Seventy-two grids of stellar evolutionary tracks, along with the means to generate isochrones and luminosity/color functions from them, are presented in this investigation Sixty of them extend (and encompass) the sets of models reported by VandenBerg et al for 17 [Fe/H] values from -231 to -030 and ?-element abundances corresponding to [?/Fe] = 00, 03, and 06 (at each iron abundance) to the solar metallicity and to sufficiently high masses (up to ~22 M?) that isochrones may be computed for ages as low as 1 Gyr The remaining grids contain tracks for masses from 04 to 40 M? and 12 [Fe/H] values between -060 and +049 (assuming solar metal-to-hydrogen number abundance ratios): in this case, isochrones may be calculated down to ~02 Gyr The extent of convective core overshooting has been modeled using a parameterized version of the Roxburgh criterion, in which the value of the free parameter at a given mass and its dependence on mass have been determined from analyses of binary star data and the observed color-magnitude diagrams for several open clusters Because the calculations reported herein satisfy many empirical constraints, they should provide useful probes into the properties of both simple and complex stellar populations

The Victoria-Regina Stellar Models: Evolutionary Tracks and Isochrones for a Wide Range in Mass and Metallicity that Allow for Empirically Constrained Amounts of Convective Core Overshooting

© 2021 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. This is the accepted manuscript version of an article which has been published in final form at https://doi.org/10.1093/mnras/stab1242

/pdf/the-galah-survey-third-data-release-2r8esvv4hi.pdf

The GALAH+ survey: Third data release

Context Numerous spectroscopic observations provide compelling evidence for non-canonical processes that modify the surface abundances of low- and intermediate-mass stars beyond the predictions of standard stellar theoryAims We study the effects of thermohaline instability and rotation-induced mixing in the 1–4 M ⊙ range at solar metallicityMethods We present evolutionary models by considering both thermohaline and rotation-induced mixing in stellar interior We discuss the effects of these processes on the chemical properties of stars from the zero age main sequence up to the end of the second dredge-up on the early-AGB for intermediate-mass stars and up to the AGB tip for low-mass stars Model predictions are compared to observational data for lithium, 12 C/13 C, [N/C], [Na/Fe], 16 O/17 O, and 16 O/18 O in Galactic open clusters and in field stars with well-defined evolutionary status, as well as in planetary nebulaeResults Thermohaline mixing simultaneously accounts for the observed behaviour of 12 C/13 C, [N/C], and lithium in low-mass stars that are more luminous than the RGB bump, and its efficiency is increasing with decreasing initial stellar mass On the TP-AGB, thermohaline mixing leads to lithium production, although the 7 Li yields remain negative Although the 3 He stellar yields are much reduced thanks to this process, we find that solar-metallicity, low-mass stars remain net 3 He producers Rotation-induced mixing is found to change the stellar structure so that in the mass range between  ~ 15 and 22 M ⊙ the thermohaline instability occurs earlier on the red giant branch than in non-rotating models Finally rotation accounts for the observed star-to-star abundance variations at a given evolutionary status, and is necessary to explain the features of CN-processed material in intermediate-mass stars Conclusions Overall, the present models account for the observational constraints very well over the whole mass range presently investigated

https://www.aanda.org/articles/aa/pdf/2010/14/aa14432-10.pdf

Thermohaline instability and rotation-induced mixing I. Low- and intermediate-mass solar metallicity stars up to the end of the AGB

The chemical evolution of the Universe is governed by the chemical yields from stars, which in turn is determined primarily by the initial stellar mass. Even stars as low as 0.9Msun can, at low metallicity, contribute to the chemical evolution of elements. Stars less massive than about 10Msun experience recurrent mixing events that can significantly change the surface composition of the envelope, with observed enrichments in carbon, nitrogen, fluorine, and heavy elements synthesized by the slow neutron capture process (the s-process). Low and intermediate mass stars release their nucleosynthesis products through stellar outflows or winds, in contrast to massive stars that explode as core-collapse supernovae. Here we review the stellar evolution and nucleosynthesis for single stars up to ~10Msun from the main sequence through to the tip of the asymptotic giant branch (AGB). We include a discussion of the main uncertainties that affect theoretical calculations and review the latest observational data, which are used to constrain uncertain details of the stellar models. We finish with a review of the stellar yields available for stars less massive than about 10Msun and discuss efforts by various groups to address these issues and provide homogeneous yields for low and intermediate-mass stars covering a broad range of metallicities.

/pdf/the-dawes-review-2-nucleosynthesis-and-stellar-yields-of-low-4aeg2ibvyx.pdf

The Dawes Review 2: Nucleosynthesis and stellar yields of low and intermediate-mass single stars

We show that the masses of red giant stars can be well predicted from their photospheric carbon and nitrogen abundances, in conjunction with their spectroscopic stellar labels log g, Teff, and [Fe/H]. This is qualitatively expected from mass-dependent post-main-sequence evolution. We here establish an empirical relation between these quantities by drawing on 1475 red giants with asteroseismic mass estimates from Kepler that also have spectroscopic labels from Apache Point Observatory Galactic Evolution Experiment (APOGEE) DR12. We assess the accuracy of our model, and find that it predicts stellar masses with fractional rms errors of about 14 per cent (typically 0.2 M⊙). From these masses, we derive ages with rms errors of 40 per cent. This empirical model allows us for the first time to make age determinations (in the range 1–13 Gyr) for vast numbers of giant stars across the Galaxy. We apply our model to ∼52 000 stars in APOGEE DR12, for which no direct mass and age information was previously available. We find that these estimates highlight the vertical age structure of the Milky Way disc, and that the relation of age with [α/M] and metallicity is broadly consistent with established expectations based on detailed studies of the solar neighbourhood.

/pdf/red-giant-masses-and-ages-derived-from-carbon-and-nitrogen-94lut6xn63.pdf

Red giant masses and ages derived from carbon and nitrogen abundances

The Hipparcos orbiting observatory has revealed a large number of helium-core-burning "clump" stars in the Galactic field. These low-mass stars exhibit signatures of extra-mixing processes that require modeling beyond the first dredge-up of standard models. The 12C/13C ratio is the most robust diagnostic of deep mixing, because it is insensitive to the adopted stellar parameters. In this work we present 12C/13C determinations in a sample of 34 Galactic clump stars as well as abundances of nitrogen, carbon and oxygen. Abundances of carbon were studied using the C2 Swan (0,1) band head at 5635.5 A. The wavelength interval 7980-8130 A with strong CN features was analysed in order to determine nitrogen abundances and 12C/13C isotope ratios. The oxygen abundances were determined from the [O I] line at 6300 A. Compared with the Sun and dwarf stars of the Galactic disk, mean abundances in the investigated clump stars suggest that carbon is depleted by about 0.2 dex, nitrogen is enhanced by 0.2 dex and oxygen is close to abundances in dwarfs. Comparisons to evolutionary models show that the stars fall into two groups: the one is of first ascent giants with carbon isotope ratios altered according to the first dredge-up prediction, and the other one is of helium-core-burning stars with carbon isotope ratios altered by extra mixing. The stars investigated fall to these groups in approximately equal numbers.

C, N and O abundances in red clump stars of the Milky Way

The main atmospheric parameters and abundances of the iron group elements (vanadium, chromium, iron, cobalt and nickel) are determined for 62 red giant "clump" stars revealed in the Galactic field by the Hipparcos orbiting observatory. The stars form a homogeneous sample with the mean value of temperature T=4750 +- 160K, of surface gravity log g = 2.41 +- 0.26 and the mean value of metallicity [Fe/H] = -0.04 +- 0.15 dex. A Gaussian fit to the [Fe/H] distribution produces the mean [Fe/H] = -0.01 dex and dispersion of [Fe/H] = 0.08 dex. The near-solar metallicity and small dispersion of [Fe/H] of clump stars of the Galaxy obtained in this work confirm the theoretical model of the Hipparcos clump by Girardi & Salaris (2001). This suggests that nearby clump stars are (in the mean) relatively young objects, reflecting mainly the near-solar metallicities developed in the local disk during the last few Gyrs of its history. We find iron group element to iron abundance ratios in clump giants to be close to solar.

High resolution spectroscopic study of red clump stars in the Galaxy: iron group elements

Hipparcos orbiting observatory has revealed a large number of helium-coreburning “clump” stars of the Galactic field. These low-mass stars exhibit signatures of extra-mixing processes that require modeling beyond the standard stellar theory. In this contribution we overview available results of C, C, N and O abundances obtained by high-resolution spectra for clump stars and discuss them in the light of current predictions of stellar evolution models.

/pdf/cno-abundance-pattern-in-the-red-clump-stars-of-the-milky-52jj0d6etw.pdf

CNO abundance pattern in the red clump stars of the Milky Way

Low-mass stars exhibit signatures of extra-mixing processes that require modeling beyond the standard stellar theory and observational data for stars of different masses and metallicity. Abundances of 12C, 13C, N and O chemical elements in atmospheres of 17 low-mass helium-core burning stars were determined from the high-resolution spectra obtained on the Nordic Optical Telescope with the SOFIN spectrograph. The stars belong to the red clump of the Galaxy and according to the analysis are in the metallicity range of ‑0.28 < [Fe/H] < 0.14 and mass range 1.2 < M /M[Sun]< 2.3. Abundances of carbon were studied using the C[2 ]Swan (0,1) band head at 5635.5 A. The wavelength interval 7980-8130 A with strong CN features was analysed in order to determine nitrogen abundances and 12C/13C isotope ratios. The oxygen abundances were determined from the [O I] line at 6300 A. In comparison to the chemical composition in field dwarfs, the results show that carbon abundance is depleted and [C/H] is lowered in all the star by about 0.2 dex which is in agreement with results for other stars of this type and the theory of the 1st dredge-up. The results of C/N quite closely follow the C/N vs. mass trend predicted by the 1st dredge-up models. The extra-mixing model by Boothroyd & Sackmann (1999, ApJ, 510, 232) does not predict C/N changes to be noticeable at this metallicity and mass as well. Comparing the results with the same theoretical study by Boothroyd & Sackmann (1999) in the 12C/13C, mass plot the stars separate into two groups, one of which follow the trend of 1st dredge-up with 12C/13C ratio being in the range of 20-30, depending of mass. The 12C/13C ratios of the other group of stars is equal to about 15 which show the evidence of extra-mixing. The analysis of a larger sample of Galaxy red clump stars as well as of metal deficient horizontal branch stars is needed for further progress in revealing of extent of mixing in atmospheres of low mass stars.

/pdf/abundances-of-c-n-and-o-as-probes-of-mixing-in-low-mass-3t41pfku1b.pdf

Abundances of C, N and O as probes of mixing in low-mass helium-core burning stars

Hipparcos data have allowed the identification of a large number of clump stars in the solar neighbourhood. We discuss our present knowledge of their distributions of metallicities, CNO abundances, carbon isotope ratios and memberships of the first ascent giants and helium-core-burning stars.

Chemical Properties of the Hipparcos Red Clump

Handle everyday research tasks with reliable, citation-backed results

Your personal Research Agent to handle research tasks with citation-backed results

Popular Tasks used by Researchers

How can I help with your research?

Meet SciSpace

Get more enhanced response by uploading the PDFs you want me to reference.

No relevant PDFs in your library

SciSpace is the AI research assistant for academics. Run systematic literature reviews on 280M+ papers, and write papers with cited sources. Trusted by 1M+ students, PhDs & researchers.

SciSpace | AI for Research

Analyze PDFs

Code & Manuscripts

Funding & Grants

Literature & Patents

Medical & Clinical Data

Systematic Review

Visualize & Present

Web & Data

Build a Google Scholar-like website for your research.

Build a website

Create charts and images for your research

Create a Chart

Write a paper for submission to a journal

Draft a manuscript

Patent Search

Design eye-catching scientific posters in minutes.

Scientific Poster Generation

Systematic Literature Review

One task is running at the moment. Your messages will be shown right after.

Drag and drop or click here to browse

Loved by <highlight>1 million+</highlight> researchers

Extract a list of specific topics and their sources from unstructured text

Topics

Compare and analyze relevant papers that matches with your search

Papers

Get insights from PDFs and bookmarked papers from your library

My library

Recent searches

Try searching for:

Catch AI-generated content in scholarly and non-scholarly content

{ai} Detector

Ai Writer

Get PDF Summaries, highlighted text explanations 

Chat with PDF

Effortlessly create in-text citations and bibliographies in APA and 2,500 other formats

Citation generator

Get explanations, summaries, and answers on academic papers

Ease up your research workflow with {scispace}'s cohort of exciting AI tools

Elevate your academic writing skills and convey your ideas the way you want

Paraphraser

Explore our range of reading and writing tools

Your file is being prepared and should be ready in a few minutes. If it's a large file, it might take a bit longer. You can close this window, and we'll email you the file when it's done.

You have reached a maximum limit of <strong>{limit}</strong> columns in the table. Remove at least <strong>1</strong> column to add or create another one.

E. Puzeras

Author Tools

Chat about Author