Central Bureau for Astronomical Telegrams
IAUC 6761: 1987A; C/1997 T1
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Circular No. 6761
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
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SUPERNOVA 1987A IN THE LARGE MAGELLANIC CLOUD
P. Garnavich, R. Kirshner, and P. Challis, Harvard-Smithsonian
Center for Astrophysics, report on behalf of the Supernova
Intensive Study team: "Long-slit spectra of SN 1987A and its
circumstellar emission rings were obtained with the Space Telescope
Imaging Spectrograph aboard the Hubble Space Telescope (HST).
Ultraviolet spectra (range 113-170 nm) were obtained on Sept. 27
UT, and low-resolution optical spectra (range 530-1000 nm) were
taken on Oct. 6. The spectra show evidence of both the interaction
of the supernova ejecta with the inner H II region and the
collision between the ejecta and the circumstellar ring. The 0".5-
wide slit for the ultraviolet spectra was set at p.a. 33 deg to
include the 'hot spot' (cf. IAUC 6665, 6710), which is a protrusion
of the inner ring being shocked by the supernova ejecta. Emission
lines of N V, O IV, N IV, C IV, and He II are detected at the hot-
spot location 0".1 interior to the ring. The presence of C IV
emission, which is normally absorbed by interstellar gas, indicates
the emission is blueshifted relative to the rest of the ring.
Bright Lyman-alpha emission is seen as a blueshifted arc on the
north side of the ring and a fainter, redshifted arc on the south
side. At low velocity, the blueshifted arc extends to within 0".1
of the ring and reaches peak brightness at 11 000 km/s with a
projected distance of 0".2 from the supernova position. The
blueshifted arc becomes undetectable beyond 15 000 km/s at the
position of the supernova. The brightness difference between the
redshifted and blueshifted Lyman-alpha emission implies either an
asymmetry in the interaction between the near side and far side, or
an increase in brightness on a timescale faster than the light
travel time across the ring. Weak emission redward of Lyman-alpha
is possibly due to N V 124-nm, as predicted by Michael et al.
(1997, Ap.J., submitted). The HST optical spectrum taken with a
0".2 slit shows a high-velocity, blueshifted arc of H-alpha,
corresponding to the Lyman-alpha emission. The H-alpha arc begins
0".1 inside of the peak of the ring flux and is clearly visible to
12 000 km/s. The redshifted arc is significantly fainter and
visible only to 5000 km/s."
COMET C/1997 T1 (UTSUNOMIYA)
H. Kawakita, Osaka, Japan; and M. Fujii, Okayama, Japan,
obtained a low-dispersion (resolution about 3 nm, range 380-730
nm) spectrogram of this comet with the 1.01-m telescope at Bisei
Astronomical Observatory on Oct. 11.6 UT. CN, C_3, C_2, NH_2 and
[O I] emissions are present.
(C) Copyright 1997 CBAT
1997 October 27 (6761) Daniel W. E. Green
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