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WFCBSC: Help

WFCBSC - ROSAT Wide Field Camera Bright Source Catalogue

Overview

The WFCBSC database contains the ROSAT Wide Field Camera Bright Source Catalogue. It contains 384 bright EUV sources found during the ROSAT all sky survey of July 1990 to January 1991. The information in this pre-publication database is based on what will be published by Pounds et al in MNRAS.

Description

The British Wide Field Camera 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. It is sensitive in the range 60 to 200 Angstroms (60 to 200 eV). The WFC is coaligned with the larger 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 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.


Parameters

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.

Optical Identifications

Information on possible counterparts within the 99.9% WFC position error circle is given. The counterpart listed is thought to be the most likely identification from the information available in existing catalogues and from follow-up work on some sources. Extensive use was made of the SIMBAD database, particularly for obtaining information on multiple names for sources. Two names are given for the counterpart; the first is usually a common or variable star name, and the second is an HD or WD (McCook and Sion 1987) number, where available. Information on many of the source names used here can be found in Fernandez et al (1983).

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.


References

"The ROSAT all-sky survey of Extreme Ultraviolet sources: I The Bright Source Catalogue" Pounds, K. A., et al., 1992, to be submitted to MNRAS.

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.


Contact Person

Questions regarding the WFCBSC database table can be addressed to the HEASARC User Hotline.
If you have any problems, please consult the help page or mail ledas-help@star.le.ac.uk
 
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