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IAUC 8633: 2005gj

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IAUC number

                                                  Circular No. 8633
Central Bureau for Astronomical Telegrams
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
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     J. Prieto, Ohio State University (OSU); P. Garnavich,
University of Notre Dame; and D. DePoy, J. Marshall, J. Eastman,
and S. Frank, OSU, on behalf of the SDSS-II Supernova Collaboration,
report that spectra (range 390-730 nm; resolution 0.31 nm/pixel) of
SN 2005gj (cf. CBET 247, IAUC 8616) were obtained with the MDM
2.4-m telescope (+ CCDS) approximately once per week since its
discovery.  Initially classified as a type-IIn event based on the
presence of resolved Balmer emission, the spectrum has evolved to
show broad absorption features at about 440, 475, 510, and 610 nm
(rest-frame for z = 0.062), while the Balmer emission lines remain.
The spectrum obtained on Nov. 12.3 UT is remarkably similar to the
spectrum of the peculiar type-Ia supernova 2002ic (cf. IAUC 8019,
8151, 8157, 8161) obtained on 2002 Dec. 27 (Hamuy et al. 2003,
Nature 424, 651).  It is concluded that SN 2005gj is a 1991T-like
type-Ia event interacting with circumstellar material and giving
rise to the resolved emission lines on top of the characteristic
type-Ia spectrum.  This is the second clear detection of hydrogen
in the spectrum of a type-Ia supernova.  The preliminary SDSS-II
light curve indicates that it has just passed maximum light (at
magnitude r about 17.2).  The study of SN 2005gj at all wavelengths
is urged, as such data could help to understand better the nature
of the progenitors of thermonuclear supernovae.
     S. Immler, Goddard Space Flight Center (GSFC), NASA, and
Universities Space Research Association; R. Petre, GSFC; and P.
Brown, Pennsylvania State University, on behalf of the Swift-
satellite team, report on Swift Ultraviolet/Optical Telescope
(UVOT; wavelength range 170-650 nm) and X-Ray Telescope (XRT;
energy range 0.3-10 keV) observations of SN 2005gj obtained on Nov.
24.181 UT.  A new source is detected at R.A. = 3h01m11s.91, Decl. =
-0o33'13".2 (equinox 2000.0), when compared to Digitized Sky Survey
images -- consistent with the reported Sloan Digital Sky Survey II
position in CBET 247.  UVOT magnitudes are V = 17.5 (641-s
exposure), UVW1 [181-321 nm] = 19.1 (80 s), UVM2 [166-268 nm] =
20.0 (1272 s), and UVW2 [112-264 nm] = 19.5 (2847 s); statistical
and systematic errors are 0.1 mag each.  No x-ray source is
detected at the position of SN 2005gj in a simultaneous 4695-s XRT
observation.  The 3-sigma upper limit to the (0.3-10-keV band)
count rate is 1.85 x 10**-3 counts/s, corresponding to an x-ray
flux of 1.06 x 10**-13 erg cm**-2 s**-1 for an assumed thermal
plasma spectrum with a temperature of 8 keV and an absorbing
foreground column density of 7.08 x 10**20 cm**-2 (Dickey and
Lockman 1990, ARAA 28, 215).

                      (C) Copyright 2005 CBAT
2005 November 24               (8633)            Daniel W. E. Green

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