Refined metallicity indices for M dwarfs using the SLoWPoKES catalog of wide, low-mass binaries

Saurav Dhital, Andrew A. West, Keivan G. Stassun, John J. Bochanski, Angela P. Massey, Fabienne A. Bastien

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We report the results from spectroscopic observations of 113 ultra-wide, low-mass binary systems, largely composed of M0-M3 dwarfs, from the SLoWPoKES catalog of common proper motion pairs identified in the Sloan Digital Sky Survey. Radial velocities of each binary member were used to confirm that they are comoving and, consequently, to further validate the high fidelity of the SLoWPoKES catalog. Ten stars appear to be spectroscopic binaries based on broad or split spectral features, supporting previous findings that wide binaries are likely to be hierarchical systems. We measured the Hα equivalent width of the stars in our sample and found that components of 81% of the observed pairs have similar Hα levels. The difference in Hα equivalent width among components with similar masses was smaller than the range of Hα variability for individual objects. We confirm that the Lépine et al. ζ-index traces iso-metallicity loci for most of our sample of Mdwarfs. However, we find a small systematic bias in ζ, especially in the early-type Mdwarfs. We use our sample to recalibrate the definition of ζ. While representing a small change in the definition, the new ζ is a significantly better predictor of iso-metallicity for the higher-mass Mdwarfs.

Original languageEnglish (US)
Article number67
JournalAstronomical Journal
Issue number3
StatePublished - Mar 2012

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


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