Chauvin, G. and Lagrange, A.-M. and Bonavita, M. and Zuckerman, B. and Dumas, C. and Bessell, M. S. and Beuzit, J.-L. and Bonnefoy, M. and Desidera, S. and Farihi, J. and Lowrance, P. and Mouillet, D. and Song, I. (2010) Deep imaging survey of young, nearby austral stars: VLT/NACO near-infrared Lyot-coronographic observations. Astronomy and Astrophysics, 509 . Art. No. A52. ISSN 0004-6361 http://resolver.caltech.edu/CaltechAUTHORS:20100302-135655153
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Context. High contrast and high angular resolution imaging is the optimal search technique for substellar companions to nearby stars at physical separations larger than typically 10 AU. Two distinct populations of substellar companions, brown dwarfs and planets, can be probed and characterized. As a result, fossile traces of processes of formation and evolution can be revealed by physical and orbital properties, both for individual systems and as an ensemble. Aims. Since November 2002, we have conducted a large, deep imaging, survey of young, nearby associations of the southern hemisphere. Our goal is detection and characterization of substellar companions with projected separations in the range 10–500 AU. We have observed a sample of 88 stars, primarily G to M dwarfs, younger than 100 Myr, and within 100 pc of Earth. Methods. The VLT/NACO adaptive optics instrument of the ESO Paranal Observatory was used to explore the faint circumstellar environment between typically 0.1 and 10". Diffraction-limited observations in H and K_s-band combined with Lyot-coronagraphy enabled us to reach primary star-companion brightness ratios as small as 10^(-6). The existence of planetary mass companions could therefore be probed. We used a standardized observing sequence to precisely measure the position and flux of all detected sources relative to their visual primary star. Repeated observations at several epochs enabled us to discriminate comoving companions from background objects. Results. We report the discovery of 17 new close (0.1–5.0") multiple systems. HIP 108195 AB and C (F1 III-M6), HIP 84642 AB (a~14 AU, K0-M5) and TWA22 AB (a~1.8 AU; M6-M6) are confirmed comoving systems. TWA22 AB is likely to be a rare astrometric calibrator that can be used to test evolutionary model predictions. Among our complete sample, a total of 65 targets were observed with deep coronagraphic imaging. About 240 faint companion candidates were detected around 36 stars. Follow-up observations with VLT or HST for 83% of these stars enabled us to identify a large fraction of background contaminants. Our latest results that pertain to the substellar companions to GSC 08047-00232, AB Pic and 2M1207 (confirmed during this survey and published earlier), are reviewed. Finally, a statistical analysis of our complete set of coronagraphic detection limits enables us to place constraints on the physical and orbital properties of giant planets between typically 20 and 150 AU.
|Additional Information:||© ESO 2010. Received 23 January 2009. Accepted 14 June 2009. We thank the ESO Paranal staff for performing the service mode observations. We also acknowledge partial financial support from the PNPS and Agence National de la Recherche, in France, from INAF through PRIN 2006 “From disk to planetray systems: understanding the origin and demographics of solar and extrasolar planetary systems” and from NASA in the USA. We also would like to thanks France Allard and Isabelle Baraffe for their inputs on evolutionary models and synthetic spectral libraries. Finally, our anonymous referee for her/his detailed and very constructive report.|
|Subject Keywords:||instrumentation: adaptive optics; instrumentation: high angular resolution; methods: observational; methods: statistical; brown dwarfs; planetary systems|
|Official Citation:||Deep imaging survey of young, nearby austral stars - VLT/NACO near-infrared Lyot-coronographic observations G. Chauvin, A.-M. Lagrange, M. Bonavita, B. Zuckerman, C. Dumas, M. S. Bessell, J.-L. Beuzit, M. Bonnefoy, S. Desidera, J. Farihi, P. Lowrance, D. Mouillet and I. Song A&A 509 A52 (2010) DOI: 10.1051/0004-6361/200911716|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Tony Diaz|
|Deposited On:||02 Mar 2010 23:19|
|Last Modified:||26 Dec 2012 11:48|
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