Bright Variable Stars in NGC 6819 - An Open Cluster in the Kepler Field

TL;DR

This study identifies and characterizes variable stars in the open cluster NGC 6819, including eclipsing binaries and blue stragglers, to help constrain the cluster's age and understand stellar interactions.

Contribution

It reports the discovery of new variable stars, including eclipsing binaries and blue stragglers, and discusses their potential to inform cluster properties and stellar evolution.

Findings

Four new detached eclipsing binaries detected near the cluster turnoff.

Three brightest variables are likely cluster blue stragglers, including a delta Scuti pulsator.

Evidence suggests some systems may result from multi-star interactions.

Abstract

We describe a variability study of the moderately old open cluster NGC 6819. We have detected 4 new detached eclipsing binaries near the cluster turnoff (one of which may be in a triple system). Several of these systems should be able to provide mass and radius information, and can therefore constrain the age of the cluster. We have also newly detected one possible detached binary member about 3.5 magnitudes below the turnoff. One EW-type binary (probably not a cluster member) shows unusually strong night-to-night light curve variations in sets of observations separated by 8 years. According to the best current information, the three brightest variables we detected (2 of them new) are cluster members, making them blue stragglers. One is a delta Scu pulsating variable, one is a close but detached binary, and the third contains a detached short period binary that shows total eclipses. In each case, however, there is evidence hinting that the system may have been produced through the interaction of more than two stars.