2011A&A...530A.100H


Query : 2011A&A...530A.100H

2011A&A...530A.100H - Astronomy and Astrophysics, volume 530A, 100-100 (2011/6-1)

Asteroseismic inferences on red giants in open clusters NGC 6791, NGC 6819, and NGC 6811 using Kepler.

HEKKER S., BASU S., STELLO D., KALLINGER T., GRUNDAHL F., MATHUR S., GARCIA R.A., MOSSER B., HUBER D., BEDDING T.R., SZABO R., DE RIDDER J., CHAPLIN W.J., ELSWORTH Y., HALE S.J., CHRISTENSEN-DALSGAARD J., GILLILAND R.L., STILL M., McCAULIFF S. and QUINTANA E.V.

Abstract (from CDS):

Four open clusters are present in the Kepler field of view and timeseries of nearly a year in length are now available. These timeseries allow us to derive asteroseismic global oscillation parameters of red-giant stars in the three open clusters NGC 6791, NGC 6819 and NGC 6811. From these parameters and effective temperatures, we derive masses, radii and luminosities for the clusters as well as field red giants. We study the influence of evolution and metallicity on the observed red-giant populations. The global oscillation parameters are derived using different published methods and the effective temperatures are derived from 2MASS colours. The observational results are compared with BaSTI evolution models. We find that the mass has significant influence on the asteroseismic quantities Δν vs. νmax relation, while the influence of metallicity is negligible, under the assumption that the metallicity does not affect the excitation/damping of the oscillations. The positions of the stars in the H-R diagram depend on both mass and metallicity. Furthermore, the stellar masses derived for the field stars are bracketed by those of the cluster stars. Both the mass and metallicity contribute to the observed difference in locations in the H-R diagram of the old metal-rich cluster NGC 6791 and the middle-aged solar-metallicity cluster NGC 6819. For the young cluster NGC 6811, the explanation of the position of the stars in the H-R diagram challenges the assumption of solar metallicity, and this open cluster might have significantly lower metallicity [Fe/H] in the range -0.3 to -0.7dex. Also, nearly all the observed field stars seem to be older than NGC 6811 and younger than NGC 6791.

Abstract Copyright:

Journal keyword(s): stars: late-type - open clusters and associations: general - methods: observational - techniques: photometric - asteroseismology

Simbad objects: 8

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Number of rows : 8
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024
#notes
1 NGC 104 GlC 00 24 05.359 -72 04 53.20     4.09     ~ 3911 0
2 NGC 2682 OpC 08 51 23.0 +11 48 50           ~ 2339 0
3 NGC 6397 GlC 17 40 42.09 -53 40 27.6     5.17     ~ 1974 0
4 NGC 6791 OpC 19 20 53.0 +37 46 41   10.52 9.5     ~ 1038 0
5 V* V568 Lyr EB* 19 20 57.3346763352 +37 45 36.739962972   18.295   16.823   ~ 43 0
6 NGC 6811 OpC 19 37 21.6 +46 22 41   7.47 6.8     ~ 377 0
7 NGC 6819 OpC 19 41 18.5 +40 11 24   8.21 7.3     ~ 634 0
8 NGC 6866 OpC 20 03 55.9 +44 09 29   8.04 7.6     ~ 166 0

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