Circular No. 2788 Central Bureau for Astronomical Telegrams INTERNATIONAL ASTRONOMICAL UNION Postal Address: Central Bureau for Astronomical Telegrams Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A. Cable Address: SATELLITES, NEWYORK Western Union: RAPID SATELLITE CAMBMASS X-RAY INCREASE OF AQL X-1 J. Buff, Massachusetts Institute of Technology, reports that their group has observed a dramatic increase in the intensity of Aql X-1 (3U 1908+0) with the SAS-3 satellite. Between 1975 June 2 and June 7 the 1.5-keV intensity increased by a factor of 20 so that it is now as bright as the Crab Nebula. The source is presently observable in the energy range 0.5 to 20 keV. Limits on periodic pulsing of 2% have been set on the range 1 to 50 seconds. OUTBURST OF CI CYGNI Janet A. Mattei, Director of the American Association of Variable Star Observers, reports the outburst of the symbiotic variable CI Cygni (cf. IAUC 2335, 2575) and communicates the following visual magnitude estimates by AAVSO members: 1975 UT mv Observer May 17.2 10.5 W. Lowder 18.1 10.1 J. Bauer 28.2 9.5 W. Lowder 29.3 9.3 E. Hayden 29.9 9.4 J. Bauer NOVA OR OTHER ERUPTIVE VARIABLE P. Wild, Astronomisches Institute der Universitat Bern, cables the discovery of the following eruptive object: 1975 UT R. A. (1950) Decl. mpv June 6.0868 19 15 26.9 +04 41 44.3 11.5 June 9 12 A0535+26 Corrigendum: On IAUC 2787, line 22, for fourth and fifth harmonics read third and fourth harmonics. 1975 June 11 (2788) Owen Gingerich
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