X-ray Observations of Cyg X-3 Near the Time of Radio Outbursts

Abstract

FOLLOWING the announcement of Gregory et al.¹ and Hjellming and Balick² that the radio source identified with Cyg X-3 had undergone a substantial increase in radio flux output some time between August 31, 1972, and September 2, 1972, we made a search through all data available for dates near this event from the Vela 5B spacecraft to determine if any associated increase in X-ray flux could be detected. Scans of the appropriate region of the sky were made on the four dates shown in Table 1. Cyg X-3 lies close enough on the sky to Cyg X-1 that the two sources were barely resolvable with the angular response of the X-ray detectors on the spacecraft; however, estimates of the strength of Cyg X-3 relative to Cyg X-1 were possible. In all cases, the flux observed from Cyg X-3 in the 3 to 12 keV energy range was consistent with the ratio of 1:3 (flux from Cyg X-3/flux from Cyg X-1) reported in previous observations of these sources (for example, Gursky et al.3).