X-RAY EMISSION FROM THE WEAK-LINED T TAURI BINARY SYSTEM KH 15D

摘要

The unique eclipsing, weak-lined T Tauri star KH 15D has been detected as an X-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) ergs s~(-1) is derived in the 0.5-8 keV band, corresponding to L_X/L_(bol) = 7.5 x 10~(-5). Comparison with samples of stars of similar effective temperature in NGC 2264 and in the Orion Nebula cluster shows that this value is about an order of magnitude lower than that for a typical star of its mass and age. We argue that the relatively low luminosity cannot be attributed to absorption along the line of sight but implies a real deficiency in X-ray production. Possible causes for this are considered in the context of a recently proposed eccentric binary model for KH 15D. In particular, we note that the visible component rotates rather slowly for a weak-lined T Tauri star and has possibly been pseudosynchronized by tidal interaction with the primary near periastron.