Central Bureau for Astronomical Telegrams
IAUC 8413: 2004et
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 8414
.dvi or
.ps format.
Circular No. 8413
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
CBAT@CFA.HARVARD.EDU (science)
URL http://cfa-www.harvard.edu/iau/cbat.html ISSN 0081-0304
Phone 617-495-7440/7244/7444 (for emergency use only)
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.33, Decl. =
+60o07'17".7 (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 D_2 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).
H. Yamaoka, Kyushu University, reports that K. Itagaki (Teppo-
cho, Yamagata, Japan) found nothing at the location of SN 2004et on
an unfiltered CCD image taken on Sept. 19.655 UT with a 0.60-m
reflector (limiting mag 18.5). A. Klotz, C. Pollas and M. Boer,
Observatoire de Haute Provence, report R magnitudes for 2004et,
obtained with the robotic TAROT telescope: Sept. 19.989, [19.2 +/-
0.45; 21.021, [17.6 +/- 1.3; 22.017, [19.4 +/- 1.2; 22.983, 15.17
+/- 0.16; 25.978, 12.7 +/- 0.3; 27.035, 12.8 +/- 0.4; 27.974, 12.2
+/- 0.1; 28.092, 12.6 +/- 0.5.
W. Li and A. V. Filippenko, University of California, Berkeley;
and S. D. Van Dyk, Infrared Processing and Analysis Center,
California Institute of Technology, report that SN 2004et was
imaged on Sept. 30 UT with the 0.76-m Katzman Automatic Imaging
Telescope (KAIT) at Lick Observatory, yielding position end figures
25s.37, 17".8 (equinox 2000.0; uncertainty about 0".2 in each
coordinate). A faint object, possibly extended, appears at this
location on multi-band images of NGC 6946 taken with the Kitt Peak
0.9-m telescope on 1989 May 30. Based on calibrations of the field
on three photometric nights with the Lick Nickel 1-m telescope,
they measure the object at R = 20.8 +/- 0.2, adding that it was not
detected in the Kitt Peak B- and I-band images (B > 21.3, I > 19.7).
Using a distance of 5.5 Mpc to NGC 6946 (Shapley et al. 2001, Ap.J.
Suppl. 137, 139), and E(B-V) = 0.41 mag (from Zwitter and Munari,
above), the absolute magnitudes of the object are M_B > -9.1, M_R =
-8.9, and M_I > -9.7. The high luminosity makes it likely to be a
star cluster rather than a single star. Unfortunately, there do
not appear to be Hubble Space Telescope or KAIT pre-explosion
images of the site of SN 2004et.
(C) Copyright 2004 CBAT
2004 September 30 (8413) Daniel W. E. Green
Read IAUC 8414
.dvi or
.ps format.
Our Web policy. Index to the CBAT/MPC/ICQ pages.
