J/A+A/660/A38 Ultracool dwarfs with spectra in LAMOST DR7 (Wang+, 2022)
Ultracool dwarfs identified with spectra in LAMOST DR7.
Wang Y.-F., Luo A-L., Chen W.-P., Jones H.R.A., Du B., Li Y.-B., Zhang S.,
Bai Z.-R., Kong X., Guo Y.-X.
<Astron. Astrophys. 660, A38 (2022)>
=2022A&A...660A..38W 2022A&A...660A..38W (SIMBAD/NED BibCode)
ADC_Keywords: Surveys ; Stars, dwarfs ; Stars, late-type ; Spectroscopy ;
Optical
Keywords: surveys - stars: low-mass - brown dwarfs - binaries: visual -
stars: late-type
Abstract:
We identify 734 ultracool dwarfs having spectral type M6 or later
including one L0, of which, 625 are having spectral observation for
the first time with LAMOST. All these ultracool dwarfs are within 360
pc, with the Gaia G magnitude brighter than ∼19.2mag. Studying the
spectra and checking their stellar parameters (Teff, logg and
[M/H]) derived with the LAMOST pipeline, we found their cool red
nature and their metallicity consistent with being Galaxy thin disk
objects. Furthermore, 77 of them show lithium absorption line at
6708Å indicating their young ages and substellar nature. Kinematics
obtained through LAMOST radial velocities combining with the proper
motion and parallax from Gaia EDR3, also suggest the majority of our
targets are thin disk objects. Kinematic ages are estimated through
the relationship between the velocity dispersion and the average age
for a certain population. Moreover, 35 binaries are identified, among
which 6 are reported as binaries for the first time.
Description:
734 late-type M dwarfs identified visually from LAMOST DR7 are
presented in Table 1. The atmospheric parameters(Teff, Logg, and M/H),
radial velocity and signal to noise in SDSS i and z band, and radial
velocity from LAMOST DR7 are presented in Table 2. We also listed the
flag of the lithium strength in Table 2. In Table 3, we list the
kinematic parameters calculated for 571 objects of our ultracool dwarf
sample with radial velocity from LAMOST DR7, and photometry and
astrometric from Gaia EDR3.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 173 734 The ultracool dwarfs
table2.dat 102 734 Radial velocity and atmosphere parameters in LDR7
table3.dat 155 571 Kinematic parameters
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See also:
I/350 : Gaia EDR3 (Gaia Collaboration, 2020)
http://dr7.lamost.org : LAMOST DR7 Home Page
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- Seq [1/734] Running number
6- 15 A10 --- obsid LAMOST obsid
16- 27 F12.5 deg RAdeg Right ascension (J2000.0)
28- 39 F12.5 deg DEdeg Declination (J2000.0)
40- 44 A5 --- SpType1 Spectral type from LAMOST DR7
45- 64 A20 --- GaiaEDR3 Gaia EDR3 source_id
65- 74 F10.2 mas plx ?=-9999.99 parallax from Gaia EDR3
75- 84 F10.2 mas e_plx ?=-9999.99 uncertainty of parallax
from Gaia EDR3
85- 94 F10.2 mas/yr pmRA ?=-9999.99 Proper motion in RA direction,
pmRA*cosDE, from Gaia EDR3
95-104 F10.2 mas/yr e_pmRA ?=-9999.99 Uncertainty of proper motion in
RA direction
from Gaia EDR3
105-114 F10.2 mas/yr pmDE ?=-9999.99 Proper motion in Dec direction
from Gaia EDR3
115-124 F10.2 mas/yr e_pmDE ?=-9999.99 Uncertainty of proper motion
in Dec direction from Gaia EDR3
125-134 F10.3 --- RUWE ?=-9999.99 RUWE from Gaia EDR3
139-144 F6.3 mag Gmag G band magnitude from Gaia EDR3
145-154 F10.3 mag BPmag ?=-9999.99 BP band magnitude from Gaia EDR3
155-164 F10.3 mag RPmag ?=-9999.99 RP band magnitude from Gaia EDR3
165-173 A9 --- SpType2 Spectral type from the literature (SIMBAD)
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Seq [1/734] Running number
6- 14 F9.5 deg RAdeg Right ascension (J2000.0)
18- 26 F9.5 deg DEdeg Declination (J2000.0)
27- 34 F8.2 km/s RV ?=-9999 Radial velocity from LAMOST DR7
36- 40 I5 K Teff ?=-9999 Effective temperature from LAMOST DR7
42- 46 I5 K e_Teff ?=-9999 Uncertainty of effective temperature
from LAMOST DR7
49- 56 F8.2 [cm/s2] logg ?=-9999.99 Surface gravity from LAMOST DR7
59- 66 F8.2 [cm/s2] e_logg ?=-9999.99 Uncertainty of surface gravity
from LMAOST DR7
69- 76 F8.2 [-] MH ?=-9999.99 Metallicity from LAMOST DR7
79- 86 F8.2 [-] e_MH ?=-9999.99 Uncertainty of metallicity
from LAMOST DR7
90 A1 --- Li [HMLN] Flag of the lithium strength (1)
94- 96 I3 --- SNRi Signal to noise ratio in SDSS i band
from LAMOST DR7
98-102 I5 --- SNRz Signal to noise ratio in SDSS z band
from LAMOST DR7
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Note (1): Flag of the lithium strength as follows:
H = strong
M = medium
L = weak
N = no
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Seq [1/733] Running number
5- 13 F9.5 deg RAdeg Right ascension (J2000.0)
17- 25 F9.5 deg DEdeg Declination (J2000.0)
27- 33 F7.2 km/s U Galactic U velocity
36- 39 F4.2 km/s E_U Upper uncertainty of Galactic U velocity
43- 46 F4.2 km/s e_U Lower uncertainty of Galactic U velocity
48- 54 F7.2 km/s V Galactic V velocity
57- 60 F4.2 km/s E_V Upper uncertainty of Galactic V velocity
64- 67 F4.2 km/s e_V Lower uncertainty of Galactic V velocity
69- 75 F7.2 km/s W Galactic W velocity
77- 81 F5.2 km/s E_W Upper uncertainty of Galactic W velocity
84- 88 F5.2 km/s e_W Lower uncertainty of Galactic W velocity
90- 96 F7.2 pc zgal Galactic height
98-102 F5.2 pc E_zgal Upper uncertainty of Galactic height
105-109 F5.2 pc e_zgal Lower uncertainty of Galactic height
115-121 F7.2 pc rgal Distance to the Galactic center on the
Galactic plane
124-128 F5.2 pc E_rgal Upper uncertainty of distance to the
Galactic center on the Galactic plane
131-135 F5.2 pc e_rgal Lower uncertainty of distance to the
Galactic center on the Galactic plane
138-145 F8.2 --- TDD ?=-9999.99 probability ratio of thick disk
over disk
151-155 I5 --- TDH ?=-9999 probability ratio of thick disk
over halo
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Acknowledgements:
Ali Luo, lal(at)bao.ac.cn
(End) Ali Luo [NAOC, China], Patricia Vannier [CDS] 28-Mar-2022