SUPERNOVA 2004et IN NGC 6946
T. Zwitter, University of Ljubljana; and U. Munari,
Astronomical Observatory, Padova, report the discovery by
S. Moretti, on unfiltered CCD images taken on Sept. 27 with
a 0.4-m telescope at Ravenna, of a bright supernova (mag 12.8)
in NGC 6946. The new object is located at R.A. = 20h35m25s.4,
Decl. = +60o07'17".6 (equinox 2000.0). A high-resolution
spectrogram, secured on Sept. 28 with the echelle spectrograph
at the 1.82-m telescope in Asiago, shows a relatively featureless
spectrum with a very broad, low-contrast H_alpha emission. Sharp
interstellar Na I absorption lines are observed at heliocentric
radial velocities of -21.1 (+/- 0.7) and +45.2 (+/- 0.4) km/s,
matching expectation for separate origin within our galaxy and
NGC 6946. The equivalent width of Na I D2 lines corresponds to a
total reddening of E(B-V) = 0.41 mag, following the calibration by
Munari and Zwitter (1997, A.Ap. 318, 269). |