X‐Ray Emission from the Weak‐lined T Tauri Binary System KH 15D

The unique eclipsing, weak-lined T Tauri star KH 15D has been detected as anX-ray source in a 95.7 ks exposure from the Chandra X-ray Observatory archives.A maximum X-ray luminosity of 1.5 x 10^{29} erg s$^{-1}$ is derived in the0.5--8 keV band, corresponding to L_{X}/L_bol = 7.5 x 10^{-5}. Comparison withsamples of stars of similar effective temperature in NGC 2264 and in the OrionNebula Cluster shows that this is about an order of magnitude low for a typicalstar of its mass and age. We argue that the relatively low luminosity cannot beattributed to absorption along the line of sight but implies a real deficiencyin X-ray production. Possible causes for this are considered in the context ofa recently proposed eccentric binary model for KH 15D. In particular, we notethat the visible component rotates rather slowly for a weak-lined T Tauri starand has possibly been pseudosynchronized by tidal interaction with the primarynear periastron