J/MNRAS/469/4718 Kepler red-clump stars in NGC6819 and NGC6791 (Bossini+, 2017)
Kepler red-clump stars in the field and in open clusters:
constraints on core mixing.
Bossini D., Miglio A., Salaris M., Vrard M., Cassisi S., Mosser B.,
Montalban J., Girardi L., Noels A., Bressan A., Pietrinferni A., Tayar J.
<Mon. Not. R. Astron. Soc., 469, 4718-4725 (2017)>
=2017MNRAS.469.4718B 2017MNRAS.469.4718B (SIMBAD/NED BibCode)
ADC_Keywords: Asteroseismology ; Clusters, open
Keywords: asteroseismology - stars: evolution - stars: interiors -
stars: low-mass
Abstract:
Convective mixing in helium-core-burning (HeCB) stars is one of the
outstanding issues in stellar modelling. The precise asteroseismic
measurements of gravity-mode period spacing (ΔΠ1) have
opened the door to detailed studies of the near-core structure of such
stars, which had not been possible before. Here, we provide stringent
tests of various core-mixing scenarios against the largely unbiased
population of red-clump stars belonging to the old-open clusters
monitored by Kepler, and by coupling the updated precise inference on
ΔΠ1 in thousands of field stars with spectroscopic
constraints. We find that models with moderate overshooting
successfully reproduce the range observed of ΔΠ1 in
clusters. In particular, we show that there is no evidence for the
need to extend the size of the adiabatically stratified core, at least
at the beginning of the HeCB phase. This conclusion is based primarily
on ensemble studies of ΔΠ1 as a function of mass and
metallicity. While ΔΠ1 shows no appreciable dependence on
the mass, we have found a clear dependence of ΔΠ1 on
metallicity, which is also supported by predictions from models.
Description:
Observational constraints on red clump stars in the old-open
clusters NGC 6791 and NGC 6819 are taken from Vrard et al.
(2016A&A...588A..87V 2016A&A...588A..87V, Cat. J/A+A/588/A87) and, crucially, include
measurements of the gravity-mode period spacing. Among all the stars
observed by Kepler in NGC 6791 and NGC 6819.
The final sample of red clump stars in NGC 6819 and NGC 6791 consists
of, respectively, 14 and 16 stars (see Tables A1 and A2 for a complete
list of targets).
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
tablea1.dat 96 67 *NGC 6819 stellar catalogue
tablea2.dat 91 106 *NGC 6791 stellar catalogue
--------------------------------------------------------------------------------
Note on *.dat: Stellar classes were chosen considering the classification
in Stello et al. (2011ApJ...739...13S 2011ApJ...739...13S) and {DELTA}{PI}1, {DELTA}ν,
and νmax in Vrard et al. (2016A&A...588A..87V 2016A&A...588A..87V, Cat. J/A+A/588/A87).
--------------------------------------------------------------------------------
See also:
V/133 : Kepler Input Catalog (Kepler Mission Team, 2009)
J/A+A/588/A87 : Seismic global parameters of 6111 KIC (Vrard+, 2016)
Byte-by-byte Description of file: tablea1.dat tablea2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- N Sequential number, within the cluster
5- 11 I7 --- KIC KIC number
13- 18 F6.2 uHz numax ? Frequency of maximum oscillation power
20- 24 F5.2 uHz Dnu ? Mean large frequency separation of modes with
the same degree and consecutive order,
{DELTA}nu
26- 31 F6.2 s DPi1 ? Gravity-mode period spacing, {DELTA}{PI}1
33- 37 F5.2 s e_DPi1 ? rms uncertainty on DPi1
39- 41 A3 --- ClassV [Yes ] Classified as red clump in Vrard et al.
(2016A&A...588A..87V 2016A&A...588A..87V, Cat. J/A+A/588/A87)
43- 49 A7 --- Class [RC RGB Unclear] This work classification (1)
51- 53 A3 --- RCsel [Yes No] Selected RC stars ?
55- 96 A42 --- Notes Notes
--------------------------------------------------------------------------------
Note (1): Classificatino as follows:
RC = red clump
RGB = red giant star
Unclear = unclear
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 19-Apr-2020