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<jats:title>Abstract</jats:title> <jats:p>The James Webb Space Telescope’s (JWST) NIRSpec instrument will unveil the nature of exoplanet atmospheres across the wealth of planet types, from temperate terrestrial worlds to ultrahot Jupiters. In particular, the 0.6–5.3 <jats:italic>μ</jats:italic>m PRISM mode is especially well suited for efficient spectroscopic exoplanet observations spanning a number of important spectral features. We analyze a lab-measured NIRSpec PRISM mode Bright Object Time Series observation from the perspective of a JWST user to understand the instrument performance and detector properties. We create two realistic transiting exoplanet time-series observations by performing injection-recovery tests on the lab-measured data to quantify the effects of real instrument jitter, drift, intrapixel sensitivity variations, and 1/<jats:italic>f</jats:italic> noise on measured transmission spectra. By fitting the time-series systematics simultaneously with the injected transit, we can obtain more realistic transit-depth uncertainties that take into account noise sources that are currently not modeled by traditional exposure time calculators. We find that sources of systematic noise related to intrapixel sensitivity variations and point-spread function motions are apparent in the data at the level of a few hundred ppm but can be effectively detrended using a low-order polynomial with detector position. We recover the injected spectral features of GJ 436 b and TRAPPIST-1 d and place a 3<jats:italic>σ</jats:italic> upper limit on the detector noise floor of 14 ppm. We find that the noise floor is consistent with &lt;10 ppm at the 1.7<jats:italic>σ</jats:italic> level, which bodes well for future observations of challenging targets with faint atmospheric signatures.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The symbiotic X-ray binary Sct X-1 was suggested to be the first known neutron star accreting from a red supergiant companion. Although known for nearly 50 yr, detailed characterization of the donor remains lacking, particularly due to the extremely high reddening toward the source (<jats:italic>A</jats:italic> <jats:sub> <jats:italic>V</jats:italic> </jats:sub> ≳ 25 mag). Here, we present (i) improved localization of the counterpart using Gaia and Chandra observations, (ii) the first broadband infrared spectrum (≈1–5 <jats:italic>μ</jats:italic>m; <jats:italic>R</jats:italic> ≈ 2000) obtained with SpeX on the NASA Infrared Telescope Facility, and (iii) the <jats:italic>J</jats:italic>-band light curve from the Palomar Gattini-IR survey. The infrared spectrum is characterized by (i) deep water absorption features (H<jats:sub>2</jats:sub>O index ≈ 40%), (ii) strong TiO, VO, and CO features, and (iii) weak/absent CN lines. We show that these features are inconsistent with known red supergiants but suggest an M8-9 III–type O-rich Mira donor star. We report the discovery of large-amplitude (Δ<jats:italic>J</jats:italic> ≈ 3.5 mag) periodic photometric variability, suggesting a pulsation period of 621 ± 36 (systematic) ± 8 (statistical) days, which we use to constrain the donor to be a relatively luminous Mira (<jats:italic>M</jats:italic> <jats:sub> <jats:italic>K</jats:italic> </jats:sub> = −8.6 ± 0.3 mag) at a distance of <jats:inline-formula> <jats:tex-math> <?CDATA ${3.6}_{-0.7}^{+0.8}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>3.6</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.7</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.8</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac5b11ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> kpc. Comparing these characteristics to recent models, we find the donor to be consistent with a ≈3–5 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> star at an age of ≈0.1–0.3 Gyr. Together, we show that Sct X-1 was previously misclassified as an evolved high-mass X-ray binary; instead, it is an intermediate-mass system with the first confirmed Mira donor in an X-ray binary. We discuss the implications of Mira donors in symbiotic X-ray binaries and highlight the potential of wide-field infrared time-domain surveys and broadband infrared spectroscopy to unveil their demographics.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We calculated the electron–positron pair-production rate at the base of the jet of 3C 120 due to collisions of photons from the hot accretion flow using the measurement of its average soft gamma-ray spectrum by the Compton Gamma Ray Observatory. We found that this rate approximately equals the flow rate of leptons emitting the observed synchrotron radio-to-IR spectrum of the jet core, calculated using the extended jet model following Blandford &amp; Königl. This coincidence shows the jet composition is likely to be pair dominated. We then calculated the jet power in the bulk motion of ions and found it greatly exceeds that achievable by the magnetically arrested disk scenario for the maximum black hole spin unless the jet contains mostly pairs. Next, we found that the magnetic flux through the synchrotron-emitting jet equals the maximum poloidal flux that can thread the black hole. Finally, we compared two estimates of the magnetization parameter at the onset of the synchrotron emission and found they are in agreement only if pairs dominate the jet content.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Einstein’s theory of general relativity (GR) has been precisely tested on solar system scales, but extragalactic tests are still poorly performed. In this work, we use a newly compiled sample of galaxy-scale strong gravitational lenses to test the validity of GR on kiloparsec scales. In order to solve the circularity problem caused by the presumption of a specific cosmological model based on GR, we employ the distance sum rule in the Friedmann–Lemaître–Robertson–Walker metric to directly estimate the parameterized post-Newtonian (PPN) parameter <jats:italic>γ</jats:italic> <jats:sub>PPN</jats:sub> and the cosmic curvature Ω<jats:sub> <jats:italic>k</jats:italic> </jats:sub> by combining observations of strong lensing and Type Ia supernovae. This is the first simultaneous measurement of <jats:italic>γ</jats:italic> <jats:sub>PPN</jats:sub> and Ω<jats:sub> <jats:italic>k</jats:italic> </jats:sub> without any assumptions about the contents of the universe or the theory of gravity. Our results show that <jats:inline-formula> <jats:tex-math> <?CDATA ${\gamma }_{\mathrm{PPN}}={1.11}_{-0.09}^{+0.11}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>γ</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>PPN</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>1.11</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.09</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.11</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac551eieqn1.gif" xlink:type="simple" /> </jats:inline-formula> and <jats:inline-formula> <jats:tex-math> <?CDATA ${{\rm{\Omega }}}_{k}={0.48}_{-0.71}^{+1.09}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi mathvariant="normal">Ω</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>k</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>0.48</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.71</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>1.09</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac551eieqn2.gif" xlink:type="simple" /> </jats:inline-formula>, indicating a strong degeneracy between the two quantities. The measured <jats:italic>γ</jats:italic> <jats:sub>PPN</jats:sub>, which is consistent with the prediction of 1 from GR, provides a precise extragalactic test of GR with a fractional accuracy better than 9.0%. If a prior of the spatial flatness (i.e., Ω<jats:sub> <jats:italic>k</jats:italic> </jats:sub> = 0) is adopted, the PPN parameter constraint can be further improved to <jats:inline-formula> <jats:tex-math> <?CDATA ${\gamma }_{\mathrm{PPN}}={1.07}_{-0.07}^{+0.07}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>γ</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>PPN</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>1.07</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.07</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.07</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac551eieqn3.gif" xlink:type="simple" /> </jats:inline-formula>, representing a precision of 6.5%. On the other hand, in the framework of GR (i.e., <jats:italic>γ</jats:italic> <jats:sub>PPN</jats:sub> = 1), our results are still marginally compatible with zero curvature (<jats:inline-formula> <jats:tex-math> <?CDATA ${{\rm{\Omega }}}_{k}=-{0.12}_{-0.36}^{+0.48}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi mathvariant="normal">Ω</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>k</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mo>−</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>0.12</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.36</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.48</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac551eieqn4.gif" xlink:type="simple" /> </jats:inline-formula>), supporting no significant deviation from a flat universe.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Multiple stellar populations (MPs) representing star-to-star light-element abundance variations are common in nearly all ancient Galactic globular clusters (GCs). Here we provide the strongest evidence yet that the populous, ∼1.7 Gyr old Large Magellanic Cloud cluster NGC 2173 also exhibits light-element abundance variations. Thus, our results suggest that NGC 2173 is the youngest cluster for which MPs have been confirmed to date. Our conclusion is based on the distinct bifurcation at the tip of its red giant branch in high-quality color–magnitude diagrams generated from Hubble Space Telescope imaging observations. Our results are further supported by a detailed analysis of “pseudo-<jats:italic>UBI</jats:italic>” maps, which reveal clear evidence of a bimodality in the cluster’s red giant branch color distribution. Young clusters in the Magellanic Clouds can provide critical insights into galaxy evolution histories. Our discovery of MPs in NGC 2173 suggests that ancient Galactic GCs and young massive clusters might share a common formation process.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Accurate tracers of the stellar magnetic field and rotation are cornerstones for the study of M dwarfs and for reliable detection and characterization of their exoplanetary companions. Such measurements are particularly challenging for old, slowly rotating, fully convective M dwarfs. To explore the use of new activity and rotation tracers, we examined multiyear near-infrared (NIR) spectroscopic monitoring of two such stars—GJ 699 (Barnard’s Star) and Teegarden’s Star—carried out with the Habitable-zone Planet Finder spectrograph. We detected periodic variations in absorption line widths across the stellar spectrum, with higher amplitudes toward longer wavelengths. We also detected similar variations in the strength and width of the 12435.67 Å neutral potassium (K <jats:sc>i</jats:sc>) line, a known tracer of the photospheric magnetic field. Attributing these variations to rotational modulation, we confirm the known 145 ± 15 day rotation period of GJ 699, and measure the rotation period of Teegarden’s Star to be 99.6 ± 1.4 days. Based on simulations of the K <jats:sc>i</jats:sc> line and the wavelength dependence of the line-width signal, we argue that the observed signals are consistent with varying photospheric magnetic fields and the associated Zeeman effect. These results highlight the value of detailed line profile measurements in the NIR for diagnosing stellar magnetic field variability. Such measurements may be pivotal for disentangling activity and exoplanet-related signals in spectroscopic monitoring of old, low-mass stars.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We study the formation and gravitational collapse of supersonically induced gas objects (SIGOs) in the early universe. We run cosmological hydrodynamics simulations of SIGOs, including relative streaming motions between baryons and dark matter. Our simulations also follow nonequilibrium chemistry and molecular hydrogen cooling in primordial gas clouds. A number of SIGOs are formed in the run with fast-streaming motions of 2 times the rms of the cosmological velocity fluctuations. We identify a particular gas cloud that condensates by H<jats:sub>2</jats:sub> cooling without being hosted by a dark matter halo. The SIGO remains outside the virial radius of its closest halo, and it becomes Jeans unstable when the central gas-particle density reaches ∼100 cm<jats:sup>−3</jats:sup> with a temperature of ∼200 K. The corresponding Jeans mass is ∼10<jats:sup>5</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>, and thus the formation of primordial stars or a star cluster is expected in the SIGO.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Post-asymptotic giant branch (AGB) stars are exquisite probes of AGB nucleosynthesis. However, the previous lack of accurate distances jeopardized comparison with theoretical AGB models. The Gaia Early Data Release 3 (Gaia EDR3) has now allowed for a breakthrough in this research landscape. In this study, we focus on a sample of single Galactic post-AGBs for which chemical abundance studies were completed. We combined photometry with geometric distances to carry out a spectral energy distribution (SED) analysis and derive accurate luminosities. We subsequently determined their positions on the Hertzsprung-Russell (HR) diagram and compared this with theoretical post-AGB evolutionary tracks. While most objects are in the post-AGB phase of evolution, we found a subset of low-luminosity objects that are likely to be in the post-horizontal branch phase of evolution, similar to AGB-manqué objects found in globular clusters. Additionally, we also investigated the observed bimodality in the <jats:italic>s</jats:italic>-process enrichment of Galactic post-AGB single stars of similar <jats:italic>T</jats:italic> <jats:sub>eff</jats:sub> and metallicities. This bimodality was expected to be a direct consequence of luminosity with the <jats:italic>s</jats:italic>-process rich objects having evolved further on the AGB. However, we find that the two populations, the <jats:italic>s</jats:italic>-process enriched and non-enriched, have similar luminosities (and hence initial masses), revealing an intriguing chemical diversity. For a given initial mass and metallicity, AGB nucleosynthesis appears inhomogeneous and sensitive to other factors, which could be mass loss, along with convective and non-convective mixing mechanisms. Modeling individual objects in detail will be needed to investigate which parameters and processes dominate the photospheric chemical enrichment in these stars.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Eruptions of solar filaments often show rotational motion about their rising direction, but the mechanism governing such rotation, and how the rotation is related to the initial morphology of the preeruptive filament (and cospatial sigmoid), filament chirality, and magnetic helicity, remains elusive. The conventional view of rotation as a result of a magnetic flux rope (MFR) undergoing ideal kink instability still has difficulty explaining these relationships. Here we propose an alternative explanation for the rotation during eruptions by analyzing a magnetohydrodynamic simulation in which magnetic reconnection initiates an eruption from a sheared arcade configuration, and an MFR is formed during eruption via reconnection. The simulation reproduces a reverse-S-shaped MFR with dextral chirality, and the axis of this MFR rotates counterclockwise while rising, which compares favorably with a typical filament eruption observed from dual viewing angles. By calculating the twist and writhe numbers of the modeled MFR during its eruption, we found that, accompanied by the rotation, the nonlocal writhe of the MFR’s axis decreases while the twist of its surrounding field lines increases, and this is distinct from kink instability, which converts magnetic twist into the writhe of the MFR axis.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Perihelion passes on Parker Solar Probe orbits 6–9 have been studied to show that solar wind core electrons emerged from 15 solar radii with a temperature of 55 ± 5 eV, independent of the solar wind speed, which varied from 300 to 800 km s<jats:sup>−1</jats:sup>. After leaving 15 solar radii and in the absence of triggered ion acoustic waves at greater distances, the core electron temperature varied with radial distance, <jats:italic>R</jats:italic>, in solar radii, as 1900<jats:italic>R</jats:italic> <jats:sup>−4/3</jats:sup> eV because of cooling produced by the adiabatic expansion. The coefficient, 1900, reproduces the minimum core electron perpendicular temperature observed during the 25 days of observation. In the presence of triggered ion acoustic waves, the core electrons were isotropically heated as much as a factor of two above the minimum temperature, 1900<jats:italic>R</jats:italic> <jats:sup>−4/3</jats:sup> eV. Triggered ion acoustic waves were the only waves observed in coincidence with the core electron heating. They are the dominant wave mode at frequencies greater than 100 Hz at solar distances between 15 and 30 solar radii.</jats:p>