Central Bureau for Astronomical Telegrams
IAUC 4996: U Gem; 1987A; N Sct 1989
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Circular No. 4996
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
U GEMINORUM
J. A. Mattei, AAVSO, reports that this dwarf nova, which is
on the observing list for the ASTRO-1 mission, is undergoing an
outburst, as indicated by the following visual magnitude estimates:
Jan. 22.08 UT, [13.9 (P. Schmeer, Bischmisheim, W. Germany); Apr.
15.86, 13.5 (Schmeer); 16.06, 12.8 (R. Hays, Worth, IL); 16.10,
12.5 (E. Mayer, Akron, OH); 16.16, 12.3 (Hays); 17.03, 9.4 (G.
Dyck, N. Dartmouth, MA).
SUPERNOVA 1987A IN THE LARGE MAGELLANIC CLOUD
N. Suntzeff, M. Phillips, J. Elias, D. Depoy and A. Walker,
Cerro Tololo Interamerican Observatory, report: "Further to
the information on IAUC 4995, the bolometric lightcurve is not
consistent with models where 56Co is the only energy source (Pinto
et al. 1988, Ap.J. 331, L101). Other plausible energy sources are
57Co or a pulsar. Alternatively, an infrared light echo may
contribute significantly to the observed luminosity, as suggested by
CCD and infrared images obtained around day 1050 that show the
presence of extended emission to a radius of 4" from the supernova.
Using models kindly provided to us by Woosley, we can fit the
bolometric light curve with purely radioactive energy input, provided
that the ratio of 57Co to 56Co is four times the solar ratio
at the time of explosion. Any contribution from an echo would lower
the amount of 57Co needed to fit the data. Although energy input
from a pulsar could also be used to fit the data, it is not required.
Optical and near-infrared spectra obtained between days 950 and 1100
have revealed no major changes from previous observations other than
a decline in the strengths of the [Fe II] emission lines with respect
to lines of neutral elements, presumably due to recombination, and a
decrease in the blueshift of the peaks of the [O I] 630.0-nm and
Mg I] 457.1-nm emission lines from -750 to -450 km/s, suggesting that
obscuration due to dust in the ejecta is now diminishing."
NOVA SCUTI 1989
Visual magnitude estimates (cf. IAUC 4928): Mar. 2.16 UT, 12.9
(A. Boattini, Florence, Italy); 27.87, 13.1 (A. Pearce, Scarborough,
W. Australia); Apr. 4.15, 12.9 (P. Schmeer, Bischmisheim, W. Germany);
6.86, 13.2 (Pearce).
1990 April 18 (4996) Daniel W. E. Green
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