Variable Star Population in the Open Cluster NGC 6819 Observed by the Kepler Spacecraft
S. Sanjayan1,2, A.S. Baran1,3, P. Németh1,4,5 and K. Kinemuchi6,7
1ARDASTELLA Research Group
2Centrum Astronomiczne im. MikoĊaja Kopernika, Polskiej Akademii Nauk, ul. Bartycka 18, 00-716 Warszawa, Poland
3Astronomical Observatory, University of Warsaw, Al. Ujazdowskie 4, 00-478 Warszawa, Poland
4Astroserver.org, Fötér 1, 8533 Malomsok, Hungary
5Astronomical Institute of the Czech Academy of Sciences, Fričova 298, CZ-251~65 Ondřejov, Czech Republic
6Department of Astronomy, New Mexico State University, Box 30001, MSC 4500, Las Cruces, NM 88003, USA
7Apache Point Observatory, 2001 Apache Point Road, P.O. Box 59, Sunspot, NM 88349-0059
Received: November 22, 2022
ABSTRACT
We present the list of variable stars we found in the Kepler
superstamp data covering approximately nine arcminutes from the central
region of NGC 6819. This is a continuation of our earlier work.
We classified the variable stars based on the
variability type and we established their cluster membership based on the
available Gaia Data Release 3 astrometry. Our search revealed 385
variable stars but only 128 were found to be cluster members. In the case
of eclipsing and contact binaries we calculated the mid-times of eclipses
and derived ephemerides. We searched for eclipse timing variation using
the observed minus calculated diagrams. Only five objects show
significant orbital period variation. We used isochrones calculated
within the MESA Isochrones and Stellar Tracks project and derived the
average age (2.54 Gyr), average distance (2.3 kpc) and iron content
[Fe/H]=-0.01(2), of NGC 6819. We confirm this distance by the one
derived from Gaia astrometry of the cluster members with membership
probabilities greater than 0.9.
Key words:
open clusters and associations:
individual: NGC 6819 - Stars: variables: general
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