A Photometric Monitoring of Barium Stars

Abstract

An uvby photometric monitoring of a sample of 19 Ba II stars has been performed since July 1984 at ESO on the Danish and ESO 50 cm telescopes, as part of the “Long Term Program for Variable Stars” (Sterken, 1983). The sample contains southern Ba II stars with variable radial velocities (from McClure, 1983 and Jorissen and Mayor, 1988) as well as Ba II stars already monitored by Landolt (1983). The observations are done differentially, using two comparison giants of the same spectral type located within a few degrees of the Ba II star. The reduction to the standard uvby system is performed using the algorithm described in Manfroid and Heck (1983), taking into account all the measurements performed on the considered telescope since the beginning of the monitoring. With such a reduction procedure, the scatter in the magnitude difference between two comparison stars (of magnitude 5 to 7) can be as low as 0.003-0.004 mag rms.