Sazuna/UAT_keywords huggingface dataset:
A First Look at Spatially Resolved Infrared Supernova Remnants in M33 with JWST. We present the first spatially resolved infrared images of supernova remnants (SNRs) in M33 with the unprecedented sensitivity and resolution of JWST. We analyze 40 SNRs in four JWST fields: two covering central and southern M33 with separate NIRCam (F335M, F444W) and MIRI (F560W, F2100W) observations, one ∼5 kpc-long radial strip observed with MIRI F770W, and one covering the giant H II region NGC 604 with multiple NIRCam and MIRI broad/narrowband filters. Of the 21 SNRs in the MIRI (F560W+F2100W) field, we found three clear detections (i.e., identical infrared and Hα morphologies), and six partial-detections, implying a detection fraction of 43% in these bands. One of the SNRs in this field, L10-080, is a potential candidate for having freshly formed ejecta dust, based on its size and centrally concentrated 21 μm emission. In contrast, only one SNR (out of 16) is detectable in the NIRCam F335M+F444W field. Two SNRs near NGC 604 have strong evidence of molecular (H2) emission at 4.7 μm, making them the farthest known SNRs with visible molecular shocks. Five SNRs have F770W observations, with the smaller younger objects showing tentative signs of emission, while the older, larger ones have voids. Multiwavelength data indicate that the clearly detected SNRs are also among the smallest, brightest at other wavelengths (Hα, radio, and X-ray), have the broadest line widths (Hα FWHM ∼ 250─350 km s−1), and the densest environments. No correlation between the JWST-detectability and local star formation history of the SNRs is apparent.

Keywords: Supernova remnants, Shocks, James Webb Space Telescope, Interstellar medium
Ocean Tides on Asynchronously Rotating Planets Orbiting Low-mass Stars. Planets in the liquid-water habitable zone of low-mass stars experience large tidal forces, 103–104 times those on Earth, due to the small distance between the habitable zone and the host stars. Therefore, interior solid tides, ocean tides, and atmospheric tides on these planets could be much stronger than those on Earth, but little work has been done to explicitly simulate the ocean tides. Here, for the first time, we perform global ocean tide simulations and show that ocean tides on asynchronously rotating planets with large eccentricities can reach  O(1000)m  in height and  O(10)ms‑1  in flow speed. Interactions between tide and bottom topography can induce large energy dissipation,  ∼O(100)Wm‑2  in the global mean. This tidal energy dissipation can strongly accelerate orbital evolution by 1–2 orders of magnitude. However, for planets with small eccentricities, the ocean tides are much weaker but still comparable to those on modern Earth. Our results suggest that ocean tides on eccentric planets orbiting low-mass stars are orders of magnitude more powerful than those on Earth and can dramatically influence surface geography and orbital evolution.

Keywords: Tidal friction, Tidal distortion, Exoplanet tides, Ocean planets
Energy-dependent Transport of Cosmic Rays in the Multiphase, Dynamic Interstellar Medium. We investigate the transport of spectrally resolved cosmic-ray (CR) protons with kinetic energies between 1 and 100 GeV within the multiphase, dynamic interstellar medium (ISM), using a two-moment CR fluid solver applied to a TIGRESS MHD simulation with conditions similar to the solar neighborhood. Our CR transport prescription incorporates space- and momentum-dependent CR scattering coefficients σ = κ‑1, computed from the local balance between streaming-driven Alfvèn wave growth and damping processes. We find that advection combines with momentum-dependent diffusion to produce a CR distribution function f(p) ∝ p‑γ with γ ≈ 4.6 that agrees with observations, steepened from an injected power-law slope γinj = 4.3. The CR pressure is uniform in the highly diffusive, mostly neutral midplane region, but decreases exponentially in the ionized extraplanar region where scattering is efficient. To interpret these numerical results, we develop a two-zone analytic model that captures and links the two (physically and spatially) distinct regimes of CR transport in the multiphase, dynamic ISM. At low momenta, CR transport is dominated by gas advection, while at high momenta, both advection and diffusion contribute. At high momentum, the analytic prediction for the spectral slope approaches γ = (4/3)γinj ‑ 1, and the predicted scaling of grammage with momentum is  X∝p1‑γinj/3 , consistent with the simulations. These results support a physical picture in which CRs are confined within the neutral midplane by the surrounding ionized gas, with their escape regulated by both the CR scattering rate in the ionized extraplanar gas and the velocity and Alfvén speed of that gas, at effective speed  vc,eff≈(1/2)[κ∥d(v+vA,i)/dz]1/2 .

Keywords: Magnetohydrodynamics, Interstellar medium, Cosmic rays
Atmospheric Circulation of Close-in Extrasolar Giant Planets: The Diabatic Equivalent-barotropic Model. We extend the description of equivalent-barotropic equations for exoplanets to the diabatic case—that is, with explicit heating and/or cooling representation, rather than with a stationary deflection of the bottom bounding surface. In the diabatic case, the equation for potential temperature (or entropy) is directly forced and cannot be decoupled from the equations for momentum and nonlinear pressure (the mass-like variable); hence, the isentropic surfaces do not remain coincident with material surfaces. Here the formalism is presented for an atmosphere with the Lamb vertical structure, as the formalism is substantially simplified while still remaining physically useful under the structure. The equations presented set the stage for accurate global simulations, which permit small-scale vortices, gravity waves, and fronts observed in current three-dimensional global simulations to be studied in detail.

Keywords: Hydrodynamical simulations, Hot Jupiters, Hydrodynamics, Planetary atmospheres, Exoplanet atmospheres
Discovery of WINERED-HVS1: A Metal-rich Hypervelocity Star Candidate Ejected from the Galactic Center. We report the discovery of a metal-rich red-giant star, WINERED-HVS1, which is a candidate for a hypervelocity star (HVS). Its past trajectory suggests that this star may have been ejected by the Galactic supermassive black hole (SMBH; Sgr A*), with a modest ejection velocity of at least 500 km s‑1. Since WINERED-HVS1 is gravitationally bound to the Milky Way and is not necessarily young, it is not an unambiguous HVS candidate from a kinematic perspective, unlike the previously confirmed A-type main-sequence HVS known as S5-HVS1. Therefore, the chemical characterization of this star is essential for understanding its origin. Through a spectroscopic follow-up observation with Magellan/WINERED, we determined its metallicity  [Fe/H]=‑0.147‑0.045+0.046 , as well as the abundances of Na, Mg, Si, S, K, Ca, Ti, Cr, Ni, and Sr. The high-metallicity value suggests that this star was ejected from the Galactic center and is unlikely to be a halo star with a radial orbit. The abundance pattern of this star—including the patterns of [α/Fe], [Mg/Fe], [Si/Mg], and [Ca/Mg]—is consistent with that of the nuclear star cluster surrounding the SMBH, further supporting our view. This discovery opens a new window to look through the Galactic center environment without the hindrance of dust extinction, by using the HVSs moving in the halo region where dust extinction is minimal.

Keywords: Supermassive black holes, High-velocity stars, Hypervelocity stars, Stellar abundances
Fractal Algorithm for Multiple-lens Analyses. A microlensing exoplanet search is a unique method for finding planets orbiting distant stars. However, in the past, the method used to analyze microlensing data could not deal with complex lens systems. The number of lenses was limited to three or less. Position calculations of images and their integration suffered from severe round-off errors because of singularities. We developed a new algorithm to calculate the light curves of multiple-lens systems. In this algorithm, fractal-like consecutive self-similar division (SSD) is used to find sparse images. SSD is also useful for integrating images to efficiently obtain magnifications. The new algorithm does not use root finding for the lens equation and is free from caustic singularities. There is no limit on the number of lenses that can be used with this algorithm. Compared to inverse-ray shooting, this method dramatically improves the computing time. The calculation can be adjusted to obtain either a high-precision final result or a high-speed quick result. Although this new algorithm was developed for a microlensing planet search, its application to quasar microlensing is also expected. This paper discusses problems in the modeling of a multiple-lens system and then presents the new algorithm in detail.

Keywords: Gravitational microlensing, Gravitational microlensing exoplanet detection, Quasar microlensing, Astronomy data modeling
A Unified Volumetric Rate–Energy Relation from Magnetar Radio Bursts to Fast Radio Bursts. Fast radio bursts (FRBs) are millisecond radio pulses with extremely high bright temperature. Their physical origin is still a mystery. The discovery of FRB 20020428 supports the idea that at least a portion of FRBs is generated by magnetars. However, FRB 20200428 and other radio bursts of SGR 1935+2154 are much less energetic than those of extragalactic FRBs. Thus, whether the progenitors of extragalactic FRBs are magnetars is still controversial. Here, we investigate the volumetric rates of radio bursts from SGR 1935+2154, nonrepeating FRBs, and FRB 20180916B using the uniform samples detected by the Canadian Hydrogen Intensity Mapping Experiment. We find that they share a similar relation between the volumetric rate R and the burst energy E, i.e., R ∝ E‑γ with γ = 1.31 ± 0.13 from 1029 to 1042 erg. Our results support the hypothesis that both repeating and nonrepeating FRBs originate from magnetars.

Keywords: Magnetars, Radio transient sources
Radiation Spectrum of the Photospheric Emission for a Turbulent Relativistic Jet. The prompt gamma rays of gamma-ray bursts (GRBs) may originate from the photosphere of a relativistic jet. However, only a few GRBs have been observed with evident blackbody-like emission, for example, GRB 090902B. It has been demonstrated that internal dissipation processes, such as magnetic reconnection, can occur within the relativistic jet and thereby drive violent turbulence in the dissipation region. In this paper, we study the photospheric emission of a jet with turbulence below its photosphere. Here, the turbulence is modeled phenomenologically under the assumption that the four-velocity of its eddies follows a Gaussian distribution in the jet's comoving frame. It is found that the turbulence scatters photons to high energies and thus intensifies the emission in the high-energy regime. The corresponding distortion of the radiation field can be preserved if and only if the turbulence occurs in a region with incomplete photon–electron coupling. Consequently, the observed radiation spectrum can be reshaped into a Band-like spectrum.

Keywords: Gamma-ray bursts, High energy astrophysics
Optical and Near-infrared Spectroscopy of the Outbursting Comet 12P/Pons-Brooks. We present optical and near-infrared (NIR) observations of the outbursting, Halley-type comet 12P/Pons-Brooks (12P). Three NIR spectra were obtained during two outbursts in 2023 October and November, with the 3 m Infrared Telescope Facility and the Palomar 200 inch Telescope, respectively. The NIR spectra exhibited absorption features at 1.5 and 2.0 μm, consistent with the diagnostic absorption bands of water ice, superimposed on a red dust-scattering continuum. We find that the absorption bands and the red continuum can be well explained by micrometer-sized crystalline ice at 140–170 K, along with submicrometer-sized refractory grains (e.g., amorphous carbon). In addition, an optical spectrum was obtained with the Lijiang 2.4 m Telescope during the 2023 November outburst, which exhibited the emission bands of gaseous CN, C3, C2, and NH2. The C3/CN and C2/CN ratios suggest that 12P was "typical" in C3 abundance but somewhat depleted in C2. The specific kinetic energy of the 2023 November outburst is estimated to be ∼8 × 103 J kg‑1, suggesting a likely triggering mechanism similar to 332P/Ikeya–Murakami and 17P/Holmes, i.e., the crystallization of amorphous water ice. A refractory-to-ice ratio of ∼1.7–3.2 is derived from the total mass loss of dust and gas, aligning with the lower-end estimates for 67P/Churyumov-Gerasimenko and 1P/Halley. This suggests either a less evolved nucleus or an outburst region enriched in icy materials relative to the bulk nucleus.

Keywords: Comae, Coma dust, Long period comets, Spectroscopy, Near infrared astronomy
Metallicity Gradients in Modern Cosmological Simulations. I. Tension between Smooth Stellar Feedback Models and Observations. The metallicity of galaxies, and its variation with galactocentric radius, provides key insights into the formation histories of galaxies and the physical processes driving their evolution. In this work, we analyze the radial metallicity gradients of star-forming galaxies in the EAGLE, Illustris, IllustrisTNG, and SIMBA cosmological simulations across broad mass (108.0 M⊙ ≤ M⋆ ≲ 1012.0 M⊙) and redshift (0 ≤ z ≤ 8) ranges. We find that all simulations predict strong negative (i.e., radially decreasing) metallicity gradients at early cosmic times, likely due to their similar treatments of relatively smooth stellar feedback not providing sufficient mixing to quickly flatten gradients. The strongest redshift evolution occurs in galaxies with stellar masses of 1010.0–1011.0 M⊙, while galaxies with stellar mass &lt; 1010M⊙ and &gt;1011M⊙ exhibit weaker redshift evolution. Our result of negative gradients at high redshift contrast with the many positive and flat gradients in the 1 &lt; z &lt; 4 observational literature. At z &gt; 6, the negative gradients observed with JWST and the Atacama Large Millimeter/submillimeter Array are flatter than those in simulations, albeit with closer agreement than at lower redshift. Overall, we suggest that these smooth stellar feedback galaxy simulations may not sufficiently mix their metal content radially, and that either stronger stellar feedback or additional subgrid turbulent metal diffusion models may be required to better reproduce observed metallicity gradients.

Keywords: Galaxy evolution, Chemical enrichment, High-redshift galaxies, Stellar feedback
Ion-rich Acceleration during an Eruptive Flux Rope Event in a Multiple Null-point Configuration. We report on the γ-ray emission above 100 MeV from the GOES M3.3 flare SOL2012-06-03. The hard X-ray (HXR) and microwave emissions have typical time profiles with a fast rise to a well-defined peak followed by a slower decay. The &gt;100 MeV emission during the prompt phase displayed a double-peaked temporal structure with the first peak following the HXR and microwaves, and the second one, about 3 times stronger, occurring 17 ± 2 s later. The time profiles seem to indicate two separate acceleration mechanisms at work, where the second γ-ray peak reveals a potentially pure or at least largely dominant ion acceleration. The Atmospheric Imaging Assembly imaging shows a bright elliptical ribbon and a transient brightening in the northwestern (NW) region. Nonlinear force-free extrapolations at the time of the impulsive peaks show closed field lines connecting the NW region to the southeastern part of the ribbon, and the magnetic topology revealed clusters of nulls. These observations suggest a spine-and-fan geometry, and based on these observations, we interpret the second γ-ray peak as being due to the predominant acceleration of ions in a region with multiple null points. The &gt;100 MeV emission from this flare also exhibits a delayed phase with an exponential decay of roughly 350 s. We find that the delayed emission is consistent with ions being trapped in a closed flux tube with gradual escape via their loss cone to the chromosphere.

Keywords: Solar coronal waves, Solar flares, Gamma-rays
Enhanced Star Formation and Black Hole Accretion Rates in Galaxy Mergers in IllustrisTNG50. Many theoretical and observational studies have suggested that galaxy mergers may trigger enhanced star formation or active galactic nucleus activity. We present an analysis of merging and nonmerging galaxies from 0.2 ≤ z ≤ 3 in the IllustrisTNG50 simulation. These galaxies encompass a range of masses (M⋆ &gt; 108 M⊙) and mass ratios (≥1:10) and multiple merger stages. We examine the effect that galaxy mergers have on star formation and black hole accretion rates in the TNG50 universe. We additionally investigate how galaxy and black hole mass, merger stage, merger mass ratio, and redshift affect these quantities. Mergers in our sample show excess specific star formation rates (sSFR) at z ≤ 3 and enhanced specific black hole accretion rates (sBHAR) at z ≲ 2. The difference between sSFRs and sBHARs in the merging sample compared to the nonmerging sample increases as redshift decreases. Additionally, we show that these enhancements persist for at least ∼1 Gyr after the merger event. Investigating how mergers behave in the TNG50 simulation throughout cosmic time enables both a better appreciation of the importance of spatial resolution in cosmological simulations and a better basis to understand our high-z Universe with observations from JWST.

Keywords: AGN host galaxies, Interacting galaxies, Galaxies, Magnetohydrodynamical simulations
Sometimes They Come Back: Pulsations in A 0538─66 at 69 ms Rediscovered with NICER. We report on Neutron Star Interior Composition Explorer (NICER) X-ray observations of the Be X-ray binary A 0538─66 located in the Large Magellanic Cloud. Fast pulsations (69 ms) in this source were discovered in 1980 during a bright outburst in which it reached a luminosity of ∼8 × 1038 erg s−1 but were never reobserved since then. We clearly detected the pulsations at P = 69.3055 ± 0.0005 ms with a pulsed fraction of ∼20% during a short time interval (∼11 minutes) on 2023 January 9, when A 0538─66 had a luminosity of ∼8 × 1036 erg s−1 (0.3─10 keV). The pulsations were not detected in other NICER observations (total exposure ∼162.7 ks), during which A 0538─66 had a similar or lower luminosity. On 2023 February 8─9 the source exhibited a strong variability, with short flares reaching ∼1038 erg s−1, but no periodic pulsations were detected. Assuming the magnetospheric radius lies within the corotation radius during pulsations, we estimate the neutron star magnetic field is below ∼2.7 × 1010 G. This would make A 0538─66 the high-mass X-ray binary with the weakest known magnetic field. We discuss implications for magnetic field evolution in accreting pulsars and propose that, alternatively, A 0538─66 has a stronger magnetic field, and during the NICER detection, a centrifugal barrier may have been active while part of the plasma accumulated at the magnetosphere sporadically leaked through it via an instability mechanism, allowing accretion onto the polar caps.

Keywords: Neutron stars, High mass x-ray binary stars
Can Gamma-Ray Burst Empirical Correlations Be Used for Population Studies?. Only a small fraction of gamma-ray bursts (GRBs) have independent redshift measurements, which are essential for understanding their intrinsic properties. For this reason, empirical correlations of GRBs have often been touted as useful distance indicators, for both individual GRBs as well as population studies. Building upon our previous work, we test the ability of the Yonetoku, 3D Dainotti, and the  LX‑Ta∗‑Eiso  correlation to adequately constrain the GRB rate, ΨGRB. Our analysis demonstrates that, even under idealized conditions that neglect substantial uncertainties, the derived redshift solutions cannot accurately constrain ΨGRB, regardless of the intrinsic distribution's characteristic width. We thus demonstrate unequivocally that—notwithstanding the questionable assumption of no selection biases—empirical GRB correlations alone cannot serve as reliable distance indicators at either the individual or population level.

Keywords: Gamma-ray bursts, High energy astrophysics
Alfvén Waves from Interchange Reconnection at Separators as a Possible Source of Switchbacks. Parker Solar Probe has observed Alfvénic fluctuations of amplitude large enough to occasionally reverse the local magnetic field direction—a phenomenon known as a switchback. Some have attributed switchbacks to reconnection in the low corona between open and closed field lines, called interchange reconnection. This has not been investigated thoroughly enough to conclusively make the association. We make a small-scale magnetic model of a coronal hole to which PSP was briefly magnetically connected and show that no more than about 15% of the photosphere anchors magnetic field lines open to the heliosphere. The model's field line mapping is characterized by a web of separatrices, an S-web, outlining ∼10 Mm cells reflecting the magnetic carpet. We find that PSP's magnetic footpoint crossed S-web boundaries at a rate similar to encountering large magnetic field deflections. The model also reveals that interchange reconnection in the vicinity of an S-web separatrix generally occurs at a low-lying magnetic separator, and that such reconnection would launch a nonlinear Alfvén wave polarized within the separatrix surface. We use a thin flux tube model to infer that interchange reconnection at a low-lying separator can produce a wave with magnetic deflection as large as in a switchback. The average mass, momentum, and energy carried by a population of waves is estimated to be comparable to the solar wind itself. These findings appear to support the plausibility of interchange reconnection as a possible source of switchbacks.

Keywords: Solar coronal holes, Solar wind
Optical Detection of the X-Ray Flash in the Very Fast Nova V1674 Her: Optical Contribution of the Irradiated Accretion Disk. V1674 Her is one of the fastest and brightest novae, characterized by dense optical photometry in the premaximum phase—a rise from g = 17 to 7 mag, over one-quarter of a day. We present a composite theoretical V light-curve model of its early rising phase, starting from a quiescent brightness of g = 19.2 mag. Our light-curve model consists of a hot and bright white dwarf (WD) and an irradiated accretion disk and companion star. We find that the earliest optical detection of an All Sky Automated Survey for Supernovae g-band brightness of g = 17.0 at t = 0.014 days from the onset of thermonuclear runaway can be explained with the irradiated accretion disk and companion star in the X-ray-flash phase of a 1.35 M⊙ WD. This is the first detection in the optical of an X-ray-flash phase of a nova. Optically thick winds emerge from the WD photosphere at t = 0.04 days, and the optical flux is dominated by free–free emission from optically thin ejecta just outside the WD photosphere. Our free–free emission model V light curve reasonably reproduces the dense g light curve of Evryscope that spans from g = 14.8 (at 0.078 days) to g = 7.1 (at 0.279 days), including a sudden change of slope in the g light curve from a slow to a rapid rise at g = 14.3 on day 0.1. There is no indication of shocking power during the rising phase from g = 14.8 to 7.1.

Keywords: X-ray astronomy, Fast novae, Cataclysmic variable stars, Classical novae