Scientific Results

One of the best known results of Cos-B was the 2CG catalogue of point sources (Ref.3). This early catalogue was based on the selected data from only 30 observations made during the first three years of operation. It was searched for the presence of discrete, or localised, sources of gamma radiation under the assumption of a flat, or smoothly varying background. Thus 25 candidate sources were reported.

In view of the availability of the total mission data as well as more realistic background models, the interpretation of these enhancements has evolved rapidly. In the following pages, reference to the historical designation of the sources in the 2CG catalogue is adhered to for convenience.

Detailed Results

Where to find the data

The COS-B event files are available for world wide access via the EXOSAT web site

They are presently in


and have the following naming convention:


where H is ether N or S depending on whether the declination is north or south, and NN is a two digit number running from 00 to 64, for all 65 observations. (e.g CB2251S18P41.evt was the 42nd observation, and the source coordinates are RA 2251 DEC -18). If you have difficulties with this convention, let us know.

Using the COS-B files

To make use of the COS-B files, copy them to a node which has FTOOLS installed and then run the F2DHISTO FTOOLS utility to create the fits image, which can then be read directly with SAOIMAGE.

The COS-B Database - db_cosb:[phot]

All the Cos-B data were subjected to a consistent analysis and selection process and compiled into a single data-set. The final database (which is available to the public) contains 200 000 events in the energy range 50 MeV - 5 GeV. This corresponds to an average count rate 10 events per sq. deg of observed sky.

Supplied with the database is the full information on sensitivity which exhibited variations ±25% over 6.8 years. The background which varied in phase with the solar cycle and with pointing direction can be taken account of using suitable derived background parameters supplied with the database (Ref.2).