Central Bureau for Astronomical Telegrams

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IAUC 7675: 2001dk; 2001dl; WZ Sge

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                                                  Circular No. 7675
Central Bureau for Astronomical Telegrams
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
URL http://cfa-www.harvard.edu/iau/cbat.html  ISSN 0081-0304
Phone 617-495-7440/7244/7444 (for emergency use only)

     G. M. Hurst, Basingstoke, England, reports the discovery of an
apparent supernova (mag 15.6) by T. Boles (Coddenham, England) on
an unfiltered CCD image (limiting mag about 18.5) secured for the
U.K. Nova/Supernova Patrol on July 29.959 UT with a 0.36-m Schmidt-
Cassegrain telescope.  Nothing was visible on Boles' CCD image from
1999 Sept. 22 (limiting mag 18.5).  The new object is located at
R.A. = 1h22m14s.59, Decl. = +34o40'11".3 (equinox 2000.0), which is
5" west and 3" north of the nucleus of UGC 913.  M. Armstrong
(Rolvenden) confirmed the presence of SN 2001dk at about the same
brightness on a CCD image taken on July 31.039, which yielded the
following position end figures:  14s.50, 11".4.

SUPERNOVA 2001dl IN UGC 11725
     C. Yu and W. D. Li, University of California at Berkeley,
report the discovery by LOTOSS (cf. IAUC 7514) of an apparent
supernova in unfiltered images taken with the Katzman Automatic
Imaging Telescope (KAIT) on July 30.4 (mag about 17.1) and 31.3 UT
(mag about 17.0).  The new object is located at R.A. = 21h21m01s.73,
Decl. = +9 10'50".4 (equinox 2000.0), which is 1".8 west and 10".6
north of the nucleus of UGC 11725.  A KAIT image taken on July 25.4
showed nothing at this position (limiting mag about 19.0).

     D. Steeghs and T. Marsh, Southampton University; E. Kuulkers,
Space Research Organization Netherlands and Utrecht University; and
W. Skidmore, University of St. Andrews, on behalf of a larger
collaboration, report:  "Strong spiral waves are present in the
accretion disk of WZ Sge during the first week of its outburst
(IAUC 7669, 7670).  Phase-resolved spectroscopy, obtained between
July 28.02 and 28.24 UT with the 2.5-m Isaac Newton Telescope (+
CCD spectrograph) at La Palma, yielded 2411 spectra (resolution
5700) covering four binary orbits that were used to construct
Doppler tomograms showing the distribution of line emission in the
binary frame.  The He II (468.6 nm) and C III (464.7 nm) images
reveal that the accretion-disk emission is dominated by two spiral
arms.  The H-beta and He I (492.1 nm) lines, on the other hand, are
dominated by highly variable absorption cores.  This is the first
time that spiral arms have been observed in WZ Sge, making it also
the first low-mass-ratio cataclysmic variable that displays spiral
arms in its disk during outburst.  We encourage follow-up
spectroscopy to track the evolution of these structures."

                      (C) Copyright 2001 CBAT
2001 July 31                   (7675)            Daniel W. E. Green

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