Central Bureau for Astronomical Telegrams
IAUC 4324: 1987A; N Cyg 1986
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Circular No. 4324
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
TWX 710-320-6842 ASTROGRAM CAM Telephone 617-495-7244/7440/7444
SUPERNOVA 1987A IN THE LARGE MAGELLANIC CLOUD
C. Gry, A. Cassatella, W. Wamsteker and L. Sanz, ESA IUE
Observatory; and N. Panagia, Space Telescope Science Institute,
communicate for the European IUE SN Team: "Extensive observations of
SN 1987A were made with the International Ultraviolet Explorer
over the wavelength interval 115-320 nm. The observations, made
both in high and in low resolution on Feb. 25, 26 and 27, showed
the following. (1) On Feb. 25, the ultraviolet spectrum displayed
prominent and broad features with a width corresponding to 14 000
to 26 000 km/s. On this date the spectrum did not resemble that
of any supernova (either type I or type II) observed previously in
the ultraviolet. The spectrum showed a strong continuum between
320 and 280 nm and a sharp drop between 280 and 260 nm. At the
shorter wavelengths the spectrum is fairly flat with strong peaks
at 239.2, 202.4, 187.2, 162.4, 148.8 and 131.6 nm. (2) On Feb. 26
the overall spectral appearance had changed dramatically, and the
spectrum was remarkably similar to that of the SN 1983N in M83
about a week before maximum. The ultraviolet spectrum was at this
moment typical of a type I supernova. The peaks in the spectrum
were at 292.0, 277.5 and 186.4 nm, with the 292.0-nm peak much more
pronounced than on the day before. (3) The evolution of the
lightcurve in the ultraviolet is much faster than seen in any previous
type I supernova, possibly consistent with the low luminosity of
this object. The ultraviolet lightcurve evolution is illustrated
by the flux measurements (in units of 10**-13 erg s-1 cm-2 A-1) at
135 nm: Feb 25.15 UT, 300; 25.44, 150; 26.22, 20; 26.43, 10; 27.41,
1.2. Although the flux is decreasing over the whole ultraviolet
range, this decrease is less pronounced toward the longer
wavelengths. (4) The high-resolution spectra taken show the presence
of numerous sharp interstellar lines of ions at all ionizations
from Mg I to Si IV. All lines are seen clearly to consist of many
components extending in velocity from the galactic foreground to
the LMC velocity of 260 km/s. Many components are seen covering
the whole velocity range. No obvious features could be identified
with the supernova itself."
NOVA CYGNI 1986
Photoelectric observations made by R. Monella, Covo, Italy:
1986 Dec. 23.753 UT, V = 11.93, B-V = +0.42, U-B = -0.57; 1987
Feb. 21.198, 12.63, +0.36, -0.86; Feb. 23.203, 12.71, +0.41,
-0.95; Feb. 24.194, 12.67, +0.49, -1.03.
1987 February 28 (4324) Brian G. Marsden
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