Near-infrared time-series photometry in the field of Cygnus OB2 association II. Mapping the variability of candidate members
Journal
Date Issued
2020
Author(s)
Abstract
We present the results of a J, H, and K photometric variability survey of the
central 0.78 square degrees of the young OB association Cygnus OB2. We used
data observed with the Wide-Field CAMera at the United Kingdom Infrared
Telescope in 2007 (spanning 217 days) to investigate the light curves of 5083
low mass candidate members in the association and explore the occurrence and
main characteristics of their near-infrared variability. We identified 2529
stars ($\sim$50$\%$ of the sample) with significant variability with
time-scales ranging from days to months. We classified the variable stars into
the following three groups according to their light curve morphology: periodic
variability (1697 stars), occultation variability (124 stars), and other types
of variability (726 stars). We verified that the disk-bearing stars in our
sample are significantly more variable in the near-infrared than diskless
stars, with a steep increase in the disk-fraction among stars with higher
variability amplitude. We investigated the trajectories described by variable
stars in the color-space and measured slopes for 335 stars describing linear
trajectories. Based on the trajectories in the color-space, we inferred that
the sample analyzed is composed of a mix of young stars presenting variability
due to hot and cold spots, extinction by circumstellar material, and changes in
the disk emission in the near-infrared. We contemplated using the use of
near-infrared variability to identify disk-bearing stars and verified that
53.4$\%$ of the known disk-bearing stars in our sample could have been
identified as such based solely on their variability. We present 18 newly
identified disk-bearing stars and 14 eclipsing binary candidates among CygOB2
lower-mass members.
Volume
640
Start page
A128
Issn Identifier
0004-6361
Ads BibCode
2020A&A...640A.128R
Rights
open.access
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