Astronomy and Astrophysics, volume 458, 317-325 (2006/10-4)
Coronagraphic imaging of three weak-line T Tauri stars: evidence of planetary formation around PDS 70.
RIAUD P., MAWET D., ABSIL O., BOCCALETTI A., BAUDOZ P., HERWATS E. and SURDEJ J.
Abstract (from CDS):
High angular resolution imaging of nearby pre-main sequence stars with ages between 1 and 30Myr can give valuable information on planet formation mechanisms. This range of ages is thought to correspond to the dissipation of the optically thick dust disks surrounding young stars and to the end of the planet formation. This paper presents new observations of three weak-line T Tauri Stars (WTTS) of intermediate ages ranging from 7 to 16Myr. It aims at increasing the knowledge and sample of circumstellar disks around ``old'' WTTS.We observed three stars with the VLT's NAOS-CONICA adaptive optics system in coronagraphic mode. The four-quadrant phase mask coronagraph was used to improve the dynamic range (by a factor of ∼100) while preserving the high angular resolution (inner working angle of 0.15"). One object of our sample (PDS 70), a K5 star, exhibits a brown dwarf companion and a disk in scattered light with a surface brightness power law of r–2.8, extending from a distance of 14 to 140AU (assuming a stellar distance of 140pc) and an integrated luminosity of 16.7mJy in the Ks-band. The mass of the companion can be estimated to be within a range between 27 and 50 Jupiter masses with an effective temperature of 2750 ±100K. This object also shows a resolved outflow stretching up to ∼550AU. This newly detected circumstellar disk shows strong similarities with the disk around TW Hya, and adds to the observed population of ``old'' TTS surrounded by circumstellar material. Moreover, three clues of planetary formation are brought to light by this study.