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J/A+A/600/A19       Spectra of 28 nearby young late-M dwarfs  (Phan-Bao+, 2017)

Detection of lithium in nearby young late-M dwarfs. Phan-Bao N., Bessell M.S., Nguyen-Thanh D., Martin E.L., Ho P.T.P., Lee C.F., Parsons H. <Astron. Astrophys. 600, A19 (2017)> =2017A&A...600A..19P (SIMBAD/NED BibCode)
ADC_Keywords: Stars, nearby ; Stars, M-type ; Spectroscopy Keywords: brown dwarfs - radio continuum: stars - techniques: spectroscopic - circumstellar matter - techniques: photometric - stars: flare Abstract: 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. 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. Based on theoretical models, we used the color I-J, the J-band absolute magnitude, and the detection of the LiI 6708Å 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 850um. 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 ∼15pc is an excellent benchmark for further studying physical properties of brown dwarfs in the range 100-150Myr. 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. Description: We observed 28 late-M dwarfs from 2005 to 2008 with the double-beam grating spectrograph (DBS) on the 2.3m telescope at Siding Spring Observatory. The red channel of the DBS covers the wavelength range of 6480-7485Å. The 1200g/mm grating was used, providing a medium-resolution of approximately 1.0Å, at 0.5Å/pixel. Table 1 lists the observing date of our targets. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 109 28 Hα, Li I 6708Å and Na I (8170-8200Å) equivalent widths of 28 nearby late-M dwarfs fits/* 0 28 Individual fits spectra
See also: B/denis : The DENIS database (DENIS Consortium, 2005) Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 15 A15 --- DENIS-P DENIS-P name (JHHMMSS+DDMMSS) (Cat. B/denis) 16 A1 --- n_DENIS-P [a] Note on DENIS-P (1) 18- 32 A15 --- OName Other name 33 A1 --- n_OName [bcd] Note on ONAme (1) 35- 38 A4 --- SpType MK spectral type 40- 43 F4.1 pc Dist Distance 45- 47 F3.1 pc e_Dist rms uncertainty on Dist 49- 58 A10 "date" Obs.date UT observing date 60 A1 --- l_EWHa Limit flag on EW 61- 65 F5.1 0.1nm EWHa Hα equivalent width (2) 67- 69 F3.1 0.1nm e_EWHa ? rms uncertainty on EWHa 71 A1 --- l_EWLi Limit flag on EWLi 72- 74 F3.1 0.1nm EWLi Lithium equivalent width (2) 76- 78 F3.1 0.1nm e_EWLi ? rms uncertainty on EWLi 79 A1 --- n_EWLi [e] Note on EWLi (1) 81- 83 F3.1 0.1nm EWNaI ? NaI equivalent width (3) 85- 87 F3.1 0.1nm e_EWNaI ? rms uncertainty on EWNaI 89 I1 --- Ref References for spectral type and distance (4) 91-109 A19 --- FileName Name of the fits spectrum file in subdirectory fits
Note (1): Notes as follows: a = a young binary of M6.5+M9.0 (Reiners et al., 2010A&A...513L...9R) b = a triple system of M5.5+M8.0+M8.5 (Phan-Bao et al., 2005A&A...439L..19P, 2006ApJ...645L.153P) c = a binary with photometric spectral types of M6.0+L1 estimated in Montagnier et al. (2006A&A...460L..19M) d = a binary of M8.5+T5.5 (Henry et al., 2004AJ....128.2460H; Biller et al., 2006ApJ...641L.141B) e = the lithium is marginally detected Note (2): The Hα and Li I EWs measured from the medium-resolution spectra. Note (3): The NaI EWs measured from low-resolution spectra published in Crifo et al. (2005, Cat. J/A+A/441/653) and Phan-Bao & Bessell (2006, Cat. J/A+A/446/515) (see Sect. 4.2). Note (4): References for spectral type and distance as follows: 1 = Phan-Bao & Bessell (2006, Cat. J/A+A/446/515) 2 = Phan-Bao et al. (2006MNRAS.366L..40P) 3 = Crifo et al. (2005, Cat. J/A+A/441/653) 4 = Phan-Bao et al. (2005A&A...439L..19P) 5 = this paper
Acknowledgements: Ngoc Phan-Bao, pbngoc(at)hcmiu.edu.vn
(End) Patricia Vannier [CDS] 21-Mar-2017
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