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Abstract The JWST Disk Infrared Spectral Chemistry Survey (JDISCS) aims to understand the evolution of the chemistry of inner protoplanetary disks using the Mid-InfraRed Instrument (MIRI) on the James Webb Space Telescope (JWST). With a growing sample of >30 disks, the survey implements a custom method to calibrate the MIRI Medium Resolution Spectrometer (MRS) to contrasts of better than 1:300 across its 4.9–28μm spectral range. This is achieved using observations of Themis family asteroids as precise empirical reference sources. The high spectral contrast enables precise retrievals of physical parameters, searches for rare molecular species and isotopologues, and constraints on the inventories of carbon- and nitrogen-bearing species. JDISCS also offers significant improvements to the MRS wavelength and resolving power calibration. We describe the JDISCS calibrated data and demonstrate their quality using observations of the disk around the solar-mass young star FZ Tau. The FZ Tau MIRI spectrum is dominated by strong emission from warm water vapor. We show that the water and CO line emission originates from the disk surface and traces a range of gas temperatures of ∼500–1500 K. We retrieve parameters for the observed CO and H₂O lines and show that they are consistent with a radial distribution represented by two temperature components. A high water abundance ofn(H₂O) ∼ 10⁻⁴fills the disk surface at least out to the 350 K isotherm at 1.5 au. We search the FZ Tau environs for extended emission, detecting a large (radius of ∼300 au) ring of emission from H₂gas surrounding FZ Tau, and discuss its origin. 

Abstract We present a multi-epoch spectroscopic study of LkCa 4, a heavily spotted non-accreting T Tauri star. Using SpeX at NASA’s Infrared Telescope Facility (IRTF), 12 spectra were collected over five consecutive nights, spanning ≈1.5 stellar rotations. Using the IRTF SpeX Spectral Library, we constructed empirical composite models of spotted stars by combining a warmer (photosphere) standard star spectrum with a cooler (spot) standard weighted by the spot filling factor,f_spot. The best-fit models spanned two photospheric component temperatures,T_phot= 4100 K (K7V) and 4400 K (K5V), and one spot component temperature,T_spot= 3060 K (M5V) with anA_Vof 0.3. We find values off_spotto vary between 0.77 and 0.94 with an average uncertainty of ∼0.04. The variability off_spotis periodic and correlates with its 3.374 day rotational period. Using a mean value forf^mean_spotto represent the total spot coverage, we calculated spot corrected values forT_effandL_⋆. Placing these values alongside evolutionary models developed for heavily spotted young stars, we infer mass and age ranges of 0.45–0.6M_⊙and 0.50–1.25 Myr, respectively. These inferred values represent a twofold increase in the mass and a twofold decrease in the age as compared to standard evolutionary models. Such a result highlights the need for constraining the contributions of cool and warm regions of young stellar atmospheres when estimatingT_effandL_⋆to infer masses and ages as well as the necessity for models to account for the effects of these regions on the early evolution of low-mass stars. 

Abstract We use the known surface boulder-size distribution of the C-type rubble pile asteroid Ryugu (NEA 162173) to determine its macroporosity, assuming it is a homogeneous granular aggregate. We show that the volume-frequency distribution of its boulders, cobbles, and pebbles, is well-represented by a lognormal function withσ= 2.4 ± 0.1 andμ= 0.2 ± 0.05. Application of linear-mixture packing theory yields a value for the macroporosity ofϕ= 0.14 ± 0.04. Given its low bulk density of 1.19 gm cm⁻³, this implies an average density for Ryugu’s rocks of 1.38 ± 0.07 gm cm⁻³throughout its volume, consistent with a recent determination for surface boulders based on their thermal properties. This supports the spectrum-based argument that interplanetary dust particles may be the best analog material available on Earth, and it suggests that high-density, well-lithified objects such as chondrules and chondrule-bearing chondrites may be rare on Ryugu. Implications of this result for the origin of chondrules, a long-standing problem in cosmochemistry, are discussed. We propose that chondrules and most chondrites formed together in rare lithification events, which occurred during the accretion of chondritic envelopes to large, differentiated planetesimals at a time when they were still hot from²⁶Al decay. 

Abstract This paper documents the seventeenth data release (DR17) from the Sloan Digital Sky Surveys; the fifth and final release from the fourth phase (SDSS-IV). DR17 contains the complete release of the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey, which reached its goal of surveying over 10,000 nearby galaxies. The complete release of the MaNGA Stellar Library accompanies this data, providing observations of almost 30,000 stars through the MaNGA instrument during bright time. DR17 also contains the complete release of the Apache Point Observatory Galactic Evolution Experiment 2 survey that publicly releases infrared spectra of over 650,000 stars. The main sample from the Extended Baryon Oscillation Spectroscopic Survey (eBOSS), as well as the subsurvey Time Domain Spectroscopic Survey data were fully released in DR16. New single-fiber optical spectroscopy released in DR17 is from the SPectroscipic IDentification of ERosita Survey subsurvey and the eBOSS-RM program. Along with the primary data sets, DR17 includes 25 new or updated value-added catalogs. This paper concludes the release of SDSS-IV survey data. SDSS continues into its fifth phase with observations already underway for the Milky Way Mapper, Local Volume Mapper, and Black Hole Mapper surveys. 

ABSTRACT We present the second data release for the H i-MaNGA programme of H i follow-up observations for the SDSS-IV MaNGA survey. This release contains measurements for 3669 unique galaxies, combining 2108 Green Bank Telescope observations with an updated crossmatch of the MaNGA sample with the ALFALFA survey. We combine these data with MaNGA spectroscopic measurements to examine relationships between H i-to-stellar mass ratio ($${\rm M_{H\, {\small I}}/{M_*}}$$) and average ISM/star formation properties probed by optical emission lines. $${\rm M_{H\, {\small I}}/{M_*}}$$ is very weakly correlated with the equivalent width of H α, implying a loose connection between the instantaneous star formation rate and the H i reservoir, although the link between $${\rm M_{H\, {\small I}}/{M_*}}$$ and star formation strengthens when averaged even over only moderate time-scales (∼30 Myr). Galaxies with elevated H i depletion times have enhanced [O i]/H α and depressed H α surface brightness, consistent with more H i residing in a diffuse and/or shock-heated phase that is less capable of condensing into molecular clouds. Of all optical lines, $${\rm M_{H\, {\small I}}/{M_*}}$$ correlates most strongly with oxygen equivalent width, EW(O), which is likely a result of the existing correlation between $${\rm M_{H\, {\small I}}/{M_*}}$$ and gas-phase metallicity. Residuals in the $${\rm M_{H\, {\small I}}/{M_*}}$$−EW(O) relation are again correlated with [O i]/H α and H α surface brightness, suggesting they are also driven by variations in the fraction of diffuse and/or shock-heated gas. We recover the strong anticorrelation between $${\rm M_{H\, {\small I}}/{M_*}}$$ and gas-phase metallicity seen in previous studies. We also find a relationship between $${\rm M_{H\, {\small I}}/{M_*}}$$ and [O i]6302/H α, suggesting that higher fractions of diffuse and/or shock-heated gas are more prevalent in gas-rich galaxies. 

ABSTRACT New long Chandra grating observations of the O supergiant ζ Pup show not only a brightening of the X-ray emission line flux of 13 per cent in the 18 yr since Chandra’s first observing cycle, but also clear evidence – at more than 4σ significance – of increased wind absorption signatures in its Doppler-broadened line profiles. We demonstrate this with non-parametric analysis of the profiles as well as Gaussian fitting and then use line-profile model fitting to derive a mass-loss rate of 2.47 ± 0.09 × 10−6$${\mathrm{M_{\odot }~{\mathrm{y}r^{-1}}}}$$, which is a 40 per cent increase over the value obtained from the cycle 1 data. The increase in the individual emission line fluxes is greater for short-wavelength lines than long-wavelength lines, as would be expected if a uniform increase in line emission is accompanied by an increase in the wavelength-dependent absorption by the cold wind in which the shock-heated plasma is embedded.