M Subdwarf Secondaries: A Test of the Metallicity Scale

Abstract

We present spectra of three M subdwarfs which are common proper motion companions to F or G subdwarfs of known metallicity. The assumption that the companions have the same composition allows us to test the Gizis (1997, AJ, 113, 806) M subdwarf classification system and its correspondence to metallicity. The results are in excellent agreement with the Gizis (1997) scale, thereby showing that the Allard & Hauschildt (1995, ApJ, 445, 433) Extended model atmospheres agree well in the 6200 -- 7400 Angstrom region for cool metal-poor stars. We also show that the results are consistent with the main sequences of globular clusters using the Reid (1997, AJ, 114, 161) distance scale.

10 pages, 3 figures, AASTeX, to appear in the November 1997 PASP

Cited by in corpus (14)

• Near-infrared Metallicities, Radial Velocities and Spectral Types for 447 Nearby M Dwarfs
• Revised metallicity classes for low-mass stars: dwarfs (dM), subdwarfs (sdM), extreme subdwarfs (esdM), and ultra subdwarfs (usdM)
• CARMENES input catalogue of M dwarfs. I. Low-resolution spectroscopy with CAFOS
• Identical or fraternal twins? : The chemical homogeneity of wide binaries from Gaia DR2
• Discovery of an ultra-cool subdwarf: LSR1425+7102, first star with spectral type sdM8.0
• The distance to NGC 6397 by M-subdwarf main-sequence fitting
• Trigonometric Parallaxes for Two Late-Type Subdwarfs: LSR1425+71 (sdM8.0) and the Binary LSR1610-00 (sd?M6pec)
• Using APOGEE Wide Binaries to Test Chemical Tagging with Dwarf Stars
• A CCD Imaging Search for Wide Metal-Poor Binaries
• Wide Binaries in Tycho-Gaia II: Metallicities, Abundances, and Prospects for Chemical Tagging
• CCD Parallaxes for 309 Late-type Dwarfs and Subdwarfs
• Metallicity of M dwarfs I. A photometric calibration and impact on the mass-luminosity relation at the bottom of the main sequence
• HST Observations of M Subdwarfs
• Photometric Monitoring of Open Clusters I. The Survey