Sazuna/UAT_keywords huggingface dataset:
Catastrophic Events in Protoplanetary Disks and Their Observational Manifestations. Observations of protoplanetary disks with high angular resolution using an ALMA interferometer showed that ring-shaped structures are often visible in their images, indicating strong disturbances in the disks. The mechanisms of their formation are vividly discussed in the literature. This article shows that the formation of such structures can be the result of destructive collisions of large bodies (planetesimals and planetary embryos) accompanied by the formation of a large number of dust particles, and the subsequent evolution of a cloud of dust formed in this way.

Keywords: Planetary system formation, Hydrodynamical simulations, Protoplanetary disks
Upscattered Cocoon Emission in Short Gamma-Ray Bursts as High-energy Gamma-Ray Counterparts to Gravitational Waves. We investigate prolonged engine activities of short gamma-ray bursts (SGRBs), such as extended and/or plateau emissions, as high-energy gamma-ray counterparts to gravitational waves (GWs). Binary neutron-star mergers lead to relativistic jets and merger ejecta with r-process nucleosynthesis, which are observed as SGRBs and kilonovae/macronovae, respectively. Long-term relativistic jets may be launched by the merger remnant as hinted in X-ray light curves of some SGRBs. The prolonged jets may dissipate their kinetic energy within the radius of the cocoon formed by the jet-ejecta interaction. Then the cocoon supplies seed photons to nonthermal electrons accelerated at the dissipation region, causing high-energy gamma-ray production through the inverse Compton scattering process. We numerically calculate high-energy gamma-ray spectra in such a system using a one-zone and steady-state approximation, and show that GeV-TeV gamma-rays are produced with a duration of 102-105 s. They can be detected by Fermi/LAT or CTA as gamma-ray counterparts to GWs.

Keywords: Gamma-ray bursts, High energy astrophysics, Relativistic jets, Gravitational wave astronomy, Non-thermal radiation sources, Gamma-ray astronomy, Gamma-ray transient sources
Discovery of a Powerful &gt;10<SUP>61</SUP> erg AGN Outburst in the Distant Galaxy Cluster SPT-CLJ0528-5300. We present ∼103 ks of Chandra observations of the galaxy cluster SPT-CLJ0528-5300 (SPT0528, z = 0.768). This cluster harbors the most radio-loud (L 1.4GHz = 1.01 × 1033 erg s-1 Hz-1) central active galactic nucleus (AGN) of any cluster in the South Pole Telescope (SPT) Sunyaev-Zeldovich survey with available X-ray data. We find evidence of AGN-inflated cavities in the X-ray emission, which are consistent with the orientation of the jet direction revealed by Australia Telescope Compact Array radio data. The combined probability that two such depressions—each at ∼1.4-1.8σ significance, oriented ∼180° apart and aligned with the jet axis—would occur by chance is 0.1%. At ≳1061 erg, the outburst in SPT0528 is among the most energetic known in the universe, and certainly the most powerful known at z &gt; 0.25. This work demonstrates that such powerful outbursts can be detected even in shallow X-ray exposures out to relatively high redshifts (z ∼ 0.8), providing an avenue for studying the evolution of extreme AGN feedback. The ratio of the cavity power ({P}cav}=(9.4+/- 5.8)× {10}45 erg s-1) to the cooling luminosity (L cool = (1.5 ± 0.5) × 1044 erg s-1) for SPT0528 is among the highest measured to date. If, in the future, additional systems are discovered at similar redshifts with equally high P cav/L cool ratios, it would imply that the feedback/cooling cycle was not as gentle at high redshifts as in the low-redshift universe.

Keywords: Galaxy clusters, Radio galaxies, Active galactic nuclei, X-ray astronomy
Multispacecraft Observation of Unidirectional and Bidirectional Alfvén Waves within Large-scale Magnetic Clouds. Recent years have seen growing evidence of the existence of Alfvén waves within interplanetary magnetic flux ropes, which are believed to be an important aspect of dynamics connecting the Sun and the heliosphere. Previous studies, due to localized observation by single spacecraft, focused on sunward or antisunward Alfvén waves propagating along with magnetic field lines. In this Letter, for the first time, we use multispacecraft observations to verify and analyze two large-scale magnetic clouds (MCs), when the spacecraft had quite different spatial separations. What surprises us is that not only unidirectional but bidirectional Alfvén waves exist in the large-scale MC, which is rooted to the Sun. We speculate that unidirectional Alfvén waves within an MC are generated by distortions produced within a preexisting flux rope, and bidirectional Alfvén waves are emitted from the center of reconnection and then travel outward along with two loop legs of an MC.

Keywords: Slow solar wind, Alfven waves, Solar coronal mass ejections
Physical Constraints from Near-infrared Fast Photometry of the Black Hole Transient GX 339-4. We present results from the first multi-epoch X-ray/IR fast-photometry campaign on the black hole transient GX 339-4, during its 2015 outburst decay. We studied the evolution of the power spectral densities finding strong differences between the two bands. The X-ray power spectral density follows standard patterns of evolution, plausibly reflecting changes in the accretion flow. The IR power spectral density instead evolves very slowly, with a high-frequency break consistent with remaining constant at 0.63 ± 0.03 Hz throughout the campaign. We discuss this result in the context of the currently available models for the IR emission in black hole transients. While all models will need to be tested quantitatively against this unexpected constraint, we show that an IR-emitting relativistic jet that filters out the short-timescale fluctuations injected from the accretion inflow appears as the most plausible scenario.

Keywords: Stellar accretion disks, Black hole physics, Low-mass x-ray binary stars, Jets
Mass-Metallicity Trends in Transiting Exoplanets from Atmospheric Abundances of H<SUB>2</SUB>O, Na, and K. Atmospheric compositions can provide powerful diagnostics of formation and migration histories of planetary systems. We investigate constraints on atmospheric abundances of H2O, Na, and K, in a sample of transiting exoplanets using the latest transmission spectra and new H2 broadened opacities of Na and K. Our sample of 19 exoplanets spans from cool mini-Neptunes to hot Jupiters, with equilibrium temperatures between ∼300 and 2700 K. Using homogeneous Bayesian retrievals we report atmospheric abundances of Na, K, and H2O, and their detection significances, confirming 6 planets with strong Na detections, 6 with K, and 14 with H2O. We find a mass-metallicity trend of increasing H2O abundances with decreasing mass, spanning generally substellar values for gas giants and stellar/superstellar for Neptunes and mini-Neptunes. However, the overall trend in H2O abundances, from mini-Neptunes to hot Jupiters, is significantly lower than the mass-metallicity relation for carbon in the solar system giant planets and similar predictions for exoplanets. On the other hand, the Na and K abundances for the gas giants are stellar or superstellar, consistent with each other, and generally consistent with the solar system metallicity trend. The H2O abundances in hot gas giants are likely due to low oxygen abundances relative to other elements rather than low overall metallicities, and provide new constraints on their formation mechanisms. The differing trends in the abundances of species argue against the use of chemical equilibrium models with metallicity as one free parameter in atmospheric retrievals, as different elements can be differently enhanced.

Keywords: Exoplanets, Hot Jupiters, Abundance ratios, Hot Neptunes, Exoplanet systems, Exoplanet astronomy, Spectroscopy, Mini Neptunes, Metallicity, Exoplanet atmospheres
A NICER View of PSR J0030+0451: Millisecond Pulsar Parameter Estimation. We report on Bayesian parameter estimation of the mass and equatorial radius of the millisecond pulsar PSR J0030+0451, conditional on pulse-profile modeling of Neutron Star Interior Composition Explorer X-ray spectral-timing event data. We perform relativistic ray-tracing of thermal emission from hot regions of the pulsar’s surface. We assume two distinct hot regions based on two clear pulsed components in the phase-folded pulse-profile data; we explore a number of forms (morphologies and topologies) for each hot region, inferring their parameters in addition to the stellar mass and radius. For the family of models considered, the evidence (prior predictive probability of the data) strongly favors a model that permits both hot regions to be located in the same rotational hemisphere. Models wherein both hot regions are assumed to be simply connected circular single-temperature spots, in particular those where the spots are assumed to be reflection-symmetric with respect to the stellar origin, are strongly disfavored. For the inferred configuration, one hot region subtends an angular extent of only a few degrees (in spherical coordinates with origin at the stellar center) and we are insensitive to other structural details; the second hot region is far more azimuthally extended in the form of a narrow arc, thus requiring a larger number of parameters to describe. The inferred mass M and equatorial radius R eq are, respectively, {1.34}-0.16+0.15 {M}☉  and {12.71}-1.19+1.14 {km}, while the compactness {GM}/{R}eq}{c}2={0.156}-0.010+0.008 is more tightly constrained; the credible interval bounds reported here are approximately the 16% and 84% quantiles in marginal posterior mass.

Keywords: Neutron stars, Neutron star cores, Rotation powered pulsars, Millisecond pulsars, Pulsars, Nuclear astrophysics, Matter density, X-ray stars
A Nicer View of PSR J0030+0451: Implications for the Dense Matter Equation of State. Both the mass and radius of the millisecond pulsar PSR J0030+0451 have been inferred via pulse-profile modeling of X-ray data obtained by NASA’s Neutron Star Interior Composition Explorer (NICER) mission. In this Letter we study the implications of the mass-radius inference reported for this source by Riley et al. for the dense matter equation of state (EoS), in the context of prior information from nuclear physics at low densities. Using a Bayesian framework we infer central densities and EoS properties for two choices of high-density extensions: a piecewise-polytropic model and a model based on assumptions of the speed of sound in dense matter. Around nuclear saturation density these extensions are matched to an EoS uncertainty band obtained from calculations based on chiral effective field theory interactions, which provide a realistic description of atomic nuclei as well as empirical nuclear matter properties within uncertainties. We further constrain EoS expectations with input from the current highest measured pulsar mass; together, these constraints offer a narrow Bayesian prior informed by theory as well as laboratory and astrophysical measurements. The NICER mass-radius likelihood function derived by Riley et al. using pulse-profile modeling is consistent with the highest-density region of this prior. The present relatively large uncertainties on mass and radius for PSR J0030+0451 offer, however, only a weak posterior information gain over the prior. We explore the sensitivity to the inferred geometry of the heated regions that give rise to the pulsed emission, and find a small increase in posterior gain for an alternative (but less preferred) model. Lastly, we investigate the hypothetical scenario of increasing the NICER exposure time for PSR J0030+0451.

Keywords: Neutron stars, Neutron star cores, Bayesian statistics, Millisecond pulsars, Pulsars, Nuclear astrophysics, X-ray stars
A NICER View of PSR J0030+0451: Evidence for a Global-scale Multipolar Magnetic Field. Recent modeling of Neutron Star Interior Composition Explorer observations of thermal X-ray pulsations from the surface of the isolated millisecond pulsar PSR J0030+0451 suggests that the hot emitting regions on the pulsar’s surface are far from antipodal, which is at odds with the classical assumption that the magnetic field in the pulsar magnetosphere is predominantly that of a centered dipole. Here, we review these results and examine previous attempts to constrain the magnetospheric configuration of PSR J0030+0451. To the best of our knowledge, there is in fact no direct observational evidence that PSR J0030+0451’s magnetic field is a centered dipole. Developing models of physically motivated, non-canonical magnetic field configurations and the currents that they can support poses a challenging task. However, such models may have profound implications for many aspects of pulsar research, including pulsar braking, estimates of birth velocities, and interpretations of multi-wavelength magnetospheric emission.

Keywords: Neutron stars, Rotation powered pulsars, Millisecond pulsars
PSR J0030+0451 Mass and Radius from NICER Data and Implications for the Properties of Neutron Star Matter. Neutron stars are not only of astrophysical interest, but are also of great interest to nuclear physicists because their attributes can be used to determine the properties of the dense matter in their cores. One of the most informative approaches for determining the equation of state (EoS) of this dense matter is to measure both a star’s equatorial circumferential radius R  e  and its gravitational mass M. Here we report estimates of the mass and radius of the isolated 205.53 Hz millisecond pulsar PSR J0030+0451 obtained using a Bayesian inference approach to analyze its energy-dependent thermal X-ray waveform, which was observed using the Neutron Star Interior Composition Explorer (NICER). This approach is thought to be less subject to systematic errors than other approaches for estimating neutron star radii. We explored a variety of emission patterns on the stellar surface. Our best-fit model has three oval, uniform-temperature emitting spots and provides an excellent description of the pulse waveform observed using NICER. The radius and mass estimates given by this model are {R}e={13.02}-1.06+1.24 km and M={1.44}-0.14+0.15 {M}☉  (68%). The independent analysis reported in the companion paper by Riley et al. explores different emitting spot models, but finds spot shapes and locations and estimates of R  e  and M that are consistent with those found in this work. We show that our measurements of R  e  and M for PSR J0030+0451 improve the astrophysical constraints on the EoS of cold, catalyzed matter above nuclear saturation density.

Keywords: Neutron stars, Neutron star cores, X-ray sources, Millisecond pulsars
Constraining the Neutron Star Mass-Radius Relation and Dense Matter Equation of State with NICER. I. The Millisecond Pulsar X-Ray Data Set. We present the set of deep Neutron Star Interior Composition Explorer (NICER) X-ray timing observations of the nearby rotation-powered millisecond pulsars PSRs J0437-4715, J0030+0451, J1231-1411, and J2124-3358, selected as targets for constraining the mass-radius relation of neutron stars and the dense matter equation of state (EoS) via modeling of their pulsed thermal X-ray emission. We describe the instrument, observations, and data processing/reduction procedures, as well as the series of investigations conducted to ensure that the properties of the data sets are suitable for parameter estimation analyses to produce reliable constraints on the neutron star mass-radius relation and the dense matter EoS. We find that the long-term timing and flux behavior and the Fourier-domain properties of the event data do not exhibit any anomalies that could adversely affect the intended measurements. From phase-selected spectroscopy, we find that emission from the individual pulse peaks is well described by a single-temperature hydrogen atmosphere spectrum, with the exception of PSR J0437-4715, for which multiple temperatures are required.

Keywords: Neutron stars, X-ray astronomy, Pulsar timing method, Millisecond pulsars, Pulsars, Astronomical techniques, Nuclear astrophysics, Compact objects, X-ray observatories, Spectroscopy
Constraining the Neutron Star Mass-Radius Relation and Dense Matter Equation of State with NICER. II. Emission from Hot Spots on a Rapidly Rotating Neutron Star. We describe the model of surface emission from a rapidly rotating neutron star that is applied to Neutron Star Interior Composition Explorer X-ray data of millisecond pulsars in order to statistically constrain the neutron star mass-radius relation and dense matter equation of state. To ensure that the associated calculations are both accurate and precise, we conduct an extensive suite of verification tests between our numerical codes for both the Schwarzschild + Doppler and Oblate Schwarzschild approximations, and compare both approximations against exact numerical calculations. We find superb agreement between the code outputs, as well as in comparisons against a set of analytical and semi-analytical calculations, which, combined with their speed, demonstrates that the codes are well suited for large-scale statistical sampling applications. A set of verified, high-precision reference synthetic pulse profiles is provided to the community to facilitate testing of other independently developed codes.

Keywords: Neutron stars, High energy astrophysics, Millisecond pulsars, Gravitation, Rotation powered pulsars, Special relativity, Pulsars, General relativity
NICER X-Ray Observations of Seven Nearby Rotation-powered Millisecond Pulsars. The Neutron star Interior Composition Explorer observed several rotation-powered millisecond pulsars (MSPs) to search for or confirm the presence of X-ray pulsations. When broad and sine-like, these pulsations may indicate thermal emission from hot polar caps at the magnetic poles on the neutron star surface. We report confident detections (≥4.7σ after background filtering) of X-ray pulsations for five of the seven pulsars in our target sample: PSR J0614-3329, PSR J0636+5129, PSR J0751+1807, PSR J1012+5307, and PSR J2241-5236, while PSR J1552+5437 and PSR J1744-1134 remain undetected. Of those, only PSR J0751+1807 and PSR J1012+5307 had pulsations previously detected at the 1.7σ and almost 3σ confidence levels, respectively, in XMM-Newton data. All detected sources exhibit broad sine-like pulses, which are indicative of surface thermal radiation. As such, these MSPs are promising targets for future X-ray observations aimed at constraining the neutron star mass-radius relation and the dense matter equation of state using detailed pulse profile modeling. Furthermore, we find that three of the detected MSPs exhibit a significant phase offset between their X-ray and radio pulses.

Keywords: Neutron stars, X-ray identification, Rotation powered pulsars, Millisecond pulsars
A Hot Cusp-shaped Confined Solar Flare. We analyze a confined flare that developed a hot cusp-like structure high in the corona (H ∼ 66 Mm). A growing cusp-shaped flare arcade is a typical feature in the standard model of eruptive flares, caused by magnetic reconnection at progressively larger coronal heights. In contrast, we observe a static hot cusp during a confined flare. Despite an initial vertical temperature distribution similar to that in eruptive flares, we observe a distinctly different evolution during the late (decay) phase, in the form of prolonged hot emission. The distinct cusp shape, rooted at locations of nonthermal precursor activity, was likely caused by a magnetic field arcade that kinked near the top. Our observations indicate that the prolonged heating was a result of slow local reconnection and an increased thermal pressure near the kinked apexes due to continuous plasma upflows.

Keywords: Solar ultraviolet emission, Solar flares, Solar corona, Solar x-ray emission
Kinetic Verification of the Stochastic Ion Heating Mechanism in Collisionless Magnetic Reconnection. The origin of anomalous, non-classical ion heating during magnetic reconnection has been a longstanding problem. It is verified via fully kinetic analyses and particle-in-cell simulations that stochastic heating is the main ion heating mechanism in collisionless magnetic reconnection up to moderate guide fields. Strong in-plane Hall electric fields that form during reconnection render ion motions chaotic and de facto broaden the ion distribution function. The mechanism is consistent with numerous observed features of ion heating in reconnection, such as the preferential heating of ions with higher mass-to-charge ratios and the non-conservation of the ion magnetic moment.

Keywords: Planetary magnetospheres, Solar coronal heating, Solar magnetic reconnection
Faint Repetitions from a Bright Fast Radio Burst Source. We report the detection of repeat bursts from the source of FRB 171019, one of the brightest fast radio bursts (FRBs) detected in the Australian Square Kilometre Array Pathfinder (ASKAP) fly’s eye survey. Two bursts from the source were detected with the Green Bank Telescope in observations centered at 820 MHz. The repetitions are a factor of ∼590 fainter than the ASKAP-discovered burst. All three bursts from this source show no evidence of scattering and have consistent pulse widths. The pulse spectra show modulation that could be evidence for either steep spectra or patchy emission. The two repetitions were the only ones found in an observing campaign for this FRB totaling 1000 hr, which also included ASKAP and the 64 m Parkes radio telescope, over a range of frequencies (720-2000 MHz) at epochs spanning two years. The inferred scaling of repetition rate with fluence of this source agrees with the other repeating source, FRB 121102. The detection of faint pulses from FRB 171019 shows that at least some FRBs selected from bright samples will repeat if follow-up observations are conducted with more sensitive telescopes.

Keywords: Transient sources, Radio transient sources
The Challenging Detection of Nucleobases from Pre-accretional Astrophysical Ice Analogs. Amino acids, sugars, and nucleobases are considered as the so-called molecular bricks of life, the major subunits of proteins and genetic materials. All three chemical families have been previously detected in meteorites. In dense molecular cloud ice analogs, the formation of a large set of amino acids and sugars (+derivatives) has been observed. In this contribution, we demonstrate that similar ices (H2O:13CH3OH:NH3 ices, 2:1:1) can also lead to the formation of nucleobases. Using combined UPLC-Orbitrap mass spectrometric and UPLC-SRM-triple quadrupole mass spectrometric analyses, we have unambiguously detected cytosine in these primitive, realistic astrophysical ice analogs. Additionally, a huge variety of nucleobase isomers was observed. These results indicate that all central subunits of biochemical materials may have already been present at early stages of chemical evolution of the protosolar nebula, before accretion toward planetesimals. Consequently, the formation of amino acids, sugars, and nucleobases does not necessarily require secondary alteration processes inside meteoritic parent bodies. They might have been supplied from dense molecular cloud ices toward post-accretional objects, such as nonaqueously modified comets, and subsequently delivered onto the early Earth's surface, potentially triggering the emergence of prebiotic chemistry leading to the first living systems.

Keywords: Astrobiology, Ice formation, Pre-biotic astrochemistry, Astrochemistry