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<jats:title>Abstract</jats:title> <jats:p>We present the first near-IR spectroscopy and joint analyses of multiwavelength observations for SDSS J082747.14+425241.1, a dust-reddened, weak broad emission-line quasar (WLQ) undergoing a remarkable broad-absorption line (BAL) transformation. The systemic redshift is more precisely measured to be <jats:italic>z</jats:italic> = 2.070 ± 0.001 using H<jats:italic>β</jats:italic> compared to <jats:italic>z</jats:italic> = 2.040 ± 0.003 using Mg <jats:sc>ii</jats:sc> from the literature, signifying an extreme Mg <jats:sc>ii</jats:sc> blueshift of 2140 ± 530 km s<jats:sup>−1</jats:sup> relative to H<jats:italic>β</jats:italic>. Using the H<jats:italic>β</jats:italic>-based single-epoch scaling relation with a systematic uncertainty of 0.3 dex, its black hole (BH) mass and Eddington ratio are estimated to be <jats:italic>M</jats:italic> <jats:sub>BH</jats:sub> ∼ 6.1 × 10<jats:sup>8</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> and <jats:italic>λ</jats:italic> <jats:sub>Edd</jats:sub> ∼ 0.71, indicative of being in a rapidly accreting phase. Our investigations confirm the WLQ nature and the LoBAL → HiBAL transformation, along with a factor of 2 increase in the Mg <jats:sc>ii</jats:sc>+Fe <jats:sc>ii</jats:sc> emission strength and a decrease of 0.1 in <jats:italic>E</jats:italic>(<jats:italic>B</jats:italic> − <jats:italic>V</jats:italic>) over two decades. The kinetic power of this LoBAL wind at <jats:italic>R</jats:italic> ∼ 15 pc from its BH is estimated to be ∼43% of the Eddington luminosity, sufficient for quasar feedback upon its host galaxy albeit with an order-of-magnitude uncertainty. This quasar provides a clear example of the long-sought scenario where LoBAL quasars are surrounded by dust cocoons, and wide-angle nuclear winds play a key role in the transition of red quasars evolving into the commonly seen blue quasars.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>MeV gamma-rays provide a unique window for the direct measurement of line emissions from radioisotopes, but observations have made little significant progress since COMPTEL on board the Compton Gamma-ray Observatory (CGRO). To observe celestial objects in this band, we are developing an electron-tracking Compton camera (ETCC) that realizes both bijective imaging spectroscopy and efficient background reduction gleaned from the recoil-electron track information. The energy spectrum of the observation target can then be obtained by a simple ON–OFF method using a correctly defined point-spread function on the celestial sphere. The performance of celestial object observations was validated on the second balloon SMILE-2+ , on which an ETCC with a gaseous electron tracker was installed that had a volume of 30 × 30 × 30 cm<jats:sup>3</jats:sup>. Gamma-rays from the Crab Nebula were detected with a significance of 4.0<jats:italic>σ</jats:italic> in the energy range 0.15–2.1 MeV with a live time of 5.1 hr, as expected before launch. Additionally, the light curve clarified an enhancement of gamma-ray events generated in the Galactic center region, indicating that a significant proportion of the final remaining events are cosmic gamma-rays. Independently, the observed intensity and time variation were consistent with the prelaunch estimates except in the Galactic center region. The estimates were based on the total background of extragalactic diffuse, atmospheric, and instrumental gamma-rays after accounting for the variations in the atmospheric depth and rigidity during the level flight. The Crab results and light curve strongly support our understanding of both the detection sensitivity and the background in real observations. This work promises significant advances in MeV gamma-ray astronomy.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The size of a disk encodes important information about its evolution. Combining new Submillimeter Array observations with archival Atacama Large Millimeter/submillimeter Array data, we analyze millimeter continuum and CO emission line sizes for a sample of 44 protoplanetary disks around stars with masses of 0.15–2 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> in several nearby star-forming regions. Sizes measured from <jats:sup>12</jats:sup>CO line emission span from 50 to 1000 au. This range could be explained by viscous evolution models with different <jats:italic>α</jats:italic> values (mostly of 10<jats:sup>−4</jats:sup>–10<jats:sup>−3</jats:sup>) and/or a spread of initial conditions. The CO sizes for most disks are also consistent with MHD wind models that directly remove disk angular momentum, but very large initial disk sizes would be required to account for the very extended CO disks in the sample. As no CO size evolution is observed across stellar ages of 0.5–20 Myr in this sample, determining the dominant mechanism of disk evolution will require a more complete sample for both younger and more evolved systems. We find that the CO emission is universally more extended than the continuum emission by an average factor of 2.9 ± 1.2. The ratio of the CO to continuum sizes does not show any trend with stellar mass, millimeter continuum luminosity, or the properties of substructures. The GO Tau disk has the most extended CO emission in this sample, with an extreme CO-to-continuum size ratio of 7.6. Seven additional disks in the sample show high size ratios (≳4) that we interpret as clear signs of substantial radial drift.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Stellar rotation is a complex function of mass, metallicity, and age and can be altered by binarity. To understand the importance of these parameters in main-sequence stars, we have assembled a sample of observations that spans a range of these parameters using a combination of observations from The Transiting Exoplanet Survey Satellite (TESS) and the Kepler Space Telescope. We find that while we can measure rotation periods and identify other classes of stellar variability (e.g., pulsations) from TESS light curves, instrument systematics prevent the detection of rotation signals longer than the TESS orbital period of 13.7 days. Due to this detection limit, we also use rotation periods constrained using rotational velocities measured by the APOGEE spectroscopic survey and radii estimated using the Gaia mission for both TESS and Kepler stars. From these rotation periods, we (1) find we can track rotational evolution along discrete mass tracks as a function of stellar age, (2) find we are unable to recover trends between rotation and metallicity that were observed by previous studies, and (3) note that our sample reveals that wide binary companions do not affect rotation, while close binary companions cause stars to exhibit more rapid rotation than single stars.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We report a timing analysis of near-infrared (NIR), X-ray, and submillimeter data during a 3 day coordinated campaign observing Sagittarius A*. Data were collected at 4.5 <jats:italic>μ</jats:italic>m with the Spitzer Space Telescope, 2–8 keV with the Chandra X-ray Observatory, 3–70 keV with NuSTAR, 340 GHz with ALMA, and 2.2 <jats:italic>μ</jats:italic>m with the GRAVITY instrument on the Very Large Telescope Interferometer. Two dates show moderate variability with no significant lags between the submillimeter and the infrared at 99% confidence. A moderately bright NIR flare (<jats:italic>F</jats:italic> <jats:sub>K</jats:sub> ∼ 15 mJy) was captured on July 18 simultaneous with an X-ray flare (<jats:italic>F</jats:italic> <jats:sub>2−10 keV</jats:sub> ∼ 0.1 counts s<jats:sup>−1</jats:sup>) that most likely preceded bright submillimeter flux (<jats:italic>F</jats:italic> <jats:sub>340 GHz</jats:sub> ∼ 5.5 Jy) by about <jats:inline-formula> <jats:tex-math> <?CDATA $+{34}_{-33}^{+14}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo>+</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>34</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>33</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>14</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac6104ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> minutes at 99% confidence. The uncertainty in this lag is dominated by the fact that we did not observe the peak of the submillimeter emission. A synchrotron source cooled through adiabatic expansion can describe a rise in the submillimeter once the synchrotron self-Compton NIR and X-ray peaks have faded. This model predicts high GHz and THz fluxes at the time of the NIR/X-ray peak and electron densities well above those implied from average accretion rates for Sgr A*. However, the higher electron density postulated in this scenario would be in agreement with the idea that 2019 was an extraordinary epoch with a heightened accretion rate. Since the NIR and X-ray peaks can also be fit by a nonthermal synchrotron source with lower electron densities, we cannot rule out an unrelated chance coincidence of this bright submillimeter flare with the NIR/X-ray emission.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We continue our comprehensive theoretical investigation of the spectral evolution of white dwarfs based on sophisticated simulations of element transport. In this paper, we focus on the transformation of PG 1159 stars into DO/DB white dwarfs due to the gravitational settling of heavy elements and then into DQ white dwarfs through the convective dredge-up of carbon. We study the impact of several physical parameters on the evolution of the surface carbon abundance over a wide range of effective temperatures. In the hot PG 1159 and DO phases, our calculations confirm that the temperature of the PG 1159-to-DO transition depends sensitively on the stellar mass and the wind mass-loss rate. We show that measured carbon abundances of DOZ white dwarfs are mostly accounted for by our models, with the notable exception of the coolest DOZ stars. In the cooler DB and DQ phases, the predicted atmospheric composition is strongly influenced by the stellar mass, the thickness of the envelope, the initial carbon content, the efficiency of convective overshoot, and the presence of residual hydrogen. We demonstrate that, under reasonable assumptions, our simulations reproduce very well the observed carbon abundance pattern of DQ stars, which thus allows us to constrain the extent of the overshoot region in cool helium-rich white dwarfs. We also argue that our calculations naturally explain a number of recent empirical results, such as the relative excess of low-mass DQ stars and the presence of trace hydrogen and/or carbon at the surface of most DC and DZ stars.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In galactic nuclei, the gravitational potential is dominated by the central supermassive black hole, so stars follow quasi-Keplerian orbits. These orbits are distorted by gravitational forces from other stars, leading to long-term orbital relaxation. The direct numerical study of these processes is challenging because the fast orbital motion imposed by the central black hole requires very small timesteps. An alternative approach, pioneered by Gauß, is to use the secular approximation of smearing out <jats:italic>N</jats:italic> stars over their Keplerian orbits, using <jats:italic>K</jats:italic> nodes along each orbit. In this study, we propose three novel improvements to this method. First, we reformulate the discretization of the rates of change of the variables describing the orbital states to ensure that all conservation laws are exactly satisfied. Second, we replace the pairwise sum over nodes by a multipole expansion up to order <jats:inline-formula> <jats:tex-math> <?CDATA ${{\ell }}_{\max }$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi mathvariant="italic">ℓ</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>max</mml:mi> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac602eieqn1.gif" xlink:type="simple" /> </jats:inline-formula>, reducing the overall computational cost from <jats:italic>O</jats:italic>(<jats:italic>N</jats:italic> <jats:sup>2</jats:sup> <jats:italic>K</jats:italic> <jats:sup>2</jats:sup>) to <jats:inline-formula> <jats:tex-math> <?CDATA $O({NK}{{\ell }}_{\max }^{2})$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>O</mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:mi mathvariant="italic">NK</mml:mi> <mml:msubsup> <mml:mrow> <mml:mi mathvariant="italic">ℓ</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>max</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msubsup> <mml:mo stretchy="false">)</mml:mo> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac602eieqn2.gif" xlink:type="simple" /> </jats:inline-formula>. Finally, we show that the averaged dynamical system is equivalent to 2<jats:italic>N</jats:italic> interacting unit spin vectors and provide two time integrators: a second-order symplectic scheme, and a fourth-order Lie-group Runge–Kutta method, both of which are straightforward to generalize to higher order. These new simulations recover the diffusion coefficients of stellar eccentricities obtained through analytical calculations of the secular dynamics.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We estimate the parameters of the donor of the accreting black hole binary MAXI J1820+070. The measured values of the binary period, rotational and radial velocities, and constraints on the orbital inclination imply the donor is a subgiant with the mass of <jats:inline-formula> <jats:tex-math> <?CDATA ${M}_{2}\approx {0.49}_{-0.10}^{+0.10}{M}_{\odot }$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msub> <mml:mo>≈</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>0.49</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.10</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.10</mml:mn> </mml:mrow> </mml:msubsup> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>☉</mml:mo> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac6099ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> and the radius of <jats:inline-formula> <jats:tex-math> <?CDATA ${R}_{2}\approx {1.19}_{-0.08}^{+0.08}{R}_{\odot }$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>R</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msub> <mml:mo>≈</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>1.19</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.08</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.08</mml:mn> </mml:mrow> </mml:msubsup> <mml:msub> <mml:mrow> <mml:mi>R</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>☉</mml:mo> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac6099ieqn2.gif" xlink:type="simple" /> </jats:inline-formula>. We reanalyze the previously obtained optical spectrum from the Gran Telescopio Canarias and found it yields a strict lower limit on the effective temperature of <jats:italic>T</jats:italic> &gt; 4200 K. We compile optical and infrared fluxes observed during the quiescence of this system. From the minima <jats:italic>r</jats:italic>- and <jats:italic>i</jats:italic>-band fluxes found in Pan-STARSS1 Data Release 2 prediscovery imaging and for a distance of <jats:italic>D</jats:italic> ≈ 3 kpc, reddening of <jats:italic>E</jats:italic>(<jats:italic>B </jats:italic>–<jats:italic> V</jats:italic>) = 0.23, and <jats:italic>R</jats:italic> <jats:sub>2</jats:sub> ≈ 1.11<jats:italic>R</jats:italic> <jats:sub>⊙</jats:sub>, we find <jats:italic>T</jats:italic> ≲ 4230 K, very close to the above lower limit. For a larger distance, the temperature can be higher, up to about 4500 K (corresponding to a K5 spectral type, preferred by previous studies) at <jats:italic>D</jats:italic> = 3.5 kpc, allowed by the Gaia parallax. We perform evolutionary calculations for the binary system and compare them to the observational constraints. Our model fitting the above temperature and radius constraints at <jats:italic>D</jats:italic> ≈ 3 kpc has a mass of 0.4<jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>, <jats:italic>T</jats:italic> ≈ 4200 K, and solar metallicity. Two alternative models require <jats:italic>D</jats:italic> ≳ 3.3–3.4 kpc at 0.4<jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>, <jats:italic>T</jats:italic> ≈ 4500 K and half-solar metallicity, and 0.5<jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>, <jats:italic>T</jats:italic> ≈ 4300 K, and solar metallicity. These models yield mass-transfer rates of ∼10<jats:sup>−10</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> yr<jats:sup>−1</jats:sup>, compatible with those based on the estimated accreted mass of ≈2 × 10<jats:sup>25</jats:sup> g and the time between the 2018 discovery and the 1934 historical outburst.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We report on the first uniform and systematic study of dust and molecular gas in nearby molecular clouds. We use surveys of dust extinction and emission to determine the opacity and map the distribution of the dust within a dozen local clouds in order to derive a uniform set of basic cloud properties. We find (1) the average dust opacity 〈<jats:italic>κ</jats:italic> <jats:sub> <jats:italic>d</jats:italic>,353</jats:sub>〉 = 0.8 cm<jats:sup>2</jats:sup> g<jats:sup>−1</jats:sup> with variations of a factor of ∼2 between clouds, (2) cloud probability density functions are exquisitely described by steeply falling power laws with a narrow range of slope, and (3) a tight <jats:inline-formula> <jats:tex-math> <?CDATA ${M}_{\mathrm{GMC}}\sim {R}_{\mathrm{GMC}}^{2}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>GMC</mml:mi> </mml:mrow> </mml:msub> <mml:mo>∼</mml:mo> <mml:msubsup> <mml:mrow> <mml:mi>R</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>GMC</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac5d58ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> scaling relation for the cloud sample, indicative of a cloud population with an exactingly constant average surface density above a common fixed boundary. We compare these results to uniformly analyzed CO surveys. We measure the CO mass conversion factors and assess the efficacy of CO for tracing the physical properties of molecular clouds. We find 〈<jats:italic>α</jats:italic> <jats:sub>CO</jats:sub>〉 = 4.31 ± 0.67 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> (K km s<jats:sup>−1</jats:sup> pc<jats:sup>2</jats:sup>)<jats:sup>−1</jats:sup> (corresponding to <jats:italic>X</jats:italic> <jats:sub>CO</jats:sub> = 1.97 ×10<jats:sup>20</jats:sup> cm<jats:sup>−2</jats:sup>(K km s<jats:sup>−1</jats:sup>)<jats:sup>−1</jats:sup>). We demonstrate that CO observations are a poor tracer of column density and structure on sub-cloud spatial scales. On cloud scales, CO observations can provide measurements consistent with those of the dust, provided data are analyzed in a similar, self-consistent fashion. Measurements of average giant molecular cloud surface density are sensitive to choice of cloud boundary. Care must be exercised to adopt common fixed boundaries when comparing surface densities for cloud populations within and between galaxies.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Hot and warm Jupiters (HJs and WJs, correspondingly) are gas giants orbiting their host stars at very short orbital periods (<jats:italic>P</jats:italic> <jats:sub>HJ</jats:sub> &lt; 10 days; 10 &lt; <jats:italic>P</jats:italic> <jats:sub>WJ</jats:sub> &lt; 200 days). HJs and a significant fraction of WJs are thought to have migrated from initially farther-out birth locations. While such migration processes have been extensively studied, the thermal evolution of gas giants and its coupling with migration processes are usually overlooked. In particular, gas giants end their core accretion phase with large radii, then contract slowly to their final radii. Moreover, intensive heating can slow the contraction at various evolutionary stages. The initial large inflated radii lead to faster tidal migration, due to the strong dependence of tides on the radius. Here, we explore this accelerated migration channel, which we term inflated eccentric migration, using a semi-analytical, self-consistent model of the thermal–dynamical evolution of the migrating gas giants, later validated by our numerical model (see the companion paper, paper II). We demonstrate our model for specific examples and carry out a population synthesis study. Our results provide a general picture of the properties of the formed HJs and WJs via inflated migration, and their dependence on the initial parameters/distributions. We show that the tidal migration of gas giants could occur much more rapidly then previously thought, and could lead to the accelerated destruction and formation of HJs and an enhanced formation rate for WJs. Accounting for the coupled thermal–dynamical evolution is therefore critical to understanding the formation of HJs/WJs, and the evolution and final properties of the population, and it plays a key role in their migration processes.</jats:p>