ROSAT performed a 6-month all-sky survey in the interval July 30, 1990 to January 25, 1991, during which 96 percent of the sky was covered. During the survey two filters were alternated daily to provide two EUV passbands. These were S1 [60-140 A (90-206 eV)] and S2 [110-200 A (62-110 eV)]. Sky coverage was greatest at the ecliptic poles, where integrated exposures reached 70,000 seconds in each filter; at the ecliptic equator exposures were lowest, being around 1,500 seconds per filter.
The sources listed in this Bright Source Catalogue were initially detected using a circular sliding box technique and a Poisson significance test. A maximum likelihood technique was used to determine source parameters. The criteria for inclusion of an EUV source in this catalogue were: greater than 4.5 sigma detection in one filter, and visual confirmation of the source. Simulations suggests that less than one false detection can be expected in the WFC Bright Source Catalogue.
Catalog_Designation WFC Bright Source Catalogue sources are named following the IAU convention. The prefix 'RE' stands for 'Rosat EUV source'. The rest of the catalog designation is made from the J2000 ecliptic coordinates as follows: HHMM+/-DDM, where HH and MM are hours and minutes of RA and DD and M are degrees and arcminutes of Declination. Coordinates are truncated, not rounded. RA The Right Ascension of the centroid of the EUV source. Dec The declination of the centroid of the EUV source. S1 `S1` is the count rate seen in the S1a filter, in counts per kilosecond. `S1 error` is the statistical 1 sigma error on the S1 count rate (in counts per kilosecond). If `S1 error` is zero, then the S1 value represents a 3 sigma upper limit, not a source detection. S2 `S2` is the count rate seen in the S2a filter, in counts per kilosecond. `S2 error` is the statistical 1 sigma error on the S2 count rate (in counts per kilosecond). If `S2 error` is zero, then the S2 value represents a 3 sigma upper limit, not a source detection. Name The name of the most likely optical counterpart to the detected EUV source. Coincidences with hot white dwarfs, central stars of planetary nebulae, active stars, cataclysmic variables, X-ray binaries and active galaxies in directions of low interstellar absorption were considered most probable identifications, followed by nearby or blue stars, with non-descript stars being considered last. The probability of chance coincidence with the categories of likely EUV sources mentioned above is sufficiently small that the identifications are expected to be valid in almost all cases. Blank if no optical counterpart name was found. Alt_Name An alternative name for the most likely optical counterpart. Blank if none. Type Plain text spectral classification of the most likely optical counterpart. Blank if unknown. Class Browse class code for the optical counterpart. NB RSCVn stars are given an RSCVn classification in preference to the individual spectral type classification. R90 The 90% WFC error circle radius in arcseconds. The value given includes both statistical and systematic components. Other The number of other possible optical counterparts in the 99.9% EUV error circle.
Source types for the counterparts are given, with multiple spectral type classifications from different catalogues separated by slashes. More detailed and accurate spectral type classifications are available for the active binaries from the Strassmeier catalogue (Strassmeier et al 1988).
Where there are one or more stars within the error circle, visual or spectroscopic binary companions cannot be ruled out as the source of EUV emission. This is especially likely in the case of isolated A stars.
For additional information, see also the help for the `name` parameter.
Fernandez, A., Lortet, M.-C., & Spite, F. (1983) A&A Supp. Ser., vol 52.
McCook, G. P. & Sion, E. M. (1987) AP.J.Supp., vol65, p603.
Strassmeier, K. G. et al. (1988) A&A Supp. Ser., vol 72, p291.
HEASARC User Hotline.