The GALAH survey: Verifying abundance trends in the open cluster M67 using non-LTE modelling

the GALAH collaboration

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

Open cluster members are coeval and share the same initial bulk chemical composition. Consequently, differences in surface abundances between members of a cluster that are at different evolutionary stages can be used to study the effects of mixing and internal chemical processing. We carry out an abundance analysis of seven elements (Li, O, Na, Mg, Al, Si, and Fe) in 66 stars belonging to the open cluster M67, based on high resolution GALAH spectra, 1D MARCS model atmospheres, and non-local thermodynamic equilibrium (non-LTE) radiative transfer. From the non-LTE analysis, we find a typical star-to-star scatter in the abundance ratios of around 0.05 dex. We find trends in the abundance ratios with effective temperature, indicating systematic differences in the surface abundances between turn-off and giant stars; these trends are more pronounced when LTE is assumed. However, trends with effective temperature remain significant for Al and Si also in non-LTE. Finally, we compare the derived abundances with prediction from stellar evolution models including effects of atomic diffusion. We find overall good agreement for the abundance patterns of dwarfs and sub-giant stars, but the abundances of cool giants are lower relative to less evolved stars than predicted by the diffusion models, in particular for Mg.

Original languageEnglish
Pages (from-to)2666-2684
Number of pages19
JournalMonthly Notices of the Royal Astronomical Society
Volume481
Issue number2
DOIs
Publication statusPublished - 1 Dec 2018

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open clusters
thermodynamic equilibrium
thermodynamics
trends
modeling
stars
giant stars
trend
stellar evolution
local thermodynamic equilibrium
radiative transfer
chemical composition
temperature
atmospheres
atmosphere
high resolution
prediction
predictions

Cite this

@article{086ecef16b1449efb49d4b4ff2591f0f,
title = "The GALAH survey: Verifying abundance trends in the open cluster M67 using non-LTE modelling",
abstract = "Open cluster members are coeval and share the same initial bulk chemical composition. Consequently, differences in surface abundances between members of a cluster that are at different evolutionary stages can be used to study the effects of mixing and internal chemical processing. We carry out an abundance analysis of seven elements (Li, O, Na, Mg, Al, Si, and Fe) in 66 stars belonging to the open cluster M67, based on high resolution GALAH spectra, 1D MARCS model atmospheres, and non-local thermodynamic equilibrium (non-LTE) radiative transfer. From the non-LTE analysis, we find a typical star-to-star scatter in the abundance ratios of around 0.05 dex. We find trends in the abundance ratios with effective temperature, indicating systematic differences in the surface abundances between turn-off and giant stars; these trends are more pronounced when LTE is assumed. However, trends with effective temperature remain significant for Al and Si also in non-LTE. Finally, we compare the derived abundances with prediction from stellar evolution models including effects of atomic diffusion. We find overall good agreement for the abundance patterns of dwarfs and sub-giant stars, but the abundances of cool giants are lower relative to less evolved stars than predicted by the diffusion models, in particular for Mg.",
keywords = "Radiative transfer, Stars: abundances, Stars: atmospheres, Stars: late-type",
author = "{the GALAH collaboration} and Xudong Gao and Karin Lind and Amarsi, {Anish M.} and Sven Buder and Aaron Dotter and Thomas Nordlander and Martin Asplund and Joss Bland-Hawthorn and {De Silva}, {Gayandhi M.} and Valentina D'Orazi and Freeman, {Ken C.} and Janez Kos and Lewis, {Geraint F.} and Jane Lin and Martell, {Sarah L.} and Schlesinger, {Katharine J.} and Sanjib Sharma and Simpson, {Jeffrey D.} and Zucker, {Daniel B.} and Tomaž Zwitter and Costa, {Gary Da} and Borja Anguiano and Jonathan Horner and Hyde, {Elaina A.} and Kafle, {Prajwal R.} and Nataf, {David M.} and Warren Reid and Dennis Stello and Ting, {Yuan Sen}",
year = "2018",
month = "12",
day = "1",
doi = "10.1093/MNRAS/STY2414",
language = "English",
volume = "481",
pages = "2666--2684",
journal = "Monthly Notices of the Royal Astronomical Society",
issn = "0035-8711",
publisher = "OXFORD UNIV PRESS UNITED KINGDOM",
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}

The GALAH survey : Verifying abundance trends in the open cluster M67 using non-LTE modelling. / the GALAH collaboration.

In: Monthly Notices of the Royal Astronomical Society, Vol. 481, No. 2, 01.12.2018, p. 2666-2684.

Research output: Contribution to journalArticle

TY - JOUR

T1 - The GALAH survey

T2 - Verifying abundance trends in the open cluster M67 using non-LTE modelling

AU - the GALAH collaboration

AU - Gao, Xudong

AU - Lind, Karin

AU - Amarsi, Anish M.

AU - Buder, Sven

AU - Dotter, Aaron

AU - Nordlander, Thomas

AU - Asplund, Martin

AU - Bland-Hawthorn, Joss

AU - De Silva, Gayandhi M.

AU - D'Orazi, Valentina

AU - Freeman, Ken C.

AU - Kos, Janez

AU - Lewis, Geraint F.

AU - Lin, Jane

AU - Martell, Sarah L.

AU - Schlesinger, Katharine J.

AU - Sharma, Sanjib

AU - Simpson, Jeffrey D.

AU - Zucker, Daniel B.

AU - Zwitter, Tomaž

AU - Costa, Gary Da

AU - Anguiano, Borja

AU - Horner, Jonathan

AU - Hyde, Elaina A.

AU - Kafle, Prajwal R.

AU - Nataf, David M.

AU - Reid, Warren

AU - Stello, Dennis

AU - Ting, Yuan Sen

PY - 2018/12/1

Y1 - 2018/12/1

N2 - Open cluster members are coeval and share the same initial bulk chemical composition. Consequently, differences in surface abundances between members of a cluster that are at different evolutionary stages can be used to study the effects of mixing and internal chemical processing. We carry out an abundance analysis of seven elements (Li, O, Na, Mg, Al, Si, and Fe) in 66 stars belonging to the open cluster M67, based on high resolution GALAH spectra, 1D MARCS model atmospheres, and non-local thermodynamic equilibrium (non-LTE) radiative transfer. From the non-LTE analysis, we find a typical star-to-star scatter in the abundance ratios of around 0.05 dex. We find trends in the abundance ratios with effective temperature, indicating systematic differences in the surface abundances between turn-off and giant stars; these trends are more pronounced when LTE is assumed. However, trends with effective temperature remain significant for Al and Si also in non-LTE. Finally, we compare the derived abundances with prediction from stellar evolution models including effects of atomic diffusion. We find overall good agreement for the abundance patterns of dwarfs and sub-giant stars, but the abundances of cool giants are lower relative to less evolved stars than predicted by the diffusion models, in particular for Mg.

AB - Open cluster members are coeval and share the same initial bulk chemical composition. Consequently, differences in surface abundances between members of a cluster that are at different evolutionary stages can be used to study the effects of mixing and internal chemical processing. We carry out an abundance analysis of seven elements (Li, O, Na, Mg, Al, Si, and Fe) in 66 stars belonging to the open cluster M67, based on high resolution GALAH spectra, 1D MARCS model atmospheres, and non-local thermodynamic equilibrium (non-LTE) radiative transfer. From the non-LTE analysis, we find a typical star-to-star scatter in the abundance ratios of around 0.05 dex. We find trends in the abundance ratios with effective temperature, indicating systematic differences in the surface abundances between turn-off and giant stars; these trends are more pronounced when LTE is assumed. However, trends with effective temperature remain significant for Al and Si also in non-LTE. Finally, we compare the derived abundances with prediction from stellar evolution models including effects of atomic diffusion. We find overall good agreement for the abundance patterns of dwarfs and sub-giant stars, but the abundances of cool giants are lower relative to less evolved stars than predicted by the diffusion models, in particular for Mg.

KW - Radiative transfer

KW - Stars: abundances

KW - Stars: atmospheres

KW - Stars: late-type

UR - http://www.scopus.com/inward/record.url?scp=85057299308&partnerID=8YFLogxK

U2 - 10.1093/MNRAS/STY2414

DO - 10.1093/MNRAS/STY2414

M3 - Article

VL - 481

SP - 2666

EP - 2684

JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

SN - 0035-8711

IS - 2

ER -