Interrelations between Vilnius and Strömgren photometric systems: The luminosity indicator (v – X)^*

¹ Department of Physics & Astronomy, University of Wisconsin Oshkosh, 800 Algoma Blvd., Oshkosh, WI 54901-8644, USA
² Niels Bohr Institute for Astronomy, Physics and Geophysics, Juliane Maries Vej 30, 2100 Copenhagen Ø, Denmark e-mail: indus@astro.ku.dk
³ Department of Astronomy, University of Sofia, 5 J. Bourchier Ave., 1164 Sofia, Bulgaria e-mail: vladimir@phys.uni-sofia.bg

Corresponding author: N. Kaltcheva, kaltchev@uwosh.edu

Received: 4 April 2003
Accepted: 18 May 2003

Abstract

Using the largest database of near-IR Ca II Triplet indices currently available (Cenarro et al. [CITE],b), we confirm our finding about the influence of the Ca II stellar lines on the X magnitude of the Vilnius photometric system. This effect is significant for spectral sub-classes from early F until mid K. For this spectral range there is a linear relation between the  index and the strength of the infrared Ca II Triplet, which implies that the Ca II H&K lines should influence the difference in a similar way. For the spectral interval studied, repeats the behavior of the Ca II Triplet with respect to gravity, temperature and metallicity. The Ca II Triplet lines are a powerful diagnostic of the stellar populations in galaxies because of their sensitivity to the main stellar atmospheric parameters. Being much easily achievable observationally and virtually reddening free, the index may find similar applications. is log g sensitive but additional means are required to break the dwarf – giant duplicity. For this purpose we have studied the variation of the v(Strömgren)-B(Johnson) index with gravity, temperature and the equivalent width of the Ca II Triplet. Since v(Strömgren)-B(Johnson) have a none overlapping variation with the Ca II Triplet the dwarfs and giants may be separated and T_eff and log g may be estimated. The v(Strömgren)-B(Johnson) index has furthermore the advantage that .