Astronomy and Astrophysics, volume 384, 999-1011 (2002/3-4)
HST, VLT, and NTT imaging search for wide companions to bona-fide and candidate brown dwarfs in the Cha I dark cloud.
NEUHAEUSER R., BRANDNER W., ALVES J., JOERGENS V. and COMERON F.
Abstract (from CDS):
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 25mag, 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
=0.47mag) as towards the primary, the companion candidate has log (Lbol
)=-3.0±0.3. At the age of the primary (1 to 5Myrs), the faint object would have a mass of 3 to 15 Jupiter masses according to Burrows et al. (1997ApJ...491..856B
) and Chabrier & Baraffe (2000ARA&A..38..337C
) models. The probability for this companion candidate to be an unrelated fore- or background object is ≤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 ∼1Mjup
with separations ≥2'' (≥320AU) and all above ∼5Mjup
at ≥0.35'' (≥50AU).
stars: binaries: visual - individual: Cha Hα 1 to 12 - low-mass, brown dwarfs - pre-main sequence
Table 2: [NBA2002] HA NN cc N N=3+1+8+3+1.
In ref list, Neuhaueser, 1999: 360 is a misprint for 350 (1999A&A.350.612N). Reid, 2001: ApJ is a misprint for AJ.
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