THE ASTRONOMER Electronic Circular No 504 1991 Mar 31 15.46UT Ed:Guy M Hurst, 16,Westminster Close, Kempshott Rise, Basingstoke, Hants, RG22 4PP, England. Telephone: (0256)471074 Int:+44256471074 Telex: 9312111261 Answerback: TA G JANET BOXES: GMH at UK.AC.CAM.ASTRONOMY.STARLINK or GUYH at UK.AC.SUSSEX.CLUSTER TELECOM GOLD: 10074:MIK2885 PRESTEL 256471074 ------------------------------------------------------------------- SUPERNOVA 1991N IN NGC 3310 S. Perlmutter et al, communicate: "The Berkeley Automated Supernova Search reports the discovery of a supernova of mv about 15 located 5" east and 7" south of the core of galaxy NGC 3310 (R.A. = 10h35m.7, Decl. = +53 46', equinox 1950.0) in two separate images taken on Mar. 29.4 UT. The discovery was confirmed on an image taken on Mar. 30.2, when the supernova was about the same brightness. The most recent previous image was taken on Feb. 20.4 and showed no supernova to limit of mag 17.5." NOVA HERCULIS 1991 M.Yamamoto, Japan reports that a photograph taken on 1991 Mar 23.77UT did not show the nova to a limit of magnitude 10. R. M. Wagner, R. Bertram, and B. Ali, Ohio State University; and S. G. Starrfield, Arizona State University, report: "Optical spectra were obtained on Mar. 29.5 UT with the Perkins 1.8-m telescope and CCD spectrograph (resolution 1 nm, range 335-980 nm) at Lowell Observatory. Broad emissions are visible at 447.1, 587.6, and 706.5 nm (He I); 566.7 and 568.0 nm (N II); 597.8, 634.7, and 637.1 nm (Si II); 744.0, 820, and 870 nm (N I); 777.4 and 844.6 nm (O I); 787.7 and 789.6 nm (Mg II); and 911 (C I). The FWHM width of H-alpha emission was about 4500 km/s. This spectrum is strikingly similar to that of Nova V1500 Cyg obtained on 1975 Sept. 6-7 and shown by Tomkin et al. (1976, A.Ap. 48, 319). The appearance of He I lines after maximum light in Nova Her 1991 (IAUC 5224) also coincides with the same development observed in V1500 Cyg. The large ejection velocities, the rapid decline in optical light, the correspondence of optical spectroscopic features, and the red color of the progenitor all suggest that this is another case of a nova outburst occurring on a strongly magnetized white dwarf." IAUC 5227 G.Sonneborn et al, Goddard Flight Center report detailed observations with the International Ultraviolet Explorer on IAUC 5226. They include visual magnitude estimates from Fine Error Sensor measurements: Mar 25.8, 7.1; 27.0, 8.0; 28.8, 8.4. The Editor notes that t3 (time for drop of first three magnitudes from maximum) is about 4d. This appears to be the second fastest known decline (V1500 Cyg =3.6d; MU Ser = 5d, Duerbeck). Further visual estimates: 1991 Mar 28.19, 8.1 (Roy Panther, Northampton); 28.5, 8.0 (R.Royer, USA); 28.59, 9.2 (Timo Kinnunen, Finland); 29.109, 8.8 (Patrick Schmeer, Germany); 30.095, 9.0 (Schmeer); 30.099, 9.0 (Schmeer); 30.119, 9.0 (Schmeer); 30.156, 9.0 (Stefan Korth, Germany); 30.169, 9.0 (Schmeer); 30.79, 9.3 (R.McNaught, Australia); Mike Collins, Sandy draws our attention to a second catalogued variable in the field of the nova: KZ Herculis RA 18h44m53s DEC +12 24.1'(1950), magn 12.2-[17p. To adjust the (e) version of the (b) chart (cf E502), delete E84 on the last code line and add: M,12,98,20 -L,B,KZ Her E,85 Paper versions of (A), (B) and (C) charts are now available upon e-mail request, Guy M Hurst