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<jats:title>Abstract</jats:title> <jats:p>Compact object mergers which produce both detectable gravitational waves and electromagnetic (EM) emission can provide valuable insights into the neutron star equation of state, the tension in the Hubble constant, and the origin of the <jats:italic>r</jats:italic>-process elements. However, EM follow-up of gravitational wave sources is complicated by false-positive detections, and the transient nature of the associated EM emission. <jats:monospace>GWSkyNet-Multi</jats:monospace> is a machine learning model that attempts facilitate EM follow-up by providing real-time predictions of the source of a gravitational wave detection. The model uses information from Open Public Alerts (OPAs) released by LIGO–Virgo within minutes of a gravitational wave detection. <jats:monospace>GWSkyNet</jats:monospace> was introduced in Cabero et al. as a binary classifier and uses the OPA skymaps to classify sources as either astrophysical or as glitches. In this paper, we introduce <jats:monospace>GWSkyNet-Multi</jats:monospace>, an extension of <jats:monospace>GWSkyNet</jats:monospace> which further distinguishes sources as binary black hole mergers, mergers involving a neutron star, or non-astrophysical glitches. <jats:monospace>GWSkyNet-Multi</jats:monospace> is a sequence of three one-versus-all classifiers trained using a class-balanced and physically motivated source mass distribution. Training on this data set, we obtain test set accuracies of 93.7% for binary black hole-versus-all, 94.4% for neutron star-versus-all, and 95.1% for glitch-versus-all. We obtain an overall accuracy of 93.4% using a hierarchical classification scheme. Furthermore, we correctly identify 36 of the 40 gravitational wave detections from the first half of LIGO–Virgo’s third observing run (O3a) and present predictions for O3b sources. As gravitational wave detections increase in number and frequency, <jats:monospace>GWSkyNet-Multi</jats:monospace> will be a powerful tool for prioritizing successful EM follow-up.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The surface temperature distributions of central compact objects (CCOs) are powerful probes of their crustal magnetic field strengths and geometries. Here we model the surface temperature distribution of RX J0822−4300, the CCO in the Puppis A supernova remnant, using 471 ks of XMM-Newton data. We compute the energy-dependent pulse profiles in 16 energy bands, fully including the general relativistic effects of gravitational redshift and light bending, to accurately model the two heated surface regions of different temperatures and areas, in addition to constraining the viewing geometry. This results in precise measurements of the two temperatures: <jats:inline-formula> <jats:tex-math> <?CDATA ${{kT}}_{\mathrm{warm}}=(1+z)\times {0.222}_{-0.019}^{+0.018}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi mathvariant="italic">kT</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>warm</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mo stretchy="false">(</mml:mo> <mml:mn>1</mml:mn> <mml:mo>+</mml:mo> <mml:mi>z</mml:mi> <mml:mo stretchy="false">)</mml:mo> <mml:mo>×</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>0.222</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.019</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.018</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac4d9aieqn1.gif" xlink:type="simple" /> </jats:inline-formula> keV and <jats:italic>kT</jats:italic> <jats:sub>hot</jats:sub> = (1 + <jats:italic>z</jats:italic>) × 0.411 ± 0.011 keV. The two heated surface regions are likely located very close to the rotational poles, with the most probable position of the hotter component ≈ 6° from the rotational pole. For the first time, we are able to measure a deviation from a pure antipodal hot-spot geometry, with a longitudinal offset <jats:inline-formula> <jats:tex-math> <?CDATA ${\delta }_{\gamma }=11\buildrel{\circ}\over{.} {7}_{-2\buildrel{\circ}\over{.} \,5}^{+2\buildrel{\circ}\over{.} \,6}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>δ</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>γ</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>11</mml:mn> <mml:mo>.°</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>7</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>2</mml:mn> <mml:mo>.°</mml:mo> <mml:mspace width="0.25em" /> <mml:mn>5</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>2</mml:mn> <mml:mo>.°</mml:mo> <mml:mspace width="0.25em" /> <mml:mn>6</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac4d9aieqn2.gif" xlink:type="simple" /> </jats:inline-formula>. The discovery of this asymmetry, along with the factor of ≈2 temperature difference between the two emitting regions, may indicate that RX J0822−4300 was born with a strong, tangled crustal magnetic field.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>This work examines the recent X-ray observations of the active galactic nucleus KIC 11606854 (nicknamed “Spikey”) by the Chandra space telescope. Based on previous observations of a symmetric flare in the system’s light curve by the Kepler space telescope, Spikey has been proposed to be a self-lensing supermassive black hole binary system in which the more massive black hole gravitationally lenses the accretion flow of its smaller companion. The recent Chandra observations (2020 March–May) correspond to the time when the next pulse was expected to occur and were separated in enough time to observe the apparent relativistic Doppler boosting effect from the high orbital velocities of the black holes. We model the expected self-lensing plus Doppler boosting light curve using our wavelength-dependent extended source self-lensing model combined with our relativistic orbital motion code. This orbital motion code is capable of modeling the expected apsidal precession for Spikey, which can be used to predict future pulses. We show that the expected signal was undetectable in the Chandra data as the intrinsic X-ray variability associated with the system was large relative to the changes expected by self-lensing and Doppler boosting. Expected flux increases in more favorable wavelengths were also calculated using our wavelength-dependent self-lensing model, revealing a relationship between the observing wavelength and measured orbital inclination.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present the average gas properties derived from Atacama Large Millimeter Array (ALMA) Band 6 dust continuum imaging of 126 massive (log <jats:italic>M</jats:italic> <jats:sub>⋆</jats:sub>/<jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> ≳ 10.5), star-forming cluster galaxies across 11 galaxy clusters at <jats:italic>z</jats:italic> = 1–1.75. Using stacking analysis on the ALMA images, combined with UV–far-infrared data, we quantify the average infrared spectral energy distributions (SEDs) and gas properties (molecular gas masses, <jats:italic>M</jats:italic> <jats:sub>mol</jats:sub>;gas depletion timescales, <jats:italic>τ</jats:italic> <jats:sub>depl</jats:sub>; and gas fractions, f<jats:sub>gas</jats:sub>) as functions of cluster-centric radius and properties including stellar mass and distance from the main sequence. We find a significant dearth in the ALMA fluxes relative to that expected in the field—with correspondingly low <jats:italic>M</jats:italic> <jats:sub>mol</jats:sub> and f<jats:sub>gas</jats:sub>, and short <jats:italic>τ</jats:italic> <jats:sub>depl</jats:sub>—with weak or no dependence on cluster-centric radius out to twice the virial radius. The Herschel+ALMA SEDs indicate warmer dust temperatures (∼36–38 K) than coeval field galaxies (∼30 K). We perform a thorough comparison of the cluster galaxy gas properties to field galaxies, finding deficits of 2–3×, 3–4×, and 2–4× in <jats:italic>M</jats:italic> <jats:sub>mol</jats:sub>, <jats:italic>τ</jats:italic> <jats:sub>depl</jats:sub>, and f<jats:sub>gas</jats:sub> compared to coeval field stacks, and larger deficits compared to field scaling relations built primarily on detections. The cluster gas properties derived here are comparable with stacking analyses of (proto-)clusters in the literature, and at odds with findings of field-like <jats:italic>τ</jats:italic> <jats:sub>depl</jats:sub> and enhanced f<jats:sub>gas</jats:sub> reported using CO and dust continuum detections. Our analysis suggests that environment has a considerable impact on gas properties out to large radii, in good agreement with cosmological simulations which project that gas depletion begins beyond the virial radius and largely completes by first passage of the cluster core.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present the largest systematic, Hubble Space Telescope (HST)–based search to date for luminous <jats:italic>z</jats:italic> ≳ 8 galaxy candidates using ∼1267 arcmin<jats:sup>2</jats:sup> of (pure-)parallel observations from a compilation of 288 random sightlines with Advanced Camera for Surveys and Wide Field Camera 3 observations, derived from the (Super)Brightest of Reionizing Galaxies (SuperBoRG) data set and together representing a factor ∼1.12× larger than existing space-based data sets. Using near-infrared (NIR) color cuts and careful photo-<jats:italic>z</jats:italic> analyses, we find 31 <jats:italic>z</jats:italic> ≳ 8 galaxy candidates over 29 unique sightlines, and derive global galaxy properties such as <jats:italic>UV</jats:italic> magnitudes and continuum slopes, sizes, and rest-frame optical properties (e.g., star formation rates (SFRs), stellar masses, <jats:italic>A</jats:italic> <jats:sub>v</jats:sub>). Taking advantage of the (pure-)parallel nature of our data set—making it one of the most representative thus far—and derived SFRs, we evaluate the cosmic SFR density for the bright end of the <jats:italic>UV</jats:italic> luminosity function (LF) at <jats:italic>z</jats:italic> ∼ 8–10 and test the validity of luminosity-function-derived results using a conversion factor. We find that our method yields comparable results to those derived with LFs. Furthermore, we present follow-up observations of five (Super)BoRG targets with the Keck Multi-Object Spectrometer For Infra-Red Exploration (MOSFIRE) instrument, finding no evidence of Ly<jats:italic>α</jats:italic> in &gt;3 hr of <jats:italic>Y</jats:italic>-band observations in either, consistent with a largely neutral medium at <jats:italic>z</jats:italic> ∼ 8. Our results offer a definitive HST legacy on the bright end of the LF and provide a valuable benchmark as well as targets for follow-up with the James Webb Space Telescope.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We study the early growth of massive seed black holes (BHs) via accretion in protogalactic nuclei where the stellar bulge component is assembled, performing axisymmetric two-dimensional radiation hydrodynamical simulations. We find that when a seed BH with <jats:italic>M</jats:italic> <jats:sub>•</jats:sub> ∼ 10<jats:sup>5</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> is embedded in dense metal-poor gas (<jats:italic>Z</jats:italic> = 0.01 <jats:italic>Z</jats:italic> <jats:sub>⊙</jats:sub>) with a density of ≳ 100 cm<jats:sup>−3</jats:sup> and bulge stars with a total mass of <jats:italic>M</jats:italic> <jats:sub>⋆</jats:sub> ≳ 100 <jats:italic>M</jats:italic> <jats:sub>•</jats:sub>, a massive gaseous disk feeds the BH efficiently at rates of ≳ 0.3–1 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> yr<jats:sup>−1</jats:sup>, and the BH mass increases nearly tenfold within ∼2 Myr. This rapid accretion phase lasts until a good fraction of the gas bounded within the bulge accretes onto the BH, although the feeding rate is regulated owing to strong outflows driven by ionizing radiation emitted from the accreting BH. The transient growing mode can be triggered for seed BHs formed in massive dark-matter halos with masses of ≳ 10<jats:sup>9</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> at <jats:italic>z</jats:italic> ∼ 15–20 (the virial temperature is <jats:italic>T</jats:italic> <jats:sub>vir</jats:sub> ≃ 10<jats:sup>5</jats:sup> K). The host halos are heavier and rarer than those of typical first galaxies, but are more likely to end up in quasar hosts by <jats:italic>z</jats:italic> ≃ 6. This mechanism naturally yields a mass ratio of <jats:italic>M</jats:italic> <jats:sub>•</jats:sub>/<jats:italic>M</jats:italic> <jats:sub>⋆</jats:sub> &gt; 0.01 higher than the value seen in the local universe. The existence of such overmassive BHs provides us with a unique opportunity to detect highly accreting seed BHs at <jats:italic>z</jats:italic> ∼ 15 with AB magnitude of <jats:italic>m</jats:italic> <jats:sub>AB</jats:sub> ∼ 26–29 mag at 2 <jats:italic>μ</jats:italic>m (rest frame 10 eV) by the upcoming observations by the James Webb Space Telescope and Nancy Grace Roman Space Telescope.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>A 3D fully self-consistent multifluid hydrodynamic aeronomy model is applied to simulate the hydrogen-helium expanding upper atmosphere of the hot Jupiter HD189733b, and related absorption in the Ly<jats:italic>α</jats:italic> line and the 10830 Å line of metastable helium. We studied the influence of a high-energy stellar flux, a stellar wind, and Ly<jats:italic>α</jats:italic> cooling to reproduce the available observations. We found that to fit the width of the absorption profile of the 10830 Å line the escaping upper atmosphere of the planet should be close to the energy-limited escape achieved with significantly reduced Ly<jats:italic>α</jats:italic> cooling at the altitudes with an H <jats:sc>i</jats:sc> density higher than 3 × 10<jats:sup>6</jats:sup> cm<jats:sup>−3</jats:sup>. Based on the performed simulations, we constrain the helium abundance in the upper atmosphere of HD189733b to be a rather low value of He/H ∼ 0.005. We show that under the conditions of a moderate stellar wind similar to that of the Sun the absorption of the Ly<jats:italic>α</jats:italic> line takes place mostly within the Roche lobe due to thermal broadening at a level of about 7%. For an order of magnitude stronger wind, a significant absorption of about 15% at high blueshifted velocities of up to 100 km s<jats:sup>−1</jats:sup> is generated in the bowshock region, due to Doppler broadening. These blueshifted velocities are still lower than those (∼200 km s<jats:sup>−1</jats:sup>) detected in one of the observations. We explain the differences between the performed observations, though not in all of the details, by stellar activity and the related fluctuations of the ionizing radiation (in the case of the 10830 Å line), and the stellar wind (in the case of the Ly<jats:italic>α</jats:italic> line).</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present two bright galaxy candidates at <jats:italic>z</jats:italic> ∼ 12–13 identified in our <jats:italic>H</jats:italic>-dropout Lyman break selection with 2.3 deg<jats:sup>2</jats:sup> near-infrared deep imaging data. These galaxy candidates, selected after careful screening of foreground interlopers, have spectral energy distributions showing a sharp discontinuity around 1.7 <jats:italic>μ</jats:italic>m, a flat continuum at 2–5 <jats:italic>μ</jats:italic>m, and nondetections at &lt;1.2 <jats:italic>μ</jats:italic>m in the available photometric data sets, all of which are consistent with a <jats:italic>z</jats:italic> &gt; 12 galaxy. An ALMA program targeting one of the candidates shows a tentative 4<jats:italic>σ</jats:italic> [O <jats:sc>iii</jats:sc>] 88 <jats:italic>μ</jats:italic>m line at <jats:italic>z</jats:italic> = 13.27, in agreement with its photometric redshift estimate. The number density of the <jats:italic>z</jats:italic> ∼ 12–13 candidates is comparable to that of bright <jats:italic>z</jats:italic> ∼ 10 galaxies and is consistent with a recently proposed double-power-law luminosity function rather than the Schechter function, indicating little evolution in the abundance of bright galaxies from <jats:italic>z</jats:italic> ∼ 4 to 13. Comparisons with theoretical models show that the models cannot reproduce the bright end of rest-frame ultraviolet luminosity functions at <jats:italic>z</jats:italic> ∼ 10–13. Combined with recent studies reporting similarly bright galaxies at <jats:italic>z</jats:italic> ∼ 9–11 and mature stellar populations at <jats:italic>z</jats:italic> ∼ 6–9, our results indicate the existence of a number of star-forming galaxies at <jats:italic>z</jats:italic> &gt; 10, which will be detected with upcoming space missions such as the James Webb Space Telescope, Nancy Grace Roman Space Telescope, and GREX-PLUS.</jats:p>