Joel H. Kastner, E. Thompson, R. Montez Jr., S. J. Murphy, M. S. Bessell, G. G. Sacco
The early-K star T Cha, a member of the relatively nearby (D ~ 100 pc)
epsilon Cha Association, is a relatively "old" (age ~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 ~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 ~<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.
View original:
http://arxiv.org/abs/1202.0262
No comments:
Post a Comment