Light curves and periods of Mira variables ^*,**

¹ Centre d'Analyse des Images CNRS/INSU/MAMA, Observatoire de Paris, France
² Observatoire de Paris (DEMIRM)/URA 336 du CNRS, 77, Avenue Denfert-Rochereau F-75014 Paris, France
³ Observatoire de Lyon (CRAL), F-69561 Saint Genis Laval Cedex, France

Send offprint request to: C. Alard

Received: 7 April 1995
Accepted: 9 April 1996

Abstract

Good distance indicators are needed in studies of the galactic structure. Pulsating variables can be used, but the problem is to find a homogenous sample obeying a period-luminosity relation with low scatter. In this paper, we show how such a sample can be produced using the Terzan catalogue of Variables and available Schmidt plates. We have selected 150 large amplitude variables discovered by Terzan in a field of 25 sq degrees near the Galactic Centre. A set of 22 red plates was scanned with the MAMA machine, providing time series for all the variables. The times series were analysed using both the periodogram and Renson's method. Periods could be derived for 122 stars of the sample showing clearly that most of these objects are Miras. As a conclusion we show that with some infrared photometry, these Miras could be used as good distance indicators in this region.