Near-infrared photometric variability of stars toward the Chamaeleon I molecular cloud

We present the results of a J, H, and K, photometric monitoring campaign of a 0.degrees72x6degrees area centered on the Chamaeleon I star-forming region. Data were obtained on 15 separate nights over a 4 month time interval using the Two Micron All Sky Survey south telescope. Out of a total of 34,539 sources brighter than the photometric completeness limits (J=16.0, H=15.2, and K-s=14.8), 95 exhibit near-infrared variability in one or more bands. The variables can be grouped into a population of bright, red objects that are associated with the Chamaeleon I association and a population of faint, blue variables that are dispersed over the full 6degrees of the survey and are likely field stars or older pre-main-sequence stars unrelated to the present-day Chamaeleon I molecular cloud. Ten new candidate members of Chamaeleon I, including eight brown dwarf candidates, have been identified based on variability and/or near-infrared-excess emission in the J-H versus H-K-s color-color diagram. We also provide a compendium of astrometry and J, H, and I, photometry for previously identified members and candidate members of Chamaeleon I.