The Peculiar Periodic YSO WL 4 in p Ophiuchus

摘要

We present the discovery of 130.87 day periodic near-infrared flux variability for theClass II T Tauri star WL 4 (= 2MASS J16271848-2429059, ISO-Oph 128). Our data are from the2MASS Calibration Point Source Working Database, and constitute 1580 observations in J, H andK_s of a field inpOphiuchus used to calibrate the 2MASS All-Sky Survey. We identify a light curvefor WL 4 with eclipse amplitudes of ~0.4 mag lasting more than one-quarter the period, and colorvariations in J-H and H-K_s ofmag. The long period cannot be explained by stellar rotation.We propose that WL 4 is a triple YSO system, with an inner binary orbital period of 130.87 days.We posulate that we are observing each component of the inner binary alternately being eclipsedby a circum-binary disk with respect to our line of sight. This system will be useful in investigating terrestrial zone YSO disk properties and dynamics atMyr.