Cygnus X-1

N. Oda and the Hakucho Team, Institute of Space and Aeronautical Science, University of Tokyo, communicate: "Hakucho observed a short transition from low to high state between Nov. 8.12 and 10.00 UT of what is probably Cyg X-1. The peak intensity was ~ 2 times the Crab over the range 1-12 keV on Nov. 10. The intensity declined to ~ 1 Crab on Nov. 11 and recovered to low level on Nov. 12. The last transition of Cyg X-1 to its high state occurred between 1980 May and June, and it then returned to low state in mid-July (cf. IAUC 3491 and 3502)."