Near-Infrared Photometric Variability of Stars toward the Chamaeleon I Molecular Cloud

We present the results of a J, H, and K_s photometric monitoring campaign ofa 0.72 x 6 sq deg. area centered on the Chamaeleon I star forming region. Datawere obtained on 15 separate nights over a 4 month time interval using the2MASS South telescope. Out of a total of 34,539 sources brighter than thephotometric completeness limits (J=16.0, H=15.2, K_s=14.8), 95 exhibitnear-infrared variability in one or more bands. The variables can be groupedinto a population of bright, red objects that are associated with theChamaeleon I association, and a population of faint, blue variables that aredispersed over the full 6 deg of the survey and are likely field stars or olderpre-main-sequence stars unrelated to the present-day Chamaeleon I molecularcloud. Ten new candidate members of Chamaeleon I, including 8 brown dwarfcandidates, have been identified based on variability and/or near-infraredexcess emission in the J-H vs. H-K_s color-color-diagram. We also provide acompendium of astrometry and J, H, and K_s photometry for previously identifiedmembers and candidate members of Chamaeleon I.