Sazuna/UAT_keywords huggingface dataset:
On the Jet-Ejecta Interaction in 3D GRMHD Simulations of a Binary Neutron Star Merger Aftermath. Short γ-ray burst (sGRB) jets form in the aftermath of a neutron star merger, drill through disk winds and dynamical ejecta, and extend over four to five orders of magnitude in distance before breaking out of the ejecta. We present the first 3D general-relativistic magnetohydrodynamic sGRB simulations to span this enormous scale separation. They feature three possible outcomes: jet+cocoon, cocoon, and neither. Typical sGRB jets break out of the dynamical ejecta if (i) the bound ejecta's isotropic equivalent mass along the pole at the time of the BH formation is ≲10-4 M ⊙, setting a limit on the delay time between the merger and BH formation, otherwise, the jets perish inside the ejecta and leave the jet-inflated cocoon to power a low-luminosity sGRB; (ii) the postmerger remnant disk contains a strong large-scale vertical magnetic field, ≳1015 G; and (iii) if the jets are weak (≲1050 erg), the ejecta's isotropic equivalent mass along the pole must be small (≲10-2 M ⊙). Generally, the jet structure is shaped by the early interaction with disk winds rather than the dynamical ejecta. As long as our jets break out of the ejecta, they retain a significant magnetization (≲1), suggesting that magnetic reconnection is a fundamental property of sGRB emission. The angular structure of the outflow isotropic equivalent energy after breakout consistently features a flat core followed by a steep power-law distribution (slope ≳3), similar to hydrodynamic jets. In the cocoon-only outcome, the dynamical ejecta broadens the outflow angular distribution and flattens it (slope ~1.5).

Keywords: Neutron stars, Ejecta, Gamma-ray bursts, Jets, Stellar mergers, Relativistic jets, Polar jets
Insight-HXMT Discovery of the Highest-energy CRSF from the First Galactic Ultraluminous X-Ray Pulsar Swift J0243.6+6124. The detection of cyclotron resonance scattering features (CRSFs) is the only way to directly and reliably measure the magnetic field near the surface of a neutron star (NS). The broad energy coverage and large collection area of Insight-HXMT in the hard X-ray band allowed us to detect the CRSF with the highest energy known to date, reaching about 146 keV during the 2017 outburst of the first galactic pulsing ultraluminous X-ray source (pULX) Swift J0243.6+6124. During this outburst, the CRSF was only prominent close to the peak luminosity of ~2 × 1039 erg s-1, the highest to date in any of the Galactic pulsars. The CRSF is most significant in the spin-phase region corresponding to the main pulse of the pulse profile, and its centroid energy evolves with phase from 120 to 146 keV. We identify this feature as the fundamental CRSF because no spectral feature exists at 60-70 keV. This is the first unambiguous detection of an electron CRSF from an ULX. We also estimate a surface magnetic field of ~1.6 × 1013 G for Swift J0243.6+6124. Considering that the dipole magnetic field strengths, inferred from several independent estimates of magnetosphere radius, are at least an order of magnitude lower than our measurement, we argue that the detection of the highest-energy CRSF reported here unambiguously proves the presence of multipole field components close to the surface of the neutron star. Such a scenario has previously been suggested for several pulsating ULXs, including Swift J0243.6+6124, and our result represents the first direct confirmation of this scenario.

Keywords: Accretion, Neutron stars, High mass x-ray binary stars, Ultraluminous x-ray sources, Magnetic fields, Binary pulsars
The Doppler Flip in HD 100546 as a Disk Eruption: The Elephant in the Room of Kinematic Protoplanet Searches. The interpretation of molecular-line data using hydrodynamical simulations of planet-disk interactions fosters new hope for the indirect detection of protoplanets. In a model-independent approach, embedded protoplanets should be found at the roots of abrupt Doppler flips in velocity centroid maps. However, the largest velocity perturbation known for an unwarped disk, in the disk of HD 100546, leads to a conspicuous Doppler flip that coincides with a thick dust ring, in contradiction with an interpretation in terms of a ≳1 M jup body. Here we present new ALMA observations of the 12CO(2-1) kinematics in HD 100546, with a factor of 2 finer angular resolutions. We find that the disk rotation curve is consistent with a central mass 2.1 &lt; M ⋆/M ⊙ &lt; 2.3 and that the blueshifted side of the Doppler flip is due to vertical motions, reminiscent of the disk wind proposed previously from blueshifted SO lines. We tentatively propose a qualitative interpretation in terms of a surface disturbance to the Keplerian flow, i.e., a disk eruption, driven by an embedded outflow launched by a ~10 M earth body. Another interpretation involves a disk-mass-loading hot spot at the convergence of an envelope accretion streamer.

Keywords: Radio interferometry, Protoplanetary disks, Planet formation
Detection of an Extremely Large Impact Flash on Jupiter by High-cadence Multiwavelength Observations. We report the detection of an optical impact flash on Jupiter on 2021 October 15 by a dedicated telescope, Planetary ObservatioN Camera for Optical Transient Surveys, for the first time. Our temporally resolved three-band observations of the flash allowed investigations of its optical energy without the need for approximations on the impact brightness temperature. The kinetic energy of the impactor was equivalent to approximately two megatons of TNT, an order of magnitude greater than that of previously detected flashes on Jupiter and comparable with the Tunguska impact on Earth in 1908. This detection indicates that Tunguska-like impact events on Jupiter occur approximately once per year, two to three orders of magnitude more frequently than terrestrial impacts. The observed flash displayed a single-temperature blackbody spectrum with an effective temperature of approximately 8300 K without clear temporal variation, possibly representing common radiative features of terrestrial Tunguska-class superbolides.

Keywords: Impact phenomena, Planetary atmospheres, Jupiter, Time domain astronomy, Solar system astronomy
Faraday Conversion in Pair-symmetric Winds of Magnetars and Fast Radio Bursts. We consider the propagation of polarization in the inner parts of pair-symmetric magnetar winds, close to the light cylinder. Pair plasmas in magnetic field is birefringent, a ∝ B 2 effect. As a result, such plasmas work as phase retarders: Stokes parameters follow a circular trajectory on the Poincare sphere. In the highly magnetized regime, ω, ω  p  ≪ ω  B , the corresponding rotation rates are independent of the magnetic field. A plasma screen with dispersion measure DM ~ 10-6 pc cm-3 can induce large polarization changes, including large effective rotation measures (RMs). The frequency scaling of the (generalized) RM, ∝ λ  α , mimics the conventional RM with α = 2 for small phase shifts, but can be as small as α = 1. In interpreting observations, the frequency scaling of polarization parameters should be fitted independently. The model offers explanations for (i) the large circular polarization component observed in FRBs, with right-left switching; (ii) large RM, with possible sign changes (when the observation bandwidth is small); and (iii) time-dependent variable polarization. A relatively dense and slow wind is needed-the corresponding effect in regular pulsars is small.

Keywords: Radio transient sources, Magnetars, Plasma astrophysics, Radio pulsars
Inferring Late-stage Enrichment of Exoplanet Atmospheres from Observed Interstellar Comets. The discovery of the first two interstellar objects implies that, on average, every star contributes a substantial amount of material to the galactic population by ejecting such bodies from the host system. Because scattering is a chaotic process, a comparable amount of material should be injected into the inner regions of each system that ejects comets. For comets that are transported inwards and interact with planets, this Letter estimates the fraction of material that is accreted or outward-scattered as a function of planetary masses and orbital parameters. These calculations indicate that planets with escape velocities smaller than their current-day orbital velocities will efficiently accrete comets. We estimate the accretion efficiency for members of the current census of extrasolar planets and find that planetary populations including but not limited to hot and warm Jupiters, sub-Neptunes, and super-Earths can efficiently capture incoming comets. This cometary enrichment may have important ramifications for postformation atmospheric composition and chemistry. As a result, future detections and compositional measurements of interstellar comets will provide direct measurements of material that potentially enriched a subpopulation of the extrasolar planets. Finally, we estimate the efficiency of this enrichment mechanism for extrasolar planets that will be observed with the James Webb Space Telescope (JWST). With JWST currently operational and these observations imminently forthcoming, it is of critical importance to investigate how enrichment from interstellar comet analogs may affect the interpretations of exoplanet atmospheric compositions.

Keywords: Galaxy chemical evolution, Comets, Interstellar objects, Exoplanet atmospheres
Finding Lensed Direct-collapse Black Holes and Supermassive Primordial Stars. Direct-collapse black holes (DCBHs) may be the seeds of the first quasars, over 200 of which have now been detected at z &gt; 6. The James Webb Space Telescope (JWST) could detect DCBHs in the near-infrared (NIR) at z ≲ 20 and probe the evolution of primordial quasars at their earliest stages, but only in narrow fields that may not capture many of them. Wide-field NIR surveys by Euclid and the Nancy Grace Roman Space Telescope (RST) would enclose far greater numbers of DCBHs but only directly detect them at z ≲ 6-8 because of their lower sensitivities. However, their large survey areas will cover thousands of galaxy clusters and massive galaxies that could gravitationally lens flux from DCBHs, boosting them above current Euclid and RST detection limits and revealing more of them than could otherwise be detected. Here, we estimate the minimum number density of strongly lensed DCBHs and supermassive primordial stars required for detection in surveys by Euclid, RST, and JWST at z ≲ 20. We find that for reasonable estimates of host halo numbers RST, Euclid, and JWST could potentially find hundreds of strongly lensed DCBHs at z = 7-20. RST would detect the most objects at z ≲ 10 and JWST would find the most at higher redshifts. Lensed supermassive primordial stars could potentially also be found, but in fewer numbers because of their short lifetimes.

Keywords: Black hole physics, Supermassive black holes, Early universe, Quasars, Reionization, High-redshift galaxies
Black Hole to Photosphere: 3D GRMHD Simulations of Collapsars Reveal Wobbling and Hybrid Composition Jets. Long-duration γ-ray bursts (GRBs) accompany the collapse of massive stars and carry information about the central engine. However, no 3D models have been able to follow these jets from their birth via black hole (BH) to the photosphere. We present the first such 3D general-relativity magnetohydrodynamic simulations, which span over six orders of magnitude in space and time. The collapsing stellar envelope forms an accretion disk, which drags inwardly the magnetic flux that accumulates around the BH, becomes dynamically important, and launches bipolar jets. The jets reach the photosphere at ~1012 cm with an opening angle θ  j  ~ 6° and a Lorentz factor Γ j  ≲ 30, unbinding ≳90% of the star. We find that (i) the disk-jet system spontaneously develops misalignment relative to the BH rotational axis. As a result, the jet wobbles with an angle θ  t  ~ 12°, which can naturally explain quiescent times in GRB lightcurves. The effective opening angle for detection θ  j  + θ  t  suggests that the intrinsic GRB rate is lower by an order of magnitude than standard estimates. This suggests that successful GRBs are rarer than currently thought and emerge in only ~0.1% of supernovae Ib/c, implying that jets are either not launched or choked inside most supernova Ib/c progenitors. (ii) The magnetic energy in the jet decreases due to mixing with the star, resulting in jets with a hybrid composition of magnetic and thermal components at the photosphere, where ~10% of the gas maintains magnetization σ ≳ 0.1. This indicates that both a photospheric component and reconnection may play a role in the prompt emission.

Keywords: Type Ic supernovae, Gamma-ray bursts, Core-collapse supernovae, Plasma jets, Type Ib supernovae, Stellar jets, Relativistic jets, Polar jets, Magnetohydrodynamical simulations
The Streaming Instability Cannot Form Planetesimals from Millimeter-size Grains in Pressure Bumps. We present evidence that it is unlikely that the streaming instability (SI) can form planetesimals from millimeter grains inside axisymmetric pressure bumps. We conducted the largest simulation of the SI so far (7 million CPU hours), consisting of a large slice of the disk with millimeter grains, a solar-like dust-to-gas ratio (Z = 0.01), and the largest pressure bump that does not cause gravitational instability (GI) in the particle layer. We used a high resolution of 1000/H to resolve as many SI unstable modes as possible. The simulation produced a long-lived particle overdensity far exceeding the SI criteria (i.e., a critical solid abundance to headwind parameter ratio Z/Π) where strong clumping would occur if these conditions were present over an extended region of the disk; yet we observed none. The likely reason is that the time it takes particles to cross the high-Z/Π region (t cross) is shorter than the growth timescale of the SI (t grow). We propose an added criterion for planetesimal formation by the SI-that t cross &gt; t grow. We show that any bump larger than the one in this run would form planetesimals by the GI instead of the SI. Our results significantly restrict the pathways to planet formation: either protoplanetary disks regularly form grains larger than 1 mm, or planetesimals do not form by the SI in axisymmetric pressure bumps. Since bumps large enough to induce the GI are likely Rossby-wave unstable, we propose that millimeter grains may only form planetesimals in vortices.

Keywords: Planet formation, Planetesimals
A Green Pea Starburst Arising from a Galaxy-Galaxy Merger. Green Pea galaxies are low-redshift starburst dwarf galaxies, with properties similar to those of the high-redshift galaxies that reionized the universe. We report the first mapping of the spatial distribution of atomic hydrogen (HI) in and around a Green Pea, GP J0213+0056 at z = 0.0399, using the Giant Metrewave Radio Telescope (GMRT). Like many Green Peas, GP J0213+0056 shows strong HI 21 cm emission in single-dish spectroscopy, strong Lyα emission, and a high [OIII]λ5007 Å/[OII]λ3727 Å luminosity ratio, O32 ≈ 8.8, consistent with a high leakage of Lyman-continuum radiation. Our GMRT HI 21 cm images show that the HI 21 cm emission in the field of GP J0213+0056 arises from an extended broken-ring structure around the Green Pea, with the strongest emission coming from a region between GP J0213+0056 and a companion galaxy lying ≈4.7 kpc away, and little HI 21 cm emission coming from the Green Pea itself. We find that the merger between GP J0213+0056 and its companion is likely to have triggered the starburst, and led to a disturbed HI spatial and velocity distribution, which in turn allowed Lyα (and, possibly, Lyman-continuum) emission to escape the Green Pea. Our results suggest that such mergers, and the resulting holes in the HI distribution, are a natural way to explain the tension between the requirements of cold gas to fuel the starburst and the observed leakage of Lyα and Lyman-continuum emission in Green Pea galaxies and their high-redshift counterparts.

Keywords: Starburst galaxies, Radio interferometry, Galaxies, H I line emission
Cold Gas Reservoirs of Low- and High-mass Central Galaxies Differ in Response to Active Galactic Nucleus Feedback. The growth of supermassive black holes, especially the associated state of active galactic nuclei (AGNs), is generally believed to be the key step in regulating star formation in massive galaxies. As the fuel of star formation, the cold gas reservoir is a direct probe of the effect of AGN feedback on their host galaxies. However, in observations, no clear connection has been found between AGN activity and the cold gas mass. In this paper, we find observational signals of the significant depletion of the total neutral hydrogen gas reservoir in optically selected Type 2 AGN-host central galaxies of stellar mass 109-1010 M ⊙. The effect of AGN feedback on the cold gas reservoir is stronger for higher star formation rates and higher AGN luminosity. But it becomes much weaker above this mass range, consistent with previous findings focusing on massive galaxies. Our result suggests that low-mass and gas-rich AGN-host central galaxies would first form dense cores before AGN feedback is triggered, removing their neutral hydrogen gas. More massive central galaxies may undergo a significantly different formation scenario by gradually building up dense cores with less effective and recurrent AGN feedback.

Keywords: AGN host galaxies, Interstellar atomic gas, H I line emission, Star formation, Galaxy quenching
60 Candidate High-velocity Stars Originating from the Sagittarius Dwarf Spheroidal Galaxy in Gaia EDR3. Using proper motions from Gaia Early Data Release 3 (Gaia EDR3) and radial velocities from several surveys, we identify 60 candidate high-velocity stars with a total velocity greater than 75% of the escape velocity that probably originated from the Sagittarius dwarf spheroidal galaxy (Sgr) by orbital analysis. Sgr's gravity has little effect on the results and the Large Magellanic Cloud's gravity has a nonnegligible effect on only a few stars. The closest approach of these stars to the Sgr occurred when the Sgr passed its pericenter (~38.2 Myr ago), which suggests they were tidally stripped from the Sgr. The positions of these stars in the Hertzsprung-Russell diagram and the chemical properties of 19 of them with available [Fe/H] are similar to the Sgr stream member stars. This is consistent with the assumption of their accretion origin. Two of the 60 are hypervelocity stars, which may also be produced by the Hills mechanism.

Keywords: Stellar abundances, Stellar dynamics, High-velocity stars, Hertzsprung Russell diagram, Sagittarius dwarf spheroidal galaxy
Divergence in Mass Ratio Distributions between Low-mass and High-mass Coalescing Binary Black Holes. Coalescing binary black hole (BBH) systems are likely formed via several channels, and it is challenging to understand their formation/evolutionary processes. Some features in the mass function of the primary components (m 1), such as the distinct Gaussian-like peak located at ~34 M ⊙, have been previously found. In this work, we investigate the possible dependence of the mass ratio (q = m 2/m 1) distribution on the primary mass. We find a Bayesian odds ratio of 18.1 in favor of divergence in the mass ratio distributions between the low- and high-mass ranges over an invariable mass ratio distribution. BBHs with m 1 ≳ 29 M ⊙ have a stronger preference of being symmetric compared to those with m 1 ≲ 29 M ⊙ at a 97.6% credible level. Additionally, we find mild evidence that BBHs with m 1 located in the Gaussian-like peak have a mass ratio distribution different from that of other BBHs. Our findings may favor some formation channels, such as chemically homogeneous evolution and dynamical assembly in globular clusters/nuclear star clusters, which are more likely to provide symmetric BBHs in the high-mass range.

Keywords: Gravitational wave astronomy, High energy astrophysics
Hubble Space Telescope Observations of Active Asteroid P/2020 O1 (Lemmon-PANSTARRS). We present Hubble Space Telescope observations of active asteroid P/2020 O1 taken to examine its development for a year after perihelion. We find that the mass loss peaks at ≲1 kg s-1 in 2020 August and then declines to nearly zero over four months. Long-duration mass loss (~180 days) is consistent with a sublimation origin, indicating that this object is likely an ice-bearing main-belt comet. Equilibrium sublimation of water ice from an area as small as 1580 m2 can supply the observed mass loss. Time-series photometry shows tentative evidence for extremely rapid rotation (double-peaked period &lt;2 hr) of the small nucleus (effective radius ~420 m). Ejection velocities of 0.1 mm particles are comparable to the 0.3 m s-1 gravitational escape speed from the nucleus, while larger particles are ejected at speeds less than the escape velocity. These properties are consistent with the sublimation of near-surface ice aided by centripetal acceleration. If water-ice sublimation is confirmed, P/2020 O1 would be an icy asteroid with the smallest semimajor axis (highest temperature), setting new bounds on the distribution of ice in the asteroid belt.

Keywords: Main belt asteroids, Comets, Main-belt comets
Diffusion Activation Energy and Desorption Activation Energy for Astrochemically Relevant Species on Water Ice Show No Clear Relation. The activation energies for desorption (E des) and for surface diffusion (E sd) of adsorbed molecules on dust grains are two of the most important parameters for the chemistry in the interstellar medium. Although E des is often measured by laboratory experiments, the measurement of E sd is sparse. Due to the lack of data, astrochemical models usually assume a simple scaling relation, E sd = f E des, where f is a constant, irrespective of the adsorbed species. Here, we experimentally measure E sd for CH4, H2S, OCS, CH3OH, and CH3CN on water-ice surfaces using an ultrahigh-vacuum transmission electron microscope. Compiling the measured E sd values and E des values from the literature, we find that the value of f ranges from ~0.2 to ~0.7, depending on the species. Unless f (or E sd) for the majority of species is available, a natural alternative approach for astrochemical models is running multiple simulations, varying f for each species randomly. In this approach, ranges of molecular abundances predicted by multiple simulations, rather than abundances predicted by each simulation, are important. We here run 10,000 simulations of astrochemical models of molecular clouds and protostellar envelopes, randomly assigning a value of f for each species. In the former case, we identify several key species whose E sd most strongly affects the uncertainties of the model predictions; E sd for those species should be investigated in future laboratory and quantum chemical studies. In the latter case, uncertainties in the E sd of many species contribute to the uncertainties in the model predictions.

Keywords: Interstellar molecules, Interstellar dust processes, Astrochemistry