The early-K star T Cha , a member of the relatively nearby ( D \approx 100 pc ) \epsilon Cha Association , is a relatively “ old ” ( age \sim 7 Myr ) T Tauri star that is still sporadically accreting from an orbiting disk whose inner regions are evidently now being cleared by a close , substellar companion .
We report the identification , via analysis of proper motions , serendipitous X-ray imaging spectroscopy , and followup optical spectroscopy , of a new member of the \epsilon Cha Association that is very likely a low-mass companion to T Cha at a projected separation of \sim 38 kAU .
The combined X-ray and optical spectroscopy data indicate that the companion , T Cha B ( = 2M1155 - 79 ) , is a weak-lined T Tauri star ( wTTS ) of spectral type M3 and age \stackrel { < } { \sim } 10 Myr .
The serendipitous X-ray ( XMM-Newton ) observation of T Cha B , which targeted T Cha , also yields serendipitous detections of two background wTTS in the Chamaeleon cloud complex , including one newly discovered , low-mass member of the Cha cloud pre-MS population .
T Cha becomes the third prominent example of a nearby , “ old ” yet still actively accreting , K-type pre-MS star/disk system ( the others being TW Hya and V4046 Sgr ) to feature a low-mass companion at very large ( 12–40 kAU ) separation , suggesting that such wide-separation companions may affect the conditions and timescales for planet formation around solar-mass stars .