J/other/RAA/16.G7 Nearby M subdwarfs from LAMOST DR2 (Bai+, 2016)
Nearby M subdwarfs from LAMOST data release 2.
Bai Y., Luo A.-L., Comte G., Zhao J.-K., Yang H.-F., Guo Y.-X., Wang Y.-F.,
Li Y.-B., Du B., Hou W., Kong X., Yi Z.-P., Song Y.-H., Bai Z.-R.,
Zhang J.-N., Wang M.-X., Chen J.-J., Chen X.-Y., Wu K.-F., Zuo F., Wu Y.,
Cao Z.-H., Hou Y.-H., Wang Y.-F., Zhang Y.
<Research in Astron. and astroph., 16, part no 7, 7 (2016)>
=2016RAA....16..107B 2016RAA....16..107B
=2016RAA....16g...7B 2016RAA....16g...7B (SIMBAD/NED BibCode)
ADC_Keywords: Stars, M-type ; Stars, subdwarf
Keywords: stars: late-type - stars: statistics - subdwarfs
Abstract:
We identify 108 M subdwarfs (sdMs) out of more than two hundred
thousand M type spectra from the second data release (DR2) of the
LAMOST regular survey. This sample, among which 58 members are
identified for the first time, includes 33 extreme subdwarfs (esdMs)
and 11 ultra subdwarfs (usdMs). The selection is based on the usual
ratio of absorption depth of CaH2, CaH3 and TiO5 band systems. We also
emphasize the use of the CaH1 band. We provide estimates of spectral
subtype (SPT), Lepine metallicity index zeta, effective temperature
and [Fe/H]. Both zeta-[Fe/H] and SPT-Teff figures show reasonable
consistency; compared to PHOENIX model spectra, average rounded values
of [Fe/H] for sdMs, esdMs and usdMs are respectively -0.5, -1 and
-1.5. The photometric distances are estimated, indicating that most
sources are located within 500pc of the Sun and 350pc of the Galactic
disk. Velocities and 3D Galactic motions are also briefly discussed.
Among the 108 subdwarfs, seven stars appear to be active with a
significant Hα emission line. The source LAMOST
J104521.52+482823.3 is a white dwarf - M subdwarf binary, while LAMOST
J123045.52+410943.8, also active, exhibits carbon features in red.
Description:
LAMOST (Cui et al., 2012RAA....12.1197C 2012RAA....12.1197C), a 4m-class telescope,
characterized by both a large field of view (5°) and large
aperture (3.6m-4.9m), is a powerful instrument dedicated to
astronomical studies of large samples. The DR2 of the regular survey
contains 226 985 M type spectra with a resolution of R∼1800. Our sdM
sample was selected from this subset, using only spectroscopic
criteria.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 42 108 Derived parameters of the 108 sdMs
table3.dat 78 108 Observed magnitudes and adopted extinction
for the 108 sdMs
table5.dat 73 108 Distances and velocities
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See also:
V/146 : LAMOST DR1 catalogs (Luo+, 2015)
J/other/RAA/15.1154 : M-giant star candidates in LAMOST DR 1 (Zhong+, 2015)
J/other/RAA/15.1182 : M Dwarf catalog of LAMOST DR1 (Guo+, 2015)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 19 A19 --- LAMOST LAMOST ID (JHHMMSS.ss+DDMMSS.s)
20 A1 --- n_LAMOST [*] * indicates objects already known from SDSS
22- 25 F4.1 --- SPT Spectral sub-type (1)
27- 30 I4 K Teff Effective temperature
32- 37 F6.3 --- zeta zeta metallicity index (2)
39- 42 F4.1 [-] [Fe/H] Metallicity
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Note (1): The SPT results are rounded to 0.5.
Note (2): zeta index may be used to divide the subdwarfs into metallicity
subclasses as: ordinary (metal-rich) dwarf when zeta > 0.825,
subdwarf when 0.5< zeta < 0.825, extreme subdwarf when 0.2< zeta < 0.5 and
ultra subdwarf when zeta < 0.2.
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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- 19 A19 --- LAMOST LAMOST ID (JHHMMSS.ss+DDMMSS.s)
21- 25 F5.2 mag gmag SDSS g magnitude
27- 31 F5.2 mag rmag SDSS r magnitude
33- 37 F5.2 mag imag SDSS i magnitude
39- 43 F5.2 mag zmag ?=- SDSS z magnitude
45- 49 F5.2 mag Jmag Johnson J magnitude
51- 55 F5.2 mag Bmag ?=- Johnson B magnitude
57- 61 F5.2 mag Rmag ?=- Cousins R magnitude
63- 67 F5.2 mag Imag ?=- Cousins I magnitude
69- 73 F5.2 mag Vmag Johnson V magnitude
75- 78 F4.2 mag 3D-Ar Adopted extinction
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 19 A19 --- LAMOST LAMOST ID (JHHMMSS.ss+DDMMSS.s)
21- 23 I3 pc Dist ?=- Distance (1)
25- 28 I4 pc Zgal ?=- Height above the plane (1)
30- 33 I4 mas/yr pmRA ?=- Proper motion along RA (1)
35- 40 F6.1 mas/yr pmDE ?=- Proper motion along DE (1)
42- 45 I4 km/s RVP ?=- Pipeline heliocentric radial velocity (1)
47- 50 I4 km/s RVG ?=- Helicoentric radial velocity from
Gaussian fitting (1)
52- 54 I3 km/s Vt ?=- Transverse velocity (1)
56- 59 I4 km/s Uvel ?=- Galactic U velocity (1)
61- 64 I4 km/s Vvel ?=- Galactic V velocity (1)
66- 69 I4 km/s Wvel ?=- Galactic W velocity (1)
71- 73 I3 km/s Vtot ?=- Total velocity (1)
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Note (1): "---" are default values for those objects whose distance cannot be
estimated accurately.
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 15-Sep-2016