Central Bureau for Astronomical Telegrams
IAUC 5449: 1987A AND NEIGHBORING STARS; 1992 AD
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Circular No. 5449
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 1987A AND NEIGHBORING STARS
L. Wang, S. D'Odorico, C. Gouiffes, and J. Wampler, European
Southern Observatory, report: "Observations of star 3 (cf. West
1987, IAUC 4356) were obtained in 1990 Oct., 1991 Sept. and Nov.,
and 1992 Jan. with ESO's New Technology Telescope. Slit spectra
taken across star 2, the supernova, and star 3 show that there is an
emission component on top of star 3. It is seen in H-beta and H-
alpha, but not in the metal lines. The FWHM of this component is
about 150 km/s, in remarkable agreement with the pedestal reported
on IAUC 5156. Because the continua of star 2, the supernova, and
star 3 are very well separated in our slit spectra, we are able to
determine the spatial location of the broad component; it was found
to coincide exactly with the continuum of star 3. Narrow-band (
typically FWHM = 1 nm) images taken under seeing conditions of about
0".7 show that star 3 is brighter in H-alpha than star 2 but fainter
in images taken at other wavelengths. These observations lead us to
conclude that star 3 is a Be star and that the previously reported
broad H-alpha component is intrinsic to star 3. This conclusion is
supported by UBVRI photometry obtained between 1989 Sept. and 1991
Nov. at Cerro Tololo Interamerican Observatory by A. R. Walker, M.
M. Phillips, and other members of the CTIO staff. These data show
that star 3 is variable by as much as 0.3 mag over timescales of
several months. Representative photometry is as follows: U = 15.03,
B = 15.90, V = 15.86, R = 15.62, I = 15.53. These colors and the
observed variability are fully consistent with the Be star hypothesis.
Images taken at ESO in the GUNN I filter also show that the
diffuse nebulosity at the northern side of the outer loop of the
supernova (the 'Napoleon's Hat'; cf. Wampler et al. 1990, Ap.J.
362, L13-L16) has become too faint to be detectable."
1992 AD
E. Howell, R. Marcialis, R. Cutri, M. Nolan, L. Lebofsky, and
M. Sykes, University of Arizona, report: "Simultaneous thermal
infrared and CCD observations of 1992 AD have been obtained using the
Multiple Mirror Telescope and the Catalina 1.5-m telescope on Jan.
29. Using a standard thermal model (non-rotating), we find somewhat
preliminary values for the diameter (140 km) and the geometric albedo
(0.08), based on detections with signal/noise = 3 at both 10.6
and 21 microns. If a rotating model is used or the thermal inertia
of the object is significant, 1992 AD may be bigger and darker than
this."
1992 February 12 (5449) Daniel W. E. Green
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