Eclipses by a Circumstellar Dust Feature in the Pre–main-Sequence Star KH 15D

Photometry and spectroscopy of the unique pre-main sequence eclipsing objectKH15D in the young cluster NGC 2264 are presented. The orbital period is 48.34days and both the length (~16 d) and depth (~3 mag) of the eclipse haveincreased with time. A brightening near the time of central eclipse isconfirmed in the recent data but at a much smaller amplitude than wasoriginally seen. Spectra taken when the star is bright show that the primary isa weak T Tauri star of spectral type K7. During eclipse there is no detectablechange in spectral type or reddening, indicating that the obscuration is causedby rather large dust grains and/or macroscopic objects. Evidently the star iseclipsed by an extended feature in its circumstellar disk orbiting with asemi-major axis of ~0.2 AU. Continued photometric monitoring should allow us toprobe the disk structure with a spatial resolution of ~3 x 10^6 km or better.Comment: 16 pages, 3 figures, To be published in Astrophysical Journal Letter