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A&A 458, 317-325 (2006)
DOI: 10.1051/0004-6361:20065232
Coronagraphic imaging of three weak-line T Tauri stars: evidence of planetary formation around PDS 70
P. Riaud1, D. Mawet1, O. Absil1, A. Boccaletti2, P. Baudoz2, E. Herwats1, 3 and J. Surdej11 IAGL, Université de Liège, 17 Allée du 6 Août, 4000 Sart Tilman, Belgium
e-mail: riaud@astro.ulg.ac.be
2 LESIA, Observatoire de Paris-Meudon, 5 pl. Jules Janssen, 92195 Meudon, France
3 Laboratoire d'Astrophysique de l'Observatoire de Grenoble, BP 53, 38041 Grenoble Cedex 9, France
(Received 20 March 2006 / Accepted 20 June 2006)
Abstract
Context.High angular resolution imaging of nearby pre-main
sequence stars with ages between 1 and 30 Myr 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.
Aims.This paper presents new observations of three
weak-line T Tauri Stars (WTTS) of intermediate ages ranging from 7
to 16 Myr. It aims at increasing the knowledge and sample of
circumstellar disks around "old" WTTS.
Methods.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
).
Results.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 140 AU (assuming a stellar distance of 140 pc) and an
integrated luminosity of 16.7 mJy in the 
-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
K. This object also shows a resolved outflow stretching up to ~550 AU.
Conclusions.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.
Key words: stars: planetary systems: protoplanetary disks -- stars: circumstellar matter -- instrumentation: adaptive optics -- methods: observational
© ESO 2006