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In this work, we present high-resolution (R ∼ 100,000), high signal-to-noise ratio (S/N ∼ 800) spectroscopic observations for the well-known, bright, extremely metal-poor, carbon-enhanced star BD+44°493. We determined chemical abundances and upper limits for 17 elements from WIYN/NEID data, complemented with 11 abundances redetermined from Subaru and Hubble data, using the new, more accurate, stellar atmospheric parameters calculated in this work. Our analysis suggests that BD+44°493 is a low-mass (0.83 M ⊙), old (12.1–13.2 Gyr) second-generation star likely formed from a gas cloud enriched by a single metal-free 20.5 M ⊙ Population III star in the early Universe. With a disk-like orbit, BD+44°493 does not appear to be associated with any major merger event in the early history of the Milky Way. From the precision radial-velocity NEID measurements (median absolute deviation = 16 m s−1), we were able to constrain companion planetary masses around BD+44°493 and rule out the presence of planets as small as m sin i = 2 M J out to periods of 100 days. This study opens a new avenue of exploration for the intersection between stellar archaeology and exoplanet science using NEID. [ABSTRACT FROM AUTHOR]

The Core Accretion model is widely accepted as the primary mechanism for forming planets up to a few Jupiter masses. However, the formation of super-massive planets remains a subject of debate, as their formation via the Core Accretion model requires super-solar metallicities. Assuming stellar atmospheric abundances reflect the composition of protoplanetary disks, and that disk mass scales linearly with stellar mass, we calculated the total amount of metals in planet-building materials that could contribute to the formation of massive planets. In this work, we studied a sample of 172 Jupiter-mass planets and 93 planets with masses exceeding 4 M ♃ . Our results consistently demonstrate that planets with masses above 4 M ♃ form in disks with at least as much metal content as those hosting planets with masses between 1 and 4 M ♃ , often with slightly higher metallicity, typically exceeding that of the proto-solar disk. We interpret this as strong evidence that the formation of very massive Jupiters is feasible through Core Accretion and encourage planet formation modelers to test our observational conclusions. [ABSTRACT FROM AUTHOR]

Stellar evolution models serve as tools to derive stellar parameters from elemental and isotopic abundance ratios. For low-to-intermediate mass evolved stars, C/O, 12C/13C, and 17O/18O ratios are proxies of the initial mass, a largely unknown parameter in post-AGB sources, yet fundamental to establish correlations with the main properties of their post-AGB envelopes, progressing in understanding their formation and evolution. In these sources, the C/O ratio can be constrained from the detection of C- or O-bearing species in addition to CO, while the 17O/18O ratio is straightforwardly determined from the C17O-to-C18O intensity ratio of rotational lines. However, the theory is at odds with the observations. We review the status of the question, including new accurate 17O/18O ratios for 11 targets (totaling 29). Comparing the results for the 17O/ 18 O ratios and C-rich/O-rich chemical composition, we find that ∼45% of the cases are canonical, i.e., the observations align with standard model predictions. O-rich non-canonical sources, with 17 O/ 18 O ratios above the expected, can be explained by a premature interruption of their AGB evolution as a consequence of a quasi-explosive ejection of a large fraction of the initial mass. For non-canonical C-rich sources, with 17 O/ 18 O ratios below predictions, we suggest the possibility they are extrinsic C-rich stars. [ABSTRACT FROM AUTHOR]

The most metal-poor stars record the earliest metal enrichment triggered by Population III stars. By comparing observed abundance patterns with theoretical yields of metal-free stars, physical properties of their first star progenitors can be inferred, including zero-age main-sequence mass and explosion energy. In this work, the initial mass distribution of the first stars is obtained from the largest analysis to date of 406 very metal-poor stars with the newest LAMOST/Subaru high-resolution spectroscopic observations. However, the mass distribution fails to be consistent with the Salpeter initial mass function, which is also reported by previous studies. Here, we modify the standard power-law function with explodability theory. The mass distribution of Population III stars could be well explained by ensuring that the initial metal enrichment originates from successful supernova explosions. Based on the modified power-law function, we suggest an extremely top-heavy or nearly flat initial mass function with a large exponent for the explosion energy. This indicates that supernova explodability should be considered in the earliest metal enrichment process in the Universe. [ABSTRACT FROM AUTHOR]

Numerous stars exhibit surprisingly large variations in their refractory element abundances, often interpreted as signatures of planetary ingestion events. In this study, we propose that differences in the dust-to-gas ratio near stars during their formation can produce similar observational signals. We investigate this hypothesis using a suite of radiation-dust-magnetohydrodynamic STAR FORmation in Gaseous Environments (or STARFORGE) simulations of star formation. Our results show that the distribution of refractory abundance variations (Δ[X/H]) has extended tails, with about 10%–30% of all stars displaying variations around ∼0.1 dex. These variations are comparable to the accretion of 2–5 M ⊕ of planetary material into the convective zones of Sun-like stars. The width of the distributions increases with the incorporation of more detailed dust physics, such as radiation pressure and back-reaction forces, as well as with larger dust grain sizes and finer resolutions. Furthermore, our simulations reveal no correlation between Δ[X/H] and stellar separations, suggesting that dust-to-gas fluctuations likely occur on scales smaller than those of wide binaries. These findings highlight the importance of considering dust dynamics as a potential source of the observed chemical enrichment in stars. [ABSTRACT FROM AUTHOR]

The first generations of stars left their chemical fingerprints on metal-poor stars in the Milky Way and its surrounding dwarf galaxies. While instantaneous and homogeneous enrichment implies that groups of conatal stars should have the same element abundances, small amplitudes of abundance scatter are seen at fixed [Fe/H]. Measurements of intrinsic abundance scatter have been made with small high-resolution spectroscopic data sets where measurement uncertainty is small compared to this scatter. In this work, we present a method to use mid-resolution survey data, which have larger errors, to make this measurement. Using APOGEE Data Release 17, we calculate the intrinsic scatter of Al, O, Mg, Si, Ti, Ni, and Mn relative to Fe for 333 metal-poor stars across six classical dwarf galaxies around the Milky Way, and 1604 stars across 19 globular clusters (GCs). We calibrate the reported abundance errors in bins of signal-to-noise ratio and [Fe/H] using a high-fidelity halo data set. Applying these calibrated errors to the APOGEE data, we find small amplitudes of average intrinsic abundance scatter in dwarf galaxies ranging from 0.03 to 0.09 dex, with a median value of 0.047 dex. For the GCs, we find intrinsic scatters ranging from 0.01 to 0.11 dex, with particularly high scatter for Al and O. Our measurements of intrinsic abundance scatter place important upper bounds, which are limited by our calibration, on the intrinsic scatter in these systems, as well as constraints on their underlying star formation history and mixing that we can look to simulations to interpret. [ABSTRACT FROM AUTHOR]

The elemental and isotopic abundances of volatiles like carbon, oxygen, and nitrogen may trace a planet's formation location relative to H2O, CO2, CO, NH3, and N2 "snowlines," or the distance from the star at which these volatile elements sublimate. By comparing the C/O and 12C/13C ratios measured in giant exoplanet atmospheres to complementary measurements of their host stars, we can determine whether the planet inherited stellar abundances from formation inside the volatile snowlines, or nonstellar C/O and 13C enrichment characteristic of formation beyond the snowlines. To date, there are still only a handful of exoplanet systems where we can make a direct comparison of elemental and isotopic CNO abundances between an exoplanet and its host star. Here, we present a 12C/13C abundance analysis for host star WASP-77A (whose hot Jupiter's 12C/13C abundance was recently measured). We use MARCS stellar atmosphere models and the radiative transfer code TurboSpectrum to generate synthetic stellar spectra for isotopic abundance calculations. We find a 12C/13C ratio of 51 ± 6 for WASP-77A, which is subsolar (∼91) but may still indicate 13C enrichment in its companion planet WASP-77A b (12C/13C = 26 ± 16, previously reported). Together with the inventory of carbon and oxygen abundances in both the host and companion planet, these chemical constraints point to WASP-77A b's formation beyond the H2O and CO2 snowlines and provide chemical evidence for the planet's migration to its current location ∼0.024 au from its host star. [ABSTRACT FROM AUTHOR]

Ongoing improvements in the sensitivity of sub-mm- and mm-range interferometers and single-dish radio telescopes allow for the increasingly detailed study of AGB and post-AGB objects in molecular species other than CO 12 and CO 13 . With a new update introduced in the modelling tool SHAPE + shapemol, we can now create morpho-kinematical models to reproduce observations of these AGB and post-AGB circumstellar shells in different molecular species, allowing for an accurate description of their physical features as well as their molecular abundances and isotopic ratios. The pre-planetary nebula M1-92 (Minkowski's Footprint) is one of the most complex objects of this kind, with a wide range of physical conditions and more than 20 molecular species detected. We model this nebula, reproducing the observational data from IRAM-30m and HSO/HiFi spectra and NOEMA interferometric maps, trying to understand the unusual evolution of its central star in the last phases of its life. The results show interesting features that tell us the story of its death. According to standard evolution models, a O 17 / O 18 isotopic ratio of 1.6 implies a stellar initial mass of ∼1.7 M ⊙ . Such a star should have turned C-rich by the end of the AGB phase, in striking contrast to the O-rich nature of the nebula. The most plausible way of reconciling this discrepancy is that M1-92 resulted from a sudden massive ejection event, interrupting the AGB evolution of the central source and preventing its transformation into a C-rich star. We also detect a changing C 12 / C 13 ratio across the nebula, which is particularly relevant in the inner equatorial region traced by HCO + and H 13 CO + , indicating an isotopic ratio variation taking place at some point during the last 1200 yr. [ABSTRACT FROM AUTHOR]

Gas-phase abundance ratios between C2H4O2 isomers methyl formate (MF), glycolaldehyde (GA), and acetic acid (AA) are typically on the order of 100:10:1 in star-forming regions. However, an unexplained divergence from this neat relationship was recently observed toward a collection of sources in the massive protocluster NGC 6334I; some sources exhibited extreme MF:GA ratios, producing a bimodal behavior between different sources, while the MF:AA ratio remained stable. Here, we use a three-phase gas-grain hot-core chemical model to study the effects of a large parameter space on the simulated C2H4O2 abundances. A combination of high gas densities and long timescales during ice-mantle desorption (∼125–160 K) appears to be the physical cause of the high MF:GA ratios. The main chemical mechanism for GA destruction occurring under these conditions is the rapid adsorption and reaction of atomic H with GA on the ice surfaces before it has time to desorb. The different binding energies of MF and GA on water ice are crucial to the selectivity of the surface destruction mechanism; individual MF molecules rapidly escape the surface when exposed by water loss, while GA lingers and is destroyed by H. Moderately elevated cosmic-ray ionization rates can increase absolute levels of "complex organic molecule" (COM) production in the ices and increase the MF:GA ratio, but extreme values are destructive for gas-phase COMs. We speculate that the high densities required for extreme MF:GA ratios could be evidence of COM emission dominated by COMs desorbing within a circumstellar disk. [ABSTRACT FROM AUTHOR]

The source of the Galactic lithium (Li) has long been a puzzle. With the discovery of Li in novae, extensive research has been conducted. However, there still exists a significant disparity between the observed abundance of Li in novae and the existing theoretical predictions. Using the Modules for Experiments in Stellar Astrophysics, we simulate the evolution of novae with element diffusion and appropriately increase the amount of 3He in the mixtures. Element diffusion enhances the transport efficiency between the nuclear reaction zone and the convective region on the surface of the white dwarf (WD) during nova eruptions, which results in more 7Be being transmitted to the WD surface and ultimately ejected. Compared to the previous predictions, the abundance of 7Be in novae simulated in our model significantly increases. The result is able to explain almost all observed novae. Using the method of population synthesis, we calculate Li yield in the Galaxy. We find that the Galactic occurrence rate of novae is about 130 yr−1, and about 110 M ⊙ Li produced by nova eruption is ejected into the interstellar medium (ISM). About 73% of Li in the Galactic ISM originates from novae and approximately 15%–20% of the entire Galaxy. This means that novae are the important source of Li in the Galaxy. [ABSTRACT FROM AUTHOR]

Infrared spectroscopic observations have established the presence of solid methanol (CH3OH) in the interstellar medium and in solar system ices, but the abundance of frozen CH3OH cannot be deduced without accurate band strengths, optical constants, and reference spectra. In this paper we identify disagreements, omissions, and gaps in the literature on infrared (IR) intensities of methanol ices, including unaddressed concerns that reach back several decades. New spectra are presented with intensity measurements aided by new data on the index of refraction and density of solid CH3OH. The result is that the large discordant results from different laboratory groups can now be reconciled. Multiple ices have been used to determine, apparently for the first time, IR intensities of H2O + CH3OH mixtures of accurately known composition for use with observations of interstellar ices. Also for the first time, measurements on CH3OH ices with different thicknesses have allowed us to report both near-IR band strengths and optical constants for two near-IR features used by planetary scientists. We have used our new IR results to determine vapor pressures of solid CH3OH and have compared them to measurements made with a quartz-crystal microbalance. Thermal annealings of methanol ices have been carried out and phase changes in the solid state examined. Comparisons of our results to earlier work are presented where possible, and electronic versions of our new results are made available. [ABSTRACT FROM AUTHOR]

M15 is a globular cluster with a known spread in neutron-capture elements. This paper presents abundances of neutron-capture elements for 62 stars in M15. Spectra were obtained with the Michigan/Magellan Fiber System spectrograph, covering a wavelength range from ∼4430 to 4630 Å. Spectral lines from Fe i, Fe ii, Sr i, Zr ii, Ba ii, La ii, Ce ii, Nd ii, Sm ii, Eu ii, and Dy ii were measured, enabling classifications and neutron-capture abundance patterns for the stars. Of the 62 targets, 44 are found to be highly Eu-enhanced r -II stars, another 17 are moderately Eu-enhanced r -I stars, and one star is found to have an s -process signature. The neutron-capture patterns indicate that the majority of the stars are consistent with enrichment by the r -process. The 62 target stars are found to show significant star-to-star spreads in Sr, Zr, Ba, La, Ce, Nd, Sm, Eu, and Dy, but no significant spread in Fe. The neutron-capture abundances are further found to have slight correlations with sodium abundances from the literature, unlike what has been previously found; follow-up studies are needed to verify this result. The findings in this paper suggest that the Eu-enhanced stars in M15 were enhanced by the same process, that the nucleosynthetic source of this Eu pollution was the r -process, and that the r -process source occurred as the first generation of cluster stars was forming. [ABSTRACT FROM AUTHOR]

We present chemical abundances of the very bright metal‐poor star HD 1936 based on high‐resolution and high SNR spectra from AUKR. We obtain the abundances of 29 atomic species with atomic numbers between 3 and 63. In this context, the derived lithium abundance of 1.01 is consistent with the thin Li plateau observed in lower red giant branch stars. The star is a carbon‐normal with a ratio of −0.31, just like other low‐luminosity red giants on the thin Li plateau. We find the ratios of [Eu/Fe] = 0.43 and [Ba/Eu] = −0.64, indicating very little s‐process contamination. These ratios allow us to classify the star as a moderately r‐process‐enhanced (r‐I) metal‐poor star for the first time. It is worth mentioning that the star has a metallicity of −1.74, a [Cu/Fe] of −0.74, a [Zn/Fe] of 0.04, and a [Mg/C] of 0.69. The results suggest that it may be a second‐generation star formed in a multi‐enriched environment, rather than being a descendant of very massive first‐generation stars. A last point worth mentioning is the possibility that HD 1936 may host a sub‐stellar component with a mass of 18.35MJ$$ 18.35{M}_{\mathrm{J}} $$. Although our study does not confirm or deny this, we briefly discuss the possibility of the star hosting a planet. [ABSTRACT FROM AUTHOR]

Gas-phase metallicity gradients are a crucial element in understanding the chemical evolution of galaxies. We use the FOGGIE simulations to study the metallicity gradients (∇ Z ) of six Milky Way–like galaxies throughout their evolution. FOGGIE galaxies generally exhibit steep negative gradients for most of their history, with only a few short-lived instances reaching positive slopes that appear to arise mainly from interactions with other galaxies. FOGGIE concurs with other simulation results but disagrees with the robust observational finding that flat and positive gradients are common at z > 1. By tracking the metallicity gradient at a rapid cadence of simulation outputs (∼5–10 Myr), we find that theoretical gradients are highly stochastic: the FOGGIE galaxies spend ∼30%–50% of their time far away from a smoothed trajectory inferred from analytic models or other, less high-cadence simulations. This rapid variation makes instantaneous gradients from observations more difficult to interpret in terms of physical processes. Because of these geometric and stochastic complications, we explore nonparametric methods of quantifying the evolving metallicity distribution at z > 1. We investigate how efficiently nonparametric measures of the 2D metallicity distribution respond to metal production and mixing. Our results suggest that new methods of quantifying and interpreting gas-phase metallicity will be needed to relate trends in upcoming high- z James Webb Space Telescope observations with the underlying physics of gas accretion, expulsion, and recycling in early galaxies.

In this study, we present a detailed analysis of CN Lyn, an overlooked triple star system, by combining spectroscopic data from the literature, photometric Transiting Exoplanet Survey Satellite data, and kinematic techniques. We updated the fundamental parameters of the known eclipsing components in the system with high precision. The chemical composition of both eclipsing components (Aab) and the third component (B) in the system were calculated with great accuracy. According to our analysis the mass, radius, and metallicity of the eclipsing components are $1.16{6}_{-0.012}^{+0.013}\,{M}_{\odot }$ , $1.78{6}_{-0.014}^{+0.013}\,{R}_{\odot }$ , and $-0.7{8}_{-0.02}^{+0.02}$ dex for Aa and $1.14{3}_{-0.012}^{+0.013}\,{M}_{\odot }$ , $1.65{1}_{-0.013}^{+0.014}\,{R}_{\odot }$ , and $-0.5{5}_{-0.02}^{+0.03}$ dex for Ab. The pair’s age is $3.8{9}_{-0.10}^{+0.10}$ Gyr. The mass, radius, metallicity, and age for B are $0.8{5}_{-0.23}^{+0.23}\,{M}_{\odot }$ , $1.43{6}_{-0.023}^{+0.026}\,{R}_{\odot }$ , $-1.8{3}_{-0.11}^{+0.09}$ dex, and $12.{5}_{-2.5}^{+2.5}$ Gyr, respectively. It is also found that the triple system (AabB) satisfies the stability criteria for the hierarchical triple system. Kinematic and Galactic orbital parameters of CN Lyn were obtained from the astrometric and spectroscopic data of the system. Dynamical orbital analyses, taking into account the ages of the component stars in the central binary system (A), show that the CN Lyn originated at the metal-poor edge of the Galactic disk. The third component of the system was found to be a member of the halo population in terms of age, α elements, and metal abundance. Given the different chemical abundances and age of B compared to A, this suggests that the third component was captured by the central system in a region with weak gravitational interactions far beyond the Galactic disk.

We extend the methodology introduced by F. Jahandar et al. to determine the effective temperature and chemical abundances of 31 slowly rotating solar neighborhood M dwarfs (M1–M5) using high-resolution spectra from CFHT/SPIRou. This group includes 10 M dwarfs in binary systems with FGK primaries of known metallicity from optical measurements. By testing our T _eff method on various synthetic models, we find a consistent inherent synthetic uncertainty of ∼10 K at a signal-to-noise ratio greater than 100. Additionally, we find that our results align with interferometric measurements, showing a consistent residual of −29 ± 31 K. Taking the inherent uncertainties into account, we infer the T _eff values of our targets and find an excellent agreement with previous optical and near-infrared studies. Our high-resolution chemical analysis examines hundreds of absorption lines using χ ^2 minimization using PHOENIX-ACES stellar atmosphere models. We present elemental abundances for up to 10 different elements, including refractory elements such as Si, Mg, and Fe, which are important for modeling the interior structure of exoplanets. In binary systems, we find an average [Fe/H] of −0.15 ± 0.08 for M dwarfs, marginally lower than the reported metallicity of −0.06 ± 0.18 for the FGK primaries from A. W. Mann et al. We also observe slightly subsolar chemistry for various elements in our nonbinary M dwarfs, most notably for O, C, and K abundances. In particular, we find an average metallicity of −0.11 ± 0.16, lower but still consistent with the typical solar metallicity of FGK stars (e.g., [Fe/H] = 0.04 ± 0.20 from J. M. Brewer et al. 2016). This study highlights significant discrepancies in various major M dwarf surveys likely related to differences in the methodologies employed.

Building on our previous research involving multiwavelength data from UV to IR, we employ spectroscopic observations of ionized gas, as well as neutral hydrogen gas obtained from the Five-hundred Meter Aperture Spherical Telescope (FAST), to explore the intrinsic processes of star formation and chemical enrichment within NGC 628. Our analysis focuses on several key properties, including gas-phase extinction, star formation rate (SFR) surface density, oxygen abundance, and H i mass surface density. The azimuthal distributions of these parameters in relation to the morphological and kinematic features revealed by FAST H i reveal that NGC 628 is an isolated galaxy that has not undergone recent interactions. We observe a mild radial extinction gradient accompanied by a notable dispersion. The SFR surface density also shows a gentle radial gradient, characteristic of typical spiral galaxies. Additionally, we find a negative radial metallicity gradient of −0.44 dex ${R}_{25}^{-1}$ , supporting the “inside-out” scenario of galaxy formation. We investigate the resolved mass–metallicity relation (MZR) and the resolved star formation main sequence (SFMS) alongside their dependences on the physical properties of both ionized and neutral hydrogen gas. Our findings indicate no secondary dependence of the resolved MZR on SFR surface density or H i mass surface density. Furthermore, we observe that gas-phase extinction and the equivalent width of H α both increase with SFR surface density in the resolved SFMS.

Investigating the temperature and density structures of gas in massive protoclusters is crucial for understanding the chemical properties therein. In this study, we present observations of the continuum and thioformaldehyde (H2CS) lines at 345 GHz of 11 massive protoclusters using the Atacama Large Millimeter/submillimeter Array telescope. High spatial resolution and sensitivity observations have detected 145 continuum cores from the 11 sources. H2CS line transitions are observed in 72 out of 145 cores, including line-rich cores, warm cores, and cold cores. The H2 column densities of the 72 cores are estimated from the continuum emission, which are larger than the density threshold value for star formation, suggesting that H2CS can be widely distributed in star-forming cores with different physical environments. The rotation temperature and column density of H2CS are derived using the XCLASS software. The results show that the H2CS abundances increase as temperature rises and higher gas temperatures are usually associated with higher H2CS column densities. The abundances of H2CS are positively correlated with its column density, suggesting that the H2CS abundances are enhanced from cold cores, warm cores, and line-rich cores in star-forming regions. [ABSTRACT FROM AUTHOR]

Stellar evolution models serve as tools to derive stellar parameters from elemental and isotopic abundance ratios. For low-to-intermediate mass evolved stars, C/O, 12C/13C, and 17O/18O ratios are proxies of the initial mass, a largely unknown parameter in post-AGB sources, yet fundamental to establish correlations with the main properties of their post-AGB envelopes, progressing in understanding their formation and evolution. In these sources, the C/O ratio can be constrained from the detection of C- or O-bearing species in addition to CO, while the 17O/18O ratio is straightforwardly determined from the C17O-to-C18O intensity ratio of rotational lines. However, the theory is at odds with the observations. We review the status of the question, including new accurate 17O/18O ratios for 11 targets (totaling 29). Comparing the results for the 17O/18O ratios and C-rich/O-rich chemical composition, we find that ∼45% of the cases are canonical, i.e., the observations align with standard model predictions. O-rich non-canonical sources, with 17O/18O ratios above the expected, can be explained by a premature interruption of their AGB evolution as a consequence of a quasi-explosive ejection of a large fraction of the initial mass. For non-canonical C-rich sources, with 17O/18O ratios below predictions, we suggest the possibility they are extrinsic C-rich stars.

The nonlocal thermodynamical equilibrium (NLTE) line formation of Y i and Y ii is considered in 1D LTE model atmospheres of FGK-type stars. The model atom was constructed with the most up-to-date atomic data, including quantum cross sections and rate coefficients for transitions in inelastic collisions of Y i and Y ii with hydrogen atoms. For seven reference stars, we obtained an agreement between NLTE abundances inferred from the two ionization stages, while the difference in LTE abundance (Y i and Y ii) can reach up to −0.31 dex. In the atmospheres of FGK-type stars, for both Y i and Y ii lines, the NLTE abundance corrections are positive. In solar metallicity stars, the NLTE abundance corrections for Y ii lines do not exceed 0.12 dex, while in atmospheres of metal-poor stars, they do not exceed 0.21 dex. For Y i lines, the NLTE abundance corrections can reach up to ∼0.5 dex. We determined the yttrium NLTE abundances for a sample of 65 F and G dwarfs and subgiants in the −2.62 ≤ [Fe/H] ≤ +0.24 metallicity range, using high-resolution spectra. For stars with [Fe/H] ≤ −1.5, [Y/Fe] versus [Fe/H] diagram reveals a positive trend with an average value of [Y/Fe] ≃ 0. For metal-poor stars, among Sr, Y, and Zr, the arrangement [Sr/Fe] < [Y/Fe] < [Zr/Fe] remains consistent. The current study is useful for Galactic chemical evolution research. The model atom will be applied for NLTE yttrium abundance determination in very metal-poor stars studied with LAMOST and Subaru. [ABSTRACT FROM AUTHOR]

We investigated NGC 6572 through optical spectroscopy to determine its kinematical and chemical properties. Two intermediate dispersion spectra (R~5000) centered around Hα and Hβ were used to derive the nebular expansion velocity from emission lines associated with Hα, Hβ, [OIII], [NII], and [SII] ions. A low dispersion spectrum (R~1000) was used to determine the nebular electron temperature, density, and chemical composition. We performed photoionization modeling to construct a self-consistent nebular model, while intermediate-resolution spectral images showed the global elliptical structure of the nebula. The expansion velocity deduced from most of the emission lines is consistent with the typical expansion velocity of planetary nebulae, i.e., around 15-20 kms-1. The nebular physical properties align well with those determined by other studies. The nebular abundances were found to be lower than the solar abundances (except for oxygen) but still comparable with the abundances derived by other researchers. The photoionization model generated spectral lines that are consistent with the lines found in the observations. Further spectroscopic observations with higher resolution and wider range at various position angles will be very useful to reveal a more complete and detailed structure of the nebula and to improve the determination of the nebular physical properties.

We interpret the peculiar supersolar nitrogen abundance recently reported by the James Webb Space Telescope observations for GN-z11 ( z = 10.6) using our state-of-the-art chemical evolution models. The observed CNO ratios can be successfully reproduced—independently of the adopted initial mass function, nucleosynthesis yields, and presence of supermassive (>1000 M _⊙ ) stars—if the galaxy has undergone an intermittent star formation history with a quiescent phase lasting ∼100 Myr, separating two strong starbursts. Immediately after the second burst, Wolf–Rayet stars (up to 120 M _⊙ ) become the dominant enrichment source, also temporarily (

Measurements of chemical abundances in high- z star-forming (SF) galaxies place important constraints on the enrichment histories of galaxies and the physical conditions in the early Universe. The James Webb Space Telescope (JWST) is beginning to enable direct chemical abundance measurements in galaxies at z > 2 via the detection of the faint T _e -sensitive auroral line [O iii ] λ 4364. However, abundances of other elements (e.g., S and Ar) in high- z galaxies remain unconstrained owing to a lack of T _e data and wavelength coverage. Here we present multiple direct abundances in Q2343-D40, a galaxy at z = 2.9628 ± 0.0001 observed with JWST/NIRSpec as part of the CECILIA program. We report the first simultaneous measurement of T _e [O iii ] and T _e [S iii ] in a high- z galaxy, finding good agreement with the temperature trends in local SF systems. We measure a gas-phase metallicity of 12+log(O/H) = 8.07 ± 0.06, and the N/O abundance, log(N/O) = −1.37 ± 0.21, is indicative of primary nucleosynthesis. The S/O and Ar/O relative abundances, log(S/O) = −1.88 ± 0.10 and log(Ar/O) = −2.80 ± 0.12, are both >0.3 dex lower than the solar ratios. However, the relative Ar ^2+ /S ^2+ abundance is consistent with the solar ratio, suggesting that the relative S-to-Ar abundance does not evolve significantly with redshift. Recent nucleosynthesis models find that significant amounts of S and Ar are produced in Type Ia supernovae, such that the S/O and Ar/O abundances in Q2343-D40 could be the result of predominantly core-collapse supernova enrichment. Future JWST observations of high- z galaxies will uncover whether S/O and Ar/O are sensitive to the timescales of these different enrichment mechanisms.

A recent study by Hon et al. reported that a close-in planet around the red clump star, 8 UMi, should have been engulfed during the expansion phase of its parent star’s evolution. They explained the survival of this exoplanet through a binary-merger channel for 8 UMi. The key to testing this formation scenario is to derive the true age of this star: is it an old “imposter” resulting from a binary merger, or a genuinely young red clump giant? To accomplish this, we derive kinematic and chemical properties for 8 UMi using astrometric data from Gaia DR3 and the element-abundance pattern measured from a high-resolution ( R ∼ 75,000) spectrum taken by SOPHIE. Our analysis shows that 8 UMi is a normal thin-disk star with orbital rotation speed of V _ϕ = 244.96 km s ^−1 , and possesses a solar metallicity ([Fe/H] = −0.05 ± 0.07) and α -element-abundance ratio ([ α /Fe] = +0.01 ± 0.03). By adopting well-established relationships between age and space velocities/elemental abundances, we estimate a kinematic age of ${3.50}_{-2.00}^{+3.00}$ Gyr, and a chemical age of ${3.25}_{-1.50}^{+2.50}$ Gyr from [C/N] and 3.47 ± 1.96 Gyr from [Y/Mg] for 8 UMi, respectively. These estimates are consistent with the isochrone-fitting age ( ${1.90}_{-0.30}^{+1.15}$ Gyr) of 8 UMi, but are all much younger than the timescale required in a binary-merger scenario. This result challenges the binary-merger model; the existence of such a closely orbiting exoplanet around a giant star remains a mystery yet to be resolved.

Unveiling the chemical fingerprints of the first (Population III, hereafter Pop III) stars is crucial for indirectly studying their properties and probing their massive nature. In particular, very massive Pop III stars explode as energetic pair-instability supernovae (PISNe), allowing their chemical products to escape in the diffuse medium around galaxies, opening the possibility to observe their fingerprints in distant gas clouds. Recently, three z > 6.3 absorbers with abundances consistent with an enrichment from PISNe have been observed with JWST. In this Letter, we present novel chemical diagnostics to uncover environments mainly imprinted by PISNe. Furthermore, we revise the JWST low-resolution measurements by analyzing the publicly available high-resolution X-Shooter spectra for two of these systems. Our results reconcile the chemical abundances of these absorbers with those from literature, which are found to be consistent with an enrichment dominated (>50% metals) by normal Pop II SNe. We show the power of our novel diagnostics in isolating environments uniquely enriched by PISNe from those mainly polluted by other Pop III and Pop II SNe. When the subsequent enrichment from Pop II SNe is included, however, we find that the abundances of PISN-dominated environments partially overlap with those predominantly enriched by other Pop III and Pop II SNe. We dub these areas confusion regions. Yet, the odd–even abundance ratios [Mg,Si/Al] are extremely effective in pinpointing PISN-dominated environments and allowed us to uncover, for the first time, an absorber consistent with a combined enrichment by a PISN and another Pop III SN for all the six measured elements.

The unprecedented infrared spectroscopic capabilities of JWST have provided high-quality interstellar medium metallicity measurements and enabled characterization of the gas-phase mass–metallicity relation (MZR) for galaxies at z ≳ 5 for the first time. We analyze the gas-phase MZR and its evolution in a high-redshift suite of FIRE-2 cosmological zoom-in simulations at z = 5–12 and for stellar masses M _* ∼ 10 ^6 –10 ^10 M _⊙ . These simulations implement a multichannel stellar feedback model and produce broadly realistic galaxy properties, including when evolved to z = 0. The simulations predict very weak redshift evolution of the MZR over the redshift range studied, with the normalization of the MZR increasing by less than 0.01 dex as redshift decreases from z = 12 to z = 5. The median MZR in the simulations is well approximated as a constant power-law relation across this redshift range given by $\mathrm{log}(Z/{Z}_{\odot })=0.37\mathrm{log}({M}_{* }/{{\rm{M}}}_{\odot })-4.3$ . We find good agreement between our best-fit model and recent observations made by JWST at high redshift. The weak evolution of the MZR at z > 5 contrasts with the evolution at z ≲ 3, where increasing normalization of the MZR with decreasing redshift is observed and predicted by most models. The FIRE-2 simulations predict increasing scatter in the gas-phase MZR with decreasing stellar mass, in qualitative agreement with some observations.

The first (Population III) stars formed only out of H and He and were likely more massive than present-day stars. Massive Population III stars in the range 140–260 M _⊙ are predicted to end their lives as pair-instability supernovae (PISNe), enriching the environment with a unique abundance pattern, with high ratios of odd to even elements. Recently, the most promising candidate for a pure descendant of a zero-metallicity massive PISN (260 M _⊙ ) was discovered by the LAMOST survey, the star J1010+2358. However, key elements to verify the high PISN contribution, C and Al, were missing from the analysis. To rectify this, we obtained and analyzed a high-resolution Very Large Telescope/UVES spectrum, correcting for 3D and/or non-local thermodynamic equilibrium effects. Our measurements of both C and Al give much higher values (∼1 dex) than expected from a 260 M _⊙ PISN. Furthermore, we find significant discrepancies with the previous analysis and therefore a much less pronounced odd–even pattern. Our results show that J1010+2358 cannot be a pure descendant of a 260 M _⊙ PISN. Instead, we find that the best-fit model consists of a 13 M _⊙ Population II core-collapse supernova combined with a Population III supernova. Alternative, less favored solutions ( ${\chi }^{2}/{\chi }_{\mathrm{best}}^{2}\approx 2.3$ ) include a 50% contribution from a 260 M _⊙ PISN or a 40% contribution from a Population III Type Ia supernova. Ultimately, J1010+2358 is certainly a unique star giving insights into the earliest chemical enrichment; however, this star is not a pure PISN descendant.

Comets are frozen remnants of our solar system’s formation, and comparing their chemical composition to that of planet-forming systems can reveal crucial insights about our origins, potentially answering one of the most challenging questions in planetary science, i.e., whether cometary material was mainly inherited from the protosolar nebula or reprocessed during the solar system formation. Here we provide the first statistical analysis of methanol, formaldehyde, and ammonia abundances in 35 comets and 11 protostellar solar analogs and planet-forming disks. We show that comets from different dynamical families have comparable compositions on average, implying that their chemistry is preserved even after formation. While abundances retrieved from infrared and (sub)millimeter ground-based observations are in agreement, there are significant differences with those obtained via mass spectroscopy for 67P/Churyumov–Gerasimenko, target of the ESA-Rosetta mission; we discuss the implication of relying solely on the latter data for comparisons with disk abundance ratios. Finally, we find a significant difference in the [CH _3 OH]/[H _2 CO] ratio in comets observed within or farther than 1 au from the Sun, suggesting that temperature-activated mechanisms can enhance the H _2 CO production in the coma; this bias can strongly influence our understanding of comet chemistry in the context of planet formation. When compared to planet-forming systems, the [CH _3 OH]/[H _2 CO] and [NH _3 ]/[CH _3 OH] molecular abundance ratios in comets are consistent with those measured in Class 0 hot corinos and in the inner regions of Class II disks, hence suggesting an inheritance scenario.

The J = 5.5 → 4.5 and J = 5 → 4 transitions of PO and PN, respectively, have been imaged in the envelope of hypergiant star VY Canis Majoris (VY CMa) using the Atacama Large Millimeter/submillimeter Array with angular resolutions of 0.″2 and 1.″5 and data from the Submillimeter Telescope of the Arizona Radio Observatory. These maps are the first high-fidelity images of PO and PN in a circumstellar envelope. Both molecules are primarily present in a spherical, star-centered region with a radius ∼60 R _* (0.″5), indicating formation by LTE chemistry and then condensation into grains. PN, however, shows additional, fan-shaped emission 2″ southwest of the star, coincident with dust features resolved by Hubble Space Telescope (HST), as well as four newly identified distinct structures 1″–2″ toward the north, east, and west (Cloudlets I–IV), not visible in HST images. The “SW Fan” and the cloudlets are also prominent in the J = 5.5 → 4.5 transition of NS. The correlation of PN with NS, SiO, and dust knots in the SW Fan suggests a formation in shocked gas enhanced with nitrogen. Excess nitrogen is predicted to favor PN synthesis over PO. Abundances for PN and PO in the spherical source are f ∼ 4.4 × 10 ^−8 and 1.4 × 10 ^−7 , respectively, relative to H _2 . Given a cosmic abundance of phosphorus, an unusually high fraction (∼35%) is contained in PO and PN. Alternatively, the stellar winds may be enriched in P (and N) by dredge-up from the interior of VY CMa.

Planets and planetesimals acquire their volatiles through ice and gas accretion in protoplanetary disks. In these disks, the division of volatile molecules between the condensed and gaseous phases determines the quantity of volatiles accreted by planets in different regions of the disk. This division can be strongly affected by entrapment of volatiles into less volatile ice matrices, resulting in different radial profiles of common volatiles and elemental ratios than would otherwise be expected. In this study we use laboratory experiments to explore the ability of abundant interstellar and cometary ice matrices, i.e., H2O and CO2, to trap the hypervolatiles 13CO, 12CH4, 15N2, and Ar. We measure entrapment efficiencies through temperature programmed desorption for two ice thicknesses (10 and 50 monolayers) and two mixing ratios (3:1 and 10:1) for each matrix:volatile combination. We find that ice entrapment efficiencies increase with ice thickness and ice mixing ratio to a maximum of ∼65% for all hypervolatiles. Entrapment efficiencies are comparable for all hypervolatiles, and for the two ice matrices. We further find that the entrapment efficiency is relatively insensitive to the ice deposition temperature between 10 and 30 K with the possible exception of CH4 in CO2 ice. Together these results suggest that hypervolatile entrapment at low temperatures (<30 K) is a remarkably robust and species-independent process. [ABSTRACT FROM AUTHOR]

The Gemini High-resolution Optical SpecTrograph (GHOST) is the newest high-resolution spectrograph to be developed for a large-aperture telescope, recently deployed and commissioned at the Gemini-South telescope. In this paper, we present the first science results from the GHOST spectrograph taking during its commissioning runs. We have observed the bright metal-poor benchmark star HD 122563, along with two stars in the ultrafaint dwarf galaxy Reticulum II (Ret ii), one of which was previously identified as a candidate member, but did not have a previous detailed chemical abundance analysis. We find that this candidate (GDR3 0928) to be a bona fide member of Ret ii, and from a spectral synthesis analysis it is also revealed to be a CEMP- r star, with significant enhancements in several light elements (C, N, O, Na, Mg, and Si), in addition to featuring an r -process enhancement like many other Ret ii stars. The light-element enhancements in this star resemble the abundance patterns seen in the CEMP-no stars of other ultrafaint dwarf galaxies, and are thought to have been produced by an independent source from the r -process. These unusual abundance patterns are thought to be produced by faint supernovae, which may be produced by some of the earliest generations of stars. [ABSTRACT FROM AUTHOR]

We search for local extremely metal-poor galaxies (EMPGs), selecting photometric candidates by broadband color excess and machine-learning techniques with the SDSS photometric data. After removing stellar contaminants by shallow spectroscopy with Seimei and Nayuta telescopes, we confirm that three candidates are EMPGs with 0.05–0.1 Z ⊙ by deep Magellan/MagE spectroscopy for faint [Oiii] λ 4363 lines. Using a statistical sample consisting of 105 spectroscopically confirmed EMPGs taken from our study and the literature, we calculate the cross-correlation function (CCF) of the EMPGs and all SDSS galaxies to quantify environments of EMPGs. Comparing another CCF of all SDSS galaxies and comparison of SDSS galaxies in the same stellar-mass range (107.0–108.4 M ⊙), we find no significant (>1 σ) difference between these two CCFs. We also compare mass–metallicity relations (MZRs) of the EMPGs and those of galaxies at z ∼ 0–4 with a steady chemical evolution model and find that the EMPG MZR is comparable with the model prediction on average. These clustering and chemical properties of EMPGs are explained by a scenario of stochastic metal-poor gas accretion on metal-rich galaxies showing metal-poor star formation. Extending the broadband color excess technique to a high- z EMPG search, we select 17 candidates of z ∼ 4–5 EMPGs with the deep (≃30 mag) near-infrared JWST/NIRCam images obtained by ERO and ERS programs. We find galaxy candidates with negligible [Oiii] λ λ 4959,5007 emission weaker than the local EMPGs and known high- z galaxies, suggesting that some of these candidates may fall in the range of 0–0.01 Z ⊙, which potentially breaks the lowest metallicity limit known to date. [ABSTRACT FROM AUTHOR]

We investigated NGC 6572 through optical spectroscopy to determine its kinematical and chemical properties. Two intermediate dispersion spectra (R~5000) centered around Ha and Hß were used to derive the nebular expansion velocity from emission lines associated with Ha, Hß, [OIII], [NII], and [SII] ions. A low dispersion spectrum (R~1000) was used to determine the nebular electron temperature, density, and chemical composition. We performed photoionization modeling to construct a self-consistent nebular model, while intermediate-resolution spectral images showed the global elliptical structure of the nebula. The expansion velocity deduced from most of the emission lines is consistent with the typical expansion velocity of planetary nebulae, i.e., around 15-20 kms-1. The nebular physical properties align well with those determined by other studies. The nebular abundances were found to be lower than the solar abundances (except for oxygen) but still comparable with the abundances derived by other researchers. The photoionization model generated spectral lines that are consistent with the lines found in the observations. Further spectroscopic observations with higher resolution and wider range at various position angles will be very useful to reveal a more complete and detailed structure of the nebula and to improve the determination of the nebular physical properties. [ABSTRACT FROM AUTHOR]

We present emission-line measurements and physical interpretations for a sample of 117 [O iii ] emitting galaxies at z = 5.33–6.93, using the first deep JWST/NIRCam wide-field slitless spectroscopic observations. Our 9.7 hr integration is centered upon the z = 6.3 quasar J0100+2802—the first of six fields targeted by the EIGER survey—and covers λ = 3–4 μ m. We detect 133 [O iii ] doublets, but close pairs motivated by their small scale clustering excess. The galaxies are characterized by a UV luminosity M UV ∼ −19.6 (−17.7 to −22.3), stellar mass ∼108 (106.8−10.1) M ⊙, H β and [O iii ]4960+5008 EWs ≈ 850 Å (up to 3000 Å), young ages, a highly excited interstellar medium, and low dust attenuations. These high EWs are very rare in the local universe, but we show they are ubiquitous at z ∼ 6 based on the measured number densities. The stacked spectrum reveals H γ and [O iii ]4364, which shows that the galaxies are typically dust- and metal-poor (E (B − V) = 0.1, 12 + log (O / H) = 7.4) with a high electron temperature (2 × 104 K) and a production efficiency of ionizing photons (ξ ion = 1025.3 Hz erg−1). We further show the existence of a strong mass–metallicity relation. The properties of the stars and gas in z ∼ 6 galaxies conspire to maximize the [O iii ] output from galaxies, yielding an [O iii ] luminosity density at z ≈ 6 that is significantly higher than that at z ≈ 2. Thus, [O iii ] emission-line surveys with JWST prove a highly efficient method to trace the galaxy density in the Epoch of Reionization. [ABSTRACT FROM AUTHOR]

We present a sample of 330 blue edge-on low surface brightness galaxies (ELSBGs). To understand the chemical evolution of ELSBGs, we derived the gas-phase abundance and the [ α /Fe] ratio. Compared with star-forming galaxies, ELSBGs show a flatter trend in the mass–metallicity (M *– Z) relation, which suggests that the oxygen abundance enhancement is inefficient. We focused on 77 ELSBGs with H i data and found that the closed-box model cannot explain their gas fraction and metallicity relation, which implies that infall and/or outflow is needed. We derived the [ α /Fe] ratio of normal ELSBG (<109.5 M ⊙) and massive ELSBG (> = 109.5 M ⊙) using single stellar population grids from the MILES stellar library. The mean [ α /Fe] ratios are 0.18 and 0.4 for normal ELSBG and massive ELSBG, respectively. We suggest that the long timescales of star formation and/or metal-rich gas outflow events caused by SNe Ia winds are likely to be responsible for the α -enhancement of massive ELSBGs. [ABSTRACT FROM AUTHOR]

Rotating massive stars with initial progenitor masses M prog ∼ 25–140 M ⊙ can leave rapidly rotating black holes to become collapsars. The black holes and the surrounding accretion disks may develop powerful jets by magnetohydrodynamics instabilities. The propagation of the jet in the stellar envelope provides the necessary shock heating for triggering nucleosynthesis unseen in canonical core-collapse supernovae. However, the energy budget of the jet and its effects on the final chemical abundance pattern are unclear. In this exploratory work, we present a survey on the parameter dependence of collapsar nucleosynthesis on jet energetics. We use the zero-metallicity star with M prog ∼ 40 M ⊙ as the progenitor. The parameters include the jet duration, its energy deposition rate, deposited energy, and the opening angle. We examine the correlations of the following observables: (1) the ejecta and remnant masses; (2) the energy deposition efficiency; (3) the 56Ni production and its correlation with the ejecta velocity, deposited energy, and the ejected mass; (4) the Sc–Ti–V correlation as observed in metal-poor stars; and (5) the [Zn/Fe] ratio as observed in some metal-poor stars. We also provide the chemical abundance table of these explosion models for the use of the galactic chemical evolution and stellar archeology. [ABSTRACT FROM AUTHOR]

Stellar streams in the Galactic halo are useful probes of the assembly of galaxies like the Milky Way. Many tidal stellar streams that have been found in recent years are accompanied by a known progenitor globular cluster or dwarf galaxy. However, the Orphan–Chenab (OC) stream is one case where a relatively narrow stream of stars has been found without a known progenitor. In an effort to find the parent of the OC stream, we use astrometry from the early third data release of ESA's Gaia mission (Gaia EDR3) and radial velocity information from the Sloan Digital Sky Survey (SDSS)-IV Apache Point Observatory Galactic Evolution Experiment (APOGEE) survey to find up to 13 stars that are likely members of the OC stream. We use the APOGEE survey to study the chemical nature (for up to 10 stars) of the OC stream in the α (O, Mg, Ca, Si, Ti, and S), odd- Z (Al, K, and V), Fe-peak (Fe, Ni, Mn, Co, and Cr), and neutron-capture (Ce) elemental groups. We find that the stars that make up the OC stream are not consistent with a monometallic population and have a median metallicity of −1.92 dex with a dispersion of 0.28 dex. Our results also indicate that the α elements are depleted compared to the known Milky Way populations and that its [Mg/Al] abundance ratio is not consistent with second-generation stars from globular clusters. The detailed chemical pattern of these stars, namely the [ α /Fe]–[Fe/H] plane and the metallicity distribution, indicates that the OC stream progenitor is very likely to be a dwarf spheroidal galaxy with a mass of ∼106 M ⊙. [ABSTRACT FROM AUTHOR]

The first stars were born from chemically pristine gas. They were likely massive, and thus they rapidly exploded as supernovae, enriching the surrounding gas with the first heavy elements. In the Local Group, the chemical signatures of the first stellar population were identified among low-mass, long-lived, very metal-poor ([Fe/H] < −2) stars, characterized by high abundances of carbon over iron ([C/Fe] > +0.7): the so-called carbon-enhanced metal-poor stars. Conversely, a similar carbon excess caused by first-star pollution was not found in dense neutral gas traced by absorption systems at different cosmic time. Here we present the detection of 14 very metal-poor, optically thick absorbers at redshift z ∼ 3–4. Among these, 3 are carbon-enhanced and reveal an overabundance with respect to Fe of all the analyzed chemical elements (O, Mg, Al, and Si). Their relative abundances show a distribution with respect to [Fe/H] that is in very good agreement with those observed in nearby very metal-poor stars. All the tests we performed support the idea that these C-rich absorbers preserve the chemical yields of the first stars. Our new findings suggest that the first-star signatures can survive in optically thick but relatively diffuse absorbers, which are not sufficiently dense to sustain star formation and hence are not dominated by the chemical products of normal stars. [ABSTRACT FROM AUTHOR]

Optical and near-IR photometry suggests that the carbon star DY Persei exhibits fadings similar to those of R Coronae Borealis (RCB) variables. Photometric surveys of the Galaxy and Magellanic Clouds uncovered new DY Per variables with infrared photometry identifying them with cool carbon stars, perhaps, with an unusual tendency to shed mass. In an attempt to resolve DY Per's identity crisis—a cool carbon giant or a cool RCB variable?—we analyze a high-resolution IGRINS H &K-band spectrum of DY Per. The CO first-overtone bands in the K band of DY Per show a high abundance of 18O such that 16O/18O = 4 ± 1, a ratio sharply at odds with published results for regular cool carbon giants with 16O/18O ∼ 1000 but this exceptionally low ratio is characteristic of RCB variables and HdC stars. This similarity suggests that DY Per indeed may be a cool RCB variable. Current opinion considers RCB variables to result from the merger of a He onto a CO white dwarf; observed abundances of these H-deficient stars including the exceptionally low 16O/18O ratios are in fair accord with predicted compositions for white dwarf merger products. An H-deficiency for DY Per is not directly observable but is suggested from the strength of an HF line and an assumption that F may be overabundant, as observed and predicted for RCB stars. [ABSTRACT FROM AUTHOR]

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A major motivation of spectroscopic observations of giant exoplanets is to unveil planet formation processes from atmospheric compositions. Several recent studies suggested that atmospheric nitrogen, like carbon and oxygen, can provide important constraints on planetary formation environments. Since nitrogen chemistry can be far from thermochemical equilibrium in warm atmospheres, we extensively investigate under what conditions, and with what assumptions, the observable NH3 abundances can diagnose an atmosphere's bulk nitrogen abundance. In the first paper of this series, we investigate atmospheric T–P profiles across equilibrium temperature, surface gravity, intrinsic temperature, atmospheric metallicity, and C/O ratio using a 1D radiative–convective equilibrium model. Models with the same intrinsic temperature and surface gravity coincide with a shared "universal" adiabat in the deep atmosphere, across a wide equilibrium temperature range (250–1200 K), which is not seen in hotter or cooler models. We explain this behavior in terms of the classic "radiative zero solution" and then establish a semianalytical T–P profile of the deep atmospheres of warm exoplanets. This profile is then used to predict vertically quenched NH3 abundances. At solar metallicity, our results show that the quenched NH3 abundance only coincides with the bulk nitrogen abundance (within 10%) at low intrinsic temperature, corresponding to a planet with a sub-Jupiter mass (≲1 M J) and old age (≳1 Gyr). If a planet has a high-metallicity (≳10× solar) atmosphere, the quenched NH3 abundance significantly underestimates the bulk nitrogen abundance at almost all planetary masses and ages. We suggest modeling and observational strategies to improve the assessment of bulk nitrogen from NH3. [ABSTRACT FROM AUTHOR]

Chemical abundances of Milky Way disk stars are empirical tracers of its enrichment history. However, they capture joint-information that is valuable to disentangle. In this work, we quantify how individual abundances evolve across the present-day Galactic radius, at fixed supernovae contribution ([Fe/H], [Mg/Fe]). We use 18,135 Apache Point Observatory Galactic Evolution Experiment Data Release 17 red clump stars and 7943 GALactic Archaeology with HERMES Data Release 3 main-sequence stars to compare the abundance distributions conditioned on ([Fe/H], [Mg/Fe]) across 3–13 kpc and 6.5–9.5 kpc, respectively. We examine 15 elements: C, N, Al, K (light), O, Si, S, Ca, (α), Mn, Ni, Cr, Cu, (iron-peak) Ce, Ba (s -process) and Eu (r -process). We find that the conditional neutron-capture and light elements most significantly trace variations in the disk's enrichment history, with absolute conditional radial gradients ≤0.03 dex kpc−1. The other elements studied have absolute conditional gradients ≲0.01 dex kpc−1. We uncover structured conditional abundance variations with [Fe/H] for the low- α, but not the high- α , sequence. The average scatter between the mean conditional abundances at different radii is σ intrinsic ≈ 0.02 dex (Ce, Eu, Ba σ intrinsic > 0.05 dex). These results serve as a measure of the magnitude via which different elements trace Galactic radial enrichment history once fiducial supernovae correlations are accounted for. Furthermore, we uncover subtle systematic variations in moments of the conditional abundance distributions and bimodal differences in [Al/Fe]. These suggest a nonuniform enrichment of each chemical cell, and will presumably constrain chemical evolution models of the Galaxy. [ABSTRACT FROM AUTHOR]

In this work, for the first time, we use seismic data as well as surface abundances to model the supergiant α -Ori, with the goal of setting an upper bound on the axion–photon coupling constant g a γ . We find that, in general, stellar models with g a γ ∈ [0.002; 2.0] × 10−10 GeV−1 agree with the observational data, but beyond that upper limit, we do not find stellar models that are compatible with the observational constraints and the current literature. From g a γ = 3.5 × 10−10 GeV−1 on, the algorithm did not find any fitting models. Even so, all the axionic models considered present distinct internal profiles from the reference case, without axions. Moreover, as the axion energy losses become more significant, the behavior of the stellar models becomes more diversified, even with very similar input parameters. Nonetheless, the consecutive increments of g a γ still show systematic tendencies, resulting from the axion energy losses. Moreover, we establish three important conclusions: (1) the increased luminosity and higher neutrino production are measurable effects, possibly associated with axion energy losses; (2) stellar models with axion energy loss show a quite distinct internal structure; and (3) the importance of future asteroseismic missions in observing low-degree nonradial modes in massive stars is emphasized—as internal gravity waves probe the near-core regions, where axion effects are most intense. Thus, more seismic data will allow us to constrain g a γ better and to prove or dismiss the existence of axion energy loss inside massive stars. [ABSTRACT FROM AUTHOR]

We present ultradeep Keck/MOSFIRE rest-optical spectra of two star-forming galaxies at z = 2.18 in the COSMOS field with bright emission lines, representing more than 20 hr of total integration. The fidelity of these spectra enabled the detection of more than 20 unique emission lines for each galaxy, including the first detection of the auroral [O ii ] λλ 7322, 7332 lines at high redshift. We use these measurements to calculate the electron temperature in the low-ionization O+ zone of the ionized interstellar medium and derive abundance ratios of O/H, N/H, and N/O using the direct method. The N/O and α /Fe abundance patterns of these galaxies are consistent with rapid formation timescales and ongoing strong starbursts, in accord with their high specific star formation rates. These results demonstrate the feasibility of using auroral [O ii ] measurements for accurate metallicity studies at high redshift in a higher-metallicity and lower-excitation regime previously unexplored with the direct method in distant galaxies. These results also highlight the difficulty in obtaining the measurements required for direct-method metallicities from the ground. We emphasize the advantages that the JWST/NIRSpec instrument will bring to high-redshift metallicity studies, where the combination of increased sensitivity and uninterrupted wavelength coverage will yield more than an order of magnitude increase in efficiency for multiplexed auroral-line surveys relative to current ground-based facilities. Consequently, the advent of JWST promises to be the beginning of a new era of precision chemical abundance studies of the early universe at a level of detail rivaling that of local galaxy studies. [ABSTRACT FROM AUTHOR]

The Juno Microwave Radiometer has allowed observation of Jupiter's atmosphere down to previously inaccessible depths, although the complexity of the atmospheric dynamics has complicated analysis. The longest-wavelength channel (600 MHz) is sensitive to pressure levels of hundreds of bars, and has observed opacity sources other than the known gaseous and cloud components, likely caused by thermally ionized free electrons from alkali metal vapor. We extend previous analysis of limb darkening at these wavelengths, using radiative transfer and thermal equilibrium modeling, by considering the effect of anions in the deep Jovian atmosphere, which act as a sink for free electrons and will thus decrease opacity for a given alkali metal abundance. We show that MWR observations are consistent with a sodium and potassium abundance on the order of 0.1× solar around the 1-kilobar level, higher than previously estimated but still substantially depleted compared to other heavy elements, a value that would be within the range of observed alkali metal abundances on giant exoplanets; alternatively, MWR observations may be consistent with 3× solar sodium abundance, but only if potassium is even more strongly depleted. Such depletion may be the result of either chemical processes yet deeper in the atmosphere, such as in the silicate clouds, or of a long-lived stable layer shallower than the alkali salt clouds. • Electrons in Jupiter's atmosphere at 200–1000 bars are mostly attached to anions • This affects conclusions from Juno Microwave Radiometer limb darkening • If the sodium to potassium ratio is solar, abundance of both is ∼0.1× solar • 3× solar sodium, but less than 0.01× solar potassium may also be possible • Depletion explained by either deeper chemistry or inverted metallicity gradient [ABSTRACT FROM AUTHOR]

Planet engulfment has been identified as one of the mechanisms for enhancing lithium abundance in stars. However, comprehensive investigations into lithium signatures following such events remain limited. Stars born together, sharing a common origin and stellar characteristics, provide a unique opportunity to study these signatures and compare lithium abundances. We demonstrate that the distinctive signature of planet engulfment in lithium abundance is only discernible among highly similar stellar twins. We present lithium abundance measurements for 125 comoving pairs of stars, representing the largest sample to date with a single, homogeneous assessment of high-precision lithium abundance. While lithium abundance enhancements in pairs showing planet engulfment signatures are within 0.35 dex, we find that even at fixed stellar parameters (temperature and age), the intrinsic scatter in lithium abundance is typically 0.35 dex for G/F dwarfs and can be as large as 0.6 dex for older and cooler stars due to internal stellar evolution processes. Since the planet engulfment signature from lithium can be masked by stellar intrinsic scatter, our findings raise questions about relying solely on lithium as an indicator for planet engulfment or attributing lithium-richness in stars primarily to planet engulfment events.

Linking atmospheric measurements to the bulk planetary composition and ultimately the planetary origin is a key objective in planetary science. In this work, we identify the cases in which the atmospheric composition represents the bulk composition. We simulate the evolution of giant planets considering a wide range of planetary masses (0.3–2 M _J ), initial entropies ( $8-11\,{k}_{{\rm{B}}}{m}_{{\rm{u}}}^{-1}$ ), and primordial heavy-element profiles. We find that convective mixing is most efficient at early times (ages ≲10 ^7 yr) and that primordial composition gradients can be eroded. In several cases, however, the atmospheric composition can differ widely from the planetary bulk composition, with the exact outcome depending on the details. We show that the efficiency of convection is primarily controlled by the underlying entropy profile: For low primordial entropies of $8-9\,{k}_{{\rm{B}}}{m}_{{\rm{u}}}^{-1}$ , convective mixing can be inhibited and composition gradients can persist over billions of years. The scaling of mixing efficiency with mass is governed by the primordial entropy. For the same primordial entropy, low-mass planets mix more efficiently than high-mass planets. If the primordial internal entropy would increase with mass, however, this trend could reverse. We also present a new analytical model that predicts convective mixing under the existence of composition (and entropy) gradients. Our results emphasize the complexity in the interpretation of atmospheric abundance measurements and show the great need to better understand the planetary formation process as it plays a key role in determining the planetary evolution and final structure.

Infrared (IR) spectral features of interstellar and solar system ices have been attributed to solid organic and inorganic compounds for over 50 yr, but in many cases the laboratory IR data needed to fully quantify such work have never been published, forcing researchers to rely on assumptions about gas- or liquid-phase measurements to interpret data for ices. Here, we report the first mid-IR intensity measurements for isocyanic acid (HNCO) ices that are free of such assumptions, providing new results for use by both observational and laboratory astrochemists. We also report similar new IR data for both formaldehyde (H _2 CO) and formic acid (HCOOH), which have been discussed in the astrochemical literature for decades, but again without adequate laboratory data to help quantify observational results. Densities and refractive indices of HNCO, H _2 CO, and HCOOH as amorphous ices also are reported. Two applications of the new H _2 CO work are presented, the first vapor-pressure measurements of solid H _2 CO, along with an enthalpy of sublimation, at 100 to 109 K and a set of IR intensities of H _2 CO in H _2 O + H _2 CO ices. Band strengths, absorption coefficients, and optical constants are calculated for all three compounds. Extensive comparisons are made to older results, which are not recommended for future use.

We present a study of the abundance of calcium in the innermost disk of 70 T Tauri stars in the star-forming regions of Chamaeleon I, Lupus, and Orion OB1b. We use calcium as a proxy for the refractory material that reaches the inner disk. We used magnetospheric accretion models to analyze the Ca ii emission lines and estimate abundances in the accretion flows of the stars, which feed from the inner disks. We find Ca depletion in disks of all three star-forming regions, with 57% of the sample having [Ca/H] < –0.30 relative to the solar abundance. All disks with cavities and/or substructures show depletion, consistent with trapping of refractories in pressure bumps. Significant Ca depletion ([Ca/H] < –0.30) is also measured in 60% of full disks, although some of those disks may have hidden substructures or cavities. We find no correlation between Ca abundance and stellar or disk parameters except for the mass accretion rate onto the star. This could suggest that the inner and outer disks are decoupled, and that the mass accretion rate is related to a mass reservoir in the inner disk, while refractory depletion reflects phenomena in the outer disk related to the presence of structure and forming planets. Our results of refractory depletion and timescales for depletion are qualitatively consistent with expectations of dust growth and radial drift, including partitioning of elements, and constitute direct evidence that radial drift of solids locked in pebbles takes place in disks.

Galactic globular clusters contain two main groups of stars, the pristine or 1P stars, and the polluted or 2P stars. The pristine-star fraction in clusters, F _1 _P , is a decreasing function of the cluster present-day mass, m _prst . Paper I has introduced a model mapping the region of the ( m _prst , F _1 _P ) space occupied by clusters, with the cluster mass threshold for 2P-star formation a key building block. We now expand this model to the pristine-star fraction in dependence of the pristine- and polluted-population masses. A. P. Milone et al. found that F _1 _P anticorrelates more tightly with the polluted-population present-day mass, m _2 _P _,prst , than with the cluster total mass, m _prst . By contrast, F _1 _P anticorrelates poorly with the pristine-population current mass, m _1 _P _,prst . We show the loose anticorrelation between F _1 _P and m _1 _P _,prst to result from a roughly constant pristine-population mass in clusters as they start their long-term evolution in the Galactic tidal field. As for the tight anticorrelation between m _2 _P _,prst and F _1 _P , it stems from the initially shallow relation between m _2 _P and F _1 _P . Clusters of the Large and Small Magellanic Clouds (LMC and SMC, respectively) appear to behave unexpectedly with respect to each other. For a given F _1 _P , LMC clusters are more massive than SMC clusters despite their enduring a stronger tidal field. This is opposite to how the Galactic outer- and inner-halo clusters behave. The explanation may lie in cluster formation conditions. Finally, we wonder whether the single-population clusters NGC 419 and Rup 106 formed as multiple-population clusters.