Characterization of M dwarfs using optical mid-resolution spectra for exploration of small exoplanets. (28th December 2020)

• Record Type: Journal Article
• Authors: Koizumi, Yohei; Kuzuhara, Masayuki; Omiya, Masashi; Hirano, Teruyuki; Wisniewski, John; Aoki, Wako; Sato, Bun'ei
• Is Part Of: Publications of the Astronomical Society of Japan. Volume 73:Number 1(2021)
• Page Start: 154
• Page End: 173
• Publication Date: 2020-12-28
• Subjects: stars: fundamental parameters -- stars: late-type -- stars: low-mass; Astronomy -- Periodicals; 520.5
• DOI: 10.1093/pasj/psaa112
• Languages: English
• ISSNs: 0004-6264

Abstract

Abstract: We present the optical spectra of 338 nearby M dwarfs, and compute their spectral types, effective temperatures ( T eff ), and radii. Our spectra were obtained using several optical spectrometers with spectral resolutions that range from 1200 to 10000. As many as 97% of the observed M-type dwarfs have a spectral type of M3–M6, with a typical error of 0.4 subtype, among which the spectral types M4–M5 are the most common. We infer the T eff of our sample by fitting our spectra with theoretical spectra from the PHOENIX model. Our inferred T eff is calibrated with the optical spectra of M dwarfs whose T eff have been well determined with the calibrations that are supported by previous interferometric observations. Our fitting procedures utilize the VO absorption band (7320–7570 Å) and the optical region (5000–8000 Å), yielding typical errors of 128 K (VO band) and 85 K (optical region). We also determine the radii of our sample from their spectral energy distributions. We find most of our sample stars have radii of <0.6 R ⊙, with the average error being 3%. Our catalog enables efficient sample selection for exoplanet surveys around nearby M-type dwarfs.