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Journal Articles The Astrophysical Journal Year : 2021

M-subdwarf Research. II. Atmospheric Parameters and Kinematics

Shuo Zhang
  • Function : Author
A. -Li Luo
  • Function : Author
Rui Wang
  • Function : Author
Yin-Bi Li
  • Function : Author
Bing Du
  • Function : Author
Wen Hou
  • Function : Author
Li Qin
  • Function : Author
John Gizis
  • Function : Author
Jian-Jun Chen
  • Function : Author
Xiang-Lei Chen
  • Function : Author
Yan Lu
  • Function : Author
Yi-Han Song
  • Function : Author
Hua-Wei Zhang
  • Function : Author
Fang Zuo
  • Function : Author

Abstract

We applied the revised M subdwarf classification criteria discussed in Zhang et al. to Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) DR7 and combined the result with the M subdwarf sample from Savcheva et al. to construct a new M subdwarf sample for further study. The atmospheric parameters for each object were derived from fitting to the PHOENIX grid, and the sources with available astrometry and photometry from Gaia DR2 were combined for further analysis. The relationship between the gravity and metallicity was explored according to the locus both in the color-absolute magnitude diagram and the reduced proper motion diagram. Objects that have both the largest gravity and the lowest metallicity are located away from the main-sequence cloud and may be considered as the intrinsic M subdwarfs, which can be classified as luminosity class VI. Another group of objects whose spectra show typical M subdwarf characteristics have lower gravity and relatively moderate metal deficiency and occupy part of the ordinary M dwarf region in both diagrams. The Galactic U, V, W space velocity components and their dispersion show that the local Galactic halo population sampled in the solar neighborhood is represented by objects of high gravity and an inconspicuous bimodal metallicity distribution, with a fraction of prograde orbits. The other M subdwarfs seem to belong in part to the thick disk component, with a significant fraction of thin disk, moderately metal-poor objects intricately mixed with them. However, selection effects, especially the favored anticenter direction of investigation in the LAMOST subsample, as well as contamination by multiplicity and parameter coupling, could play important roles and need to be investigated further.

Dates and versions

insu-03585860 , version 1 (23-02-2022)

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Cite

Shuo Zhang, A. -Li Luo, Georges Comte, Rui Wang, Yin-Bi Li, et al.. M-subdwarf Research. II. Atmospheric Parameters and Kinematics. The Astrophysical Journal, 2021, 908, 18 pp. ⟨10.3847/1538-4357/abcfc5⟩. ⟨insu-03585860⟩
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