Seven-color Vilnius photometry and classification of stars in the region of the North Ecliptic Pole^⋆

Institute of Theoretical Physics and Astronomy, Vilnius University, Goštauto 12, Vilnius, LT-01108, Lithuania
e-mail: vytautas.straizys@tfai.vu.lt

Received: 5 April 2012
Accepted: 20 June 2012

Abstract

The results of photometry of 948 stars down to V = 16.2 mag in the Vilnius seven-color system at the North Ecliptic Pole (NEP) are presented. Among them, 293 stars have all seven magnitudes, 331 stars have no ultraviolet magnitudes and 324 stars have no ultraviolet and violet magnitudes. Photometric data are used to classify about 500 stars in spectral and luminosity classes. For the remaining stars one-dimensional spectral classes are given. Some stars are suspected as new F and G subdwarfs and metal-deficient giants. The dependence of interstellar extinction on distance in the direction of NEP is discussed. The average extinction in the area for stars with d > 500 pc is found to be A_V = 0.10 ± 0.01 mag, with the standard deviation 0.14 mag. The results of photometry and classification can be used to supplement the catalog of Gaia standard stars near the Ecliptic poles. To facilitate this, we present transformation of the Vilnius magnitudes to the magnitudes of the SDSS and Gaia systems.