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<jats:title>Abstract</jats:title> <jats:p> <jats:italic>δ</jats:italic> Scuti variables are stars which exhibit periodic changes in their luminosity through radial and nonradial pulsations. Internally, these stars have relatively small convective cores, and convective overshoot can significantly affect the size. Recently, models of radial pulsation in <jats:italic>δ</jats:italic> Scuti stars found a strong correlation between the pulsation constant (<jats:italic>Q</jats:italic>) as a function of effective temperature and the amount of convective overshoot within the star. However, only models with metallicities of <jats:italic>Z</jats:italic> = 0.02 were examined, leaving the dependence of` this relationship on chemical composition unknown. In this work, we have extended the model grid to cover a range of metallicities using Modules for Experiments in Stellar Astrophysics <jats:monospace>(</jats:monospace>), and analyzed the models’ pulsation properties using <jats:monospace>GYRE</jats:monospace>. By varying the models’ mass, rotation speed, convective overshoot, and metallicity, we studied the behavior of <jats:italic>Q</jats:italic> at low temperature. We found that the updated convective boundary treatment in <jats:monospace>MESA</jats:monospace> changes the overshoot dependence found previously, and the value of the slope depends on both rotation and overshoot. We also found that there is a metallicity dependence in the <jats:italic>Q</jats:italic> values. The lowest metallicity models in our grid reached higher temperatures than previously studied, revealing a parabolic relation between <jats:inline-formula> <jats:tex-math> <?CDATA $\mathrm{log}Q$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>log</mml:mi> <mml:mi>Q</mml:mi> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac3980ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> and <jats:inline-formula> <jats:tex-math> <?CDATA $\mathrm{log}{T}_{\mathrm{eff}}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>log</mml:mi> <mml:msub> <mml:mrow> <mml:mi>T</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>eff</mml:mi> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac3980ieqn2.gif" xlink:type="simple" /> </jats:inline-formula>.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>New mass estimates and cumulative mass profiles with Bayesian credible regions for the Milky Way (MW) are found using the Galactic Mass Estimator (GME) code and dwarf galaxy (DG) kinematic data from multiple sources. GME takes a hierarchical Bayesian approach to simultaneously estimate the true positions and velocities of the DGs, their velocity anisotropy, and the model parameters for the Galaxy’s total gravitational potential. In this study, we incorporate meaningful prior information from past studies and simulations. The prior distributions for the physical model are informed by the results of Eadie &amp; Jurić, who used globular clusters instead of DGs, as well as by the subhalo distributions of the Ananke Gaia-like surveys from Feedback in Realistic Environments-2 cosmological simulations (see Sanderson et al.). Using DGs beyond 45 kpc, we report median and 95% credible region estimates for <jats:italic>r</jats:italic> <jats:sub>200</jats:sub> = 212.8 (191.12, 238.44) kpc, and for the total enclosed mass <jats:italic>M</jats:italic> <jats:sub>200</jats:sub> = 1.19 (0.87, 1.68) × 10<jats:sup>12</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> (adopting Δ<jats:sub> <jats:italic>c</jats:italic> </jats:sub> = 200). Median mass estimates at specific radii are also reported (e.g., <jats:italic>M </jats:italic>(&lt; 50 kpc) = 0.52 × 10<jats:sup>12</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> and <jats:italic>M </jats:italic>(100 kpc) = 0.78 × 10<jats:sup>12</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>). Estimates are comparable to other recent studies using Gaia DR2 and DGs, but notably different from the estimates of Eadie &amp; Jurić. We perform a sensitivity analysis to investigate whether individual DGs and/or a more massive Large Magellanic Cloud on the order of 10<jats:sup>11</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> may be affecting our mass estimates. We find possible supporting evidence for the idea that some DGs are affected by a massive LMC and are not in equilibrium with the MW.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We investigate the impact of cosmic filaments on the gas accretion rate, <jats:inline-formula> <jats:tex-math> <?CDATA ${\dot{M}}_{\mathrm{gas}}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mover accent="true"> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>̇</mml:mo> </mml:mrow> </mml:mover> </mml:mrow> <mml:mrow> <mml:mi>gas</mml:mi> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac37b9ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>, of dark matter halos in filaments, based on cosmological hydrodynamic simulation. We find that for halos less massive than 10<jats:sup>12.0</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>, <jats:inline-formula> <jats:tex-math> <?CDATA ${\dot{M}}_{\mathrm{gas}}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mover accent="true"> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>̇</mml:mo> </mml:mrow> </mml:mover> </mml:mrow> <mml:mrow> <mml:mi>gas</mml:mi> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac37b9ieqn2.gif" xlink:type="simple" /> </jats:inline-formula> of halos residing in prominent filaments (with width <jats:italic>D</jats:italic> <jats:sub>fil</jats:sub> &gt; 3 Mpc <jats:italic>h</jats:italic> <jats:sup>−1</jats:sup>) is lower than halos residing in tenuous filaments (<jats:italic>D</jats:italic> <jats:sub>fil</jats:sub> &lt; 3 Mpc <jats:italic>h</jats:italic> <jats:sup>−1</jats:sup>) by 20%–30% at <jats:italic>z</jats:italic> = 0.5 and by a factor of 2–3 at <jats:italic>z</jats:italic> = 0. However, <jats:inline-formula> <jats:tex-math> <?CDATA ${\dot{M}}_{\mathrm{gas}}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mover accent="true"> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>̇</mml:mo> </mml:mrow> </mml:mover> </mml:mrow> <mml:mrow> <mml:mi>gas</mml:mi> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac37b9ieqn3.gif" xlink:type="simple" /> </jats:inline-formula> depends weakly on the physical distance between halo center and the spine of filaments from high redshift to <jats:italic>z</jats:italic> = 0 and only shows a clear difference between the inner and outer regions in prominent filaments at <jats:italic>z</jats:italic> = 0. We further probe the thermal properties of gas in prominent and tenuous filaments, which appear in relatively highly and intermediate overdense regions, respectively. The gas in prominent filaments is hotter. Around 26%, 38%, and 45% of gases in prominent filaments are hotter than 10<jats:sup>6</jats:sup> K at <jats:italic>z</jats:italic> = 1.0, 0.5, and 0.0, respectively. The corresponding fractions in tenuous filaments are merely ∼6%, 9%, and 11%. The suppressed gas accretion rate for low-mass halos in prominent filaments at <jats:italic>z</jats:italic> ≲ 0.5 may result from the hotter ambient gas, which could provide a physical processing mechanism to cut down the supply of gas to halos before they enter clusters. This process partially meets the need of the preheating mechanism implemented in some semianalytical models of galaxy formation but works only for ∼20% of halos at <jats:italic>z</jats:italic> &lt; 1.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The luminosity function of active galactic nuclei (AGN) probes the history of supermassive black hole assembly and growth across cosmic time. To mitigate selection biases, we present a consistent analysis of the AGN luminosity functions (LFs) derived for both X-ray and mid-infrared (MIR) selected AGN in the XMM-Large Scale Structure field. There are 4268 AGN used to construct the MIR luminosity function (IRLF) and 3427 AGN used to construct the X-ray luminosity function (XLF), providing the largest census of the AGN population out to <jats:italic>z</jats:italic> = 4 in both bands with significant reduction in uncertainties. We are able for the first time to see the knee of the IRLF at <jats:italic>z</jats:italic> &gt; 2 and observe a flattening of the faint-end slope as redshift increases. The bolometric luminosity density, a proxy for the cosmic black hole accretion history, computed from our LFs, shows a peak at <jats:italic>z</jats:italic> ≈ 2.25, consistent with recent estimates of the peak in the star formation rate density (SFRD). However, at earlier epochs, the AGN luminosity density is flatter than the SFRD. If confirmed, this result suggests that the build up of black hole mass outpaces the growth of stellar mass in high-mass systems at <jats:italic>z</jats:italic> ≳ 2.5. This is consistent with observations of redshift <jats:italic>z</jats:italic> ∼ 6 quasars that lie above the local <jats:italic>M</jats:italic> − <jats:italic>σ</jats:italic> relationship. The luminosity density derived from the IRLF is higher than that from the XLF at all redshifts. This is consistent with the dominant role of obscured AGN activity in the cosmic growth of supermassive black holes.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Atmospheric heat redistribution shapes the remote appearance of rocky exoplanets, but there is currently no easy way to predict a planet’s heat redistribution from its physical properties. This paper proposes an analytical scaling theory for the heat redistribution on tidally locked rocky exoplanets. The main parameters of the scaling are a planet’s equilibrium temperature, surface pressure, and broadband longwave optical thickness. The scaling compares favorably against idealized general circulation model simulations of TRAPPIST-1b, GJ1132b, and LHS 3844b. For these planets, heat redistribution generally becomes efficient, and a planet’s observable thermal phase curve and secondary eclipse start to deviate significantly from that of a bare rock, once surface pressure exceeds <jats:inline-formula> <jats:tex-math> <?CDATA ${ \mathcal O }(1)$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi mathvariant="italic"></mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:mn>1</mml:mn> <mml:mo stretchy="false">)</mml:mo> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac3b48ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> bar. The scaling additionally points to planetary scenarios for which heat transport can be notably more or less efficient, such as H<jats:sub>2</jats:sub> and CO atmospheres or hot lava ocean worlds. The results thus bridge the gap between theory and imminent observations with the James Webb Space Telescope. They can also be used to parameterize the effect of 3D atmospheric dynamics in 1D models, thereby improving the self-consistency of such models.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present new discoveries and results from long-term timing of 72 pulsars discovered in the Pulsar Arecibo <jats:italic>L</jats:italic>-band Feed Array (PALFA) survey, including precise determination of astrometric and spin parameters, and flux density and scatter broadening measurements at 1.4 GHz. Notable discoveries include two young pulsars (characteristic ages ∼30 kyr) with no apparent supernova remnant associations, three mode-changing, 12 nulling and two intermittent pulsars. We detected eight glitches in five pulsars. Among them is PSR J1939+2609, an apparently old pulsar (characteristic age ∼1 Gy), and PSR J1954+2529, which likely belongs to a newly emerging class of binary pulsars. The latter is the only pulsar among the 72 that is clearly not isolated: a nonrecycled neutron star with a 931 ms spin period in an eccentric (<jats:italic>e</jats:italic> = 0.114) wide (<jats:italic>P</jats:italic> <jats:sub> <jats:italic>b</jats:italic> </jats:sub> = 82.7 days) orbit with a companion of undetermined nature having a minimum mass of ∼0.6 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>. Since operations at Arecibo ceased in 2020 August, we give a final tally of PALFA sky coverage, and compare its 207 pulsar discoveries to the known population. On average, they are 50% more distant than other Galactic plane radio pulsars; PALFA millisecond pulsars (MSPs) have twice the dispersion measure per unit spin period than the known population of MSP in the plane. The four intermittent pulsars discovered by PALFA more than double the population of such objects, which should help to improve our understanding of pulsar magnetosphere physics. The statistics for these, rotating radio transients, and nulling pulsars suggest that there are many more of these objects in the Galaxy than was previously thought.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We report on NICER X-ray monitoring of the magnetar SGR 1830−0645 covering 223 days following its 2020 October outburst, as well as Chandra and radio observations. We present the most accurate spin ephemerides of the source so far: <jats:italic>ν</jats:italic> = 0.096008680(2) Hz, <jats:inline-formula> <jats:tex-math> <?CDATA $\dot{\nu }=-6.2(1)\times {10}^{-14}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mover accent="true"> <mml:mrow> <mml:mi>ν</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>̇</mml:mo> </mml:mrow> </mml:mover> <mml:mo>=</mml:mo> <mml:mo>−</mml:mo> <mml:mn>6.2</mml:mn> <mml:mo stretchy="false">(</mml:mo> <mml:mn>1</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>14</mml:mn> </mml:mrow> </mml:msup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac3756ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> Hz s<jats:sup>−1</jats:sup>, and significant second and third frequency derivative terms indicative of nonnegligible timing noise. The phase-averaged 0.8–7 keV spectrum is well fit with a double-blackbody (BB) model throughout the campaign. The BB temperatures remain constant at 0.46 and 1.2 keV. The areas and flux of each component decreased by a factor of 6, initially through a steep decay trend lasting about 46 days, followed by a shallow long-term one. The pulse shape in the same energy range is initially complex, exhibiting three distinct peaks, yet with clear continuous evolution throughout the outburst toward a simpler, single-pulse shape. The rms pulsed fraction is high and increases from about 40% to 50%. We find no dependence of pulse shape or fraction on energy. These results suggest that multiple hot spots, possibly possessing temperature gradients, emerged at outburst onset and shrank as the outburst decayed. We detect 84 faint bursts with NICER, having a strong preference for occurring close to the surface emission pulse maximum—the first time this phenomenon is detected in such a large burst sample. This likely implies a very low altitude for the burst emission region and a triggering mechanism connected to the surface active zone. Finally, our radio observations at several epochs and multiple frequencies reveal no evidence of pulsed or burst-like radio emission.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In this study, we analyze high-spatial-resolution (0.″24) magnetograms and high-spatial-resolution (0.″10) H<jats:italic>α</jats:italic> off-band (± 0.8 Å) images taken by the 1.6 m Goode Solar Telescope to investigate the magnetic properties associated with small-scale ejections in a coronal hole boundary region from a statistical perspective. With one and a half hours of optical observations under excellent seeing, we focus on the magnetic structure and evolution by tracking the magnetic features with the Southwest Automatic Magnetic Identification Suite (SWAMIS). The magnetic field at the studied coronal hole boundary is dominated by negative polarity with flux cancellations at the edges of the negative unipolar cluster. In a total of 1250 SWAMIS-detected magnetic cancellation events, ∼39% are located inside the coronal hole with an average flux cancellation rate of 2.0 × 10<jats:sup>18</jats:sup> Mx Mm<jats:sup>−2</jats:sup> hr<jats:sup>−1</jats:sup>, and ∼49% are located outside the coronal hole with an average flux cancellation rate of 8.8 × 10<jats:sup>17</jats:sup> Mx Mm<jats:sup>−2</jats:sup> hr<jats:sup>−1</jats:sup>. We estimated that the magnetic energy released due to flux cancellation inside the coronal hole is six times more than that outside the coronal hole. Flux cancellation accounts for ∼9.5% of the total disappearance of magnetic flux. Other forms of its disappearance are mainly due to fragmentation of unipolar clusters or merging with elements of the same polarity. We also observed a number of significant small-scale ejections associated with magnetic cancellations at the coronal hole boundary that have corresponding EUV brightenings.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Dust permeates the interstellar medium, reddening and polarizing background starlight, but dust properties vary with local environment. In order to characterize dust in a highly irradiated diffuse cloud, we measure the reddening and optical polarization toward 27 stars surrounding the midlatitude <jats:italic>b</jats:italic> = +24° O9.2IV star <jats:italic>ζ</jats:italic> Ophiuchi, using new optical spectroscopy and polarimetry. We incrementally deredden and depolarize with distance, allowing us to distinguish dust components along these sight lines. The data indicate three distinct dust populations: a foreground component characteristic of average Milky Way dust (<jats:italic>R</jats:italic> <jats:italic> <jats:sub>V</jats:sub> </jats:italic> ≈ 3.1, <jats:italic>d</jats:italic> ≲ 180 pc), a highly polarizing mid-distance component in the vicinity of <jats:italic>ζ</jats:italic> Oph (<jats:italic>R</jats:italic> <jats:italic> <jats:sub>V</jats:sub> </jats:italic> ≈ 2.4, 200 pc &lt; <jats:italic>d</jats:italic> &lt; 300 pc), and a nonpolarizing distant component (<jats:italic>R</jats:italic> <jats:italic> <jats:sub>V</jats:sub> </jats:italic> ≈ 3.6, 600 pc &lt; <jats:italic>d</jats:italic> &lt; 2000 pc). Prominent 8 <jats:italic>μ</jats:italic>m infrared striations spanning the field of view likely have high polycyclic aromatic hydrocarbon content and are illuminated by <jats:italic>ζ</jats:italic> Oph. Foreground-subtracted polarizations roughly align with these striations, which, we argue, lie immediately behind <jats:italic>ζ</jats:italic> Oph and constitute the highly polarizing mid-distance dust. This component polarizes very efficiently (<jats:italic>P</jats:italic> <jats:italic> <jats:sub>V</jats:sub> </jats:italic> &gt; 9.1<jats:italic>E</jats:italic>(<jats:italic>B</jats:italic> − <jats:italic>V</jats:italic>)), implying a high degree of grain alignment and suggesting that the bulk of the polarization occurs in a small fraction of the volume. The large <jats:italic>R</jats:italic> <jats:italic> <jats:sub>V</jats:sub> </jats:italic> in the distant component reveals that dust above the Galactic plane (<jats:italic>z</jats:italic> &gt; 250 pc) may contain a greater fraction of large grains than the Milky Way average.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>New spectroscopic parameters have been calculated to aid in the laboratory and observational detection of AlCH, AlCH<jats:sup>+</jats:sup>, MgCH, MgCH<jats:sup>+</jats:sup>, and their deuterated analogs. All species exist in <jats:italic>linear</jats:italic> geometry except for AlCH<jats:sup>+</jats:sup>, which exhibits a <jats:italic>bent</jats:italic> structure. Rotational frequencies have been calculated and the transition with maximum intensity is discussed for three temperature regions present in space: 100 K for a central circumstellar envelope (CSE), 30 K for an outer CSE, and 3 K indicative of the interstellar medium. Pertinent frequencies range from 25 to 250 GHz, depending on the species. At 30 K, the most intense transition is expected to be <jats:italic>J</jats:italic> = 4 → 3 for all species. The vibrational spectrum of each molecule is expected to be complicated due to the flat nature of the potential energy surface along the bending angle and the presence of anharmonic resonances. Deuteration produces a decrease in vibrational frequency, which may be utilized in experiments to confirm detection of these molecules. The electronic absorption spectrum of both AlCH and MgCH is predicted to be congested and broad. Various high-oscillator-strength transitions are predicted. Upon photoexcitation in the 220–300 nm region, facile dissociation on a repulsive excited state along the Al–C coordinate is predicted to be a source of Al in the colder regions of space. Photodissociation of MgCH requires several nonradiative processes that will control the product state distribution of the fragments.</jats:p>