2.1. Accurate masses for M dwarfs
We adopt a 10% mass accuracy cutoff for inclusion in our new M dwarf M/L relations, as a compromise between good statistics and the quality of the individual measurements. To our knowledge 32 M dwarfs fulfill this criterion. They can be divided into four broad categories:
Table 1 lists the basic properties of the selected systems: parallaxes, spectral types and integrated photometry. Table 2 lists the magnitude differences for the V, R, I, J, H and K photometric bands. The near-IR flux ratios were obtained either from litterature infrared speckle observations, or extracted from our adaptics images (Ségransan et al. 2000). For the three eclipsing systems the visible flux ratios were adopted from analyses of the light curves (Leung & Schneider 1978; Delfosse et al. 1999a; Lacy 1977). For the visual binaries, they were preferentially adopted from the FGS work of Henry et al. (1999), with the standard errors quoted in that article. When such measurements were unavailable, we relied instead on spectroscopic magnitude differences, using the relative areas of the ELODIE cross-correlation peaks as a proxy for the V band magnitude difference. The ELODIE cross-correlation has an effective bandpass centered close to the central wavelenghth of the Johnson V filter, but it is significantly broader. A "colour-tranformation" would thus in principle be needed to derive V band magnitude differences. A comparison with the direct measurements of Henry et al. (1999) for the sources in common shows maximum relative errors of 10% from neglecting this transformation: a 0.5 magnitude contrast is in error by at most 0.05 magnitude, and a 2 magnitudes one by at most 0.2 magnitude. We have therefore adopted the larger of 0.05 magnitude and 10% of the magnitude difference as a conservative estimate of the standard error for these spectroscopic magnitude differences.
Table 1. Basic parameters for the M-dwarf systems with accurate masses. The parallaxes mostly originate from the Hipparcos catalog (ESA 1997), the Yale General Catalog of trigonometric Parallaxes (Van Altena et al. 1995), and from Ségransan et al. (2000). In that paper we derived optimal combinations of orbital and astrometric parallaxes, which often have a strong contribution from either an Hipparcos or a Yale catalog astrometric parallax. Some individual entries are additionally taken from Soderhjelm (1999), Forveille et al. (1999), and Benedict et al. (2000). All spectral types are from either Reid et al. (1995) or Hawley et al. (1997) and refer to the integrated light of the system. The photometry is taken from the extensive homogenized compilation of Leggett (1992), except for YY Gem, Gl 702AB and GJ2069A. The photometry of GJ2069A is from Weiss (1991). The optical photometry of YY Gem is from Kron et al. (1957) (RI), Eggen (1968) (UBV), Barnes et al. (1978) (UBVRI), and the infrared photometry from Johnson (1965), Glass (1975), and Veeder (1974). The optical photometry for Gl 702AB is from Bessel (1990) and the infrared photometry from Alonso et al. (1994). All photometry was converted to the Johnson-Cousins-CIT sytem adopted by Leggett (1992) using the colour transformations listed in that paper. Multiple measurements for the same band were averaged with equal weights.
Table 2. Magnitude differences for M-dwarf systems with accurate masses. Reference codes are: TYC for the Tycho catalogue HIP for the Hipparcos catalogue L77 for Lacy (1977), L78 for Leung & Schneider (1978), Hen93 for Henry & McCarthy (1993), C94 for Coppenbarger et al. (1994), B96 for Barbieri et al. (1996), Ben00 for Benedict et al. (2000), Tor99 for Torres et al. (1999) Hen99 for Henry et al. (1999), D99a for Delfosse et al. (1999a), For99 for Forveille et al. (1999), and D00 for the present paper. S stands for spectroscopic magnitude differences, infered from the relative line depths for double-lined spectroscopic binaries.
© European Southern Observatory (ESO) 2000
Online publication: December 15, 2000