Massive and Distant Clusters of WISE Survey 2: Detection of Splashback Radii in Galaxy Cluster Total Light Stacks. The splashback radius, the radius of the apocenter of the first orbit of infalling material, is a measurable quantity marking the boundary between a galaxy cluster and its infalling region. We report detections of splashback radii in total light stacks, i.e., image stacks centered on the cores of galaxy clusters. Our analysis uses Wide-field Infrared Survey Explorer (WISE) W1 and W2 images of 83,345 candidate clusters at 0.5 ≲ z ≲ 1.9 from the Massive and Distant Clusters of WISE Survey 2 (MaDCoWS2). The clusters are organized in stacks by redshift and signal-to-noise (S/N) ratios. We adopt a statistical approach, using 1000 bootstrap realizations to determine the median projected splashback radius and its confidence interval in a given bin. We compare our splashback radii with the measurements made by K. Thongkham et al. on a similar sample of MaDCoWS2 clusters using galaxy-cluster cross-correlation and find that they are consistent, although our method yields larger error bars. Our main systematic error is the accuracy of the background subtraction, but its impact remains small: the consistency of K. Thongkham et al. and our results suggests that neither method suffers from large systematics. The sensitivity of total light stacking to the contribution of faint galaxies can be advantageous to locate splashback radii when only the brightest galaxies are detected in individual images, such as at high redshifts. We present a potential application of this new technique to probe the evolution of the stellar mass in cluster infalling regions.

Keywords: Galaxy clusters, High-redshift galaxy clusters, Galaxy environments, Infrared astronomy, Galaxy evolution, Cosmic web
Delayed Radio Emission in Tidal Disruption Events from Collisions of Outflows Driven by Disk Instabilities. Delayed radio emission has been associated with a growing proportion of tidal disruption events (TDEs). For many events, the radio synchrotron emission is inferred to originate from the interaction of mildly relativistic outflows, launched with delay times of ∼100─1000 days after the TDE optical peak. The mechanism behind these outflows remains uncertain but may relate to instabilities or state transitions in the accretion disk formed from the TDE. We model the radio emission powered by the collision of mass outflows ("flares") from TDE accretion disks, considering scenarios in which two successive disk flares collide with each other, as well as collisions between the outflow and the circumnuclear medium (CNM). For flare masses of ∼0.01─0.1 M⊙, varied CNM densities, and different time intervals between ejected flares, we demonstrate that the shocks formed by the collisions have velocities 0.05c─0.3c at ∼1017 cm and power bright radio emission of Lν ∼1027─1030 erg s−1 Hz−1, consistent with the properties inferred for observed events. We quantify how the typical peak timescale and flux varies for different properties of our models, and we compare our model predictions to a selection of TDEs with delayed radio emission. Our models successfully reproduce the light curves and spectral energy distributions for several events, supporting the idea that delayed outflows from disk instabilities and state transitions can power late-time radio emission in TDEs.

Keywords: Supermassive black holes, Tidal disruption, Transient sources, Radio transient sources
PEARLS: NuSTAR and XMM-Newton Extragalactic Survey of the JWST North Ecliptic Pole Time-Domain Field III. The James Webb Space Telescope North Ecliptic Pole (NEP) Time-Domain Field (TDF) has been monitored by Nuclear Spectroscopic Telescope Array (NuSTAR) and XMM-Newton with a regular cadence for 5 yr, starting in 2019. The survey has accumulated 3.5 Ms of NuSTAR exposure and 228 ks quasi-simultaneous XMM-Newton observations covering 0.31 deg2. This paper presents the results from the most recent 2 years' worth of 2 Ms NuSTAR and 166 ks XMM observations in NuSTAR cycles 8 and 9. These observations reached a 20% area flux of 2.20 × 10−14 erg cm−2 s−1 in the 8─24 keV band. Note that 75 NuSTAR sources and 274 XMM-Newton sources are detected at 99% reliability level. The logN─logS measured in cycles 8+9 are consistent with those measured in the previous cycle 5+6 NuSTAR NEP survey, but in a larger area (0.3 deg2 compared with 0.19 deg2). The slope of the cycles 8+9 8−24 keV logN─logS curve is flatter than other works (α89 = 1.13 ± 0.46), but is consistent with the Euclidean value of α = 1.50. In addition, we found ∼36% of the NuSTAR sources to be heavily obscured (NH ≥ 1023 cm−2). The Compton-thick (NH ≥ 1024 cm−2) active galactic nuclei fraction is  9−8+18%  in the NEP-TDF, which is consistent with the measurements in previous surveys.

Keywords: Hardness ratio, James Webb Space Telescope, Active galactic nuclei, Time domain astronomy, X-ray surveys, Extragalactic astronomy
Exploring the Statistical Properties of Double Radio Relics in the TNG-cluster and TNG300 Simulations. Double radio relics, pairs of diffuse radio features located on opposite sides of merging galaxy clusters, are a rare subclass of radio relics that are believed to trace merger shocks and provide valuable constraints on plasma acceleration models and merger history. With the number of known double relics growing in recent and upcoming radio surveys, statistical analyses of their properties are becoming feasible. In this study, we utilize the cosmological magnetohydrodynamics zoomed-in simulations TNG-Cluster, in combination with TNG300-1, to examine the statistical properties of double radio relics. The simulated double-relic pairs exhibit a wide range of luminosity ratios, broadly consistent with the observations. We find that the two relics in a given double system often differ significantly in their shock properties and magnetic field strengths. This diversity implies that the observed brightness asymmetry in the pair cannot be explained by a single factor alone, but instead reflects an interplay of multiple physical parameters. Nevertheless, double radio relics tend to align with the collision axis within ∼30°, and their separation (ddrr) correlates tightly with the time since collision (TSC) as TSC [Gyr] = 0.52ddrr/R500c − 0.24, allowing it to be inferred with an accuracy of ∼0.2 Gyr. With the statistical samples of simulated radio relics, we predict that low-mass clusters will constitute the dominant population of double radio relic systems detected with upcoming surveys such as the Square Kilometre Array. These results demonstrate that double radio relics can serve as robust probes of merger dynamics and plasma acceleration, and that simulations provide critical guidance for interpreting the large samples expected from next-generation radio surveys.

Keywords: Galaxy clusters, Intracluster medium, Magnetohydrodynamical simulations, Radio continuum emission
High-resolution Solar X-Ray Spectroscopy from Archived Solar Maximum Mission Data. Archived high-resolution X-ray spectra in the 13─22 Å range from the Flat Crystal Spectrometer (FCS), an instrument on the Solar Maximum Mission operating in the 1980s, are analyzed with reference to nonflaring active regions, and to the Fe XVII line emission in light of laboratory and atomic data for nearby Fe XVI satellites. The satellites allow temperature to be found for these relatively low-temperature spectra, at which more conventional temperature-dependent line ratios are unavailable. By this means, the spectra can be arranged by temperature, showing that the Fe XVII lines are evident at temperatures of &lt;3 MK. We confirm that the problem of the underintense Fe XVII 3C and 3D lines is not due to resonant scattering, and instead suggest that, for comparison with CHIANTI spectra, the problem may lie with a needed revision of collisional excitation rates. The line ratio 3G/3H is in theory density-dependent but for Fe XVII the ratio is in the low-density limit. However, we suggest that spectra taken during the impulsive stage of flares might reveal a departure from this limit and so allow densities to be derived and hence properties of the flaring plasma. Suggestions for the design of future crystal spectrometers are made in the light of the fluorescence background in FCS spectra.

Keywords: Solar physics
Characterizing Dust Extinction and Spatially Resolved Paschen-α Emission within 97 Galaxies at 1 &lt; z &lt; 1.6 with JWST NIRCam Slitless Spectroscopy. We present results on the Paschen-α (Paα) emitting galaxies observed as part of the JWST FRESCO survey in the GOODS-North and GOODS-South fields. Utilizing the JWST NIRCam wide field slitless spectroscopy (WFSS), we analyze emission line fluxes, star formation rates, and spatially resolved flux distributions of 97 Paα emitters at 1 &lt; z &lt; 1.6. To assess dust extinction within our sample, we combine Paα fluxes with archival Hα data taken with the Hubble Space Telescope WFC3 G141 grism. We employ 2D Paα and F444W mapping to trace the distributions of star formation and stellar mass, respectively. Our observations indicate that lower mass galaxies are almost dust free in Paα and exhibit smaller sizes both in star formation and underlying stellar continuum. In contrast, galaxies with stellar masses above 109.5M⊙ display diverse dust extinction and star formation patterns. This indicates that the structures and properties of massive galaxies evolve through different phases, which involve, e.g., star formation in massive clumps, compaction, and inside-out quenching. While average dust extinction rises with stellar mass, there is significant scatter among high-mass systems. This study demonstrates the capabilities of JWST WFSS in conducting systematic investigations of emission line galaxies and highlights the pivotal role of Paα in advancing our understanding of dust extinction and obscured star formation in the early Universe.

Keywords: Galaxy structure, Galaxy evolution, Interstellar medium