Sazuna/UAT_keywords huggingface dataset:
Periodic and Phase-locked Modulation in PSR B1929+10 Observed with FAST. We present a detailed single-pulse analysis for PSR B1929+10 based on observations with the Five-hundred-meter Aperture Spherical radio Telescope (FAST). The main pulse (MP) and interpulse (IP) are found to be modulated with a periodicity of ∼12 times the pulsar's rotational period (P). The ∼12P modulation is confirmed as a periodic amplitude modulation instead of systematic drifting. The periodic amplitude modulation in the IP is found to be anti-correlated with that in the weak preceding component of the MP (MP_I), but correlated with that in the first two components of the MP (MP_II), which implies that the modulation patterns in the IP and the MP are phase-locked. What is more interesting is that the modulation in MP_II is delayed from that in the IP by about 1P. Furthermore, high-sensitivity observations by FAST reveal that weak emission exists between the MP and the IP. In addition, we confirm that the separation between the IP and the MP is independent of radio frequency. The above results are a conundrum for pulsar theories and cannot be satisfactorily explained by the current pulsar models. Therefore, our results observed with FAST provide an opportunity to probe the structure of pulsar emission and the neutron star's magnetosphere.

Keywords: Neutron stars, Observational astronomy, Magnetospheric radio emissions, Pulsars, Radio pulsars
New Bistable Solutions in Molecular Cloud Chemistry: Nitrogen and Carbon Autocatalysis. We have investigated the chemistry of dense interstellar clouds and found new bistable solutions in the nitrogen and carbon chemistries. We identify the autocatalytic processes that are present in the pure, reduced, chemical networks and find, as previously found for oxygen chemistry, that He+ plays an important role. The applicability of these results to astronomical environments is briefly discussed. The bistable solutions found for carbon chemistry occur for low densities and high ionization fractions that are not compatible with those found in cold, dense clouds. Bistability in the pure nitrogen chemistry occurs for conditions that are relevant for prestellar cores in which significant CO depletion has taken place. We conclude that several autocatalyses are embedded in gas-phase interstellar chemistry and that many more are potentially present.

Keywords: Interstellar abundances, Dark interstellar clouds, Astrochemistry
Oceanic Superrotation on Tidally Locked Planets. Is there oceanic superrotation on exoplanets? Atmospheric superrotation, characterized by west-to-east winds over the equator, is a common phenomenon in the atmospheres of Venus, Titan, Saturn, Jupiter, and tidally locked exoplanets. The stratospheric atmosphere of Earth is also superrotating during the westerly phase of the quasi-biennial oscillation. However, whether the same phenomenon can occur in the ocean is poorly known. Through numerical simulations, here we show that oceanic superrotation does occur on tidally locked terrestrial planets around low-mass stars. Its formation (spun up from rest) is associated with surface winds, the equatorward momentum convergence by Rossby waves, and the eastward propagation of Kelvin waves in the ocean. Its maintenance is driven by equatorward momentum transports of coupled Rossby-Kelvin waves in the ocean excited from the uneven stellar radiation distribution. The width of the superrotation is mainly constrained by the Rossby deformation radius in the ocean, while its strength is more complex. Many factors can influence the strength, including planetary rotation rate, stellar flux, greenhouse gas concentration, seawater salinity, and bottom drag, but a scaling theory for the strength of the oceanic superrotation is lacking. This work confirms that oceanic superrotation can occur on tidally locked terrestrial planets with seawater oceans and suggests that it may also occur on tidally locked hot planets with magma oceans that will possibly be observed in the near future.

Keywords: Ocean planets, Exoplanets
Evolutions of Young Type Ia Supernova Remnants with Two Initial Density Profiles in a Turbulent Medium. The expansion index and relative contact discontinuity positions of young type Ia supernova remnants (SNRs) evolving in a turbulent medium are investigated via implementing two-dimensional cylindrical magnetohydrodynamic simulations. In our simulations, two kinds of initial ejecta density profiles are considered: a power-law (PL) profile and an exponential (Exp) profile; large-scale density and magnetic field fluctuations are calculated and mapped into the computational domain before the simulations; the back reaction of the accelerated particles is mimicked through a time-dependent effective adiabatic index γeff(n, t). Our simulation results reveal that the density distributions and magnetic field structures have similar results for both initial profiles. Concerning the expansion index, both the PL and Exp profiles exhibit significant azimuthal variations along the remnant periphery, while the Exp profile manifests itself in a quick path down to the Sedov value as time proceeds. The derived expansion index distributions with both initial profiles are compatible with observations of two typical young type Ia SNRs: SN 1006 and Tycho. As for the relative contact discontinuity positions, when γeff(n, t) works, the derived profiles of both scenarios are globally compatible with the observations despite some deviations. Besides, there are no obvious ejecta protrusions beyond the forward shock, with a lowest derived ratio reaching ∼1.01-1.02 for both initial profiles. Moreover, for purposes of comparison, we have also considered two supplementary scenarios: (1) the aforementioned two density profiles expanding in a homogeneous medium, and (2) a uniform ejecta profile evolving in a turbulent medium.

Keywords: Supernova remnants, Interstellar medium
Evolution of LMXBs under Different Magnetic Braking Prescriptions. Magnetic braking (MB) likely plays a vital role in the evolution of low-mass X-ray binaries (LMXBs). However, there is still uncertainty around the physics of MB, and there are various proposed scenarios for MB in the literature. To examine and discriminate the efficiency of MB, we investigate the LMXB evolution with five proposed MB laws. Combining detailed binary evolution calculation with binary population synthesis, we obtain the expected properties of LMXBs and their descendant binary millisecond pulsars. We then discuss the strength and weakness of each MB law by comparing the calculated results with observations. We conclude that the τ-boosted MB law seems to best match the observational characteristics.

Keywords: Neutron stars, X-ray binary stars, Binary pulsars
Effects of Forcing Mechanisms on the Multiscale Properties of Magnetohydrodynamics. We performed numerical simulations to study the response of magnetohydrodynamics (MHD) to large-scale stochastic forcing mechanisms parameterized by one parameter, 0 ≤ a ≤ 1, going from direct injection on the velocity field (a = 1) to stirring acts on the magnetic field only (a = 0). We study the multiscale properties of the energy transfer by splitting the total flux in channels mediated by (i) the kinetic nonlinear advection, (ii) the Lorentz force, (iii) the magnetic advection, and (iv) the magnetic stretching term. We further decompose the fluxes into two subchannels given by heterochiral and homochiral components in order to distinguish forward, inverse, and flux-loop cascades. We show that there exists a quasi-singular role of the magnetic forcing mechanism for a ∼ 1: a small injection on the magnetic field a &lt; 1 can strongly deplete the mean flux of kinetic energy transfer throughout the kinetic nonlinear advection channel. We also show that this negligible mean flux is the result of a flux-loop balance between heterochiral (direct) and homochiral (inverse) transfers. Conversely, both homochiral and heterochiral channels transfer energy forward for the other three channels. Cross-exchange between velocity and the magnetic field is reversed around a = 0.4, and except when a ∼ 1, we always observe that heterochiral mixed velocity-magnetic energy triads tend to move energy from magnetic to velocity fields. Our study is an attempt to further characterize the multiscale nature of MHD dynamics by disentangling different properties of the total energy transfer mechanisms, which can be useful for improving subgrid modeling.

Keywords: Interplanetary turbulence, Magnetohydrodynamics, Magnetohydrodynamical simulations
SN 2017hpa: A Nearby Carbon-rich Type Ia Supernova with a Large Velocity Gradient. We present extensive, well-sampled optical and ultraviolet photometry and optical spectra of the Type Ia supernova (SN Ia) 2017hpa. The light curves indicate that SN 2017hpa is a normal SN Ia with an absolute peak magnitude of ${M}_{\max }^{B}\approx $ &lt;!-- --&gt; -19.12 ± 0.11 mag and a postpeak decline rate Δm15(B) = 1.02 ± 0.07 mag. According to the quasi-bolometric light curve, we derive a peak luminosity of 1.25 × 1043 erg s-1 and a 56Ni mass of 0.63 ± 0.02 M⊙. The spectral evolution of SN 2017hpa is similar to that of normal Ia supernovae (SNe Ia), while it exhibits an unusually rapid velocity evolution resembling that of SN 1991bg-like SNe Ia or the high-velocity subclass of SNe Ia, with a postpeak velocity gradient of ∼130 ± 7 km s-1 day-1. Moreover, its early spectra (t &lt; - 7.9 days) show a prominent C II λ6580 absorption feature, which disappeared in near-maximum-light spectra but reemerged at phases from t ∼ + 8.7 days to t ∼ + 11.7 days after maximum light. This implies that some unburned carbon may mix deep into the inner layer and is supported by the low C II λ6580-to-Si II λ6355 velocity ratio (∼0.81) observed in SN 2017hpa. The O I λ7774 line shows a velocity distribution like that of carbon. The prominent carbon feature, the low velocity seen in carbon and oxygen, and the large velocity gradient make SN 2017hpa stand out from other normal SNe Ia and are more consistent with predictions from a violent merger of two white dwarfs. Detailed modeling is still needed to reveal the nature of SN 2017hpa.

Keywords: Type Ia supernovae, Supernovae
ALMA Observations of Massive Clouds in the Central Molecular Zone: Ubiquitous Protostellar Outflows. We observe 1.3 mm spectral lines at 2000 au resolution toward four massive molecular clouds in the Central Molecular Zone (CMZ) of the Galaxy to investigate their star formation activities. We focus on several potential shock tracers that are usually abundant in protostellar outflows, including SiO, SO, CH3OH, H2CO, HC3N, and HNCO. We identify 43 protostellar outflows, including 37 highly likely ones and 6 candidates. The outflows are found toward both known high-mass star-forming cores and less massive, seemingly quiescent cores, while 791 out of the 834 cores identified based on the continuum do not have detected outflows. The outflow masses range from less than 1 M⊙ to a few tens of M⊙, with typical uncertainties of a factor of 70. We do not find evidence of disagreement between relative molecular abundances in these outflows and in nearby analogs such as the well-studied L1157 and NGC 7538S outflows. The results suggest that (i) protostellar accretion disks driving outflows ubiquitously exist in the CMZ environment, (ii) the large fraction of candidate starless cores is expected if these clouds are at very early evolutionary phases, with a caveat on the potential incompleteness of the outflows, (iii) high-mass and low-mass star formation is ongoing simultaneously in these clouds, and (iv) current data do not show evidence of a difference between the shock chemistry in the outflows that determines the molecular abundances in the CMZ environment and in nearby clouds.

Keywords: Interstellar line emission, Galactic center, Stellar jets, Astrochemistry, Star formation
The Cosmic-Ray Composition between 2 PeV and 2 EeV Observed with the TALE Detector in Monocular Mode. We report on a measurement of the cosmic-ray composition by the Telescope Array Low-energy Extension (TALE) air fluorescence detector (FD). By making use of the Cherenkov light signal in addition to air fluorescence light from cosmic-ray (CR)-induced extensive air showers, the TALE FD can measure the properties of the cosmic rays with energies as low as ∼2 PeV and exceeding 1 EeV. In this paper, we present results on the measurement of ${X}_{\max }$ &lt;!-- --&gt; distributions of showers observed over this energy range. Data collected over a period of ∼4 yr were analyzed for this study. The resulting ${X}_{\max }$ &lt;!-- --&gt; distributions are compared to the Monte Carlo (MC) simulated data distributions for primary cosmic rays with varying composition and a four-component fit is performed. The comparison and fit are performed for energy bins, of width 0.1 or 0.2 in ${\mathrm{log}}_{10}(E/\mathrm{eV})$ &lt;!-- --&gt; ,spanning the full range of the measured energies. We also examine the mean ${X}_{\max }$ &lt;!-- --&gt; value as a function of energy for cosmic rays with energies greater than 1015.8 eV. Below 1017.3 eV, the slope of the mean ${X}_{\max }$ &lt;!-- --&gt; as a function of energy (the elongation rate) for the data is significantly smaller than that of all elements in the models, indicating that the composition is becoming heavier with energy in this energy range. This is consistent with a rigidity-dependent cutoff of events from Galactic sources. Finally, an increase in the ${X}_{\max }$ &lt;!-- --&gt; elongation rate is observed at energies just above 1017 eV, indicating another change in the cosmic-ray composition.

Keywords: Cosmic ray showers, Cosmic ray detectors, Particle astrophysics, Cosmic rays
A Complex Luminosity Function for the Anomalous Globular Clusters in NGC 1052-DF2 and NGC 1052-DF4. NGC 1052-DF2 and NGC 1052-DF4 are ultradiffuse galaxies that have extremely low velocity dispersions, indicating that they have little or no dark matter. Both galaxies host anomalously luminous globular clusters (GCs), with a peak magnitude of their GC luminosity function (GCLF) that is ∼1.5 mag brighter than the near-universal value of MV ≈ -7.5. Here we present an analysis of the joint GCLF of the two galaxies, making use of new Hubble Space Telescope photometry and Keck spectroscopy and a recently improved distance measurement. We apply a homogeneous photometric selection method to the combined GC sample of DF2 and DF4. The new analysis shows that the peak of the combined GCLF remains at MV ≈ -9 mag. In addition, we find a subpopulation of less luminous GCs at MV ≈ -7.5 mag, where the near-universal GCLF peak is located. The number of GCs in the magnitude range of -5 to -8 is ${7}_{-4}^{+7}$ &lt;!-- --&gt; in DF2 and ${9}_{-5}^{+8}$ &lt;!-- --&gt; in DF4, similar to that expected from other galaxies of the same luminosity. The total GC number between MV of -5 and -11 is ${19}_{-4}^{+9}$ &lt;!-- --&gt; for DF2 and ${19}_{-5}^{+9}$ &lt;!-- --&gt; for DF4, calculated from the background-subtracted GCLF. The data are consistent with both galaxies having two GC populations: the one expected for their luminosity, and a very luminous population composing ∼90% of the total cluster mass. The number of GCs does not scale with the halo mass in either DF2 or DF4, suggesting that NGC is not directly determined by the merging of halos.

Keywords: Globular star clusters, Galaxy structure, Low surface brightness galaxies
The Impact of Limited Time Resolution on the Forward-scattering Polarization in the Solar Sr I 4607 Å Line. Theoretical investigations predicted that high spatiotemporal resolution observations in the Sr I 4607 Å line must show a conspicuous scattering polarization pattern at the solar disk center, which encodes information on the unresolved magnetism of the intergranular photospheric plasma. Here we present a study of the impact of limited time resolution on the observability of such forward-scattering (disk-center) polarization signals. Our investigation is based on three-dimensional radiative transfer calculations in a time-dependent magnetoconvection model of the quiet solar photosphere, taking into account anisotropic radiation pumping and the Hanle effect. This type of radiative transfer simulation is computationally costly, which is why the time variation had not been investigated before for this spectral line. We compare our theoretical results with recent disk-center filter polarimetric observations in the Sr I 4607 Å line, showing that there is good agreement in the polarization patterns. We also show what we can expect to observe with the Visible Spectro-Polarimeter at the upcoming Daniel K. Inouye Solar Telescope.

Keywords: Solar atmosphere, Quiet sun, The Sun, Solar physics, Solar magnetic fields
Revisited Cold Gas Content with Atomic Carbon [C I] in z = 2.5 Protocluster Galaxies. We revisit the cold gas contents of galaxies in a protocluster at z = 2.49 using the lowest neutral atomic carbon transition [C I] 3P1 - 3P0 from Atacama Large Millimeter/submillimeter Array observations. We aim to test if the same gas-mass calibration adopted in field galaxies can be applied to protocluster galaxies. Five galaxies out of 16 targeted galaxies are detected in the [C I] line, and these are all previously detected in CO (3-2) and CO (4-3) and three in 1.1 mm dust continuum. We investigate the line luminosity relations between CO and [C I] in the protocluster and compare with other previous studies. We then compare the gas mass based on three gas tracers of [C I], CO(3-2), and dust if at least one of the last two tracers are available. Using the calibration adopted for field main-sequence galaxies, the [C I]-based gas measurements are lower than or comparable to the CO-based gas measurements by -0.35 dex at the lowest with the mean deviation of -0.14 dex. The differences between [C I]- and the dust- based measurements are relatively mild by up to 0.16 dex with the mean difference of 0.02 dex. Taking these all together with calibration uncertainties, with the [C I] line, we reconfirm our previous findings that the mean gas fraction is comparable to field galaxies for a stellar-mass range of $\mathrm{log}({M}_{\mathrm{star}}/{M}_{\odot })=[10.6,11.3]$ &lt;!-- --&gt; . However, at least for these secure five detections, the depletion timescale decreases more rapidly with stellar mass than field galaxies that might be related to earlier quenching in dense environments.

Keywords: Star formation, Galaxy evolution, Interstellar medium, High-redshift galaxy clusters
Three-dimensional Reconstruction of Coronal Mass Ejections by the Correlation-aided Reconstruction Technique through Different Stereoscopic Angles of the Solar Terrestrial Relations Observatory Twin Spacecraft. Recently, we developed the correlation-aided reconstruction (CORAR) method to reconstruct solar wind inhomogeneous structures, or transients, using dual-view white-light images. This method is proved to be useful for studying the morphological and dynamical properties of transients like blobs and coronal mass ejection (CME), but the accuracy of the reconstruction may be affected by the separation angle between the two spacecrafts. Based on the dual-view CME events from the Heliospheric Imager CME Join Catalogue in the Heliospheric Cataloguing, Analysis and Techniques Service (HELCATS) project, we study the quality of the reconstruction of CME using the CORAR method under different STEREO stereoscopic angles. We find that when the separation angle of the spacecraft is around 150°, most CME events can be well reconstructed. If the collinear effect is considered, the optimal separation angle should locate between 120° and 150°. Compared with the direction of the CME given in the Heliospheric Imager Geometrical Catalogue from HELCATS, the parameters of the CME obtained by the CORAR method are reasonable. However, the CORAR-obtained directions deviate toward the meridian plane in longitude, and toward the equatorial plane in latitude. An empirical formula is proposed to correct these deviations. This study provides the basis for the configuration of the spacecraft of our recently proposed Solar Ring mission concept.

Keywords: Optical observation, Solar wind, Solar coronal mass ejections, Heliosphere
The Effects of Three-dimensional Radiative Transfer on the Resonance Polarization of the Ca I 4227 Å Line. The sizable linear polarization signals produced by the scattering of anisotropic radiation in the core of the Ca I 4227 Å line constitute an important observable for probing the inhomogeneous and dynamic plasma of the lower solar chromosphere. Here we show the results of a three-dimensional (3D) radiative transfer complete frequency redistribution investigation of the line's scattering polarization in a magnetohydrodynamical 3D model of the solar atmosphere. We take into account not only the Hanle effect produced by the model's magnetic field but also the symmetry breaking caused by the horizontal inhomogeneities and macroscopic velocity gradients. The spatial gradients of the horizontal components of the macroscopic velocities produce very significant forward scattering polarization signals without the need of magnetic fields, while the Hanle effect tends to depolarize them at the locations where the model's magnetic field is stronger than about 5 G. The standard 1.5D approximation is found to be unsuitable for understanding the line's scattering polarization, but we introduce a novel improvement to this approximation that produces results in qualitative agreement with the full 3D results. The instrumental degradation of the calculated polarization signals is also investigated, showing what we can expect to observe with the Visible Spectro-Polarimeter at the upcoming Daniel K. Inouye Solar Telescope.

Keywords: Spectropolarimetry, Radiative transfer, Quiet solar chromosphere
Polarization Predictions in the GRB Prompt Phase with the Internal Shock Model. As the standard gamma-ray burst (GRB) prompt-emission model, the internal shock (IS) model can reproduce the fast-rise and slow-decay features of the pulses in the GRB light curve. The time- and energy-dependent polarization can deliver important physical information on the emission region and can be used to test models. Polarization predictions for the GRB prompt phase with the magnetized IS model should be investigated carefully. The magnetic field of the magnetized IS model is very likely to be mixed and decays with radius. The synchrotron emission in the presence of such a decaying magnetic field can recover the Band-like spectrum of the GRB prompt phase. We investigate the dependence of the polarization of GRB prompt emission on both time and energy in the framework of the magnetized IS model. Due to the large range of parameters, it is hard to distinguish the magnetized IS model and the magnetic-reconnection model through polarization degree (PD) curves. The energy-dependent PD could increase toward the high-energy band for the magnetized IS model, while it decreases to zero above the megaelectronvolt band for the dissipative photosphere model. Therefore, we conclude that the energy dependence of PD can be used to distinguish these two models for the GRB prompt emission. Finally, we find that, independent of the observational energy band, the profiles of the ξB - PD curve for the time-integrated and time-resolved PDs are very similar, where ξB is the magnetic field strength ratio of the ordered component to the random component.

Keywords: Gamma-ray bursts, Magnetic fields