Evidence of a Continuous Change in the Period of Cygnus X-3

Abstract

Summary. Cygnus X-3 has been observed, in the 2-12 keV energy range, continuously from 1977 June 8.46 to 1977 July 14.79 by the ESA satellite COS-B. The basic parameters of the system have been determined. A fit of the COS-B data with the values obtained previously by ANS and Uhuru gives: Pdot=(2.83+/-0.67)10^-9 s/s The value Pdot/P0=(5.2+/-1.2) 10^-6 yr^-1 compares to the 2 sigma upper limit Pdot/P0 < 1.6 10^-5 yr^-1 previously given by ANS. Key words: CO S-B - X-ray astronomy - Cygnus X-3