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<jats:title>Abstract</jats:title> <jats:p>Using the relativistic mean-field model with nonlinear couplings between the isoscalar and isovector mesons, we study the properties of isospin-asymmetric nuclear matter. Not only the vector mixing, <jats:italic>ω</jats:italic> <jats:sub> <jats:italic>μ</jats:italic> </jats:sub> <jats:italic>ω</jats:italic> <jats:sup> <jats:italic>μ</jats:italic> </jats:sup> <jats:bold> <jats:italic>ρ</jats:italic> </jats:bold> <jats:sub> <jats:italic>ν</jats:italic> </jats:sub> <jats:bold> <jats:italic>ρ</jats:italic> </jats:bold> <jats:sup> <jats:italic>ν</jats:italic> </jats:sup>, but also the quartic interaction due to the scalar mesons, <jats:italic>σ</jats:italic> <jats:sup>2</jats:sup> <jats:bold> <jats:italic>δ</jats:italic> </jats:bold> <jats:sup>2</jats:sup>, is taken into account to investigate the density dependence of nuclear symmetry energy, <jats:italic>E</jats:italic> <jats:sub>sym</jats:sub>, and the neutron star properties. It is found that the <jats:italic>δ</jats:italic> meson increases <jats:italic>E</jats:italic> <jats:sub>sym</jats:sub> at high densities, whereas the <jats:italic>σ</jats:italic>–<jats:italic>δ</jats:italic> mixing makes <jats:italic>E</jats:italic> <jats:sub>sym</jats:sub> soft above the saturation density. Furthermore, the <jats:italic>δ</jats:italic> meson and its mixing have a large influence on the radius and tidal deformability of a neutron star. In particular, the <jats:italic>σ</jats:italic>–<jats:italic>δ</jats:italic> mixing reduces the neutron star radius; thus, the present calculation can simultaneously reproduce the dimensionless tidal deformabilities of a canonical 1.4 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> neutron star observed from the binary neutron star merger GW170817 and the compact binary coalescence GW190814.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The ultrarelativistic jets triggered by neutrino annihilation processes or Blandford–Znajek (BZ) mechanisms in stellar-mass black hole (BH) hyperaccretion systems are generally considered to power gamma-ray bursts (GRBs). Due to the high accretion rate, the central BHs might grow rapidly on a short timescale, providing a new way to understand <jats:italic>the lower mass gap</jats:italic> problem. In this paper, we use the BH hyperaccretion model to investigate BH mass growth based on observational GRB data. The results show that (i) if the initial BH mass is set as 3 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>, the neutrino annihilation processes are capable of fueling the BHs to escape the lower mass gap for more than half of long-duration GRBs (LGRBs), while the BZ mechanism is inefficient in triggering BH growth for LGRBs; (ii) the mean BH mass growth in the case of LGRBs without observable supernova (SN) association is much larger than that in the case of LGRBs associated with SNe for both mechanisms, which implies that more massive progenitors or lower SN explosion energies prevail throughout the former cases; (iii) for the short-duration GRBs, the mean BH mass growth is satisfied with the mass supply limitation in the scenario of compact object mergers, but the hyperaccretion processes are unable to rescue BHs from the gap in binary neutron star (NS) mergers or the initial BH mass being 3 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> after NS−BH mergers.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We analyze Chandra X-ray Observatory imaging of 108 galaxies hosting nuclear star clusters (NSCs) to search for signatures of massive black holes (BHs). NSCs are extremely dense stellar environments with conditions that can theoretically facilitate massive BH formation. Recent work by Stone et al. finds that sufficiently dense NSCs should be unstable to the runaway growth of a stellar-mass BH into a massive BH via tidal captures. Furthermore, there is a velocity dispersion threshold (40 km s<jats:sup>−1</jats:sup>) above which NSCs should inevitably form a massive BH. To provide an observational test of these theories, we measure X-ray emission from NSCs and compare it to the measured velocity dispersion and tidal capture runaway timescale. We find that NSCs above the 40 km s<jats:sup>−1</jats:sup> threshold are X-ray detected at roughly twice the rate of those below (after accounting for contamination from X-ray binaries). These results are consistent with a scenario in which dense, high-velocity NSCs can form massive BHs, providing a formation pathway that does not rely on conditions found only at high redshift.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present an investigation of partial filament eruption on 2012 June 17 in the active region NOAA 11504. For the first time, we observed the vertical splitting process during the partial eruption with high-resolution narrowband images at 10830 Å. The active filament was rooted in a small <jats:italic>δ</jats:italic>-sunspot of the active region. Particularly, it underwent the partial eruption in three steps, i.e., the precursor, the first eruption, and the second eruption, while the latter two were associated with a C1.0 flare and a C3.9 flare, respectively. During the precursor, slow magnetic reconnection took place between the filament and the adjoining loops that also rooted in the <jats:italic>δ</jats:italic>-sunspot. The continuous reconnection not only caused the filament to split into three groups of threads vertically but also formed a new filament, which was growing and accompanied brightening took place around the site. Subsequently, the growing filament erupted together with one group splitted threads, resulted in the first eruption. At the beginning of the first eruption, a subsequent magnetic reconnection occurred between the erupting splitted threads and another ambient magnetic loop. After about 3 minutes, the second eruption occurred as a result of the eruption of two larger unstable filaments induced by the magnetic reconnection. The high-resolution observation provides a direct evidence that magnetic reconnection between filament and its ambient magnetic fields could induce the vertical splitting of the filament, resulting in partial eruption.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present a comparison of the interstellar medium traced by [C <jats:sc>ii</jats:sc>] (Atacama Large Millimeter/submillimeter Array), and ionized halo gas traced by Ly<jats:italic>α</jats:italic> (Multi Unit Spectroscopic Explorer), in and around QSO host galaxies at <jats:italic>z</jats:italic> ∼ 6. To date, 18 QSOs at this redshift have been studied with both MUSE and high-resolution ALMA imaging; of these, 8 objects display a Ly<jats:italic>α</jats:italic> halo. Using data cubes matched in velocity resolution, we compare and contrast the spatial and kinematic information of the Ly<jats:italic>α</jats:italic> halos and the host galaxies’ [C <jats:sc>ii</jats:sc>] (and dust-continuum) emission. We find that the Ly<jats:italic>α</jats:italic> halos extend typically 3−30 times beyond the interstellar medium of the host galaxies. The majority of the Ly<jats:italic>α</jats:italic> halos do not show ordered motion in their velocity fields, whereas most of the [C <jats:sc>ii</jats:sc>] velocity fields do. In those cases where a velocity gradient can be measured in Ly<jats:italic>α</jats:italic>, the kinematics do not align with those derived from the [C <jats:sc>ii</jats:sc>] emission. This implies that the Ly<jats:italic>α</jats:italic> emission is not tracing the outskirts of a large rotating disk, which is a simple extension of the central galaxy seen in [C <jats:sc>ii</jats:sc>] emission. It rather suggests that the kinematics of the halo gas are decoupled from those of the central galaxy. Given the scattering nature of Ly<jats:italic>α</jats:italic>, these results need to be confirmed with James Webb Space Telescope Integral Field Unit observations that can constrain the halo kinematics further using the nonresonant H<jats:italic>α</jats:italic> line.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>High-precision magnetic field measurements are of great significance for the in-depth study of the physical processes in the astrophysical plasma environment. To obtain accurate natural magnetic fields, in-flight calibration is one key step to obtaining zero offset of the spaceborne fluxgate magnetometer (FGM). Mirror mode structures, widely existing in the solar wind and planetary magnetosheaths and magnetospheres, can be used to calculate the zero offset. However, it is difficult to obtain an accurate zero offset by the current methods using mirror mode structures in the planetary magnetosheath. Here, we develop a new method to calculate the zero offset of the spaceborne FGM using magnetic dips, which are a kind of mirror mode structure. This method is based on the assumption that the magnetic field is zero in the cross section of the magnetic dip. Our method is able to calculate the zero offset using only one magnetic dip. We test this method by using the data from the Magnetospheric Multiscale Mission, and find that the calculation errors of 78.1% of the estimated zero offsets are &lt;0.5 nT when using 25 magnetic dips in the terrestrial magnetosheath. This suggests that our method is able to achieve a high accuracy of the zero offset in the planetary magnetosheath.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We report on numerical simulations of a propagating momentum pulse, representing an inclined jet structure in a stratified lower solar atmosphere model. Here, the numerical jets were generated via injection of a momentum pulse misaligned with the radial magnetic field, which resulted in a collimated structure that mimicked the observed inclined jet features in the chromosphere. The influence of inclination angle was examined for a variety of initial driver conditions (amplitude, period) and magnetic field magnitudes to identify their potential role in determining the morphological and dynamical characteristics of chromospheric jets. The numerical jets in our computational domain were consistent with the observed magnitudes of apex height and cross-sectional width for average inclination of chromospheric features. Furthermore, with an increasing misalignment between the momentum pulse and ambient magnetic field, the simulated structures showed a drop in the maximum apex height and length, while an increase in cross-sectional width magnitudes. Our numerical experiments also revealed the development of a <jats:italic>pulse-like</jats:italic> transverse motions in jets along with high density edges/nodes in the direction of jet displacement. It is postulated that dynamic kink instability might be responsible for the observed kinematic behavior of the inclined jet structures in the solar chromosphere.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Using photometry and proper motions from Gaia Early Data Release 3, we detect a 45° long trailing stellar debris stream associated with the old, metal-poor globular cluster NGC 7089. With a width on the order of 100 pc, the extended stream appears to be as dynamically cold as the coldest known streams found to date. There is some evidence for an extended leading tail extending between 28° and 37° from the cluster, though the greater distance of this tail, combined with proper motions that are virtually indistinguishable from those of foreground stars, make the detection much less certain. The proper motion profile and the path on the sky of the trailing tail are not well matched using a simple Galactic potential composed purely of a disk, bulge, and spherical halo. However, the addition of a moving, massive (<jats:italic>M</jats:italic> = 1.88 × 10<jats:sup>11</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>) Large Magellanic Cloud brings the model predictions into much better agreement with the observables. We provide tables of the most highly ranked candidate stream stars for follow-up by ongoing and future spectroscopic surveys.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present the median-stacked Lyman<jats:italic>-α (</jats:italic>Ly<jats:italic>α</jats:italic>) surface brightness profiles of 968 spectroscopically selected Ly<jats:italic>α</jats:italic> emitting galaxies (LAEs) at redshifts 1.9 &lt; <jats:italic>z</jats:italic> &lt; 3.5 in the early data of the Hobby-Eberly Telescope Dark Energy Experiment. The selected LAEs are high-confidence Ly<jats:italic>α</jats:italic> detections with high signal-to-noise ratios observed with good seeing conditions (point-spread function FWHM &lt;1.″4), excluding active galactic nuclei. The Ly<jats:italic>α</jats:italic> luminosities of the LAEs are 10<jats:sup>42.4</jats:sup>–10<jats:sup>43</jats:sup> erg s<jats:sup>−1</jats:sup>. We detect faint emission in the median-stacked radial profiles at the level of <jats:inline-formula> <jats:tex-math> <?CDATA $(3.6\pm 1.3)\times {10}^{-20}\,\mathrm{erg}\,{{\rm{s}}}^{-1}\,{\mathrm{cm}}^{-2}\,{\mathrm{arcsec}}^{-2}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo stretchy="false">(</mml:mo> <mml:mn>3.6</mml:mn> <mml:mo>±</mml:mo> <mml:mn>1.3</mml:mn> <mml:mo stretchy="false">)</mml:mo> <mml:mo>×</mml:mo> <mml:msup> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>20</mml:mn> </mml:mrow> </mml:msup> <mml:mspace width="0.25em" /> <mml:mi>erg</mml:mi> <mml:mspace width="0.25em" /> <mml:msup> <mml:mrow> <mml:mi mathvariant="normal">s</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> <mml:mspace width="0.25em" /> <mml:msup> <mml:mrow> <mml:mi>cm</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> <mml:mspace width="0.25em" /> <mml:msup> <mml:mrow> <mml:mi>arcsec</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac5cb8ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> from the surrounding Ly<jats:italic>α</jats:italic> halos out to <jats:italic>r</jats:italic> ≃ 160 kpc (physical). The shape of the median-stacked radial profile is consistent at <jats:italic>r</jats:italic> &lt; 80 kpc with that of much fainter LAEs at 3 &lt; <jats:italic>z</jats:italic> &lt; 4 observed with the Multi Unit Spectroscopic Explorer (MUSE), indicating that the median-stacked Ly<jats:italic>α</jats:italic> profiles have similar shapes at redshifts 2 &lt; <jats:italic>z</jats:italic> &lt; 4 and across a factor of 10 in Ly<jats:italic>α</jats:italic> luminosity. While we agree with the results from the MUSE sample at <jats:italic>r</jats:italic> &lt; 80 kpc, we extend the profile over a factor of two in radius. At <jats:italic>r</jats:italic> &gt; 80 kpc, our profile is flatter than the MUSE model. The measured profile agrees at most radii with that of galaxies in the Byrohl et al. cosmological radiative transfer simulation at <jats:italic>z</jats:italic> = 3. This suggests that the surface brightness of a Ly<jats:italic>α</jats:italic> halo at <jats:italic>r</jats:italic> ≲ 100 kpc is dominated by resonant scattering of Ly<jats:italic>α</jats:italic> photons from star-forming regions in the central galaxy, whereas at <jats:italic>r</jats:italic> &gt; 100 kpc, it is dominated by photons from galaxies in surrounding dark matter halos.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Derivation of physical properties of galaxies using spectral energy distribution (SED) fitting is a powerful method, but can suffer from various systematics arising from model assumptions. Previously, such biases were mostly studied in the context of individual galaxies. In this study, we investigate potential biases arising from performing the SED fitting on the combined light of two galaxies, as would be the case in postmerger systems. We use the GALEX-SDSS-WISE Legacy Catalog of <jats:italic>z</jats:italic> &lt; 0.3 galaxies to identify 9000 galaxy pairs that could eventually merge. For these we investigate if the UV/optical SED fitting accurately determines the stellar mass and (specific) star formation rate (sSFRs) if the pair was unresolved (merged). The sum of the stellar masses (and star formation rates (SFRs)) of individual galaxies in the pair establishes the ground truth for these quantities. For star-forming galaxies no biases (&lt;0.1 dex) are found in the stellar mass, SFR, or sSFRs. Moderate systematics in SFR (∼0.1 dex) are found for systems with an extreme contrast in dust content between the two galaxies. We conclude that biases that would arise in the determination of masses and SFRs of postmerger systems on account of the two original galaxies having potentially very different star formation histories and different dust properties are small and that the approach with simple two-component star formation histories is adequate. The approach presented in this study, using flux compositing with empirically determined ground truth, offers new opportunities for testing the results of SED fitting in general.</jats:p>