Near-IR Field Variable Stars in Cygnus OB7

TL;DR

This study presents a near-infrared monitoring of the Cygnus OB7 region, identifying 149 variable stars among 9,200 observed, with most variability attributed to eclipsing binaries, stellar spots, or stochastic processes.

Contribution

First near-infrared variability survey of Cygnus OB7's field stars, revealing detailed variability characteristics and classifications.

Findings

149 variables identified out of 9,200 stars

Approximately 60 stars are strictly periodic, mainly eclipsing binaries

Most variability is due to eclipsing binaries, star spots, or stochastic processes

Abstract

We present a subset of the results of a three season, 124 night, near-infrared monitoring campaign of the dark clouds Lynds 1003 and Lynds 1004 in the Cygnus OB7 star forming region. In this paper, we focus on the field star population. Using three seasons of UKIRT J, H and K band observations spanning 1.5 years, we obtained high-quality photometry on 9,200 stars down to J=17 mag, with photometric uncertainty better than 0.04 mag. After excluding known disk bearing stars we identify 149 variables - 1.6% of the sample. Of these, about 60 are strictly periodic, with periods predominantly < 2 days. We conclude this group is dominated by eclipsing binaries. A few stars have long period signals of between 20 and 60 days. About 25 stars have weak modulated signals, but it was not clear if these were periodic. Some of the stars in this group may be diskless young stellar objects with relatively large variability due to cool star spots. The remaining ~60 stars showed variations which appear to be purely stochastic.