Detection of lithium in nearby young late-M dwarfs⋆
1 Department of Physics, HCM International University-Vietnam National University, Block 6, Linh Trung Ward, Thu Duc District, HCM city, Viet Nam
2 Institute of Astronomy and Astrophysics, Academia Sinica. PO Box 23-141, Taipei 106, Taiwan, ROC
3 Research School of Astronomy and Astrophysics, Australian National University, Cotter Rd, 2611 Weston, Australia
4 Faculty of Physics and Engineering Physics, HCM University of Science-VNU, 227 Nguyen Van Cu Street, District 5, HCM city, Viet Nam
5 Centro de Astrobiologia (CSIC-INTA), Ctra. Ajalvir km 4, 28850 Torrejón de Ardoz, Madrid, Spain
6 East Asian Observatory, 660 N. A’Ohoku Place University Park, Hilo, Hawaii 96720, USA
Received: 24 September 2016
Accepted: 29 December 2016
Context. Late M-type dwarfs in the solar neighborhood include a mixture of very low-mass stars and brown dwarfs that is difficult to disentangle due to the lack of constraints on their age, such as trigonometric parallax, lithium detection, and space velocity.
Aims. We search for young brown dwarf candidates among a sample of 28 nearby late-M dwarfs with spectral types between M5.0 and M9.0, and we also search for debris disks around three of them.
Methods. Based on theoretical models, we used the color I−J, the J-band absolute magnitude, and the detection of the Li I 6708 Å doublet line as a strong constraint to estimate masses and ages of our targets. For the search of debris disks, we observed three targets at submillimeter wavelength of 850 μm.
Results. We report here the first clear detections of lithium absorption in four targets and a marginal detection in one target. Our mass estimates indicate that two of them are young brown dwarfs, two are young brown dwarf candidates, and one is a young very low-mass star. The closest young field brown dwarf in our sample at only ~15 pc is an excellent benchmark for further studying physical properties of brown dwarfs in the range 100−150 Myr. We did not detect any debris disks around three late-M dwarfs, and we estimated upper limits to the dust mass of debris disks around them.
Key words: brown dwarfs / radio continuum: stars / techniques: spectroscopic / circumstellar matter / techniques: photometric / stars: flare
The reduced spectra (FITS files) are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (126.96.36.199) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/600/A19
© ESO, 2017