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ROSWFC2RE - ROSAT Catalog WFC 2RE Sources



The ROSWFC2RE database is the ROSAT Wide Field Camera 2RE Source Catalogue. It contains 479 EUV sources found during the ROSAT all-sky survey of July 1990 to January 1991. The information in this database is based on what will be published by Pye et al. (1995, MNRAS, in press). It supersedes the earlier Bright Source Catalogue (BSC; Pounds et al. 1993, MNRAS, 260, 77).

Catalog Bibcode



"The ROSAT all-sky survey of Extreme Ultraviolet sources: I The Bright Source Catalogue", Pounds K. A., et al., 1993, MNRAS, 260, 77.

"The ROSAT all-sky survey of Extreme Ultraviolet sources: II The 2RE Source Catalogue", Pye J. P., et al., 1995, MNRAS, in press.

"Optical identification of EUV sources from the ROSAT Wide Field Camera all-sky survey", Mason K.O., et al., 1995, MNRAS, in press.

"Temporal behaviour of sources in the ROSAT Extreme Ultraviolet all-sky survey", McGale P. A., Pye J. P., Barber C. R. and Page C.G., 1995, MNRAS, submitted


The British Wide Field Camera (WFC) on the German/US/UK ROSAT spacecraft consists of a 5 degree diameter field of view EUV telescope with a curved microchannel plate detector with a resistive readout at the focus. The WFC is coaligned with the German X-ray Telescope.

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 in the WFC 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.

Taking advantage of several improvements over what was possible during the course of the BSC work, the all-sky data were completely reprocessed; the new 2RE catalogue being the result. There are about 120 new sources and a significant increase in the number of detections common to both wavebands (80% versus 60%).

Two independent methods were used for point source detection, PSS (Allan, Ponman & Jefferies 1994) and SESAME (Page 1995). Both use a maximum likelihood technique. The primary criterion for inclusion of an EUV source in this catalogue was that the `combined' significance over both wavebands be >= 5.5. (Combined: square root of the sum of the squares of the significances in each passband.) Simulations suggest that the expected number of spurious sources should be less than ~20.

Two associated data products have been made available: (1) S1 and S2 images containing 2RE detections; (2) S1 and S2 exposure and background corrected source light-curves (and exposure-corrected local background light-curves).


2RE Source Catalogue sources are named following the IAU convention. The prefix '2RE' stands for 'Rosat EUV source' (2nd catalogue). The rest of the catalogue designation is made from the equinox J2000 equatorial 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.

The Right Ascension (equinox J2000) of the EUV source.

The Declination (equinox J2000) of the EUV source.

The positional, 90% confidence, error-circle radius (arcsec) due to counting statistics (only). There is an additional uncertainty of about 30 arcsec from systematic errors and errors in the aspect solution; this term is to be added quadratically to the statistical error.

`CR1` is the count rate in the S1 band, in counts per second. `CR1 error` is the statistical 1 sigma error on the S1 count rate (in counts per second). If `S1 error` is zero, then the S1 value represents a 90% confidence upper limit, not a source detection.

Error in Mean Count Rate Filter 1 (c/s)

`CR2` is the count rate in the S2 band, in counts per second. `CR2 error` is the statistical 1 sigma error on the S2 count rate (in counts per second). If `S2 error` is zero, then the S2 value represents a 90% confidence upper limit, not a source detection.

Error in Mean Count Rate Filter 2 (c/s)

Detection significance in the S1 band.

Detection significance in the S2 band.

Combined S1 and S2 detection significance. Defined as CSIG = SQRT( SIG_1**2 + SIG_2**2 ).

Source detection flag.

  30: detected at CSIG >= 5.5 by both PSS and SESAME;
  21: detected at CSIG >= 5.5 by SESAME, and at 4.0 <= CSIG < 5.5 by PSS;
  11: detected at CSIG >= 5.5 by PSS, and at 4.0 <= CSIG < 5.5 by SESAME;
  20: detected at CSIG >= 5.5 by SESAME only;
  10: detected at CSIG >= 5.5 by PSS only.

Temporal variability flag. 0: none, 1: probable, 2: high. See McGale et al. 1995, for a full discussion on the temporal EUV variability of the 2RE sources.

Detected by other EUV/X-ray missions. W: WFC-BSC (Pounds et al. 1993), E=EUVE (Bowyer et al. 1994), X=EINSTEIN IPC pointed and/or slew catalogues (Harris et al. 1990; Plummer et al. 1991).

Name of possible optical counterpart. Object must be within 2 arcmin of 2RE source position.

Alternative name for optical counterpart.

Apparent mag. of counterpart (V where available).

Spectral type of counterpart.

BROWSE DBMS classification.

2RE-optical separation (arcsec).

Catalogue from which optical counterpart is taken.

Additional information concerning identifications.

RS: RS CVn-type binary star system; BY: BY Dra-type star; CB: W UMa-type contact binary star system.

The quality of a proposed identification is indicated as follows. IDP+: positive based on the WFC optical identification programme (IDP, Mason et al. 1995); ID**: positive based on the object's known properties (other than from the IDP); ID*: probable, but based on sparse knowledge of the object's properties. If none of these flags appears, then any listed counterpart is simply based on positional coincidence, and care should be taken in using any such information.

Galactice longitude of EUV source (degrees).

Galactice latitude of of EUV source (degrees).

Root name of WFC survey image containing the EUV source.

Root name of light-curve of the EUV source.

Sub-directory containing image.

Sub-directory containing light-curve.

Contact Person

Questions regarding the ROSWFC2RE database table can be addressed to the HEASARC User Hotline.
Page Author: Browse Software Development Team
Last Modified: Wednesday, 10-Nov-2004 16:03:11 EST