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<jats:title>Abstract</jats:title> <jats:p>Switchbacks are widely acknowledged phenomena observed by the Parker Solar Probe and appear to occur in patches. Previous studies focused on the fluctuations at the magnetic reversals. However, the nature of the fluctuations inside the switchbacks remains unknown. Here we utilize the magnetic field data and plasma data measured by the Parker Solar Probe in the first four encounters. We investigate the fluctuations in the switchback intervals of 100 s with <jats:inline-formula> <jats:tex-math> <?CDATA ${B}_{R}\gt 0$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabec6cieqn1.gif" xlink:type="simple" /> </jats:inline-formula> at every instant and compare them to the fluctuations in the nonswitchback intervals of 100 s with <jats:inline-formula> <jats:tex-math> <?CDATA ${\theta }_{\mathrm{RB}}\gt 160^\circ $?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabec6cieqn2.gif" xlink:type="simple" /> </jats:inline-formula> at every instant. We calculate normalized cross-helicity <jats:inline-formula> <jats:tex-math> <?CDATA ${\sigma }_{{\rm{c}}}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabec6cieqn3.gif" xlink:type="simple" /> </jats:inline-formula>, normalized residual energy <jats:inline-formula> <jats:tex-math> <?CDATA ${\sigma }_{{\rm{r}}}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabec6cieqn4.gif" xlink:type="simple" /> </jats:inline-formula>, correlation coefficient <jats:italic>C</jats:italic> <jats:sub>vb</jats:sub> between <jats:inline-formula> <jats:tex-math> <?CDATA ${\boldsymbol{\delta }}{{\boldsymbol{v}}}_{{\rm{A}}}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabec6cieqn5.gif" xlink:type="simple" /> </jats:inline-formula> and <jats:inline-formula> <jats:tex-math> <?CDATA ${\boldsymbol{\delta }}{\boldsymbol{v}}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabec6cieqn6.gif" xlink:type="simple" /> </jats:inline-formula>, Alfvén ratio <jats:italic>r</jats:italic> <jats:sub>A</jats:sub>, and the amplitude of magnetic and kinetic fluctuations. We find that the switchback intervals exhibit a distribution of <jats:inline-formula> <jats:tex-math> <?CDATA ${\sigma }_{{\rm{c}}}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabec6cieqn7.gif" xlink:type="simple" /> </jats:inline-formula> similar with the nonswitchback intervals. However, the <jats:italic>r</jats:italic> <jats:sub>A</jats:sub> of switchback intervals is around 0.35, while the nonswitchback intervals have <jats:italic>r</jats:italic> <jats:sub>A</jats:sub> around 0.65, indicating the fluctuations in the switchbacks are more magnetically dominated. We also find that the distribution pattern of pixel average amplitude of both <jats:inline-formula> <jats:tex-math> <?CDATA ${\boldsymbol{\delta }}{{\boldsymbol{v}}}_{{\rm{A}}}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabec6cieqn8.gif" xlink:type="simple" /> </jats:inline-formula> and <jats:inline-formula> <jats:tex-math> <?CDATA ${\boldsymbol{\delta }}{\boldsymbol{v}}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabec6cieqn9.gif" xlink:type="simple" /> </jats:inline-formula> of switchback intervals in the <jats:italic>C</jats:italic> <jats:sub>vb</jats:sub>–<jats:inline-formula> <jats:tex-math> <?CDATA ${\sigma }_{{\rm{r}}}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabec6cieqn10.gif" xlink:type="simple" /> </jats:inline-formula> plane show a vertical stripe feature at <jats:inline-formula> <jats:tex-math> <?CDATA ${C}_{\mathrm{vb}}\gt 0.8$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabec6cieqn11.gif" xlink:type="simple" /> </jats:inline-formula>, illustrating the possible magnetically dominant magnetic-velocity alignment structure. These results will help us to understand the nature and the formation of the switchback turbulence.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We study the consequences of a hadron-quark phase transition (PT) in failing core-collapse supernovae (CCSNe) that give birth to stellar-mass black holes (BH). We perform a suite of neutrino-transport general-relativistic hydrodynamic simulations in spherical symmetry with 21 progenitor models and a hybrid equation of state (EoS) including hadrons and quarks. We find that the effect of the PT on the CCSN postbounce dynamics is a function of the bounce compactness parameter <jats:inline-formula> <jats:tex-math> <?CDATA ${\xi }_{2.2}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabec4cieqn1.gif" xlink:type="simple" /> </jats:inline-formula>. For <jats:inline-formula> <jats:tex-math> <?CDATA ${\xi }_{2.2}\gtrsim 0.24$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabec4cieqn2.gif" xlink:type="simple" /> </jats:inline-formula>, the PT leads to a second dynamical collapse of the protocompact star (PCS). While BH formation starts immediately after this second collapse for models with <jats:inline-formula> <jats:tex-math> <?CDATA ${\xi }_{2.2}\gtrsim 0.51$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabec4cieqn3.gif" xlink:type="simple" /> </jats:inline-formula>, the PCS experiences a second bounce and oscillations for models with <jats:inline-formula> <jats:tex-math> <?CDATA $0.24\lesssim {\xi }_{2.2}\lesssim 0.51$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabec4cieqn4.gif" xlink:type="simple" /> </jats:inline-formula>. These models emit potent oscillatory neutrino signals with a period of ∼1 ms for tens of milliseconds after the second bounce, which can be a strong indicator of the PT in failing CCSNe if detected in the future. However, no shock revival occurs and BH formation inevitably takes place in our spherically symmetric simulations. Furthermore, via a diagram of mass-specific entropy evolution of the PCS, the progenitor dependence can be understood through the appearance of a third family of compact stars emerging at large entropy induced by the PT.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The recent rediscovery of magnetic field switchbacks or deflections embedded in the solar wind flow by the Parker Solar Probe mission lead to a huge interest in the modeling of the formation mechanisms and origin of these switchbacks. Several scenarios for their generation were put forth, ranging from lower solar atmospheric origins by reconnection, to being a manifestation of turbulence in the solar wind, and so on. Here we study some potential formation mechanisms of magnetic switchbacks in the lower solar atmosphere, using three-dimensional magnetohydrodynamic (MHD) numerical simulations. The model is that of an intense flux tube in an open magnetic field region, aiming to represent a magnetic bright point opening up to an open coronal magnetic field structure, e.g., a coronal hole. The model is driven with different plasma flows in the photosphere, such as a fast up-shooting jet, as well as shearing flows generated by vortex motions or torsional oscillations. In all scenarios considered, we witness the formation of magnetic switchbacks in regions corresponding to chromospheric heights. Therefore, photospheric plasma flows around the foot-points of intense flux tubes appear to be suitable drivers for the formation of magnetic switchbacks in the lower solar atmosphere. Nevertheless, these switchbacks do not appear to be able to enter the coronal heights of the simulation in the present model. In conclusion, based on the presented simulations, switchbacks measured in the solar wind are unlikely to originate from photospheric or chromospheric dynamics.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>As the central engine of gamma-ray bursts (GRBs), a nascent magnetar can release its rotational energy by magnetic dipole radiation. This energy is injected into the outflow of the GRB jet. With the rapid evolution of the magnetic inclination angle, the perpendicular component of the magnetar’s surface magnetic field decreases rapidly. The energy loss rate of the magnetar is characterized by two different timescales. This peculiar two-stage energy injection model will affect the shape of the X-ray afterglow light curve. It is shown that a new shallow decay phase will emerge following the initial shallow decay phase. As a result, there could be two plateaus in the X-ray light curve. The effects of various physical parameters on the light curves are studied in detail. It is found that the observed afterglows of GRB 161217A and GRB 190114A, both having two plateaus in the light curve, can be well fitted in our framework.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present a sensitive search with the Karl G. Jansky Very Large Array for the radio counterpart of the gravitational wave candidate S191216ap, which is classified as a binary black hole merger and suggested to be a possible multimessenger event, based on the detection of a high-energy neutrino and a TeV photon. We carried out a blind search at <jats:italic>C</jats:italic> band (4–8 GHz) over 0.3 deg<jats:sup>2</jats:sup> of the gamma-ray counterpart of S191216ap reported by the High-Altitude Water Cerenkov Observatory (HAWC). Our search, spanning three epochs over 130 days of postmerger and having a mean source-detection threshold of 75 <jats:italic>μ</jats:italic>Jy beam<jats:sup>−1</jats:sup> (4<jats:italic>σ</jats:italic>), yielded five variable sources associated with active galactic nucleus activity and no definitive counterpart of S191216ap. We find &lt;2% (3.0% ± 1.3%) of the persistent radio sources at 6 GHz to be variable on a timescale of &lt;1 week (week–months), consistent with previous radio variability studies. Our 4<jats:italic>σ</jats:italic> radio luminosity upper limit of ∼1.2 × 10<jats:sup>28</jats:sup> erg s<jats:sup>−1</jats:sup> Hz<jats:sup>−1</jats:sup> on the afterglow of S191216ap, within the HAWC error region, is 5–10 times deeper than previous binary black hole (BBH) radio afterglow searches. Comparing this upper limit with theoretical expectations given by Perna et al. for putative jets launched by BBH mergers, for on-axis jets with energy ≃10<jats:sup>49</jats:sup> erg, we can rule out jet opening angles ≲ 20° (assuming that the counterpart lies within the 1<jats:italic>σ</jats:italic> HAWC region that we observed).</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present a new catalog of 9318 Ly<jats:italic>α</jats:italic> emitter (LAE) candidates at <jats:italic>z</jats:italic> = 2.2, 3.3, 4.9, 5.7, 6.6, and 7.0 that are photometrically selected by the SILVERRUSH program with a machine learning technique from large area (up to 25.0 deg<jats:sup>2</jats:sup>) imaging data with six narrowband filters taken by the Subaru Strategic Program with Hyper Suprime-Cam and a Subaru intensive program, Cosmic HydrOgen Reionization Unveiled with Subaru. We construct a convolutional neural network that distinguishes between real LAEs and contaminants with a completeness of 94% and a contamination rate of 1%, enabling us to efficiently remove contaminants from the photometrically selected LAE candidates. We confirm that our LAE catalogs include 177 LAEs that have been spectroscopically identified in our SILVERRUSH programs and previous studies, ensuring the validity of our machine learning selection. In addition, we find that the object-matching rates between our LAE catalogs and our previous results are ≃80%–100% at bright NB magnitudes of ≲24 mag. We also confirm that the surface number densities of our LAE candidates are consistent with previous results. Our LAE catalogs will be made public on our project webpage.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In our earlier study (Paper I) of this series, we examined the hemispheric sign preference (HSP) of magnetic helicity flux <jats:italic>dH</jats:italic>/<jats:italic>dt</jats:italic> across photospheric surfaces of 4802 samples of 1105 unique active regions (ARs) observed during solar cycle 24. Here, we investigate any association of the HSP, expressed as a degree of compliance, with flaring activity, analyzing the same set of <jats:italic>dH</jats:italic>/<jats:italic>dt</jats:italic> estimates as used in Paper I. The AR samples under investigation are assigned to heliographic regions (HRs) defined in the Carrington longitude–latitude plane with a grid spacing of 45° in longitude and 15° in latitude. For AR samples in each of the defined HRs, we calculate the degree of HSP compliance and the average soft X-ray flare index. The strongest flaring activity is found to be in one distinctive HR with an extremely low-HSP compliance of 41% as compared to the mean and standard deviation of 62% and 7%, respectively, over all HRs. This sole HR shows an anti-HSP (i.e., &lt;50%) and includes the highly flare-productive AR NOAA 12673, however this AR is not uniquely responsible for the HR’s low HSP. We also find that all HRs with the highest flaring activity are located in the southern hemisphere, and they tend to have lower degrees of HSP compliance. These findings point to the presence of localized regions of the convection zone with enhanced turbulence, imparting a greater magnetic complexity and a higher flaring rate to some rising magnetic flux tubes.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In this paper we test if the ∼0.3–15 keV XMM-Newton EPIC pn spectral continuum of IPs can be described by the thermal Comptonization <jats:sc>compTT</jats:sc> model. We used publicly observations of 12 IPs (AE Aqr, EX Hya, V1025 Cen, V2731 Oph, RX J2133.7+5107, PQ Gem, NY Lup, V2400 Oph, IGR J00234+6141, IGR J17195-4100, V1223 Sgr, and XY Ari). We find that our modeling is capable of fitting well the average spectral continuum of these sources. In this framework, UV/soft X-ray seed photons (with 〈<jats:italic>kT</jats:italic> <jats:sub>s</jats:sub>〉 of 0.096 ± 0.013 keV) coming presumably from the star surface are scattered off by electrons present in an optically thick plasma (with 〈<jats:italic>kT</jats:italic> <jats:sub>e</jats:sub>〉 of 3.05 ± 0.16 keV and optical depth 〈<jats:italic>τ</jats:italic>〉 of 9.5 ± 0.6 for plane geometry) located nearby (on top) to the more central seed photon emission regions. A soft blackbody (<jats:sc>bbody</jats:sc>) component is observed in 5 out of the 13 observations analyzed, with a mean temperature 〈<jats:italic>kT</jats:italic> <jats:sub> <jats:italic>bb</jats:italic> </jats:sub>〉 of 0.095 ± 0.004 keV. We observed that the spectra of IPs show in general two photon indices Γ, which are driven by the source luminosity and optical depth. Low luminosity IPs show 〈Γ〉 of 1.83 ± 0.19, whereas high luminosity IPs show lower 〈Γ〉 of 1.34 ± 0.02. Moreover, the good spectral fits of PQ Gem and V2400 Oph indicate that the polar subclass of CVs may be successfully described by the thermal Comptonization as well.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Magnetic fields are ubiquitous and essential in star formation. In particular, their role in regulating formation of stars across diverse environments like H <jats:sc>ii</jats:sc> regions needs to be well understood. In this study, we present magnetic field properties toward the S235 complex using near-infrared (NIR) <jats:italic>H</jats:italic>-band polarimetric observations, obtained with the Mimir and POLICAN instruments. We selected 375 background stars in the field through combination of Gaia distances and extinctions from NIR colors. The plane-of-sky (POS) magnetic field orientations inferred from starlight polarization angles reveal a curved morphology tracing the spherical shell of the H <jats:sc>ii</jats:sc> region. The large-scale magnetic field traced by Planck is parallel to the Galactic plane. We identified 11 dense clumps using 1.1 mm dust emission, with masses between 33 and 525 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>. The clump-averaged POS magnetic field strengths were estimated to be between 36 and 121 <jats:italic>μ</jats:italic>G, with a mean of ∼65 <jats:italic>μ</jats:italic>G. The mass-to-flux ratios for the clumps are found to be subcritical with turbulent Alfvén Mach numbers less than 1, indicating a strongly magnetized region. The clumps show scaling of magnetic field strength versus density with a power-law index of 0.52 ± 0.07, similar to ambipolar diffusion models. Our results indicate that the S235 complex is a region where stellar feedback triggers new stars, and the magnetic fields regulate the rate of new star formation.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In recent years, the availability of large, complete cluster samples has enabled numerous cosmological parameter inference analyses using cluster number counts. These have provided constraints on the cosmic matter density Ω<jats:sub> <jats:italic>m</jats:italic> </jats:sub> and the amplitude of matter density fluctuations <jats:italic>σ</jats:italic> <jats:sub>8</jats:sub> alternative to that obtained from other standard probes. However, systematics uncertainties, such as the mass calibration bias and selection effects, may still significantly affect these data analyses. Hence, it is timely to explore other proxies of galaxy cluster cosmology that can provide cosmological constraints complementary to those obtained from cluster number counts. Here we use measurements of the cluster sparsity from weak-lensing mass estimates of the LC<jats:sup>2</jats:sup>-<jats:italic>single</jats:italic> and HSC-XXL cluster catalogs to infer constraints on a flat ΛCDM model. The cluster sparsity has the advantage of being insensitive to selection and mass calibration bias. On the other hand, it primarily constrains a degenerate combination of Ω<jats:sub> <jats:italic>m</jats:italic> </jats:sub> and <jats:italic>σ</jats:italic> <jats:sub>8</jats:sub> (along approximately constant curves of <jats:inline-formula> <jats:tex-math> <?CDATA ${S}_{8}={\sigma }_{8}\sqrt{{{\rm{\Omega }}}_{m}/0.3}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabe9a4ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> and, to a lesser extent, the reduced Hubble parameter <jats:italic>h</jats:italic>. Hence, in order to break the internal parameter degeneracies, we perform a combined likelihood analysis of the cluster sparsity estimates with cluster gas mass fraction measurements and BAO data. We find marginal constraints that are competitive with those from other standard cosmic probes: Ω<jats:sub> <jats:italic>m</jats:italic> </jats:sub> = 0.316 ± 0.013, <jats:italic>σ</jats:italic> <jats:sub>8</jats:sub> = 0.757 ± 0.067 (corresponding to <jats:italic>S</jats:italic> <jats:sub>8</jats:sub> = 0.776 ± 0.064), and <jats:italic>h</jats:italic> = 0.696 ± 0.017 at 1<jats:italic>σ</jats:italic>. Moreover, assuming a conservative Gaussian prior on the mass bias of gas mass fraction data, we find a lower limit on the gas depletion factor <jats:italic>Y</jats:italic> <jats:sub> <jats:italic>b</jats:italic>,500<jats:italic>c</jats:italic> </jats:sub> ≳ 0.89.</jats:p>