Grupo de Sistemas Estelares

Balog, Z., Delgado, A. J., Moitinho, A., Fűrész, G., Kaszás, G., Vinkó, J., and Alfaro, E. J.
Monthly Notices of the Royal Astronomical Society, Volume 323, Issue 4, pp. 872-886.
05/2001

ABSTRACT

CCD photometry in Johnson UBV and Strömgren uvby systems and medium-resolution spectroscopy of the galactic open cluster NGC 7128 are presented. Spectral types of the brightest 12 stars in the cluster field were determined based on equivalent widths of the Hα and the Hei 6678-Å line. The spectroscopic observations also revealed two obvious and one probable Be-type stars showing Hα emission. The analysis of the photometric diagrams gave a colour excess of E(B-V)=1.03+/-0.06mag, a distance modulus DM=13.0+/-0.2mag and an age above 10Myr. Time-resolved photometric observations obtained on one night resulted in the detection of short time-scale light variations of seven new and three already known variable stars in the cluster field.