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Title:
HST, VLT, and NTT imaging search for wide companions to bona-fide and candidate brown dwarfs in the Cha I dark cloud
Authors:
Neuhäuser, R.; Brandner, W.; Alves, J.; Joergens, V.; Comerón, F.
Affiliation:
AA(MPI für extraterrestrische Physik, Giessenbachstraße 1, 85740 Garching, Germany), AB(European Southern Observatory, Karl-Schwarzschild-Straße 2, 85748 Garching, Germany), AC(European Southern Observatory, Karl-Schwarzschild-Straße 2, 85748 Garching, Germany), AD(MPI für extraterrestrische Physik, Giessenbachstraße 1, 85740 Garching, Germany), AE(European Southern Observatory, Karl-Schwarzschild-Straße 2, 85748 Garching, Germany)
Publication:
Astronomy and Astrophysics, v.384, p.999-1011 (2002) (A&A Homepage)
Publication Date:
03/2002
Origin:
A&A
A&A Keywords:
STARS: BINARIES: VISUAL, INDIVIDUAL: CHA HALPHA 1 TO 12, LOW-MASS, BROWN DWARFS, PRE-MAIN SEQUENCE
DOI:
10.1051/0004-6361:20020060
Bibliographic Code:
2002A&A...384..999N

Abstract

We present results from a deep imaging search for companions around the young bona-fide and candidate brown dwarfs Cha Hα 1 to 12 in the Cha I dark cloud, performed with HST WFPC2 (R, I, Hα ), VLT FORS1 (VRI), and NTT SofI (JHKs). We find 16 faint companion candidates around five primaries with separations between 1.5'' and 7'' 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'' SW off the M6-dwarf Cha Hα 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 (Lbol/Lsun) = -3.0 +/- 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. (\cite{Burrows97}) and Chabrier & Baraffe (\cite{Chabrier00}) 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 Hα 2 being a close ( ~ 0.2'') binary with both components very close to the sub-stellar limit. Our detection limits are such that we should have detected all companions above ~ 1 Mjup with separations >=2'' (>= 320 AU) and all above ~ 5 Mjup at >= 0.35'' (>= 50 AU). Based on observations obtained with the NASA/ESA Hubble Space Telescope in program GO 8716, ESO programs 64.I-0493, 66.C-0022, and 66.C-0310 as well as data taken from the public VLT data archive.
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