Variable Star Population in the Open Cluster NGC 6791 Observed by the Kepler Spacecraft
S. Sanjayan1,2, A.S. Baran1,3,4, P. Németh1,5,6, K. Kinemuchi7,8, J. Ostrowski1 and S.K. Sahoo1,2
1ARDASTELLA Research Group, Institute of Physics, Pedagogical University of Cracow, ul. Podchorążych 2, 30-084 Kraków, Poland
2Centrum Astronomiczne im. Mikołaja Kopernika, Polskiej Akademii Nauk, ul. Bartycka 18, 00-716 Warszawa, Polska
3Embry-Riddle Aeronautical University, Department of Physical Sciences, Daytona Beach, FL 32114, USA
4Department of Physics, Astronomy, and Materials Science, Missouri State University, Springfield, MO 65897, USA
5Astroserver.org, Fő tér 1, 8533 Malomsok, Hungary
6Astronomical Institute of the Czech Academy of Sciences, Fričova 298, CZ-251 65 Ondřejov, Czech Republic
7Department of Astronomy, New Mexico State University, Box 30001, MSC 4500, Las Cruces, NM 88003, USA
8Apache Point Observatory, 2001 Apache Point Road, P.O. Box 59, Sunspot, NM 88349-0059
Received: April 15, 2022
ABSTRACT
We present the list of variable stars we found in the Kepler
superstamp data covering approximately 9' from the central region
of NGC 6791. We classified the variable stars based on the variability
type and we established their cluster membership based on the available
Gaia Early Data Release 3 astrometry, by means of the Bayesian Gaussian
mixture models. In total we found 278 variable objects, among which 17
binaries, 45 pulsators, 62 rotational and five unclassified variables are
cluster members. The remaining 28 binaries, 25 pulsators, 83 rotational,
four unclassified and nine unidentified variables are either not members
or their membership is not established. In the case of eclipsing binaries
we calculated the mid-times of eclipses and derived ephemerides. We
searched for eclipse timing variation by means of the observed minus
calculated diagrams. Only three objects show significant orbital period
variation. Independently of a recently published report, we found 119 new
variables. We used isochrones calculated within the MIST project and
derived the age (8.91 Gyr), average distance (4134 pc) and iron content
[Fe/H] (0.26-0.28), of NGC 6791. Using the cluster members with
membership probabilities greater than 0.9, we calculated the distance to
the cluster of 4123(31) pc, which agrees with the result from our
isochrone fitting.
Key words:
open clusters and associations: individual: NGC 6791
- binaries: general - Stars: oscillations - Stars: rotation
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