The first INTEGRAL-OMC catalogue of optically variable sources^⋆

¹ Centro de Astrobiología, Departamento de Astrofísica (CSIC-INTA), POB 78 28691 Villanueva de la Cañada, Spain
e-mail: julia@cab.inta-csic.es
² European Space Astronomy Centre (ESAC), European Space Agency, POB 78, 28691 Villanueva de la Cañada, Spain

Received: 24 July 2012
Accepted: 28 September 2012

Abstract

Context. The Optical Monitoring Camera (OMC) onboard INTEGRAL provides photometry in the Johnson V-band. With an aperture of 50 mm and a field of view of 5°  ×  5°, OMC is able to detect optical sources brighter than V ~ 18, from a previously selected list of potential targets of interest. After more than nine years of observations, the OMC database contains light curves for more than 70 000 sources (with more than 50 photometric points each).

Aims. The objectives of this work have been to characterize the potential variability of the objects monitored by OMC, to identify periodic sources and to compute their periods, taking advantage of the stability and long monitoring time of the OMC.

Methods. To detect potential variability, we have performed a chi-squared test, finding 5263 variable sources out of an initial sample of 6071 objects with good photometric quality and more than 300 data points each. We have studied the potential periodicity of these sources using a method based on the phase dispersion minimization technique, optimized to handle light curves with very different shapes.

Results. In this first catalogue of variable sources observed by OMC, we provide for each object the median of the visual magnitude, the magnitude at maximum and minimum brightness in the light curve during the window of observations, the period, when found, as well as the complete intrinsic and period-folded light curves, together with some additional ancillary data.