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<jats:title>Abstract</jats:title> <jats:p>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 <jats:italic>τ</jats:italic>-boosted MB law seems to best match the observational characteristics.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We performed numerical simulations to study the response of magnetohydrodynamics (MHD) to large-scale stochastic forcing mechanisms parameterized by one parameter, 0 ≤ <jats:italic>a</jats:italic> ≤ 1, going from direct injection on the velocity field (<jats:italic>a</jats:italic> = 1) to stirring acts on the magnetic field only (<jats:italic>a</jats:italic> = 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 <jats:italic>a</jats:italic> ∼ 1: a small injection on the magnetic field <jats:italic>a</jats:italic> &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 <jats:italic>a</jats:italic> = 0.4, and except when <jats:italic>a</jats:italic> ∼ 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.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>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 <jats:inline-formula> <jats:tex-math> <?CDATA ${M}_{\max }^{B}\approx $?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabdeb9ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> −19.12 ± 0.11 mag and a postpeak decline rate Δ<jats:italic>m</jats:italic> <jats:sub>15</jats:sub>(<jats:italic>B</jats:italic>) = 1.02 ± 0.07 mag. According to the quasi-bolometric light curve, we derive a peak luminosity of 1.25 × 10<jats:sup>43</jats:sup> erg s<jats:sup>−1</jats:sup> and a <jats:sup>56</jats:sup>Ni mass of 0.63 ± 0.02 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>. 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<jats:sup>−1</jats:sup> day<jats:sup>−1</jats:sup>. Moreover, its early spectra (<jats:italic>t</jats:italic> &lt; − 7.9 days) show a prominent C <jats:sc>ii</jats:sc> <jats:italic>λ</jats:italic>6580 absorption feature, which disappeared in near-maximum-light spectra but reemerged at phases from <jats:italic>t</jats:italic> ∼ + 8.7 days to <jats:italic>t</jats:italic> ∼ + 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 <jats:sc>ii</jats:sc> <jats:italic>λ</jats:italic>6580-to-Si <jats:sc>ii</jats:sc> <jats:italic>λ</jats:italic>6355 velocity ratio (∼0.81) observed in SN 2017hpa. The O <jats:sc>i</jats:sc> <jats:italic>λ</jats:italic>7774 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.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>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, CH<jats:sub>3</jats:sub>OH, H<jats:sub>2</jats:sub>CO, HC<jats:sub>3</jats:sub>N, 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 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> to a few tens of <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>, 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.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>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 <jats:inline-formula> <jats:tex-math> <?CDATA ${X}_{\max }$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabdd30ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> distributions of showers observed over this energy range. Data collected over a period of ∼4 yr were analyzed for this study. The resulting <jats:inline-formula> <jats:tex-math> <?CDATA ${X}_{\max }$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabdd30ieqn2.gif" xlink:type="simple" /> </jats:inline-formula> 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 <jats:inline-formula> <jats:tex-math> <?CDATA ${\mathrm{log}}_{10}(E/\mathrm{eV})$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabdd30ieqn3.gif" xlink:type="simple" /> </jats:inline-formula>, spanning the full range of the measured energies. We also examine the mean <jats:inline-formula> <jats:tex-math> <?CDATA ${X}_{\max }$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabdd30ieqn4.gif" xlink:type="simple" /> </jats:inline-formula> value as a function of energy for cosmic rays with energies greater than 10<jats:sup>15.8</jats:sup> eV. Below 10<jats:sup>17.3</jats:sup> eV, the slope of the mean <jats:inline-formula> <jats:tex-math> <?CDATA ${X}_{\max }$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabdd30ieqn5.gif" xlink:type="simple" /> </jats:inline-formula> 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 <jats:inline-formula> <jats:tex-math> <?CDATA ${X}_{\max }$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabdd30ieqn6.gif" xlink:type="simple" /> </jats:inline-formula> elongation rate is observed at energies just above 10<jats:sup>17</jats:sup> eV, indicating another change in the cosmic-ray composition.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>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 <jats:italic>M</jats:italic> <jats:sub> <jats:italic>V</jats:italic> </jats:sub> ≈ −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 <jats:italic>M</jats:italic> <jats:sub> <jats:italic>V</jats:italic> </jats:sub> ≈ −9 mag. In addition, we find a subpopulation of less luminous GCs at <jats:italic>M</jats:italic> <jats:sub> <jats:italic>V</jats:italic> </jats:sub> ≈ −7.5 mag, where the near-universal GCLF peak is located. The number of GCs in the magnitude range of −5 to −8 is <jats:inline-formula> <jats:tex-math> <?CDATA ${7}_{-4}^{+7}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabdd29ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> in DF2 and <jats:inline-formula> <jats:tex-math> <?CDATA ${9}_{-5}^{+8}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabdd29ieqn2.gif" xlink:type="simple" /> </jats:inline-formula> in DF4, similar to that expected from other galaxies of the same luminosity. The total GC number between <jats:italic>M</jats:italic> <jats:sub> <jats:italic>V</jats:italic> </jats:sub> of −5 and −11 is <jats:inline-formula> <jats:tex-math> <?CDATA ${19}_{-4}^{+9}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabdd29ieqn3.gif" xlink:type="simple" /> </jats:inline-formula> for DF2 and <jats:inline-formula> <jats:tex-math> <?CDATA ${19}_{-5}^{+9}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabdd29ieqn4.gif" xlink:type="simple" /> </jats:inline-formula> 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 <jats:italic>N</jats:italic> <jats:sub>GC</jats:sub> is not directly determined by the merging of halos.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Theoretical investigations predicted that high spatiotemporal resolution observations in the Sr <jats:sc>i</jats:sc> 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 <jats:sc>i</jats:sc> 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.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We revisit the cold gas contents of galaxies in a protocluster at <jats:italic>z</jats:italic> = 2.49 using the lowest neutral atomic carbon transition [C <jats:sc>i</jats:sc>] <jats:sup>3</jats:sup> <jats:italic>P</jats:italic> <jats:sub>1</jats:sub> − <jats:sup>3</jats:sup> <jats:italic>P</jats:italic> <jats:sub>0</jats:sub> 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 <jats:sc>i</jats:sc>] 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 <jats:sc>i</jats:sc>] in the protocluster and compare with other previous studies. We then compare the gas mass based on three gas tracers of [C <jats:sc>i</jats:sc>], 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 <jats:sc>i</jats:sc>]-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 <jats:sc>i</jats:sc>]- 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 <jats:sc>i</jats:sc>] line, we reconfirm our previous findings that the mean gas fraction is comparable to field galaxies for a stellar-mass range of <jats:inline-formula> <jats:tex-math> <?CDATA $\mathrm{log}({M}_{\mathrm{star}}/{M}_{\odot })=[10.6,11.3]$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabdbb5ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>. 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.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>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.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The sizable linear polarization signals produced by the scattering of anisotropic radiation in the core of the Ca <jats:sc>i</jats:sc> 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.</jats:p>