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2005MNRAS.356...89K - Mon. Not. R. Astron. Soc., 356, 89-106 (2005/January-1)
Membership, binarity and accretion among very low-mass stars and brown dwarfs of the σ Orionis cluster.
KENYON M.J., JEFFRIES R.D., NAYLOR T., OLIVEIRA J.M. and MAXTED P.F.L.
Abstract (from CDS):
Four candidate binary cluster members are identified. Consideration of sampling and radial velocity measurement precision leads us to conclude that either the fraction of very low-mass stars and brown dwarfs in small separation (a < 1 au) binary systems is larger than in field M-dwarfs, or the distribution of separations is much less skewed towards large separations. This conclusion hinges critically on the correct identification of the small number of binary candidates, although it remains significant even when only the candidate members displaying Li absorption are considered.
Broadened Hα emission, indicative of circum(sub)stellar accretion discs is found in five or six of the candidate cluster members, three of which probably have substellar masses. The fraction of accretors (10±5 per cent) is similar to that found in stars of higher mass in the σ Ori cluster using Hα emission as a diagnostic, but much lower than found for very low-mass stars and brown dwarfs of younger clusters. The time-scale for accretion rates to drop to ≲10–11 M☉/yr is hence less than the age of the σ Ori cluster (3-7 Myr) for most low-mass objects.
Abstract Copyright: 2004 RAS
Journal keyword(s): techniques: radial velocities - techniques: spectroscopic - stars: low-mass, brown dwarfs - stars: pre-main-sequence - open clusters and associations: individual: σ Orionis
VizieR on-line data: <Available at CDS (J/MNRAS/356/89): members.dat nonmemb.dat uncert.dat>
Nomenclature: Table 4: [KJN2005] NN (Nos 1-76). Catalogue: [KJN2005] F.FF NNNN N=41001.
Status at CDS : All or part of tables of objects will not be ingested in SIMBAD.
Simbad objects: 94
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