A young hierarchical triple system harbouring a candidate debris disc

作者：Deacon N R^*; Schlieder J E; Olofsson J; Johnston K G; Henning Th

来源：Monthly Notices of the Royal Astronomical Society, 2013, 434(2): 1117-1128.

DOI：10.1093/mnras/stt1054

• surveys
• binaries: visual
• circumstellar material
• stars: late-type
• stars: pre-main-sequence

We report the detection of a wide young hierarchical triple system where the primary has a candidate debris disc. The primary, TYC 5241-986-1 A, is a known Tycho star which we classify as a late-K star with emission in the X-ray, near- and far-ultraviolet (UV) and H alpha suggestive of youth. Its proper motion, photometric distance (65-105 pc) and radial velocity lead us to associate the system with the broadly defined Local Association of young stars but not specifically with any young moving group. The presence of weak lithium absorption and X-ray and calcium H and K emission support an age in the 20 to similar to 125 Myr range. The secondary is a pair of M4.5 +/- 0.5 dwarfs with near- and far-UV and H alpha emission separated by approximately 1 arcsec (similar to 65-105 au projected separation) which lie of 145 arcsec (9200-15200 au) from the primary. The primary has a Wide-field Infrared Survey Explorer (WISE) 22 mu m excess and follow-up Herschel observations also detect an excess at 70 mu m. The excess emissions are indicative of a 100-175 K debris disc. We also explore the possibility that this excess could be due to a coincident background galaxy and conclude that this is unlikely. Debris discs are extremely rare around stars older than 15 Myr, hence if the excess is caused by a disc this is an extremely novel system.

• 出版日期2013-9