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<jats:title>Abstract</jats:title> <jats:p>Here we present a statistical study of the ∼0.15–1.5 keV suprathermal electrons observed in uncompressed/compressed slow and fast solar wind around 59 corotating interaction regions (CIRs) with good measurements by Wind 3DP from 1995 through 1997. For each of these CIRs, we fit the strahl and halo energy spectra at ∼0.15–1.5 keV to a Kappa function with a Kappa index <jats:italic>κ</jats:italic> and kinetic temperature <jats:italic>T</jats:italic> <jats:sub>eff</jats:sub>. We find that the ∼0.15–1.5 keV strahl electrons behave similarly in both slow and fast wind: the strahl number density <jats:italic>n</jats:italic> <jats:sub> <jats:italic>s</jats:italic> </jats:sub> positively correlates with the solar wind electron temperature <jats:italic>T</jats:italic> <jats:sub> <jats:italic>e</jats:italic> </jats:sub> and interplanetary magnetic field magnitude ∣<jats:italic>B</jats:italic>∣, while the strahl pitch angle width Θ<jats:sub> <jats:italic>s</jats:italic> </jats:sub> decreases with the solar wind speed <jats:italic>V</jats:italic> <jats:sub>sw</jats:sub>. These suggest that the strahl electrons are generated by a similar/same process at the Sun in both slow and fast wind that produces these correlations, and the scattering efficiency of strahl in the interplanetary medium (IPM) decreases with <jats:italic>V</jats:italic> <jats:sub>sw</jats:sub>. The ∼0.15–1.5 keV halo electrons also behave similarly in both slow and fast wind: the halo parameter positively correlates with the corresponding strahl parameter, and the halo number density <jats:italic>n</jats:italic> <jats:sub> <jats:italic>h</jats:italic> </jats:sub> positively correlates only with <jats:italic>T</jats:italic> <jats:sub> <jats:italic>e</jats:italic> </jats:sub>. These indicate that the halo formation process in the IPM retains most of the strahl properties, but it erases the relationship between <jats:italic>n</jats:italic> <jats:sub> <jats:italic>s</jats:italic> </jats:sub> and ∣<jats:italic>B</jats:italic>∣. In addition, <jats:italic>κ</jats:italic> in compressed wind distributes similarly to that in uncompressed wind, for both the strahl and halo. It shows that CIRs at 1 au are not a significant/effective acceleration source for the strahl and halo.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present our third set of results from our mid-infrared imaging survey of Milky Way Giant H <jats:sc>ii</jats:sc> regions with our detailed analysis of W49A, one of the most distant, yet most luminous, GH <jats:sc>ii</jats:sc> regions in the Galaxy. We used the FORCAST instrument on the Stratospheric Observatory For Infrared Astronomy (SOFIA) to obtain 20 and 37 <jats:italic>μ</jats:italic>m images of the entire ∼5.′0 × 3.′5 infrared-emitting area of W49A at a spatial resolution of ∼3″. Utilizing these SOFIA data in conjunction with previous multiwavelength observations from the near-infrared to radio, including Spitzer-IRAC and Herschel-PACS archival data, we investigate the physical nature of individual infrared sources and subcomponents within W49A. For individual compact sources, we used the multiwavelength photometry data to construct spectral energy distributions (SEDs) and fit them with massive young stellar object (MYSO) SED models and find 22 sources that are likely to be MYSOs. Ten new sources are identified for the first time in this work. Even at 37 <jats:italic>μ</jats:italic>m we are unable to detect infrared emission from the sources on the western side of the extremely extinguished ring of compact radio emission sources known as the Welch Ring. Utilizing multiwavelength data, we derived luminosity-to-mass ratio and virial parameters of the extended radio subregions of W49A to estimate their relative ages and find that overall the subcomponents of W49A have a very small spread in evolutionary state compared to our previously studied GH <jats:sc>ii</jats:sc> regions.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In this paper, the pulsation behavior of high-amplitude <jats:italic>δ</jats:italic> Scuti star GSC 4552-1498 was analyzed. Using the high-precision photometric data from the Transiting Exoplanet Survey Satellite, two new independent frequencies <jats:italic>F</jats:italic>1 = 22.6424(1) day<jats:sup>−1</jats:sup> and <jats:italic>F</jats:italic>2 = 28.6803(5) day<jats:sup>−1</jats:sup> were identified for this source, along with the fundamental one <jats:italic>F</jats:italic> = 17.9176(7) day<jats:sup>−1</jats:sup>, which was previously known. In addition, the classical <jats:italic>O</jats:italic> − <jats:italic>C</jats:italic> analysis was conducted to give a new ephemeris formula of BJD<jats:sub>max</jats:sub> = <jats:italic>T</jats:italic> <jats:sub>0</jats:sub> + <jats:italic>P</jats:italic> × <jats:italic>E</jats:italic> = 2453321.534716(4) + 0.055811(0) × <jats:italic>E</jats:italic>. The <jats:italic>O</jats:italic> − <jats:italic>C</jats:italic> diagram reveals a continuous period increase, but the rate of (1/<jats:italic>P</jats:italic>)(<jats:italic>dP</jats:italic>/<jats:italic>dt</jats:italic>) = 1.11(3) × 10<jats:sup>−7</jats:sup> yr<jats:sup>−1</jats:sup> seems much larger (about hundreds) than predicted by evolution theories, which is long been noticed but not well understood, possibly related to nonlinear mode interaction. Based on frequency parameters (i.e., <jats:italic>F</jats:italic>, <jats:italic>F</jats:italic>1, and <jats:italic>F</jats:italic>2), a series of theoretical models were conducted by employing the stellar evolution code. It turns out that <jats:italic>F</jats:italic>1 should be a non-radial mode and <jats:italic>F</jats:italic>2 is the second overtone radial mode. Due to the mass–metallicity degeneracy, the stellar parameter of the star can however not be determined conclusively. We suggest high-resolution spectral observation is highly desired in the future to further constrain models. We note GSC 4552-1498 is located on the main sequence in the H-R diagram.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present our investigation of the extended ultraviolet (XUV) disk galaxy, NGC 3344, conducted as part of Deciphering the Interplay between the Interstellar medium, Stars, and the Circumgalactic medium survey. We use surface and aperture photometry of individual young stellar complexes to study star formation and its effect on the physical properties of the interstellar medium. We measure the specific star formation rate (sSFR) and find it to increase from 10<jats:sup>−10</jats:sup> yr<jats:sup>−1</jats:sup> in the inner disk to &gt;10<jats:sup>−8</jats:sup> yr<jats:sup>−1</jats:sup> in the extended disk. This provides evidence for inside-out disk growth. If these sSFRs are maintained, the XUV disk stellar mass can double in ∼0.5 Gyr, suggesting a burst of star formation. The XUV disk will continue forming stars for a long time due to the high gas depletion times (<jats:italic>τ</jats:italic> <jats:sub>dep</jats:sub>). The stellar complexes in the XUV disk have high-Σ<jats:sub>H I</jats:sub> and low-Σ<jats:sub>SFR</jats:sub> with <jats:italic>τ</jats:italic> <jats:sub>dep</jats:sub> ∼ 10 Gyr, marking the onset of a deviation from the traditional Kennicutt–Schmidt law. We find that both far-ultraviolet (FUV) and a combination of FUV and 24 <jats:italic>μ</jats:italic>m effectively trace star formation in the XUV disk. H<jats:italic>α</jats:italic> is weaker in general and prone to stochasticities in the formation of massive stars. Investigation of the circumgalactic medium at 29.5 kpc resulted in the detection of two absorbing systems with metal-line species: the stronger absorption component is consistent with gas flows around the disk, most likely tracing inflow, while the weaker component is likely tracing corotating circumgalactic gas.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Particle drifts perpendicular to the background magnetic field have been proposed by some authors as an explanation for the very efficient perpendicular transport of solar energetic particles (SEPs). This process, however, competes with perpendicular diffusion caused by magnetic turbulence, which can also disrupt the drift patterns and reduce the magnitude of drift effects. The latter phenomenon is well known in cosmic-ray studies, but not yet considered in SEP models. Additionally, SEP models that do not include drifts, especially for electrons, use turbulent drift reduction as a justification of this omission, without critically evaluating or testing this assumption. This article presents the first theoretical step for a theory of drift suppression in SEP transport. This is done by deriving the turbulence-dependent drift reduction function with a pitch-angle dependence, as is applicable for anisotropic particle distributions, and by investigating to what extent drifts will be reduced in the inner heliosphere for realistic turbulence conditions and different pitch-angle dependencies of the perpendicular diffusion coefficient. The influence of the derived turbulent drift reduction factors on the transport of SEPs are tested, using a state-of-the-art SEP transport code, for several expressions of theoretically derived perpendicular diffusion coefficients. It is found, for realistic turbulence conditions in the inner heliosphere, that cross-field diffusion will have the largest influence on the perpendicular transport of SEPs, as opposed to particle drifts.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present ALMA observations on and around the radio-quiet quasar UM 287 at <jats:italic>z</jats:italic> = 2.28. Together with a companion quasar, UM 287 is believed to play a major role in powering the surrounding enormous Ly<jats:italic>α</jats:italic> nebula (ELAN), dubbed the Slug ELAN, that has an end-to-end size of 450 physical kpc. In addition to the quasars, we detect a new dusty star-forming galaxy (DSFG), dubbed the Slug-DSFG, in 2 mm continuum with a single emission line consistent with CO(4−3). The Slug-DSFG sits at a projected distance of 100 kpc southeast from UM 287, with a systemic velocity difference of −360 ± 30 km s<jats:sup>−1</jats:sup> with respect to UM 287, suggesting it is a possible contributor to the powering of the Slug ELAN. With careful modeling of the SED and dynamical analyses, it is found that the Slug-DSFG and UM 287 appear low in both gas fraction and gas-to-dust ratio, suggesting environmental effects due to the host’s massive halo. In addition, our Keck long-slit spectra reveal significant Ly<jats:italic>α</jats:italic> emissions from the Slug-DSFG, as well as a Ly<jats:italic>α</jats:italic> tail that starts at the location and velocity of the Slug-DSFG and extends toward the south, with a projected length of about 100 kpc. Supported by various analytical estimates we propose that the Ly<jats:italic>α</jats:italic> tail is a result of the Slug-DSFG experiencing ram pressure stripping. The gas mass stripped is estimated to be about 10<jats:sup>9</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>, contributing to the dense warm/cool gas reservoir that is believed to help power the exceptional Ly<jats:italic>α</jats:italic> luminosity.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>It has recently been established that the evolution of protoplanetary disks is primarily driven by magnetized disk winds, requiring a large-scale magnetic flux threading the disks. The size of such disks is expected to shrink with time, as opposed to the conventional scenario of viscous expansion. We present the first global 2D non-ideal magnetohydrodynamic simulations of protoplanetary disks that are truncated in the outer radius, aiming to understand the interaction of the disk with the interstellar environment, as well as the global evolution of the disk and magnetic flux. We find that as the system relaxes, the poloidal magnetic field threading the disk beyond the truncation radius collapses toward the midplane, leading to a rapid reconnection. This process removes a substantial amount of magnetic flux from the system and forms closed poloidal magnetic flux loops encircling the outer disk in quasi-steady state. These magnetic flux loops can drive expansion beyond the truncation radius, corresponding to substantial mass loss through a magnetized disk outflow beyond the truncation radius analogous to a combination of viscous spreading and external photoevaporation. The magnetic flux loops gradually shrink over time, the rates of which depend on the level of disk magnetization and the external environment, which eventually governs the long-term disk evolution.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Gravitational waves (GWs) provide unobscured insight into the birthplace of neutron stars and black holes in core-collapse supernovae (CCSNe). The nuclear equation of state (EOS) describing these dense environments is yet uncertain, and variations in its prescription affect the proto−neutron star (PNS) and the post-bounce dynamics in CCSN simulations, subsequently impacting the GW emission. We perform axisymmetric simulations of CCSNe with Skyrme-type EOSs to study how the GW signal and PNS convection zone are impacted by two experimentally accessible EOS parameters, (1) the effective mass of nucleons, <jats:italic>m</jats:italic> <jats:sup>⋆</jats:sup>, which is crucial in setting the thermal dependence of the EOS, and (2) the isoscalar incompressibility modulus, <jats:italic>K</jats:italic> <jats:sub>sat</jats:sub>. While <jats:italic>K</jats:italic> <jats:sub>sat</jats:sub> shows little impact, the peak frequency of the GWs has a strong effective mass dependence due to faster contraction of the PNS for higher values of <jats:italic>m</jats:italic> <jats:sup>⋆</jats:sup> owing to a decreased thermal pressure. These more compact PNSs also exhibit more neutrino heating, which drives earlier explosions and correlates with the GW amplitude via accretion plumes striking the PNS, exciting the oscillations. We investigate the spatial origin of the GWs and show the agreement between a frequency-radial distribution of the GW emission and a perturbation analysis. We do not rule out overshoot from below via PNS convection as another moderately strong excitation mechanism in our simulations. We also study the combined effect of effective mass and rotation. In all our simulations we find evidence for a power gap near ∼1250 Hz; we investigate its origin and report its EOS dependence.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>While radio emission in quasars can be contributed to by a variety of processes (involving star-forming regions, accretion disk coronas and winds, and jets), the powering of the radio loudest quasars must involve very strong jets, presumably launched by the Blandford–Znajek mechanism incorporating the magnetically arrested disk (MAD) scenario. We focus on the latter and investigate the dependence of their fraction on redshift. We also examine the dependence of the radio-loud fraction (RLF) on BH mass (<jats:italic>M</jats:italic> <jats:sub>BH</jats:sub>) and Eddington ratio (<jats:italic>λ</jats:italic> <jats:sub>Edd</jats:sub>), while excluding the redshift bias by narrowing its range. In both of these investigations, we remove the bias associated with: (1) the diversity of source selection by constructing two well-defined, homogeneous samples of quasars (first within 0.7 ≤ <jats:italic>z</jats:italic> ≤ 1.9, second within 0.5 ≤ <jats:italic>z</jats:italic> ≤ 0.7); and (2) a strong drop in the RLF of quasars at smaller BH masses by choosing those with BH masses larger than 10<jats:sup>8.5</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>. We confirm some of the previous results showing the increase in the fraction of radio-loud quasars with cosmic time and that this trend can be even steeper if we account for the bias introduced by the dependence of the RLF on BH mass, whereas the bias introduced by the dependence of the RLF on Eddington ratio is shown to be negligible. Assuming that quasar activities are triggered by galaxy mergers, we argue that such an increase can result from the slower drop with cosmic time of mixed mergers than of wet mergers.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>This study revisits the role that nitrogen inclusion in polycyclic aromatic hydrocarbons (PAHs; those with nitrogen inclusion, PANHs) plays in their infrared (IR) spectral properties. We present spectra of pure PAHs, PANHs, and protonated PANHs, computed using density functional theory and basis sets that treat polarization. We investigate trends in peak position and relative intensities as a function of nitrogen position, charge, and geometry. We use Spitzer-IRS spectral map data of the northwest photodissociation region of NGC 7023 and a database-fitting approach, using exclusively the PA(N)H spectra computed in this paper, to assess their IR contribution to the cosmic PAH emission. We find that, by including the treatment of polarization, pure PAH cations can account for the class A 6.2 <jats:italic>μ</jats:italic>m PAH emission, with the 6.2 <jats:italic>μ</jats:italic>m band position being dependent on the molecular geometry. PANH cations are required to reproduce the most blueshifted 6.2 <jats:italic>μ</jats:italic>m bands observed in class A sources, albeit PANH cations come with strong 11.0 <jats:italic>μ</jats:italic>m emission. Blind database fits demonstrate that the restriction imposed by the 11.0 <jats:italic>μ</jats:italic>m emission in the astronomical spectra limits the contribution of PANH cations and the fits have to use neutral PANHs to avoid inflating the 11.0 <jats:italic>μ</jats:italic>m feature even further. By assuming that all of the 11.0 <jats:italic>μ</jats:italic>m emission is due to PANHs, we derive an upper limit for the contribution of PANH cations to the astronomical 6.2 <jats:italic>μ</jats:italic>m PAH band of ∼12%. The fits further show hydrogenated PANHs significantly contributing in NGC 7023's more benign region, supporting the view that shielded environments could sustain protonated PA(N)Hs.</jats:p>