NEAR-INFRARED PHOTOMETRIC MONITORING OF YOUNG STELLAR OBJECTS

This paper reports infrared JHK photometry of 15 young stellar objects sampled at intervals of a few days to a few weeks during the winters of 1991 and 1992, Accretion luminosity dominates the near-infrared flu x of most of the sources. Observed variations ranged between one tenth to one full magnitude during the monitoring period and were well corr elated at all three wavelengths, Variations by individual sources in t he (H-K) vs (J-H) color-color diagram indicate that such changes can b e explained by some combination of variable extinction of the stellar photosphere and changes in the accretion properties of the sources. Th e amplitude of K-band source variability is weakly correlated with (K- L) excess, which is a reliable accretion diagnostic. Included are near -infrared light curves for V410 Tan, a rapidly-rotating, heavily-spott ed weak-emission T Tauri star as a demonstration of the accuracy and c onsistency of the photometric measurements (typically 2%-4%) and for c omparison with the extensive body of existing visible-wavelength obser vations. (C) 1996 American Astronomical Society.