期刊
ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES
卷 219, 期 2, 页码 -出版社
IOP PUBLISHING LTD
DOI: 10.1088/0067-0049/219/2/33
关键词
brown dwarfs; methods: data analysis; proper motions; stars: kinematics and dynamics; stars: low-mass
资金
- Fond de Recherche Quebecois-Nature et Technologie
- Natural Science and Engineering Research Council of Canada
- NASA Small Research Grant
- National Aeronautics and Space Administration (NASA)
- National Science Foundation
- Extrasolar Planets Encyclopaedia
- NASA
- NASA/IPAC Infrared Science Archive (IRSA)
- Rockefeller Foundation
- Gemini Observatory [GN-2013A-Q-118, GS-2013B-Q-79, GS-2014A-Q-55, GS-2014B-Q-72, GS-2014B-Q-47, GS-2015A-Q-60]
- AURA through the National Science Foundation [AST 0132798]
- IRTF [2007B023, 2007B070, 2008A050, 2008B054, 2009A055, 2010A045, 2011B071, 2012A097, 2012B015, 2013A040, 2013A055, 2013B025, 2014B026, 2015A026]
- CNTAC program [CN2013A-135]
We present the results of a near-infrared (NIR) spectroscopic follow-up survey of 182 M4-L7 low-mass stars and brown dwarfs (BDs) from the BANYAN All-Sky Survey (BASS) for candidate members of nearby, young moving groups (YMGs). We confirm signs of low gravity for 42 new BD discoveries with estimated masses between 8 and 75 M-Jup and identify previously unrecognized signs of low gravity for 24 known BDs. We refine the fraction of low-gravity dwarfs in the high-probability BASS sample to similar to 82%. We use this unique sample of 66 young BDs, supplemented with 22 young BDs from the literature, to construct new empirical NIR absolute magnitude and color sequences for low-gravity BDs. We show that low-resolution NIR spectroscopy alone cannot differentiate between the ages of YMGs younger than similar to 120 Myr, and that the BT-Settl atmosphere models do not reproduce well the dust clouds in field or low-gravity L-type dwarfs. We obtain a spectroscopic confirmation of low gravity for 2MASS J14252798-3650229, which is a new similar to 27 M-Jup, L4 gamma bona fide member of AB Doradus. We identify a total of 19 new low-gravity candidate members of YMGs with estimated masses below 13 M-Jup, 7 of which have kinematically estimated distances within 40 pc. These objects will be valuable benchmarks for a detailed atmospheric characterization of planetary-mass objects with the next generation of instruments. We find 16 strong candidate members of the Tucana-Horologium association with estimated masses between 12.5 and 14 M-Jup, a regime where our study was particularly sensitive. This would indicate that for this association there is at least one isolated object in this mass range for every 17.5(-5.0)(+6.6) main-sequence stellar member, a number significantly higher than expected based on standard log-normal initial mass function, however, in the absence of radial velocity and parallax measurements for all of them, it is likely that this over-density is caused by a number of young interlopers from other associations.
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