Central Bureau for Astronomical Telegrams
IAUC 4216: 1986G
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Circular No. 4216
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 1986G IN NGC 5128
W. Wamsteker, R. Gilmozzi and C. Gry, Vilspa; and F. Macchetto
and N. Panagia, Space Telescope Science Institute, report:
"SN 1986G was observed on May 8 with the IUE Long-Wavelength
Principal (LWP) Camera. With an exposure time of 333 min detection
was achieved only at wavelengths > 250 nm. The average flux was
0.5 x 10**-16 J m**-2 s**-1 nm**-1 in the range 285-320 nm, dropping to
0.3 around 280 nm and finally declining almost linearly down to ~
250 nm, shortward of which no signal could be detected. A number
of narrowish (halfpower width ~ 2 nm) absorption features were
also observed in the spectrum: the most prominent occurred at
280.6, 285.1, 294.6, 301.0 and 308.2 nm. The broad emission bands
around 295 and 315 nm, which had been observed in all type I
supernovae at maximum light, were not present in the spectrum of
SN 1986G. At the time of observation the fine-error-sensor
magnitude was 12.1. Comparison of the fine-error-sensor/290-nm flux
ratio with that of other type I supernovae gave an estimated
E(B-V) color excess of more than 1 mag."
R. Kirshner, Center for Astrophysics, reports that observations
of with IUE from Goddard Space Flight Center gave fine-
error-sensor magnitudes as follows: May 5.9 UT, 12.2; 6.6, 11.9;
12.5, 11.7. The May 6 observation, a 30-min LWP esposure, showed
a barely detectable spectrum near 280 nm. This is consistent with
expectation for a heavily-reddened type I supernova at mag 12. A
more satisfactory 350-min exposure on May 12 gave results that are
generally consistent with those reported above for May 8.
G. Meurer, Mount Stromlo Observatory, telexes that four
spectra (0.6-nm resolution) obtained during May 8-13 with the 1.9-m
Cassegrain spectrograph confirm this to be a type I supernova. A
red spectrum (range 480-700 nm) obtained on May 7.95 UT shows a
strong P-Cyg profile with an absorption dip at 620 nm; other dips
occur at ~ 490, 540, 560 and 590 nm. Blue spectra (range 350-600
nm) taken on May 9.99, 11.04 and 12.17 show a very strong, broad
peak in intensity at 460 nm that fades with time with respect to
the redward continuum. The single, broad absorption dip at 490 nm
now appears as two dips at 490 and 505 nm; the other most noticeable
dips in the blue spectra occur at 370, 430 and 590 nm, with
lesser dips at 470, 480, 540 and 560 nm. Comparison with supernova
1972E suggests that maximum should have occurred around Apr. 21.
1986 May 15 (4216) Brian G. Marsden
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