Central Bureau for Astronomical Telegrams
IAUC 5968: 1994I
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Circular No. 5968
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@CFA or GREEN@CFA (.SPAN, .BITNET or .HARVARD.EDU)
SUPERNOVA 1994I IN NGC 5194
J. A. Phillips, California Institute of Technology; C. J.
Chandler and M. P. Rupen, National Radio Astronomy Observatory,
report: "Using the five-element millimeter interferometer at the
Owens Valley Radio Observatory, we have observed SN 1994I at 99 and
218 GHz. We obtained synthesis images of the supernova field at 99
GHz on Apr. 5.2-5.7 and at 218 GHz on Apr. 6.2-6.7 UT. At 99 GHz,
we detected an unresolved radio source at the position of the
supernova (IAUC 5961, 5963) with flux density 11.0 +/- 0.6 mJy (3
sigma). We did not detect a radio source at 218 GHz; the rms noise
in the 218-GHz image was 4 mJy/beam. Our flux scale was established
by observations of Neptune and Uranus. The systematic uncertainty
in the absolute flux scale is about 15 percent. Comparison with
radio measurements (IAUC 5963, 5966) shows that the supernova is
already optically thin at millimeter wavelengths; therefore,
according to the circumstellar interaction model, the flux density
at millimeter wavelengths has already passed maximum and should now
be decreasing."
P. M. Rodriguez-Pascual, R. Monier, and W. Wamsteker,
International Ultraviolet Explorer (IUE) Observatory, European
Space Agency; C. Fransson, Stockholm Observatory; G. Sonneborn,
Goddard Space Flight Center; and R. P. Kirshner, Harvard-Smithsonian
Center for Astrophysics, report: "Observations of SN 1994I were
made with the IUE on Apr. 3.35, 4.9, and 5.13 UT in the long-
wavelength range (200-320 nm). A faint point-source continuum
spectrum was detected on top of an extended background, most likely
associated with the galaxy M51 itself. Although the detailed flux
estimates are complicated by the diffuse background, any increase
in flux between the first and third observations is limited to < 20
percent. Integrated fluxes in 10-nm bands on Apr. 5.13 (including
the diffuse, weak background possibly contributing some 40 percent
of the flux) are 5.8 (250 nm) and 6.1 (280 nm) x 10E-15 erg sE-1
cmE-2 AE-1 (error 15 percent). The spectral appearance is very
similar to that seen in SN 1980K a few days before optical maximum,
and shows none of the typical metal blanketing below 290 nm (as
seen in, e.g., SNe 1983N, 1987A, or 1993J). The spectra show
strong interstellar absorption lines (Mn II at 259.37 nm, Fe II at
259.94 nm, and Mg II at 279.55-280.27 nm) redshifted by 0.35 nm,
consistent with a possible origin in M51."
1994 April 8 (5968) Daniel W. E. Green
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