An infrared spectral sequence for M dwarfs

• Published in: Monthly notices of the Royal Astronomical Society Vol. 267; no. 2; pp. 413 - 423
• Main Authors: Jones, H. R. A., Longmore, A. J., Jameson, R. F., Mountain, C. M.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Oxford University Press 15.03.1994; Blackwell Science
• Subjects: Astronomy; brown dwarfs; Earth, ocean, space; Exact sciences and technology; infrared: stars; Low luminosity stars, subdwarfs, and brown dwarfs; Normal stars (by class): general or individual; Stars; stars: late-type; stars: low-mass; Infrared stars; Late type stars; Low-mass stars; Brown dwarf stars; Hertzsprung-Russell diagram; Effective temperature; Main sequence stars; M stars; Infrared spectra; Line spectra
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1093/mnras/267.2.413

We present a spectral sequence from 1 to 2.5 µm of M dwarfs, from GL411 (M2V) to the best brown dwarf candidate GD165B which is classified as cooler than M9V. This sequence shows the progressive importance of water absorption in the atmospheres of M dwarfs. We take the strength of the water absorption bands as the basis of a new method to derive a temperature from which we calculate effective temperatures and radii. We also identify many of the stronger atomic and molecular features and correlate their strengths with our derived temperature scale. For a given luminosity, this method yields temperatures close to those predicted by evolutionary models for low-mass stars, but not always close to those found by previous investigators. We find that GD165B has a temperature of $1860 \pm 160 \enspace \text K$ and that it is the only star in the sample that might be classified as a brown dwarf, but to decide its true nature a more accurate parallax and a representative model atmosphere will be necessary.