Coma Cluster - X-ray Source

X-ray Source

An extended X-ray source centered at 1300+28 in the direction of the Coma cluster of galaxies was reported before August 1966. This X-ray observation was performed by balloon, but the source was not detected in the sounding rocket flight launched by the X-ray astronomy group at the Naval Research Laboratory on November 25, 1964. A strong X-ray source was observed by the X-ray observatory satellite Uhuru close to the center of the Coma cluster and this source was suggested be designated Coma X-1.

The Coma cluster contains about 800 galaxies within a 100 x 100 arc-min area of the celestial sphere. The source near the center at RA (1950) 12h56m ± 2m Dec 28°6' ± 12' has a luminosity L_x = 2.6 x 1044 ergs/s. As the source is extended, with a size of about 45', this argues against the possibility that a single galaxy is responsible for the emission. The Uhuru observations indicated a source strength of no greater than ~10−3 photons cm−2s−1keV−1 at 25 keV, which disagrees with the earlier observations claiming a source strength of ~10−2 photons cm−2s−1keV−1 at 25 keV, and a size of 5°.