Central Bureau for Astronomical Telegrams
IAUC 5963: 1994I
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Circular No. 5963
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
M. P. Rupen and R. A. Sramek, National Radio Astronomy Observatory;
S. D. Van Dyk, University of California at Berkeley; K. W. Weiler,
Naval Research Laboratory; and N. Panagia, Space Telescope Science
Institute, report: "Observations on Apr. 3.17 UT with the Very
Large Array in its highest-resolution (A) configuration at wavelengths
1.3 and 3.6 cm (22.5, 8.4 GHz) show an unresolved (< 0".3) radio
source within 2" of the optical position of the supernova (IAUC 5961).
Flux densities were 2.32 +/- 0.52 mJy at 1.3 cm and 0.55 +/- 0.07 mJy
at 3.6 cm, where the uncertainties include both random and systematic
(calibration) errors; the random noise in these images is 0.23 and
0.04 mJy/beam, respectively. By contrast, SN 1993J was still
undetected at radio wavelengths even three days after optical
discovery (the first radio detection---0.75 mJy at 1.3 cm---occurred
five days afterward; cf. IAUC 5743, 5752). Since SN 1994I is more
distant than SN 1993J, this difference in time of turn-on is
intrinsic and probably means that the envelope of circumstellar
material around SN 1994I is relatively thin. However, the strong
radio emission does suggest a sufficiently dense circumstellar medium
that many of the associated effects sometimes seen at other
wavelengths (x-ray/ultraviolet emission, narrow optical lines,
infrared dust echoes, etc.) should also be apparent in SN 1994I. We
find a position for the supernova of R.A. = 13h27m47s.731, Decl. =
+47o26'57".84 (equinox 1950.0; uncertainty +/- 0".1 in each coordinate);
we also detect radio emission from the nucleus of M51, giving
an offset for the SN of 14".3 east and 12".3 south. VLA observations
from 1982 to 1983 (Ford et al. 1985, Ap.J. 293, 132) at 6 and 20 cm
give for the nucleus of M51 the same position (to within 0".13) and
consistent flux densities, but show no source at the position of
the supernova (6-cm flux density < 0.1 mJy). Radio monitoring is
continuing at these and other wavelengths."
M. W. Richmond, Princeton University; and A. V. Filippenko, R.
R. Treffers, and S. D. Van Dyk, University of California at Berkeley,
report that NGC 5194 has been monitored as part of the Leuschner
Observatory Supernova Search; SN 1994I was not present to a limiting
R magnitude of about 16.2 on Mar. 28 UT. Preliminary reductions of
data from the LOSS 0.76-m reflector and from the 0.5-m Berkeley
Automatic Imaging Telescope yield the following: Apr. 2.5, B =
14.38, V = 14.00, R = 13.87, I = 13.82; 3.4, V = 13.54, R = 13.43,
I = 13.55; 4.4, U = 13.79, B = 13.97, V = 13.38, R = 13.20, I = 13.19.
1994 April 4 (5963) Daniel W. E. Green
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