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<jats:title>Abstract</jats:title> <jats:p>We report the discovery in TESS data and validation of HD 56414 b (a.k.a. TOI-1228 b), a Neptune-size (<jats:italic>R</jats:italic> <jats:sub>p</jats:sub> = 3.71 ± 0.20 <jats:italic>R</jats:italic> <jats:sub>⊕</jats:sub>) planet with a 29 day orbital period transiting a young (age = 420 ± 140 Myr) A-type star in the TESS southern continuous-viewing zone. HD 56414 is one of the hottest stars (<jats:italic>T</jats:italic> <jats:sub>eff</jats:sub> = 8500 ± 150 K) to host a known sub-Jovian planet. HD 56414 b lies on the boundary of the hot Neptune desert in the planet radius–bolometric insolation flux space, suggesting that the planet may be experiencing mass loss. To explore this, we apply a photoevaporation model that incorporates the high near-ultraviolet continuum emission of A-type stars. We find that the planet can retain most of its atmosphere over the typical 1 Gyr main-sequence lifetime of an A-type star if its mass is ≥8 <jats:italic>M</jats:italic> <jats:sub>⊕</jats:sub>. Our model also predicts that close-in Neptune-size planets with masses &lt;14 <jats:italic>M</jats:italic> <jats:sub>⊕</jats:sub> are susceptible to total atmospheric stripping over 1 Gyr, hinting that the hot Neptune desert, which has been previously observed around FGKM-type stars, likely extends to A-type stars.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present the discovery of the first millimeter afterglow of a short-duration <jats:italic>γ</jats:italic>-ray burst (SGRB) and the first confirmed afterglow of an SGRB localized by the GUANO system on Swift. Our Atacama Large Millimeter/Sub-millimeter Array (ALMA) detection of SGRB 211106A establishes an origin in a faint host galaxy detected in Hubble Space Telescope imaging at 0.7 ≲ <jats:italic>z</jats:italic> ≲ 1.4. From the lack of a detectable optical afterglow, coupled with the bright millimeter counterpart, we infer a high extinction, <jats:italic>A</jats:italic> <jats:sub>V</jats:sub> ≳ 2.6 mag along the line of sight, making this one of the most highly dust-extincted SGRBs known to date. The millimeter-band light curve captures the passage of the synchrotron peak from the afterglow forward shock and reveals a jet break at <jats:inline-formula> <jats:tex-math> <?CDATA ${t}_{\mathrm{jet}}={29.2}_{-4.0}^{+4.5}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>t</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>jet</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>29.2</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>4.0</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>4.5</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac8421ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> days. For a presumed redshift of <jats:italic>z</jats:italic> = 1, we infer an opening angle, <jats:italic>θ</jats:italic> <jats:sub>jet</jats:sub> = (15.°5 ± 1.°4), and beaming-corrected kinetic energy of <jats:inline-formula> <jats:tex-math> <?CDATA $\mathrm{log}({E}_{{\rm{K}}}/\mathrm{erg})=51.8\pm 0.3$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>log</mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:msub> <mml:mrow> <mml:mi>E</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">K</mml:mi> </mml:mrow> </mml:msub> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:mi>erg</mml:mi> <mml:mo stretchy="false">)</mml:mo> <mml:mo>=</mml:mo> <mml:mn>51.8</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.3</mml:mn> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac8421ieqn2.gif" xlink:type="simple" /> </jats:inline-formula>, making this one of the widest and most energetic SGRB jets known to date. Combining all published millimeter-band upper limits in conjunction with the energetics for a large sample of SGRBs, we find that energetic outflows in high-density environments are more likely to have detectable millimeter counterparts. Concerted afterglow searches with ALMA should yield detection fractions of 24%–40% on timescales of ≳2 days at rates of ≈0.8–1.6 per year, outpacing the historical discovery rate of SGRB centimeter-band afterglows.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The presence of a strong magnetic field is a feature common to a significant fraction of degenerate stars, yet little is understood about the field’s origin and evolution. New observational constraints from volume-limited surveys point to a more complex situation than a single mechanism valid for all stars. We show that in high-mass white dwarfs, which are probably the results of mergers, magnetic fields are extremely common and very strong and appear immediately in the cooling phase. These fields may have been generated by a dynamo active during the merging. Lower-mass white dwarfs, which are often the product of single-star evolution, are rarely detectably magnetic at birth, but fields appear very slowly, and very weakly, in about a quarter of them. What we may see is an internal field produced in an earlier evolutionary stage that gradually relaxes to the surface from the interior. The frequency and strength of magnetic fields continue to increase to eventually rival those of highly massive stars, particularly after the stars cool past the start of core crystallization, an effect that could be responsible for a dynamo mechanism similar to the one that is active in Earth’s interior.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present the first measurements of H <jats:sc>i</jats:sc> galaxy scaling relations from a blind survey at <jats:italic>z</jats:italic> &gt; 0.15. We perform spectral stacking of 9023 spectra of star-forming galaxies undetected in H <jats:sc>i</jats:sc> at 0.23 &lt; <jats:italic>z</jats:italic> &lt; 0.49, extracted from MIGHTEE-H <jats:sc>i</jats:sc> Early Science data cubes, acquired with the MeerKAT radio telescope. We stack galaxies in bins of galaxy properties (stellar mass <jats:italic>M</jats:italic> <jats:sub>*</jats:sub>, star formation rateSFR, and specific star formation rate sSFR, with sSFR ≡ <jats:italic>M</jats:italic> <jats:sub>*</jats:sub>/SFR), obtaining ≳5<jats:italic>σ</jats:italic> detections in most cases, the strongest H <jats:sc>i</jats:sc>-stacking detections to date in this redshift range. With these detections, we are able to measure scaling relations in the probed redshift interval, finding evidence for a moderate evolution from the median redshift of our sample <jats:italic>z</jats:italic> <jats:sub>med</jats:sub> ∼ 0.37 to <jats:italic>z</jats:italic> ∼ 0. In particular, low-<jats:italic>M</jats:italic> <jats:sub>*</jats:sub> galaxies (<jats:inline-formula> <jats:tex-math> <?CDATA ${\mathrm{log}}_{10}({M}_{* }/{M}_{\odot })\sim 9$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>log</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> </mml:msub> <mml:mo stretchy="false">(</mml:mo> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>*</mml:mo> </mml:mrow> </mml:msub> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⊙</mml:mo> </mml:mrow> </mml:msub> <mml:mo stretchy="false">)</mml:mo> <mml:mo>∼</mml:mo> <mml:mn>9</mml:mn> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac85aeieqn1.gif" xlink:type="simple" /> </jats:inline-formula>) experience a strong H <jats:sc>i</jats:sc> depletion (∼0.5 dex in <jats:inline-formula> <jats:tex-math> <?CDATA ${\mathrm{log}}_{10}({M}_{{\rm{H}}\,{\rm\small{I}}}/{M}_{\odot })$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>log</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> </mml:msub> <mml:mo stretchy="false">(</mml:mo> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">H</mml:mi> <mml:mspace width="0.25em" /> <mml:mi mathsize="small" mathvariant="normal">I</mml:mi> </mml:mrow> </mml:msub> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⊙</mml:mo> </mml:mrow> </mml:msub> <mml:mo stretchy="false">)</mml:mo> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac85aeieqn2.gif" xlink:type="simple" /> </jats:inline-formula>), while massive galaxies (<jats:inline-formula> <jats:tex-math> <?CDATA ${\mathrm{log}}_{10}({M}_{* }/{M}_{\odot })\sim 11$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>log</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> </mml:msub> <mml:mo stretchy="false">(</mml:mo> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>*</mml:mo> </mml:mrow> </mml:msub> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⊙</mml:mo> </mml:mrow> </mml:msub> <mml:mo stretchy="false">)</mml:mo> <mml:mo>∼</mml:mo> <mml:mn>11</mml:mn> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac85aeieqn3.gif" xlink:type="simple" /> </jats:inline-formula>) keep their H <jats:sc>i</jats:sc> mass nearly unchanged. When looking at the star formation activity, highly star-forming galaxies evolve significantly in <jats:italic>M</jats:italic> <jats:sub>H I</jats:sub> (<jats:italic>f</jats:italic> <jats:sub>H I</jats:sub>, where <jats:italic>f</jats:italic> <jats:sub>H I</jats:sub> ≡ <jats:italic>M</jats:italic> <jats:sub>H I</jats:sub>/<jats:italic>M</jats:italic> <jats:sub>*</jats:sub>) at fixed SFR (sSFR), while at the lowest probed SFR (sSFR) the scaling relations show no evolution. These findings suggest a scenario in which low-<jats:italic>M</jats:italic> <jats:sub>*</jats:sub> galaxies have experienced a strong H <jats:sc>i</jats:sc> depletion during the last ∼5 Gyr, while massive galaxies have undergone a significant H <jats:sc>i</jats:sc> replenishment through some accretion mechanism, possibly minor mergers. Interestingly, our results are in good agreement with the predictions of the <jats:sc>simba</jats:sc> simulation. We conclude that this work sets novel important observational constraints on galaxy scaling relations.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>To understand the origin of the diversity observed in exoplanetary systems, it is crucial to characterize the early stages of their formation, represented by solar-type protostars. Likely, the gaseous chemical content of these objects directly depends on the composition of the dust-grain mantles formed before the collapse. Directly retrieving the ice mantle composition is challenging, but it can be done indirectly by observing the major components, such as NH<jats:sub>3</jats:sub> and CH<jats:sub>3</jats:sub>OH at centimeter wavelengths, once they are released into the gas phase during the warm protostellar stage. We observed several CH<jats:sub>3</jats:sub>OH and NH<jats:sub>3</jats:sub> lines toward three Class 0 protostars in NGC 1333 (IRAS 4A1, IRAS 4A2, and IRAS 4B), at high angular resolution (1″; ∼300 au) with the VLA interferometer at 24–26 GHz. Using a non-LTE LVG analysis, we derived a similar NH<jats:sub>3</jats:sub>/CH<jats:sub>3</jats:sub>OH abundance ratio in the three protostars (≤0.5, 0.015–0.5, and 0.003–0.3 for IRAS 4A1, 4A2, and 4B, respectively). Hence, we infer they were born from precollapse material with similar physical conditions. Comparing the observed abundance ratios with astrochemical model predictions, we constrained the dust temperature at the time of the mantle formation to be ∼17 K, which coincides with the average temperature of the southern NGC 1333 diffuse cloud. We suggest that a brutal event started the collapse that eventually formed IRAS 4A1, 4A2, and 4B, which, therefore, did not experience the usual prestellar core phase. This event could be the clash of a bubble with NGC 1333 South, which has previously been evoked in the literature.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>An X-ray flash, expected in a very early phase of a nova outburst, was at last detected with the SRG/eROSITA in the classical nova YZ Reticuli 2020. The observed flash timescale, luminosity, and blackbody temperature substantially constrain the nova model. We present light-curve models of the X-ray flash for various white dwarf (WD) masses and mass-accretion rates. We have found the WD mass in YZ Ret to be as massive as <jats:italic>M</jats:italic> <jats:sub>WD</jats:sub> ∼ 1.3 <jats:italic>M</jats:italic> <jats:sub>☉</jats:sub> with mass-accretion rates of <jats:inline-formula> <jats:tex-math> <?CDATA ${\dot{M}}_{\mathrm{acc}}\sim 5\times {10}^{-10}\mbox{--}5\times {10}^{-9}\,{M}_{\odot }$?> </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>acc</mml:mi> </mml:mrow> </mml:msub> <mml:mo>∼</mml:mo> <mml:mn>5</mml:mn> <mml:mo>×</mml:mo> <mml:msup> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>10</mml:mn> </mml:mrow> </mml:msup> <mml:mo>–</mml:mo> <mml:mn>5</mml:mn> <mml:mo>×</mml:mo> <mml:msup> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>9</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:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac85c1ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> yr<jats:sup>−1</jats:sup>, including the case where the mass-accretion rate is changing between them, consistent with the SRG/eROSITA observation. The X-ray observation confirms the luminosity to be close to the Eddington limit at the X-ray flash. The occurrence of optically thick winds, with the photospheric radius exceeding ∼0.1 <jats:italic>R</jats:italic> <jats:sub>☉</jats:sub>, terminated the X-ray flash of YZ Ret by strong absorption. This sets a constrain on the starting time of wind mass loss. A slight contamination of the hydrogen-rich envelope by the core material seems to be preferred to explain the very short duration of the X-ray flash.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>One critical remaining issue that is unclear in the initial mass function of the first (Population III) stars is the final fate of secondary protostars that formed in the accretion disk—specifically, whether they merge or survive. We focus on the magnetic effects on the formation of the first star under a cosmological magnetic field. We perform a suite of ideal magnetohydrodynamic simulations for 1000 yr after the first protostar formation. Instead of the sink particle technique, we employ a stiff equation of state approach to represent the magnetic field structure connecting protostars. Ten years after the first protostar formation in the cloud initialized with <jats:italic>B</jats:italic> <jats:sub>0</jats:sub> = 10<jats:sup>−20</jats:sup> G at <jats:italic>n</jats:italic> <jats:sub>0</jats:sub> = 10<jats:sup>4</jats:sup> cm<jats:sup>−3</jats:sup>, the magnetic field strength around the protostars has amplified from pico- to kilo-Gauss, which is the same strength as the present-day star. The magnetic field rapidly winds up since the gas in the vicinity of the protostar (≤10 au) has undergone several tens of orbital rotations in the first decade after protostar formation. As the mass accretion progresses, the vital magnetic field region extends outward, and magnetic braking eliminates the fragmentation of the disk that would happen in an unmagnetized model. On the other hand, assuming a gas cloud with a small angular momentum, this amplification might not work because the rotation would be slower. However, disk fragmentation would not occur in that case. We conclude that the exponential amplification of the cosmological magnetic field strength, about 10<jats:sup>−18</jats:sup> G, eliminates disk fragmentation around Population III protostars.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We report the discovery of Tucana B, an isolated ultra-faint dwarf galaxy at a distance of <jats:italic>D</jats:italic> = 1.4 Mpc. Tucana B was found during a search for ultra-faint satellite companions to the known dwarfs in the outskirts of the Local Group, although its sky position and distance indicate the nearest galaxy to be ∼500 kpc distant. Deep ground-based imaging resolves Tucana B into stars, and it displays a sparse red giant branch consistent with an old, metal-poor stellar population analogous to that seen in the ultra-faint dwarf galaxies of the Milky Way, albeit at fainter apparent magnitudes. Tucana B has a half-light radius of 80 ± 40 pc and an absolute magnitude of <jats:inline-formula> <jats:tex-math> <?CDATA ${M}_{V}=-{6.9}_{-0.6}^{+0.5}$?> </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>V</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mo>−</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>6.9</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.6</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.5</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac85eeieqn1.gif" xlink:type="simple" /> </jats:inline-formula> mag (<jats:inline-formula> <jats:tex-math> <?CDATA ${L}_{V}=({5}_{-2}^{+4})\times {10}^{4}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>L</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>V</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mo stretchy="false">(</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>5</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>2</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>4</mml:mn> </mml:mrow> </mml:msubsup> <mml:mo stretchy="false">)</mml:mo> <mml:mo>×</mml:mo> <mml:msup> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> <mml:mrow> <mml:mn>4</mml:mn> </mml:mrow> </mml:msup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac85eeieqn2.gif" xlink:type="simple" /> </jats:inline-formula> <jats:italic>L</jats:italic> <jats:sub>⊙</jats:sub>), which is again comparable to the Milky Way’s ultra-faint satellites. There is no evidence for a population of young stars, either in the optical color–magnitude diagram or in GALEX archival ultraviolet imaging, with the GALEX data indicating <jats:inline-formula> <jats:tex-math> <?CDATA $\mathrm{log}({\mathrm{SFR}}_{\mathrm{NUV}}/{M}_{\odot }\,{\mathrm{yr}}^{-1})\lt -5.4$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>log</mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:msub> <mml:mrow> <mml:mi>SFR</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>NUV</mml:mi> </mml:mrow> </mml:msub> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <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:mo stretchy="false">)</mml:mo> <mml:mo>&lt;</mml:mo> <mml:mo>−</mml:mo> <mml:mn>5.4</mml:mn> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac85eeieqn3.gif" xlink:type="simple" /> </jats:inline-formula> for star formation on ≲100 Myr timescales. Given its isolation and physical properties, Tucana B may be a definitive example of an ultra-faint dwarf that has been quenched by reionization, providing strong confirmation of a key driver of galaxy formation and evolution at the lowest mass scales. It also signals a new era of ultra-faint dwarf galaxy discovery at the extreme edges of the Local Group.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Accretion signatures from bound brown dwarf and protoplanetary companions provide evidence for ongoing planet formation, and accreting substellar objects have enabled new avenues to study the astrophysical mechanisms controlling the formation and accretion processes. Delorme 1 (AB)b, a ∼30–45 Myr circumbinary planetary-mass companion, was recently discovered to exhibit strong H<jats:italic>α</jats:italic> emission. This suggests ongoing accretion from a circumplanetary disk, somewhat surprising given canonical gas disk dispersal timescales of 5–10 Myr. Here, we present the first NIR detection of accretion from the companion in Pa<jats:italic>β</jats:italic>, Pa<jats:italic>γ</jats:italic>, and Br<jats:italic>γ</jats:italic> emission lines from SOAR/TripleSpec 4.1, confirming and further informing its accreting nature. The companion shows strong line emission, with <jats:italic>L</jats:italic> <jats:sub>line</jats:sub> ≈ 1–6 × 10<jats:sup>−8</jats:sup> <jats:italic>L</jats:italic> <jats:sub>⊙</jats:sub> across lines and epochs, while the binary host system shows no NIR hydrogen line emission (<jats:italic>L</jats:italic> <jats:sub>line</jats:sub> &lt; 0.32–11 × 10<jats:sup>−7</jats:sup> <jats:italic>L</jats:italic> <jats:sub>⊙</jats:sub>). Observed NIR hydrogen line ratios are more consistent with a planetary accretion shock than with local line excitation models commonly used to interpret stellar magnetospheric accretion. Using planetary accretion shock models, we derive mass accretion rate estimates of <jats:inline-formula> <jats:tex-math> <?CDATA ${\dot{M}}_{\mathrm{pla}}\sim 3$?> </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>pla</mml:mi> </mml:mrow> </mml:msub> <mml:mo>∼</mml:mo> <mml:mn>3</mml:mn> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac85efieqn1.gif" xlink:type="simple" /> </jats:inline-formula>–4 × 10<jats:sup>−8</jats:sup> <jats:italic>M</jats:italic> <jats:sub>J</jats:sub> yr<jats:sup>−1</jats:sup>, somewhat higher than expected under the standard star formation paradigm. Delorme 1 (AB)b’s high accretion rate is perhaps more consistent with formation via disk fragmentation. Delorme 1 (AB)b is the first protoplanet candidate with clear (signal-to-noise ratio ∼5) NIR hydrogen line emission.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We explore whether an independent determination of the distance‒redshift relation, and hence cosmological model parameters, can be obtained from the apparent correlations between two different wave-band luminosities or fluxes, as has been claimed in recent works using the X-ray and ultraviolet luminosities and fluxes of quasars. We show that such an independent determination is possible only if the correlation between luminosities is obtained independently of the cosmological model and measured fluxes and redshifts, for example, based on sound theoretical models or unrelated observations. In particular, we show that if the correlation is determined empirically for two luminosities obtained from fluxes and redshifts, then the method suffers from circularity. In the case where the observed correlation between fluxes in very narrow redshift bins is used as a proxy for the luminosity correlation, we show that one is dealing with a pure tautology with no information on distances and cosmological model. We argue that the problem arises because of the incomplete treatment of the correlation, and we use numerical methods with a joint X-ray and ultraviolet quasar data set to demonstrate this shortcoming.</jats:p>