Astron. Astrophys. Suppl. Ser. 139, 321-334

Stellar variability in low-extinction regions towards the Galactic Bulge

T.P. Dominici - J.E. Horvath - G.A. Medina Tanco - R. Teixeira - P. Benevides-Soares

Send offprint request: T.P. Dominici

Correspondence to: tania@orion.iagusp.usp.br

Instituto Astronomico e Geofísico, Universidade de São Paulo, Av. Miguel Stéfano 4200, São Paulo, SP 04301-904, Brazil

Received April 14; accepted July 19, 1999

Abstract:

Intensive monitoring of low-extinction windows towards the galactic bulge has provided in recent years valuable information for studies about the dynamics, kinematics and formation history of this part of the galaxy, mainly by characterizing the bulge stellar populations (Paczynski 1996). Since 1997, we have been conducting an intensive photometric-astrometric survey of the galactic bulge, with the monitoring of about 120000 stars in 12 windows uniformly distributed in galactic latitude and longitude (Blanco & Terndrup 1989; Blanco 1988) never before submitted to this kind of survey. For this purpose, we have used the IAG/USP CCD Meridian Circle of the Abrahão de Moraes Observatory. The main objective of this project is the identification and classification of variable objects. In this work we present the set up and development of the necessary tools for a project like this and the posterior analysis of our data. We briefly describe the construction of a program to organize and detect variables among the observed stars, including real time alerts (for variations greater than 0.3 magnitudes). The preliminary analysis after the processing of 76 nights of observation yielded 479 variable stars, from which 96.7% of them are new. We discuss the preliminary classification of these variables, based on: a) the observed amplitude of variation; b) the shape of light curve; c) the expected variable classes among our data and d) the calculated periods, whenever possible. Finally, we discuss the future perspectives for the project and for the applications and analysis of the discovered variable stars.

Key words: stars: variable general -- techniques: photometric -- galaxy: center