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<jats:title>Abstract</jats:title> <jats:p>We present <jats:monospace>GIGANTES</jats:monospace>, the most extensive and realistic void catalog suite ever released—containing over 1 billion cosmic voids covering a volume larger than the observable universe, more than 20 TB of data, and created by running the void finder <jats:monospace>VIDE</jats:monospace> on <jats:monospace>QUIJOTE</jats:monospace>’s halo simulations. The <jats:monospace>GIGANTES</jats:monospace> suite, spanning thousands of cosmological models, opens up the study of voids, answering compelling questions: Do voids carry unique cosmological information? How is this information correlated with galaxy information? Leveraging the large number of voids in the <jats:monospace>GIGANTES</jats:monospace> suite, our Fisher constraints demonstrate voids contain additional information, critically tightening constraints on cosmological parameters. We use traditional void summary statistics (void size function, void density profile) and the void autocorrelation function, which independently yields an error of 0.13 eV on ∑ <jats:italic>m</jats:italic> <jats:sub> <jats:italic>ν</jats:italic> </jats:sub> for a 1 <jats:italic>h</jats:italic> <jats:sup>−3</jats:sup> Gpc<jats:sup>3</jats:sup> simulation, without cosmic microwave background priors. Combining halos and voids we forecast an error of 0.09 eV from the same volume, representing a gain of 60% compared to halos alone. Extrapolating to next generation multi-Gpc<jats:sup>3</jats:sup> surveys such as the Dark Energy Spectroscopic Instrument, Euclid, the Spectro-Photometer for the History of the Universe and Ices Explorer, and the Roman Space Telescope, we expect voids should yield an independent determination of neutrino mass. Crucially, <jats:monospace>GIGANTES</jats:monospace> is the first void catalog suite expressly built for intensive machine-learning exploration. We illustrate this by training a neural network to perform likelihood-free inference on the void size function, giving a ∼20% constraint on Ω<jats:sub>m</jats:sub>. Cosmology problems provide an impetus to develop novel deep-learning techniques. With <jats:monospace>GIGANTES</jats:monospace>, machine learning gains an impressive data set, offering unique problems that will stimulate new techniques.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Aimed at the detection of cosmological gas being accreted onto galaxies in the local universe, we examined the H<jats:italic>α</jats:italic> emission in the halo of 164 galaxies in the field of view of the Multi-Unit Spectroscopic Explorer Wide survey (MUSE-Wide) with observable H<jats:italic>α</jats:italic> (redshift &lt;0.42). An exhaustive screening of the corresponding H<jats:italic>α</jats:italic> images led us to select 118 reliable H<jats:italic>α</jats:italic> emitting gas clouds. The signals are faint, with a surface brightness of <jats:inline-formula> <jats:tex-math> <?CDATA ${10}^{-17.3\pm 0.3}\,\mathrm{erg}\,{{\rm{s}}}^{-1}\,{\mathrm{cm}}^{-2}\,{\mathrm{arcsec}}^{-2}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msup> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>17.3</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.3</mml:mn> </mml:mrow> </mml:msup> <mml:mspace width="0.25em" /> <mml:mi>erg</mml:mi> <mml:mspace width="0.25em" /> <mml:msup> <mml:mrow> <mml:mi mathvariant="normal">s</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> <mml:mspace width="0.25em" /> <mml:msup> <mml:mrow> <mml:mi>cm</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> <mml:mspace width="0.25em" /> <mml:msup> <mml:mrow> <mml:mi>arcsec</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac7319ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>. Through statistical tests and other arguments, we ruled out that they are created by instrumental artifacts, telluric line residuals, or high-redshift interlopers. Around 38% of the time, the H<jats:italic>α</jats:italic> line profile shows a double peak with the drop in intensity at the rest frame of the central galaxy, and with a typical peak-to-peak separation of the order of ±200 km s<jats:sup>−1</jats:sup>. Most line emission clumps are spatially unresolved. The mass of emitting gas is estimated to be between 1 and 10<jats:sup>−3</jats:sup> times the stellar mass of the central galaxy. The signals are not isotropically distributed; their azimuth tends to be aligned with the major axis of the corresponding galaxy. The distances to the central galaxies are not random either. The counts drop at a distance &gt;50 galaxy radii, which roughly corresponds to the virial radius of the central galaxy. We explore several physical scenarios to explain this H<jats:italic>α</jats:italic> emission, among which accretion disks around rogue intermediate-mass black holes fit the observations best.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The currently available, detailed properties (e.g., isotopic ratios) of solar system planets may provide guides for constructing better approaches to exoplanet characterization. With this motivation, we explore how the measured values of the deuterium-to-hydrogen (D/H) ratio of Uranus and Neptune can constrain their formation mechanisms. Under the assumption of in situ formation, we investigate three solid accretion modes: a dominant accretion mode switches from pebble accretion to drag-enhanced three-body accretion and to canonical planetesimal accretion, as the solid radius increases. We consider a wide radius range of solids that are accreted onto (proto)Neptune-mass planets and compute the resulting accretion rate as a function of both the solid size and the solid surface density. We find that for small-sized solids, the rate becomes high enough to halt concurrent gas accretion if all the solids have the same size. For large-sized solids, the solid surface density needs to be enhanced to accrete enough amounts of solids within the gas disk lifetime. We apply these accretion modes to the formation of Uranus and Neptune and show that if the minimum-mass solar nebula model is adopted, solids with a radius of ∼1 m to ∼10 km should have contributed mainly to their deuterium enrichment; a tighter constraint can be derived if the full solid size distribution is determined. This work therefore demonstrates that the D/H ratio can be used as a tracer of solid accretion onto Neptune-mass planets. Similar efforts can be made for other atomic elements that serve as metallicity indicators.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We report on VLT/FORS2 imaging polarimetry observations in the <jats:italic>R</jats:italic> <jats:sub>Special</jats:sub> band of WISE J011601.41–050504.0 (W0116–0505), a heavily obscured hyperluminous quasar at <jats:italic>z</jats:italic> = 3.173 classified as a Hot Dust-obscured Galaxy (Hot DOG) based on its mid-IR colors. Recently, Assef et al. identified W0116–0505 as having excess rest-frame optical/UV emission and concluded that this excess emission is most likely scattered light from the heavily obscured AGN. We find that the broadband rest-frame UV flux is strongly linearly polarized (10.8% ± 1.9%, with a polarization angle of 74° ± 9°), confirming this conclusion. We analyze these observations in the context of a simple model based on scattering either by free electrons or by optically thin dust, assuming a classical dust torus with polar openings. Both can replicate the degree of polarization and the luminosity of the scattered component for a range of geometries and column densities, but we argue that optically thin dust in the ISM is the more likely scenario. We also explore the possibility that the scattering medium corresponds to an outflow recently identified for W0116–0505. This is a feasible option if the outflow component is biconical with most of the scattering occurring at the base of the receding outflow. In this scenario, the quasar would still be obscured even if viewed face-on but might appear as a reddened type 1 quasar once the outflow has expanded. We discuss a possible connection between blue-excess Hot DOGs, extremely red quasars, reddened type 1 quasars, and unreddened quasars that depends on a combination of evolution and viewing geometry.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We studied the light curves of GJ 1243, YZ CMi, and V374 Peg, as observed by TESS, for the presence of stellar spots and stellar flares. One of the main goals was to model the light curves of the spotted stars to estimate the number of spots, along with their parameters, using our original <jats:monospace>BASSMAN</jats:monospace> software. The modeled light curves were subtracted from the observations to increase the efficiency of the flare detection. The flares were detected automatically with our new dedicated software, <jats:monospace>WARPFINDER</jats:monospace>. We estimated the presence of two spots on GJ 1243, with a mean temperature of about 2800 K and a spottedness varying between 3% and 4% of the stellar surface, and two spots on V374 Peg, with a mean temperature of about 3000 K and a spottedness of about 6% of the stellar surface. On YZ CMi, we found two different models for two light curves separated in time by 1.5 yr. One of them was a three-spot model, with a mean temperature of about 3000 K and a spottedness of about 9% of the stellar surface. The second was a four-spot model, with a mean temperature of about 2800 K and a spottedness of about 7% of the stellar surface. We tested whether the flares were distributed homogeneously in phase and where there was any correlation between the presence of spots and the distribution of the flares. For YZ CMi, one spot was in anticorrelation with the distribution of the flares, while GJ 1243 shows the nonhomogeneous distribution of flares.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>A thermonuclear explosion triggered by a He-shell detonation on a carbon–oxygen white-dwarf core has been predicted to have strong UV line blanketing at early times due to the iron-group elements produced during He-shell burning. We present the photometric and spectroscopic observations of SN 2016dsg, a subluminous peculiar Type I supernova consistent with a thermonuclear explosion involving a thick He shell. With a redshift of 0.04, the <jats:italic>i</jats:italic>-band peak absolute magnitude is derived to be around −17.5. The object is located far away from its host, an early-type galaxy, suggesting it originated from an old stellar population. The spectra collected after the peak are unusually red, show strong UV line blanketing and weak O <jats:sc>i</jats:sc> <jats:italic>λ</jats:italic>7773 absorption lines, and do not evolve significantly over 30 days. An absorption line around 9700–10500 Å is detected in the near-infrared spectrum and is likely from the unburnt He in the ejecta. The spectroscopic evolution is consistent with the thermonuclear explosion models for a sub-Chandrasekhar-mass white dwarf with a thick He shell, while the photometric evolution is not well described by existing models.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The ice shell and subsurface ocean on icy worlds are strongly coupled together—heat and salinity flux from the ice shell induced by the ice thickness gradient drives circulation in the ocean, and in turn, the heat transport by ocean circulation shapes the ice shell. Since measurements in the near future are likely to remain constrained to above the ice shell, understanding this ocean−ice interaction is crucial. Using an ocean box model and a series of experiments simulating the 2D ocean circulation, we find that large icy moons with strong gravity tend to have stronger ocean heat transport under the same ice shell topography. As a result, the equilibrium ice shell geometry is expected to be flatter on moons with larger size, and vice versa. This finding is broadly consistent with the observed ice shell geometry for Enceladus and Europa.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In order to bridge the gap between heliospheric and solar observations of coronal mass ejections (CMEs), one of the key steps is to improve the understanding of their corresponding magnetic structures like the magnetic flux ropes (MFRs). But it remains a challenge to confirm the existence of a coherent MFR before or upon the CME eruption on the Sun and to quantitatively characterize the CME-MFR due to the lack of direct magnetic field measurements in the corona. In this study, we investigate MFR structures originating from two active regions (ARs), AR 11719 and AR 12158, and estimate their magnetic properties quantitatively. We perform nonlinear force-free field extrapolations with preprocessed photospheric vector magnetograms. In addition, remote-sensing observations are employed to find indirect evidence of MFRs on the Sun and to analyze the time evolution of magnetic reconnection flux associated with the flare ribbons during the eruption. A coherent “preexisting” MFR structure prior to the flare eruption is identified quantitatively for one event from the combined analysis of the extrapolation and observation. Then the characteristics of MFRs for two events on the Sun before and during the eruption forming the CME-MFR, including the axial magnetic flux, field line twist, and reconnection flux, are estimated and compared with the corresponding in situ modeling results. We find that the magnetic reconnection associated with the accompanying flares for both events injects a significant amount of flux into the erupted CME-MFRs.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present a study of the relationship between Galactic kinematics, flare rates, chromospheric activity, and rotation periods for a volume-complete, nearly all-sky sample of 219 single stars within 15 pc and with masses between 0.1 and 0.3 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> observed during the primary mission of TESS. We find all stars consistent with a common value of <jats:italic>α</jats:italic> = 1.984 ± 0.019 for the exponent of the flare frequency distribution. Using our measured stellar radial velocities and Gaia astrometry, we determine Galactic <jats:italic>UVW</jats:italic> space motions. We find 78% of stars are members of the Galactic thin disk, 7% belong to the thick disk, and for the remaining 15% we cannot confidently assign membership to either component. If we assume star formation has been constant in the thin disk for the past 8 Gyr, then based on the fraction that we observe to be active, we estimate the average age at which these stars transition from the saturated to the unsaturated flaring regime to be 2.4 ± 0.3 Gyr. This is consistent with the ages that we assign from Galactic kinematics: we find that stars with rotation period <jats:italic>P</jats:italic> <jats:sub>rot</jats:sub> &lt; 10 days have an age of 2.0 ± 1.2 Gyr, stars with 10 days &lt; <jats:italic>P</jats:italic> <jats:sub>rot</jats:sub> ≤ 90 days have an age of 5.6 ± 2.7 Gyr, and stars with <jats:italic>P</jats:italic> <jats:sub>rot</jats:sub> &gt; 90 days have an age of 12.9 ± 3.5 Gyr. We find that the average age of stars with <jats:italic>P</jats:italic> <jats:sub>rot</jats:sub> &lt; 10 days increases with decreasing stellar mass from 0.6 ± 0.3 Gyr (0.2–0.3 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>) to 2.3 ± 1.3 Gyr (0.1–0.2 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>).</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present AT2020mrf (SRGe J154754.2+443907), an extra-galactic (<jats:italic>z</jats:italic> = 0.1353) fast blue optical transient (FBOT) with a rise time of <jats:italic>t</jats:italic> <jats:sub> <jats:italic>g</jats:italic>,rise</jats:sub> = 3.7 days and a peak luminosity of <jats:italic>M</jats:italic> <jats:sub> <jats:italic>g</jats:italic>,peak</jats:sub> = −20.0. Its optical spectrum around peak shows a broad (<jats:italic>v</jats:italic> ∼ 0.1<jats:italic>c</jats:italic>) emission feature on a blue continuum (<jats:italic>T</jats:italic> ∼ 2 × 10<jats:sup>4</jats:sup> K), which bears a striking resemblance to AT2018cow. Its bright radio emission (<jats:italic>ν</jats:italic> <jats:italic>L</jats:italic> <jats:sub> <jats:italic>ν</jats:italic> </jats:sub> = 1.2 × 10<jats:sup>39</jats:sup> erg s<jats:sup>−1</jats:sup>; <jats:italic>ν</jats:italic> <jats:sub>rest</jats:sub> = 7.4 GHz; 261 days) is similar to four other AT2018cow-like events, and can be explained by synchrotron radiation from the interaction between a sub-relativistic (≳0.07–0.08c) forward shock and a dense environment (<jats:inline-formula> <jats:tex-math> <?CDATA $\dot{M}\lesssim {10}^{-3}\,{M}_{\odot }\,{\mathrm{yr}}^{-1}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mover accent="true"> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>̇</mml:mo> </mml:mrow> </mml:mover> <mml:mo>≲</mml:mo> <mml:msup> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>3</mml:mn> </mml:mrow> </mml:msup> <mml:mspace width="0.25em" /> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⊙</mml:mo> </mml:mrow> </mml:msub> <mml:mspace width="0.25em" /> <mml:msup> <mml:mrow> <mml:mi>yr</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac7a41ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> for <jats:italic>v</jats:italic> <jats:sub>w</jats:sub> = 10<jats:sup>3</jats:sup> km s<jats:sup>−1</jats:sup>). AT2020mrf occurs in a galaxy with <jats:italic>M</jats:italic> <jats:sub>*</jats:sub> ∼ 10<jats:sup>8</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> and specific star formation rate ∼10<jats:sup>−10</jats:sup> yr<jats:sup>−1</jats:sup>, supporting the idea that AT2018cow-like events are preferentially hosted by dwarf galaxies. The X-ray luminosity of AT2020mrf is the highest among FBOTs. At 35–37 days, SRG/eROSITA detected luminous (<jats:italic>L</jats:italic> <jats:sub>X</jats:sub> ∼ 2 × 10<jats:sup>43</jats:sup> erg s<jats:sup>−1</jats:sup>; 0.3–10 keV) X-ray emission. The X-ray spectral shape (<jats:italic>f</jats:italic> <jats:sub> <jats:italic>ν</jats:italic> </jats:sub> ∝ <jats:italic>ν</jats:italic> <jats:sup>−0.8</jats:sup>) and erratic intraday variability are reminiscent of AT2018cow, but the luminosity is a factor of ∼20 greater than AT2018cow. At 328 days, Chandra detected it at <jats:italic>L</jats:italic> <jats:sub>X</jats:sub> ∼ 10<jats:sup>42</jats:sup> erg s<jats:sup>−1</jats:sup>, which is &gt;200 times more luminous than AT2018cow and CSS161010. At the same time, the X-ray emission remains variable on the timescale of ∼1 day. We show that a central engine, probably a millisecond magnetar or an accreting black hole, is required to power the explosion. We predict the rates at which events like AT2018cow and AT2020mrf will be detected by SRG and Einstein Probe.</jats:p>