2008MNRAS.383..831P -
Mon. Not. R. Astron. Soc., 383, 831-844 (2008/January-3)
Discovery of new nearby L and late-M dwarfs at low Galactic latitude from the DENIS data base.
PHAN-BAO N., BESSELL M.S., MARTIN E.L., SIMON G., BORSENBERGER J., TATA R., GUIBERT J., CRIFO F., FORVEILLE T., DELFOSSE X., LIM J. and DE BATZ B.
Abstract (from CDS):
We report on new nearby L and late-M dwarfs (dphot≤ 30 pc) discovered in our search for nearby ultracool dwarfs (I-J ≥ 3.0, later than M8.0) at low Galactic latitude (|b| < 15°) over 4800 deg2 in the Deep Near Infrared Survey of the Southern Sky (DENIS) data base. We used late-M (≥ M8.0), L and T dwarfs with accurate trigonometric parallaxes to calibrate the MJ versus I-J colour-luminosity relation. The resulting photometric distances have standard errors of ∼15 per cent, which we used to select candidates dphot≤ 30 pc. We measured proper motions from multi-epoch images found in the public archives ALADIN, DSS, 2MASS and DENIS, with at least three distinct epochs and time baselines of 10-21 yr. We then used a maximum reduced proper motion cut-off to select 28 candidates as ultracool dwarfs (M8.0-L8.0) and to reject one as a distant red star. No T dwarf candidates were found in this search, which required an object to be detected in all three DENIS bands. Our low-resolution optical spectra confirmed that 26 were indeed ultracool dwarfs, with spectral types from M8.0 to L5.5. Two contaminants and one rejected by the maximum reduced proper motion cut-off were all reddened F-K main sequence stars. 20 of these 26 ultracool dwarfs are new nearby ultracool dwarf members, three L dwarfs within 15 pc with one L3.5 at only ∼10 pc. We determine a stellar density of dwarfs/pc3/mag over 11.1 ≤ MJ≤ 13.1 based on this sample of M8-L3.5 ultracool dwarfs. Our ultracool dwarf density value is in good agreement with the measurement by Cruz et al. of the ultracool dwarf density at high Galactic latitude.
Abstract Copyright:
2007 The Authors. Journal compilation © 2007 RAS
Journal keyword(s):
techniques: photometric - techniques: spectroscopic - stars: low-mass, brown dwarfs - stars: luminosity function, mass function - solar neighbourhood
VizieR on-line data:
<Available at CDS (J/MNRAS/383/831): tables.dat>
Simbad objects:
82
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