亮超新星2004et 12.8等
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). 今晚用20cm牛反看到. 比较暗但不困难.
http://www.rochesterastronomy.org/supernova.html#2004et
各照片上SN(中间)和前景星成一个小箭头
: . .
城市中, 有月光干扰. 我只看到SN和左边一颗暗星. 我看不懂英文，是NGC6946里的吗？
NGC6946上世纪有6个超新星了。 是
AAVSO http://www.aavso.org/cgi-bin/searchcharts3.pl?name=ngc%206946
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