Circular No. 5039 1990 June 26 (5039) Daniel W. E. Green Central Bureau for Astronomical Telegrams INTERNATIONAL ASTRONOMICAL UNION Postal Address: Central Bureau for Astronomical Telegrams Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A. Telephone 617-495-7244/7440/7444 (for emergency use only) TWX 710-320-6842 ASTROGRAM CAM EASYLINK 62794505 MARSDEN or GREEN@CFA.BITNET MARSDEN or GREEN@CFAPS2.SPAN SUPERNOVA 1990N IN NGC 4639 A. Maury, Observatoire de la Cote d'Azur (OCA), reports the discovery by E. Thouvenot of a supernova in NGC 4639 (R.A. = 12h40m21s, Decl. = +13 31'.9, equinox 1950.0) on a 5-min unfiltered CCD exposure taken by C. Buil, A. Maury, and L. Brunetto with the Pic du Midi 0.6-m telescope on June 22.964 UT (day 0.46). A IIa-O plate taken by D. Albanese on June 23.93 ( day 1.43) with the OCA 0.90-m Schmidt telescope shows the object at mag about 15.5 (band?????) and located 65" east and 1" south of the galaxy's center. Buil, Thouvenot, and G. Prat report magnitude differences with respect to the discovery frame: June 23.885, -0.44; 24.89, -0.84; 25.88, -1.18. An observation on June 25.90 (day 3.40) by E. Cappellaro, S. Benetti, and M. Turatto with Asiago Observatory's 1.8-m telescope at Mt. Ekar yields V = 14.84, R = 14.49 and B. Leibundgut, Center for Astrophysics, report that a spectrum (range 400-800 nm), obtained on June 26.4 (later revised to 26.2 which is day 3.7) by C. Foltz and J. Pier with the Multiple Mirror Telescope, resembles that of a classic type-Ia supernova, though the lines appear broader and smoother than in other type-Ia objects observed near maximum light, and the characteristic 615-nm feature extends further toward the blue than in typical type-Ia SNe, perhaps as a result of observing unusually fast-moving gas at a very early epoch. Circular No. 5040 1990 June 27 (5040) Daniel W. E. Green Central Bureau for Astronomical Telegrams INTERNATIONAL ASTRONOMICAL UNION Postal Address: Central Bureau for Astronomical Telegrams Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A. Telephone 617-495-7244/7440/7444 (for emergency use only) TWX 710-320-6842 ASTROGRAM CAM EASYLINK 62794505 MARSDEN or GREEN@CFA.BITNET MARSDEN or GREEN@CFAPS2.SPAN SUPERNOVA 1990N IN NGC 4639 C. Pollas, Observatoire de la Cote d'Azur, reports the following accurate position: R.A. = 12h40m25s.85, Decl. = +13 31'49".4 (equinox 1950.0). A nearby star has end figures 24s.64, 19".5. Turatto reports that an observation (made as above) on June 26.89 UT (day 4.39) gives V = 14.6, R = 14.5. Circular No. 5042 1990 June 28 (5042) Daniel W. E. Green Central Bureau for Astronomical Telegrams INTERNATIONAL ASTRONOMICAL UNION Postal Address: Central Bureau for Astronomical Telegrams Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A. Telephone 617-495-7244/7440/7444 (for emergency use only) TWX 710-320-6842 ASTROGRAM CAM EASYLINK 62794505 MARSDEN or GREEN@CFA.BITNET MARSDEN or GREEN@CFAPS2.SPAN SUPERNOVA 1990N IN NGC 4639 C. Pennypacker, S. Perlmutter, and C. K. Smith, The Berkeley Supernova Search Team, note that SN 1990N was not present at the 95-percent confidence level, down to magnitude V = 17.0 on a CCD image of NGC 4639 taken at Leuschner Observatory on June 13.27 UT (day -9.23). Circular No. 5047 1990 July 5 (5047) Brian G. Marsden Central Bureau for Astronomical Telegrams INTERNATIONAL ASTRONOMICAL UNION Postal Address: Central Bureau for Astronomical Telegrams Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A. Telephone 617-495-7244/7440/7444 (for emergency use only) TWX 710-320-6842 ASTROGRAM CAM EASYLINK 62794505 MARSDEN or GREEN@CFA.BITNET MARSDEN or GREEN@CFAPS2.SPAN SUPERNOVA 1990N IN NGC 4639 G. Sonneborn, Goddard Space Flight Center; and R. Kirshner, Center for Astrophysics, report: "Low-dispersion ultraviolet spectra (range 200-335 nm, resolution 0.6 nm) of SN 1990N have been obtained with the IUE satellite on June 26.8, 28.3, 30.6 and July 2.7 UT. SN 1990N was detected longward of 250 nm on each date. The mean flux in the range 300 +/- 15 nm was 1.9**10-14 erg cm-2 s-1 A-1 on July 2. The ultraviolet flux has approximately doubled every two days during this period, while the shape of the spectrum has changed very little. The spectrum resembles IUE spectra of other type Ia supernovae: it has the pronounced flux maximum at 310 nm. However, the secondary maximum usually seen at 290 nm (e.g., in SN 1981B) is not present in SN 1990N. The following visual magnitude estimates were obtained with the IUE Fine Error Sensor (400-700 nm) on the dates given above: 14.4, 14.0, 13.4 and 13.2, indicating that the ultraviolet has been rising at about twice the rate of the optical brightness. Detection of a large ultraviolet flux increase in a type Ia supernova is unprecedented. Photometry and spectroscopy are needed in other wavelength regions, in particular optical coverage extending shortward of 400 nm." Circular No. 5054 1990 July 18 (5054) Daniel W. E. Green Central Bureau for Astronomical Telegrams INTERNATIONAL ASTRONOMICAL UNION Postal Address: Central Bureau for Astronomical Telegrams Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A. Telephone 617-495-7244/7440/7444 (for emergency use only) TWX 710-320-6842 ASTROGRAM CAM EASYLINK 62794505 MARSDEN or GREEN@CFA.BITNET MARSDEN or GREEN@CFAPS2.SPAN SUPERNOVAE 1990N, 1990O, 1990P Filippenko and Shields also confirm that SN 1990N and SN 1990O (IAUC 5039) are of type Ia. SN 1990P (IAUC 5039), however, could not be seen to a limiting R magnitude of approximately 20.