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<jats:title>Abstract</jats:title> <jats:p>Dynamic models of solar system evolution suggest that D-type asteroids formed beyond Saturn's orbit and represent invaluable witnesses of the prevailing conditions in the outer solar system. Here, we report a comprehensive petrographic and isotopic characterization of the carbonaceous chondrite Tarda, a recent fall recovered in the Moroccan Sahara. We show that Tarda shares strong similarities with the D-type-derived chondrite Tagish Lake, implying that Tarda represents a rare sample of D-type asteroids. Both Tarda and Tagish Lake are characterized by the presence of rare <jats:sup>16</jats:sup>O-rich chondrules and chondrule fragments, high C/H ratios, and enrichments in deuterium, <jats:sup>15</jats:sup>N, and <jats:sup>13</jats:sup>C. By combining our results with literature data on carbonaceous chondrites related to C-type asteroids, we show that the outer solar system 4.56 Gy ago was characterized by large-scale oxygen isotopic homogeneities in (i) the water–ice grains accreted by asteroids and (ii) the gas controlling the formation of FeO-poor chondrules. Conversely, the zone in which D-type asteroids accreted was significantly enriched in deuterium relative to the formation regions of C-type asteroids, features likely inherited from unprocessed, D-rich, molecular-cloud materials.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The E-mode (EE) CMB power spectra measured by Planck, ACTPol, and SPTpol constrain the Hubble constant to be 70.0 ± 2.7, <jats:inline-formula> <jats:tex-math> <?CDATA ${72.4}_{-4.8}^{+3.9}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlabf56eieqn1.gif" xlink:type="simple" /> </jats:inline-formula>, and <jats:inline-formula> <jats:tex-math> <?CDATA ${73.1}_{-3.9}^{+3.3}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlabf56eieqn2.gif" xlink:type="simple" /> </jats:inline-formula> km s<jats:sup>−1</jats:sup> Mpc<jats:sup>−1</jats:sup> within the standard ΛCDM model (posterior mean and central 68% interval bounds). These values are higher than the constraints from the Planck temperature (TT) power spectrum, and consistent with the Cepheid-supernova distance ladder measurement <jats:italic>H</jats:italic> <jats:sub>0</jats:sub> = 73.2 ± 1.3 km s<jats:sup>−1</jats:sup> Mpc<jats:sup>−1</jats:sup>. If this preference for a higher value was strengthened in a joint analysis it could provide an intriguing hint at the resolution of the Hubble disagreement. We show, however, that combining the Planck, ACTPol, and SPTpol EE likelihoods yields <jats:italic>H</jats:italic> <jats:sub>0</jats:sub> = 68.7 ± 1.3 km s<jats:sup>−1</jats:sup> Mpc<jats:sup>−1</jats:sup>, 2.4<jats:italic>σ</jats:italic> lower than the distance ladder measurement. This is due to different degeneracy directions across the full parameter space, particularly involving the baryon density, Ω<jats:sub> <jats:italic>b</jats:italic> </jats:sub> <jats:italic>h</jats:italic> <jats:sup>2</jats:sup>, and scalar tilt, <jats:italic>n</jats:italic> <jats:sub> <jats:italic>s</jats:italic> </jats:sub>, arising from sensitivity to different multipole ranges. We show that the E-mode ΛCDM constraints are consistent across the different experiments within 1.4<jats:italic>σ</jats:italic>, and with the Planck TT results at 0.8<jats:italic>σ</jats:italic>. Combining the Planck, ACTPol, and SPTpol EE data constrains the phenomenological lensing amplitude, <jats:italic>A</jats:italic> <jats:sub> <jats:italic>L</jats:italic> </jats:sub> = 0.89 ± 0.10, consistent with the expected value of unity.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The joint observation of the gravitational-wave (GW) and electromagnetic (EM) signal from the binary neutron-star merger GW170817 allowed for a new independent measurement of the Hubble constant <jats:italic>H</jats:italic> <jats:sub>0</jats:sub>, albeit with an uncertainty of about 15% at 1<jats:italic>σ</jats:italic>. Observations of similar sources with a network of future detectors will allow for more precise measurements of <jats:italic>H</jats:italic> <jats:sub>0</jats:sub>. These, however, are currently largely limited by the intrinsic degeneracy between the luminosity distance and the inclination of the source in the GW signal. We show that the higher-order modes in gravitational waves can be used to break this degeneracy in astrophysical parameter estimation in both the inspiral and post-merger phases of a neutron star merger. We show that for systems at distances similar to GW170817, this method enables percent-level measurements of <jats:italic>H</jats:italic> <jats:sub>0</jats:sub> with a single detection. This would permit the study of time variations and spatial anisotropies of <jats:italic>H</jats:italic> <jats:sub>0</jats:sub> with unprecedented precision. We investigate how different network configurations affect measurements of <jats:italic>H</jats:italic> <jats:sub>0</jats:sub>, and discuss the implications in terms of science drivers for the proposed 2.5- and third-generation GW detectors. Finally, we show that the precision of <jats:italic>H</jats:italic> <jats:sub>0</jats:sub> measured with these future observatories will be solely limited by redshift measurements of EM counterparts.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The chemical compounds carrying the thiol group (-SH) have been considered essential in recent prebiotic studies regarding the polymerization of amino acids. We have searched for this kind of compound toward the Galactic Center quiescent cloud G+0.693–0.027. We report the first detection in the interstellar space of the trans-isomer of monothioformic acid (t-HC(O)SH) with an abundance of ∼1 × 10<jats:sup>−10</jats:sup>. Additionally, we provide a solid confirmation of the gauche isomer of ethyl mercaptan (g-C<jats:sub>2</jats:sub>H<jats:sub>5</jats:sub>SH) with an abundance of ∼3 × 10<jats:sup>−10</jats:sup>, and we also detect methyl mercaptan (CH<jats:sub>3</jats:sub>SH) with an abundance of ∼5 × 10<jats:sup>−9</jats:sup>. Abundance ratios were calculated for the three SH-bearing species and their OH analogs, revealing similar trends between alcohols and thiols with increasing complexity. Possible chemical routes for the interstellar synthesis of t-HC(O)SH, CH<jats:sub>3</jats:sub>SH, and C<jats:sub>2</jats:sub>H<jats:sub>5</jats:sub>SH are discussed, as well as the relevance of these compounds in the synthesis of prebiotic proteins in the primitive Earth.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Elements with low first ionization potential (FIP) are known to be 3–4 times more abundant in active region loops of the solar corona than in the photosphere. There have been observations suggesting that this observed “FIP bias” may be different in other parts of the solar corona and such observations are thus important in understanding the underlying mechanism. The Solar X-ray Monitor (XSM) on board the Chandrayaan-2 mission carried out spectroscopic observations of the Sun in soft X-rays during the 2019–2020 solar minimum, considered to be the quietest solar minimum of the past century. These observations provided a unique opportunity to study soft X-ray spectra of the quiescent solar corona in the absence of any active regions. By modeling high-resolution broadband X-ray spectra from XSM, we estimate the temperature and emission measure during periods of possibly the lowest solar X-ray intensity. We find that the derived parameters remain nearly constant over time with a temperature around 2 MK, suggesting the emission is dominated by X-ray bright points. We also obtain the abundances of Mg, Al, and Si relative to H, and find that the FIP bias is ∼2, lower than the values observed in active regions.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Solar flares, with energies ranging over several orders of magnitude, result from impulsive release of energy due to magnetic reconnection in the corona. Barring a handful, almost all microflares observed in X-rays are associated with the solar active regions. Here we present, for the first time, a comprehensive analysis of a large sample of quiet-Sun microflares observed in soft X-rays by the Solar X-ray Monitor (XSM) on board the Chandrayaan-2 mission during the 2019–2020 solar minimum. A total of 98 microflares having peak flux below GOES A-level were observed by the XSM during observations spanning 76 days. By using the derived plasma temperature and emission measure of these events obtained by fitting the XSM spectra along with volume estimates from concurrent imaging observations in EUV with the Solar Dynamics Observatory/Atmospheric Imaging Assembly, we estimated their thermal energies to be ranging from 3 × 10<jats:sup>26</jats:sup> to 6 × 10<jats:sup>27</jats:sup> erg. We present the frequency distribution of the quiet-Sun microflares with energy and discuss the implications of these observations of small-scale magnetic reconnection events outside active regions on coronal heating.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Understanding when global glaciations occur on Earth-like planets is a major challenge in climate evolution research. Most models of how greenhouse gases like CO<jats:sub>2</jats:sub> evolve with time on terrestrial planets are deterministic, but the complex, nonlinear nature of Earth’s climate history motivates study of nondeterministic climate models. Here a maximally simple stochastic model of CO<jats:sub>2</jats:sub> evolution and climate on an Earth-like planet with an imperfect CO<jats:sub>2</jats:sub> thermostat is investigated. It is shown that as stellar luminosity is increased in this model, the decrease in the average atmospheric CO<jats:sub>2</jats:sub> concentration renders the climate increasingly unstable, with excursions to a low-temperature state common once the received stellar flux approaches that of present-day Earth. Unless climate feedbacks always force the variance in CO<jats:sub>2</jats:sub> concentration to decline rapidly with received stellar flux, this means that terrestrial planets near the inner edge of the habitable zone may enter Snowball states quite frequently. Observations of the albedos and color variation of terrestrial-type exoplanets should allow this prediction to be tested directly in the future.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present the sympathetic eruption of a standard and a blowout coronal jet originating from two adjacent coronal bright points (CBP1 and CBP2) in a polar coronal hole, using soft X-ray and extreme-ultraviolet observations respectively taken by the Hinode and the Solar Dynamics Observatory. In the event, a collimated jet with obvious westward lateral motion first launched from CBP1, during which a small bright point appeared around CBP1's east end, and magnetic flux cancellation was observed within the eruption source region. Based on these characteristics, we interpret the observed jet as a standard jet associated with photospheric magnetic flux cancellation. About 15 minutes later, the westward-moving jet spire interacted with CBP2 and resulted in magnetic reconnection between them, which caused the formation of the second jet above CBP2 and the appearance of a bright loop system in between the two CBPs. In addition, we observed the writhing, kinking, and violent eruption of a small kink structure close to CBP2's west end but inside the jet base, which made the second jet brighter and broader than the first one. These features suggest that the second jet should be a blowout jet triggered by the magnetic reconnection between CBP2 and the spire of the first jet. We conclude that the two successive jets were physically connected to each other rather than a temporal coincidence, and this observation also suggests that coronal jets can be triggered by external eruptions or disturbances, as well as internal magnetic activities or magnetohydrodynamic instabilities.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Detached circumplanetary disks are unstable to tilting as a result of the stellar tidal potential. We examine how a tilted circumplanetary disk affects the evolution of the spin axis of an oblate planet. The disk is evolved using time-dependent equations for linear wave-like warp evolution, including terms representing the effect of the tidal potential and planetary oblateness. For a disk with a sufficiently large mass, we find that the planet spin quickly aligns to the misaligned disk. The tilt of the planetary spin axis then increases on the same timescale as the disk. This can be an efficient mechanism for generating primordial obliquity in giant planets. We suggest that directly imaged exoplanets at large orbital radii, where the disk mass criterion is more likely to be satisfied, could have significant obliquities due to the tilt instability of their circumplanetary disks.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In recent years, dramatic outbursts have been identified toward massive protostars via infrared and millimeter dust continuum and molecular maser emission. The longest lived outburst (&gt;6 yr) persists in NGC 6334 I-MM1, a deeply embedded object with no near-IR counterpart. Using FORCAST and HAWC+ on SOFIA, we have obtained the first mid-IR images of this field since the outburst began. Despite being undetected in pre-outburst ground-based 18 <jats:italic>μ</jats:italic>m images, MM1 is now the brightest region at all three wavelengths (25, 37, and 53 <jats:italic>μ</jats:italic>m), exceeding the UCHII region MM3 (NGC 6334 F). Combining the SOFIA data with ALMA imaging at four wavelengths, we construct a spectral energy distribution of the combination of MM1 and the nearby hot core MM2. The best-fit Robitaille radiative transfer model yields a luminosity of (4.9 ± 0.8) × 10<jats:sup>4</jats:sup> <jats:italic>L</jats:italic> <jats:sub>⊙</jats:sub>. Accounting for an estimated pre-outburst luminosity ratio MM1:MM2 = 2.1 ± 0.4, the luminosity of MM1 has increased by a factor of 16.3 ± 4.4. The pre-outburst luminosity implies a protostar of mass 6.7 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>, which can produce the ionizing photon rate required to power the pre-outburst HCHII region surrounding the likely outbursting protostar MM1B. The total energy and duration of the outburst exceed the S255IR-NIRS3 outburst by a factor of ≳3, suggesting a different scale of event involving expansion of the protostellar photosphere (to ≳20 <jats:italic>R</jats:italic> <jats:sub>⊙</jats:sub>), thereby supporting a higher accretion rate (≳0.0023 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> yr<jats:sup>−1</jats:sup>) and reducing the ionizing photon rate. In the grid of hydrodynamic models of Meyer et al., the combination of outburst luminosity and magnitude (3) places the NGC 6334 I-MM1 event in the region of moderate total accretion (∼0.1–0.3 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>) and hence long duration (∼40–130 yr).</jats:p>