Central Bureau for Astronomical Telegrams
IAUC 4481: 1987A
The following International Astronomical Union Circular may be linked-to from your own Web pages, but must not otherwise be redistributed (see these notes on the conditions under which circulars are made available on our WWW site).
Read IAUC 4482
Circular No. 4481
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
A. Chalabaev, Observatoire de Haute Provence; and C. Perrier
and J. M. Mariotti, Observatoire de Lyon, telex: "Near-infrared
speckle interferometry of SN 1987A at the European Southern Observatory
3.6-m telescope (cf. IAUC 4389, 4417) was continued on Aug.
6, yielding the detection of a weak modulation superimposed on the
visibility function of the unresolved ejecta. The data were
obtained using K, L, and M filters aligned north-south, and with the
K filter aligned east-west. The modulation is present in all
observations, which can be satisfied by one of three possibilities:
(1) the unresolved ejecta and two infrared spots, one lying to the
north (or south) and another to the east (or west) of the SN (both
being 0".35 +/- 0".04 from the SN, and each contributing about 2.5 percent
to the total flux); (2) combining the two spots into one spot lying
at an intermediate direction; or (3) a ring of 0".41 +/- 0".08 diameter,
contributing about 3 percent of the total flux. The velocity scale
of the phenomenon is at least 0.4c, meaning that we are observing
an infrared light echo. The analysis of the dust density necessary
to account for the observed flux and the axial symmetry favors the
ring as the most plausible explanation for these observations. The
whole set of ESO speckle observations carried out from May to Aug.
allows us to conclude that, during this time, the 2- to 5-micron flux
was dominated by the unresolved ejecta which contributed at least
95 percent of the total flux in each infrared band, with the exception
of the L band (where during June 16-21 the lower limit on the
ejecta contribution may be set at about 80 percent). This implies that
any suspected infrared 'excess' over 5 percent in K or M does not
come from a light echo but from the ejecta, and/or the material
within the ejecta, and/or the outer region immediately surrounding
the ejecta."
G. K. Moore and A. Deliseo, University of Wollongong, report
the following photometry obtained on Oct. 27.58 UT: V = 5.65, B-V
= +1.30, V-R = +1.06, V-I = +1.53. Corrigendum: on IAUC 4474,
Supernova 1987A, line 1, for Wollonrong read Wollongong.
Visual magnitude estimates: Oct. 22.49 UT, 5.8 (D. Seargent,
The Entrance, N.S.W.); 24.42, 5.6 (A. C. Beresford, Adelaide, South
Australia); 25.42, 5.5 (Beresford); 26.76, 5.6 (R. H. McNaught,
Siding Spring Observatory); 27.53, 5.9 (Seargent); 28.44, 5.6
(Beresford); 29.45, 5.6 (Beresford); 30.47, 5.7 (Beresford).
1987 November 2 (4481) Daniel W. E. Green
Read IAUC 4482
Our Web policy. Index to the CBAT/MPC/ICQ pages.
