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 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:
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FileName Lrecl Records Explanations
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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/* . 28 Individual fits spectra
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See also:
B/denis : The DENIS database (DENIS Consortium, 2005)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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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
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Note (1): Notes as follows:
a = a young binary of M6.5+M9.0 (Reiners et al., 2010A&A...513L...9R 2010A&A...513L...9R)
b = a triple system of M5.5+M8.0+M8.5 (Phan-Bao et al., 2005A&A...439L..19P 2005A&A...439L..19P,
2006ApJ...645L.153P 2006ApJ...645L.153P)
c = a binary with photometric spectral types of M6.0+L1 estimated in
Montagnier et al. (2006A&A...460L..19M 2006A&A...460L..19M)
d = a binary of M8.5+T5.5 (Henry et al., 2004AJ....128.2460H 2004AJ....128.2460H; Biller et al.,
2006ApJ...641L.141B 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 2006MNRAS.366L..40P)
3 = Crifo et al. (2005, Cat. J/A+A/441/653)
4 = Phan-Bao et al. (2005A&A...439L..19P 2005A&A...439L..19P)
5 = this paper
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Acknowledgements:
Ngoc Phan-Bao, pbngoc(at)hcmiu.edu.vn
(End) Patricia Vannier [CDS] 21-Mar-2017