OMC: An optical monitoring camera for INTEGRAL

The INTEGRAL payload has been designed to study simultaneously gamma-ray so urces in a wide field of view over many decades in energy (around 2 eV + 4 keV - 20 MeV) and thus make a major contribution to short time-scale high-e nergy astrophysics. The OMC will observe the optical emission from the prim e targets of the gamma-ray instruments with the support of the X-ray monito r. This capability will provide invaluable diagnostic information on the na ture and the physics of the sources over a broad wavelength range. The main scientific objectives will he: (1) to monitor the optical emission from the sources observed by the gamma- and X-ray instruments, measuring t he time and intensity structure of the optical emission for comparison with variability at high energies, and (2) to provide the brightness and positi on of the optical counterpart of any gamma- or X-ray transient taking place within its held of view. The OMC will be based on a refractive optics with an aperture of 50 mm focu sed onto a large format CCD (1024 x 2048 pixels) working in frame transfer mode (1024 x 1024 pixels imaging area). With a field of view of 5 degrees x 5 degrees it will be able to monitor sources down to V = 19 magnitudes. Typ ical exposures will consist of 10 integrations of 100 seconds each.