THE ASTRONOMER Electronic Circular No 10 1987 Mar 01 15.20UT. SUPERNOVA 1987A IN THE LARGE MAGELLANIC CLOUD The following is a copy of of the complete announcement in EWC 90 which will be issued tommorrow, some of which duplicates data on E-circular 8: Preliminary discovery announcements have been made in EWC 89A (issued to southern observers, 870224); E-circ 8(870224);NSPC 17 (870226). This object is the first SN to be observed in the LMC and the closest SN seen since 1604. The supernova was discovered by Ian Shelton at Las Campanas on a 3hr exposure with the 0.25-m astrograph, start time 1987 Feb 24.06UT when the object was of approx mag 5. Independent discoveries were made by Oscar Duhalde (Las Campanas), Feb 24.2UT, and by Albert Jones, Nelson on Feb 24.37UT, 6.5-7.0, both visually. Richard West, ESO, has obtained a CCD position as follows: RA 5h35m49s.942 DEC -69 17'57".60 (1950). The following magnitude estimates are available: Moreno and Walker, Auckland Observatory, Feb 24 454, V=4.81. Feb 24.455, 4.8 (McNaught=M); 24.472, 4.8(M); 24.635, 4.4 (Garradd=G); 24.679, 4.5 (M); 24.717, 4.4 (M); 24.8, V=4.63 (Winkler=W); 25.219, V=4.63 (Shelton=S); 25.401, 4.3 (M); 25.460, 4.2 (M); 25.572, 4.5 (M); 25.659, 4.4 (M); 26.401, 4.4 (M); 26.512, 4.1 (M); 26.646, 4.1 (M); 26.749, 4.0 (M); 27.406, 4.2 (M); 27.558, 4.4 (M); 27.715, 4.3 (M); 28.408, 4.3 (M); 28.588, 4.4 (M). McNaught also advises us that nova patrol photographs taken with the 85mm lens show prediscovery images as follows: Feb 23.443, 6.0; 23.445, 6.2. He further notes that nothing new was detected in the field to magnitude 12.5 on an exposure on Feb 22.465 or on a photo by Gordon Garradd on the same day to 14.5. In a search for the progenitor, McNaught mentions there is a blue star at or near the position. Examination of plates during this century shows no variation. M.Morel, NSW, mentions that this star is Sanduleak -69 202, an LMC member(also= CPD -69 402), measured by Rousseau at V=12.24 in 1978. Subsequently, Sanduleak and Lasker note there is a companion to the mag 12(=star 1) in pa 315, mag 16, sep approx 3"(= star 2). West's measurements suggest that star 1 is the likely candidate. Walborn et al later report another companion(=star 3) 1" pa 110. There are conflicting reports as to supernova's type from spectral analyses. Early reports from the South African Observatory suggests type I on basis of 615-nm dip, but later reports favour type II on which basis it could reach mag +1 in the coming weeks. IUE astronomers mention that on Feb 25 the ultraviolet spectrum did not resemble any SN (I or II) previously observed in the ultraviolet. On Feb 26 the spectrum has changed dramatically and resembled SN 1983N in M83, 1 week before maximum. COMET TERASAKO (1987d) Ephemeris: Earth Sun m1 Mar 1 2 07.15 -10 05.3 6 2 21.42 -07 56.0 2.042 1.586 10.6 11 2 34.50 -05 58.8 16 2 46.61 -04 12.6 2.275 1.751 11.2 Guy M Hurst measured by Rousseau at V=12.24 in 1978.