The EUV mini-survey with the ROSAT wide field camera

Following a successful launch on 1990 June 1, the ROSAT spacecraft and its payload, consisting of an X-ray and an EUV telescope, underwent two months of in-orbit calibration and detailed performance checks. A preliminary observation of a small section of the sky, carried out over July 11–16 (the ‘mini-survey’) showed all ROSAT systems to be functioning well and has allowed predictions to be made on the ultimate productivity of both ROSAT all-sky surveys. An analysis of the mini-survey data from the UK Wide Field Camera, has revealed 35 EUV sources, including several white dwarf stars, a variety of active cool stars and several other objects. In all, 23 sources have probable optical counterparts. Consideration of the effective exposure and sky coverage in the mini-survey allows the prediction that the recently completed ROSAT all-sky survey will yield in excess of a thousand new EUV sources.