Solar Abundance Research Articles

Detection of Fe and Ti on the dayside of the ultrahot Jupiter MASCARA-1b with CARMENES

Ultrahot Jupiters are a type of gaseous exoplanet that orbit extremely close to their host star, resulting in significantly high equilibrium temperatures. In recent years, high-resolution emission spectroscopy has been broadly employed in observing the atmospheres of ultrahot Jupiters. We used the CARMENES spectrograph to observe the high-resolution spectra of the dayside hemisphere of MASCARA-1b in both visible and near-infrared. Through cross-correlation analysis, we detected signals of Fe I and Ti I. Based on these detections, we conducted an atmospheric retrieval and discovered the presence of a strong inversion layer in the planet’s atmosphere. The retrieved Ti and Fe abundances are broadly consistent with solar abundances. In particular, we obtained a relative abundance of [Ti/Fe] as −1.0 ± 0.8 under the free retrieval and −0.4−0.8+0.5 under the chemical equilibrium retrieval, suggesting the absence of significant titanium depletion on this planet. Furthermore, we considered the influence of planetary rotation on spectral line profiles. The resulting equatorial rotation speed was determined to be 4.4−2.0+1.6 km s−1, which agrees with the rotation speed induced by tidal locking.

Parker Solar Probe Observations of Energetic Particles in the Flank of a Coronal Mass Ejection Close to the Sun

We present an event observed by Parker Solar Probe (PSP) at ∼0.2 au on 2022 March 2 in which imaging and in situ measurements coincide. During this event, PSP passed through structures on the flank of a streamer blowout coronal mass ejection (CME) including an isolated flux tube in front of the CME, a turbulent sheath, and the CME itself. Imaging observations and in situ helicity and principal variance signatures consistently show the presence of flux ropes internal to the CME. In both the sheath and the CME interval, the distributions are more isotropic, the spectra are softer, and the abundance ratios of Fe/O and He/H are lower than those in the isolated flux tube, and yet elevated relative to typical plasma and solar energetic particle abundances. These signatures in the sheath and the CME indicate that both flare populations and those from the plasma are accelerated to form the observed energetic particle enhancements. In contrast, the isolated flux tube shows large streaming, hard spectra, and large Fe/O and He/H ratios, indicating flare sources. Energetic particle fluxes are most enhanced within the CME interval from suprathermal through energetic particle energies (∼keV to >10 MeV), indicating particle acceleration, as well as confinement local to the closed magnetic structure. The flux-rope morphology of the CME helps to enable local modulation and trapping of energetic particles, in particular along helicity channels and other plasma boundaries. Thus, the CME acts to build up energetic particle populations, allowing them to be fed into subsequent higher-energy particle acceleration throughout the inner heliosphere where a compression or shock forms on the CME front.

The Abundance of Chlorine in the Atmosphere of HD 87240

High resolution high signal-to-noise UVES spectra of the late B-type chemically peculiar star, HD 87240, a member of the NGC 3114 open cluster, have been synthesized to measure the abundance of chlorine, an element which is rarely found in late B-type stars. Sixteen lines of Cl ii are found and the mean chlorine overabundance is about 2.1 dex higher than the solar abundance, which is slightly lower than the chlorine excess in HR 1094, another chlorine-rich late B-type star.

Likely Common Coronal Source of Solar Wind and 3He-enriched Energetic Particles: Uncoupled Transport from the Low Corona to 0.2 au

Parker Solar Probe (PSP) observations of a small dispersive event on 2022 February 27 and 28 indicate scatter-free propagation as the dominant transport mechanism between the low corona and greater than 35 solar radii. The event occurred during unique orbital conditions that prevailed along specific flux tubes that PSP encountered repeatedly between 25 and 35 Rs during outbound orbit 11. This segment of the PSP orbit exhibits almost stationary angular motion relative to the rotating solar surface, such that in the rotating frame, PSP’s motion is essentially radial. The time dispersion often observed in impulsive solar energetic particle (SEP) events continues in this case down to velocities including the core solar-wind ion velocities. Especially at the onset of this event, the 3He content is much larger than the usual SEP abundances seen in the energy range from ∼100 keV to several MeV for helium. Later in the event, iron is enhanced. The compositional signatures suggest this to be an example of an acceleration mechanism for generating the seed energetic particles required by shock (or compression) acceleration models in SEP events to account for the enrichment of various species above solar abundances in such events. A preliminary search of similar orbital conditions over the PSP mission has not revealed additional such events, although favorable conditions (isolated impulsive acceleration and well-ordered magnetic field connection with minimal magnetic field fluctuation) that would be required are infrequently realized, given the small fraction of the PSP trajectory that meets these observation conditions.

Secular Outflows from Long-Lived Neutron Star Merger Remnants

We study mass ejection from a binary neutron star merger producing a long-lived massive neutron star remnant with general-relativistic neutrino-radiation hydrodynamics simulations. In addition to outflows generated by shocks and tidal torques during and shortly after the merger, we observe the appearance of a wind driven by spiral density waves in the disk. This spiral-wave-driven outflow is predominantly located close to the disk orbital plane and have a broad distribution of electron fractions. At higher latitudes, a high electron-fraction wind is driven by neutrino radiation. The combined nucleosynthesis yields from all the ejecta components is in good agreement with Solar abundance measurements.

Abundance stratification in type Ia supernovae – VII. The peculiar, C-rich iPTF16abc: highlighting diversity among luminous events

ABSTRACT Observations of Type Ia supernovae (SNe Ia) reveal diversity, even within assumed subcategories. Here, the composition of the peculiar iPTF16abc (SN 2016bln) is derived by modelling a time series of optical spectra. iPTF16abc’s early spectra combine traits of SNe 1999aa and 1991T known for weak Si ii λ 6355 and prominent Fe iii features. However, it differs with weak early Fe iii lines, and persistent C ii lines post-peak. It also exhibits a weak Ca ii H&K feature aligning it with SN 1991T, an observation supported by their bolometric light curves. The early attenuation of Fe iii results from abundance effect. The weakening of the Si ii λ 6355 line, stems from silicon depletion in the outer shells, a characteristic shared by both SNe 1999aa and 1991T, indicating a common explosion mechanism that terminates nuclear burning at around 12 000 km s−1 unseen in normal events. Beneath a thin layer of intermediate mass elements (IMEs) with a total mass of 0.18 M⊙, extends a 56Ni rich shell totaling 0.76 M⊙ and generating a bolometric luminosity as high as Lpeak = 1.60 ± 0.1 × 1043 ergs s−1. Inner layers, typical of SNe Ia, hold neutron-rich elements, (54Fe and 58Ni), totaling 0.20 M⊙. Stable iron, exceeding solar abundance, and carbon, coexist in the outermost layers, challenging existing explosion models. The presence of carbon down to v ≈ 9000 km s−1, totalling ∼0.01 M⊙ unprecedented in this class, links iPTF16abc to SN 2003fg-like events. The retention of 91T-like traits in iPTF16abc underscores its importance in understanding the diversity of SNe Ia.

The Abundances of the Noble Gases Neon and Xenon in the Atmosphere of 53 Tau (HD 27295)

One line of Ne i and three lines of Xe ii are synthesized in order to derive the abundances of neon and xenon in the atmosphere of the Mn-rich star 53 Tau. Neon is clearly very underabundant in 53 Tau, its abundance must be lower than 10−3 times the solar neon abundance. Xenon is found to be overabundant with a factor of 3000 times the solar abundance which agrees well with earlier measurements. The underabundance of neon is expected from radiative acceleration calculations which show that neon has a very small radiative acceleration in the photosphere.

3D NLTE modelling of Y and Eu

Context. Abundances of s- and r-process elements in Sun-like stars constrain nucleosynthesis in extreme astrophysical events, such as compact binary mergers and explosions of highly magnetised rapidly rotating massive stars. Aims. We measure solar abundances of yttrium (Y) and europium (Eu) using 3D non-local thermal equilibrium (NLTE) models. We use the model to determine the abundance of Y, and also explore the model’s ability to reproduce the solar centre-to-limb variation of its lines. In addition, we determine the Eu abundance using solar disc-centre and integrated flux spectra. Methods. We developed an NLTE model of Eu and updated our model of Y with collisional data from detailed quantum-mechanical calculations. We used the IAG spatially resolved high-resolution solar spectra to derive the solar abundances of Y across the solar disc and of Eu for integrated flux and at disc centre using a set of carefully selected lines and a 3D radiation-hydrodynamics model of the solar atmosphere. Results. We find 3D NLTE solar abundances of A(Y)3D NLTE = 2.30 ± 0.03stat ± 0.07syst dex based on observations at all angles and A(Eu) = 0.57 ± 0.01stat ± 0.06syst dex based on the integrated flux and disc-centre intensity. 3D NLTE modelling offers the most consistent abundances across the solar disc, and resolves the problem of severe systematic bias in Y and Eu abundances inherent to 1D LTE, 1D NLTE, and 3D LTE modelling.

Hot subdwarf wind models with accurate abundances

Context. Helium-dominated subdwarfs are core helium burning stars stripped of their envelope. The nuclear evolution of these stars alters surface abundances. Modified abundances impact the strength of the stellar wind. Aims. We aim to understand the influence of modified surface abundances on the strength of the stellar wind in the helium-dominated subdwarfs CD–46 8926 and CD–51 11879. A modified wind strength could resolve the problem with the X-ray emission of these stars, as the expected X-ray luminosity of both stars is significantly higher than the upper limit determined from observations. Methods. We used our own optical spectroscopy combined with archival ultraviolet spectroscopy and photometry to derive basic parameters and surface abundances of selected subdwarfs. The resulting parameterst served as input for the METUJE stellar wind code, which predicts the wind structure of these stars. We compared the derived wind parameters with the predictions derived for solar abundances. Results. The optical analysis showed that both subdwarfs have effective temperatures in excess of 60 kK and a strong overabundance of carbon in the case of CD–46 8926 and nitrogen in the case of CD–51 11879. We interpret the abundance patterns as being a result of enrichment by the products of nuclear reactions. The modified abundances reduce the wind mass-loss rate by tens of percent. The reduction improves the predicted wind line profiles in comparison to observations. The change in helium abundance does not have a strong effect on the wind parameters. As a result of a lower estimated bolometric luminosity and mass-loss rate and a larger distance, the expected X-ray luminosities become lower and agree with observational upper limits. Conclusions. The nucleosynthesis does not significantly alter the strength of the wind of hot subdwarfs, but the inclusion of proper stellar parameters improves the agreement with observational wind characteristics. Our analysis indicates that subdwarfs overabundant in helium are typically able to launch wind. This conclusion is supported by data gathered for thousands of subdwarfs from the literature, which shows that subdwarfs overabundant in helium avoid the region in the Kiel diagram where the winds are predicted to be absent. This can be interpreted in terms of the gravitational settling of helium, which is suppressed by the winds.

Solar Energetic Particle Charge States and Abundances with Nonthermal Electrons

An important aspect of solar energetic particle (SEP) events is their source populations. Elemental abundance enhancements of impulsive SEP events, originating in presumed coronal reconnection episodes, can be fitted to steep power laws of A/Q, where A and Q are the atomic mass and ionic charge. Since thermal electron energies are enhanced and nonthermal electron distributions arise in the reconnection process, we might expect that ionic charge states Q would be increased through ionization interactions with those electron populations during the acceleration process. The temperature estimated from the SEPs corresponds to the charge state during the acceleration process, while the actual charge state measured in situ may be modified as the SEPs pass through the corona. We examine whether the temperature estimation from the A/Q would differ with various κ values in a κ function representing high-energy tail deviating from a Maxwellian velocity distribution. We find that the differences in the A/Q between a Maxwellian and an extreme κ distribution are about 10%–30%. We fit power-law enhancement of element abundances as a function of their A/Q with various κ values. Then, we find that the derived source region temperature is not significantly affected by whether or not the electron velocity distribution deviates from a Maxwellian, i.e., thermal, distribution. Assuming that electrons are heated in the acceleration region, the agreement of the SEP charge state during acceleration with typical active region temperatures suggests that SEPs are accelerated and leave the acceleration region in a shorter time than the ionization timescale.

On the Interpretation of XSPEC Abundances and Emission Measures

The purpose of this work is to describe the assumptions built into the X-ray spectrum fitting software XSPEC for the calculation of element abundances and emission measure of a plasma and to describe the effects when those assumptions are not accurate. The ratio of electron density to hydrogen density in XSPEC is fixed at a constant. The correct ratio can be calculated from the ionization states of the elements. We show the constant value used in XSPEC is valid to within ≃3.5% for a solar-abundance plasma. For a plasma that deviates from solar abundance, e.g., hydrogen-poor or heavy-element-rich plasmas such as those found in the ejecta of supernova remnants, this ratio can be smaller by factors of 0.1–0.001. The hydrogen emission measure, defined by integral of electron density times hydrogen density over plasma volume, is derived from the norm in XSPEC, but one needs to include the hydrogen abundance factor. For other elements, the emission measures are the XSPEC values multiplied by the element abundance factors. Using the correct electron-to-hydrogen ratio and emission measures, we show the correct electron density is smaller by the square root of the correct electron density ratio divided by the XSPEC value. Element densities and total masses (for given distance and volume) are larger by the abundance factors divided by the above square root. Because hydrogen-poor plasmas occur in the ejecta of Type Ia supernova remnants, previously estimated element masses from X-ray spectra are likely to be significantly underestimated.

Oxygen abundance of γ Vel from [O iii] 88 μm Herschel/PACS spectroscopy

ABSTRACT We present Herschel PACS spectroscopy of the [O iii] 88.4 μm fine-structure line in the nearby WC8+O binary system γ Vel to determine its oxygen abundance. The critical density of this line corresponds to several 105R* such that it is spatially extended in PACS observations at the 336 pc distance to γ Vel. Two approaches are used, the first involving a detailed stellar atmosphere analysis of γ Vel using cmfgen, extending to Ne ∼ 100 cm−3 in order to fully sample the line formation region of [O iii] 88.4 $\mu$m. The second approach involves the analytical model introduced by Barlow et al. and revised by Dessart et al., additionally exploiting ISO LWS spectroscopy of [O iii] 51.8 $\mu$m. We obtain higher luminosities for the WR and O components of γ Vel with respect to De Marco et al., log L/L⊙ = 5.31 and 5.56, respectively, primarily due to the revised (higher) interferometric distance. We obtain an oxygen mass fraction of XO = 1.0 ± 0.3 per cent for an outer wind volume filling factor of f = 0.5 ± 0.25, favouring either standard or slightly reduced Kunz et al. rates for the 12C(α, γ)16O reaction from comparison with BPASS binary population synthesis models. We also revisit neon and sulphur abundances in the outer wind of γ Vel from ISO SWS spectroscopy of [S iv] 10.5 $\mu$m, [Ne ii] 12.8 $\mu$m, and [Ne iii] 15.5 $\mu$m. The inferred neon abundance XNe = 2.0$_{-0.6}^{+0.4}$ per cent is in excellent agreement with BPASS predictions, while the sulphur abundance of XS = 0.04 ± 0.01 per cent agrees with the solar abundance, as expected for unprocessed elements.

Optical Spectroscopy and Photoionization Model of Planetary Nebula NGC 6572

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, whileintermediate-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.

Direct Formation of Massive Black Holes via Dynamical Collapse in Metal-enriched Merging Galaxies at z ∼ 10: Fully Cosmological Simulations

We present the results of the first fully cosmological hydrodynamical simulations studying the merger-driven model for massive black hole (BH) seed formation via direct collapse. Using the zoom-in technique as well as particle splitting, we achieve a final spatial resolution of 2 pc. We show that the major merger of two massive galaxies at redshift z ∼ 8 results in the formation of a nuclear supermassive disk (SMD) of only 4 pc in radius, owing to a prodigious gas inflow sustained at 100–1000 M ⊙ yr−1. The core of the merger remnant is metal-rich, well above solar abundance, and the SMD reaches a gaseous mass of 3 × 108 M ⊙ in less than a million years after the merger, despite a concurrent prominent nuclear starburst. Dynamical heating as gas falls into the deepest part of the potential well, and heating and stirring by supernova blastwaves, generate a turbulent multiphase interstellar medium, with a gas velocity dispersion exceeding 100 km s−1. As a result, only moderate fragmentation occurs in the inner 10–20 pc, despite the temperature falling below 1000 K. The SMD is Jeans-unstable as well as bar-unstable and will collapse further adiabatically, becoming warm and ionized. We show that the SMD, following inevitable contraction, will become general-relativistic-unstable and directly form a supermassive BH of mass in the range 106–108 M ⊙, essentially skipping the stage of BH seed formation. These results confirm that mergers between the most massive galaxies at z ∼ 8–10 can naturally explain the rapid emergence of bright high-redshift quasars.

On‐site floral resources and surrounding landscape characteristics impact pollinator biodiversity at solar parks

Abstract There is increasing land use change for solar parks and growing recognition that they could be used to support insect pollinators. However, understanding of pollinator response to solar park developments is limited and empirical data are lacking. We combine field observations with landcover data to quantify the impact of on‐site floral resources and surrounding landscape characteristics on solar park pollinator abundance and species richness. We surveyed pollinators and flowering plants at 15 solar parks across England in 2021, used a landcover map to assess the surrounding high‐quality habitat and aerial imagery to measure woody linear features (hedgerows, woodland edges and lines of trees). In total, 1397 pollinators were recorded, including 899 butterflies (64%), 171 hoverflies (12%), 161 bumble bees (12%), 157 moths (11%), and nine honeybees (<1%). At least 30 pollinator species were observed, the majority of which were common, generalist species. Pollinator biodiversity varied between solar parks and was explained by a combination of on‐site floral resources and surrounding landscape characteristics. Floral species richness was the most influential on‐site characteristic and woody linear feature density generally had a greater impact than the cover of surrounding high‐quality habitats, although drivers differed by pollinator group. Our findings suggest that a range of factors affect pollinator biodiversity at solar parks, but maximising floral resources within a park through appropriate management actions may be the most achievable way to support most pollinator groups, especially where solar parks are located in resource‐poor, disconnected landscapes.

Insight into the Formation of β Pic b through the Composition of Its Parent Protoplanetary Disk as Revealed by the β Pic Moving Group Member HD 181327

It has been suggested that β Pic b has a supersolar metallicity and subsolar C/O ratio. Assuming solar carbon and oxygen abundances for the star β Pic and therefore the planet’s parent protoplanetary disk, β Pic b’s C/O ratio suggests that it formed via core accretion between its parent protoplanetary disk’s H2O and CO2 ice lines. However, β Pic b’s high metallicity is difficult to reconcile with its mass M p = 11.7 M Jup. Massive stars can present peculiar photospheric abundances that are unlikely to record the abundances of their former protoplanetary disks. This issue can be overcome for early-type stars in moving groups by inferring the elemental abundances of the FGK stars in the same moving group that formed in the same molecular cloud and presumably share the same composition. We infer the photospheric abundances of the F dwarf HD 181327, a β Pic moving group member that is the best available proxy for the composition of β Pic b’s parent protoplanetary disk. In parallel, we infer updated atmospheric abundances for β Pic b. As expected for a planet of its mass formed via core-accretion beyond its parent protoplanetary disk’s H2O ice line, we find that β Pic b’s atmosphere is consistent with stellar metallicity and confirm that it has superstellar carbon and oxygen abundances with a substellar C/O ratio. We propose that the elemental abundances of FGK dwarfs in moving groups can be used as proxies for the otherwise difficult-to-infer elemental abundances of early-type and late-type members of the same moving groups.

Curve of Growth Analysis of SZ Lyn

We present one high-resolution and a time series of 561 low-resolution follow-up spectroscopic observations of SZ Lyn. It is a high-amplitude δ Scuti-type pulsating star in a binary system. The photometric observations reveal the existence of radial and non-radial oscillation modes in SZ Lyn. In spectroscopy, the variation of equivalent width of the line profiles reflects the temperature variations. The equivalent widths of the Balmer lines, Hα, Hβ, and Hγ were measured over the pulsation cycle of SZ Lyn using time sequence spectra. Hence, the temperature profile of SZ Lyn was derived using the curve of growth analysis. Furthermore, the stellar parameters were determined through the best fit analysis of observed and synthetic high-resolution spectral lines. The best fit determines a model of Teff = 6750 K, log g = 3.5 dex, and vrot = 10 km s−1 for solar abundance.

The s process in massive stars, a benchmark for neutron capture reaction rates

A clear definition of the contribution from the slow neutron-capture process (s process) to the solar abundances between Fe and the Sr-Zr region is a crucial challenge for nuclear astrophysics. Robust s-process predictions are necessary to disentangle the contribution from other stellar processes producing elements in the same mass region. Nuclear uncertainties are affecting s-process calculations, but most of the needed nuclear input are accessible to present nuclear experiments or they will be in the near future. Neutron-capture rates have a great impact on the s process in massive stars, which is a fundamental source for the solar abundances of the lighter s-process elements heavier than Fe (weak s-process component). In this work we present a new nuclear sensitivity study to explore the impact on the s process in massive stars of 86 neutron-capture rates, including all the reactions between C and Si and between Fe and Zr. We derive the impact of the rates at the end of the He-burning core and at the end of the C-burning shell, where the 22\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{22}$$\\end{document}Ne(α\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha $$\\end{document},n)25\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{25}$$\\end{document}Mg reaction is is the main neutron source. We confirm the relevance of the light isotopes capturing neutrons in competition with the Fe seeds as a crucial feature of the s process in massive stars. For heavy isotopes we study the propagation of the neutron-capture uncertainties, finding a clear difference of the impact of Fe and Co isotope rates with respect to the rates of heavier stable isotopes. The local uncertainty propagation due to the neutron-capture rates at the s-process branching points is also considered, discussing the example of 85\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{85}$$\\end{document}Kr. The complete results of our study for all the 86 neutron-capture rates are available online. Finally, we present the impact on the weak s process of the neutron-capture rates included in the new ASTRAL library (v0.2).

Synthesis of the 4400–4600 Å Spectral Range for the A2.5V star HD 176687 (ζ Sagitarii A)

The synthesis of a high resolution high signal-to-noise spectrum of HD 176687 from 4400 to 4600 Å allows the determination of LTE abundances for magnesium, calcium, scandium, titanium, chromium, iron, nickel and barium. This A2.5V star has recently been found to be the most massive star in a triple system. Magnesium and calcium are found to have a solar abundance. Scandium and titanium are depleted by a factor of 0.50, chromium, nickel by a factor of 0.70 and iron by 0.60 compared to their respective solar abundances. Barium is overabundant by a factor of 7.50. The found abundances fit well within the abundance pattern previously found for a few normal A stars. There is no sign of the recently discovered companion to HD 176687 in the spectrum analyzed.

Atomic masses with machine learning for the astrophysical r process

The astrophysical r process plays a vital role in the production of heavy elements. Modeling of the r process is sensitive to masses and further requires knowledge of masses beyond current experimental reach. Therefore, simulations of the r process offer a unique test bed for predicting mass extrapolations. We take a Machine-Learning (ML) approach to model the masses across the entire chart of nuclides. For the first time, we simulate r-process nucleosynthesis with a physics-based ML mass model. We compare simulated abundances to solar data in order to evaluate the model's performance far from stability. The resulting r-process abundances up to thorium and uranium qualitatively match those of the observed solar system abundance pattern, with the characteristic peaks well positioned. We propagate the mass uncertainties obtained from the ML model to r-process abundance yields to estimate an uncertainty band associated with our approach. The size of the uncertainty band is approximately one order of magnitude which aligns with the uncertainty reported using alternative techniques.