J/A+A/652/A75 M30 stars Teff and [M/H] (Gavel+, 2021)
Atomic diffusion and mixing in old stars.
VII. Abundances of Mg, Ti, and Fe in M 30.
Gavel A., Gruyters P., Heiter U., Korn A.J., Nordlander T.,
Scheutwinkel K.H., Richard O.A.
<Astron. Astrophys., 652, A75 (2021)>
=2021A&A...652A..75G 2021A&A...652A..75G (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, globular ; Effective temperatures ; Abundances ; Optical
Keywords: globular clusters: individual: M 30 - methods: statistical -
stars: abundances - stars: atmospheres - techniques: spectroscopic
Abstract:
We attempt to constrain the efficiency of additional transport or
mixing processes that reduce the effect of atomic diffusion in stellar
atmospheres.
We apply spectral synthesis methods to spectra observed with the
GIRAFFE spectrograph on the VLT to estimate abundances of Mg, Ti, Fe,
and Ba in stars in the metal-poor globular cluster M 30. To the
abundances we fit trends of abundances predicted by stellar evolution
models assuming different efficiencies of additional transport or
mixing processes. The fitting procedure attempts to take into account
the effects of parameter-dependent systematic errors in the derived
abundances.
We find that the parameter T0, which describes the efficiency of
additional transport or mixing processes, can almost certainly be
constrained to the narrow range log10(T0/[K]) between 6.09 and
6.2. This corresponds to decreased abundances for stars at the main
sequence turn-off point compared to the red giant branch by 0.2dex for
Mg, 0.1dex for Fe, and 0.07dex for Ti. We also find that while our
estimates do have non-negligible systematic errors stemming from the
continuum placement and the assumed microturbulence, our method can
take them into account.
Our results partly amend the results of an earlier paper in this
article series, that tentatively used a value of log10(T0/[K])=6.0
when modelling the Spite plateau of lithium. To more easily
distinguish physical effects from systematic errors, we recommend that
studies of this kind focus on elements for which the expected surface
abundances as functions of effective temperature have a distinct
structure and cover a wide range.
Description:
We have photometric and spectroscopic observations of 177 stars in the
globular cluster M30. The cluster has been selected on the basis that
it is very metal-poor, with [M/H]=-2.35, and relatively little
studied.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tableb2.dat 52 162 Individual stars, the number n of spectra coadded
for each star, and the best estimates of S/N
and stellar parameters
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See also:
J/A+A/490/777 : Abundances of Population II stars in NGC6397 (Lind+, 2008)
J/A+A/567/A72 : Stellar parameters and abundances in NGC6752 (Gruyters+, 2014)
J/A+A/589/A61 : Stellar parameters and abundances for M30 (Gruyters+, 2016)
Byte-by-byte Description of file: tableb2.dat
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Bytes Format Units Label Explanations
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1- 6 I6 --- Star Star identification number
8- 9 I2 --- n Number of spectra coadded for each star
11- 13 I3 --- S/N Best estimate of spectral-to-noise ratio
15- 18 I4 K Teff Effective temperature
20- 23 F4.2 [cm/s2] logg Surface gravity
25- 30 F6.3 [-] [M/H] Mettalicity
32- 52 A21 --- Comment Comment
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History:
From electronic version of the journal
References:
Korn et al., Paper I 2007ApJ...671..402K 2007ApJ...671..402K
Lind et al., Paper II 2008A&A...490..777L 2008A&A...490..777L, Cat. J/A+A/490/777
Nordlander et al., Paper III 2012ApJ...753...48N 2012ApJ...753...48N
Gruyters et al., Paper IV 2013A&A...555A..31G 2013A&A...555A..31G
Gruyters et al., Paper V 2014A&A...567A..72G 2014A&A...567A..72G, Cat. J/A+A/567/A72
Gruyters et al., Paper VI 2016A&A...589A..61G 2016A&A...589A..61G, Cat. J/A+A/589/A61
(End) Patricia Vannier [CDS] 20-Oct-2021