EDP Sciences
Free Access
Issue
A&A
Volume 384, Number 3, March IV 2002
Page(s) 999 - 1011
Section Formation, structure and evolution of stars
DOI https://doi.org/10.1051/0004-6361:20020060
Published online 15 March 2002


A&A 384, 999-1011 (2002)
DOI: 10.1051/0004-6361:20020060

HST, VLT, and NTT imaging search for wide companions to bona-fide and candidate brown dwarfs in the Cha I dark cloud

R. Neuhäuser1, W. Brandner2, J. Alves2, V. Joergens1 and F. Comerón2

1  MPI für extraterrestrische Physik, Giessenbachstraße 1, 85740 Garching, Germany
2  European Southern Observatory, Karl-Schwarzschild-Straße 2, 85748 Garching, Germany

(Received 6 November 2001 / Accepted 14 January 2002)

Abstract
We present results from a deep imaging search for companions around the young bona-fide and candidate brown dwarfs Cha H $\alpha$ 1 to 12 in the Cha I dark cloud, performed with HST WFPC2 ( R, I, H $\alpha$), VLT FORS1 ( VRI), and NTT SofI ( $JHK_{\rm s}$). We find 16 faint companion candidates around five primaries with separations between 1.5 $^{\prime \prime}$ and 7 $^{\prime \prime}$ and magnitudes in  R & I from 19 to 25 mag, i.e. up to 8 mag fainter than the primaries. While most of these companion candidates are probably unrelated background objects, there is one promising candidate, namely $1.5^{\prime \prime}$ SW off the M6-dwarf Cha H $\alpha$ 5. This candidate is 3.8 to 4.7 mag fainter than the primary and its colors are consistent with an early- to mid-L spectral type. Assuming the same distance (140 pc) and absorption ( AI = 0.47 mag) as towards the primary, the companion candidate has $\log$ ( $L_{\rm bol}/L_{\odot}) = -3.0 \pm 0.3$. At the age of the primary (1 to 5 Myrs), the faint object would have a mass of 3 to 15 Jupiter masses according to Burrows et al. (1997) and Chabrier & Baraffe (2000) models. The probability for this companion candidate to be an unrelated fore- or background object is $\le$ $ 0.7\%$, its colors are marginally consistent with a strongly reddened background K giant. One other companion candidate has infrared colors consistent with an early T-dwarf. In addition, we present indications for Cha H $\alpha$ 2 being a close (~ $ 0.2^{\prime \prime}$) binary with both components very close to the sub-stellar limit. Our detection limits are such that we should have detected all companions above $\sim $ $M_{\rm jup}$ with separations $\ge $ $2^{\prime \prime}$ ( $\ge $ 320 AU) and all above ~ 5  $M_{\rm jup}$ at $\ge $ $ 0.35^{\prime \prime}$ ( $\ge $ 50 AU).


Key words: stars: binaries: visual -- individual: Cha H $\alpha$ 1 to 12 -- low-mass, brown dwarfs -- pre-main sequence

Offprint request: R. Neuhäuser, rne@mpe.mpg.de

SIMBAD Objects



© ESO 2002

Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.

Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.

Initial download of the metrics may take a while.