Abstract :
Aims: In this work we develop a technique to obtain high precision determinations of both metallicity and effective temperature of M dwarfs in the optical.
Methods: A new method is presented that makes use of the information of 4104 lines in the 530-690 nm spectral region. It consists in the measurement of pseudo equivalent widths and their correlation with established scales of [Fe/H] and T
eff.
Results: Our technique achieves a rms of 0.08 ± 0.01 for [Fe/H], 91 ± 13 K for T
eff, and is valid in the (-0.85,0.26 dex), (2800, 4100 K), and (M0.0, M5.0) intervals for [Fe/H], T
eff and spectral type respectively. We also calculated the RMSE
V which estimates uncertainties of the order of 0.12 dex for the metallicity and of 293 K for the effective temperature. The technique has an activity limit and should only be used for stars with log L
Hα/L
bol< - 4.0.
Based on observations made with the HARPS instrument on the ESO 3.6 m telescope at La Silla Observatory under programme ID 072.C-0488(E)Our method is available online at
http://www.astro.up.pt/resources/mcalTables 1, 2, 4, 8 are available in electronic form at
http://www.aanda.org