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THE ASTRONOMER Electronic Circular No 2327      2007 Apr 14 19.53UT
Ed:Guy M Hurst, 16,Westminster Close, Kempshott Rise,  Basingstoke,
Hants, RG22 4PP,England.Telephone/FAX(01256)471074Int:+441256471074
INTERNET: GUY@TAHQ.DEMON.CO.UK      Backup: gmh@wdcc1.bnsc.rl.ac.uk
WORLD WIDE WEB                         http://www.theastronomer.org
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BZ URSAE MAJORIS
Aaaron Price, AAVSO, reports that this cataclysmic variable is currently 
experiencing an outburst which is peculiar for this star. Historically, 
BZ UMa has outbursts every 312 +/-114 days. These outbursts are similar 
to regular UGSU outbursts with a fast rise and a short decay over four 
days and are absent of any superhumps or other periodicity. However, no 
superoutbursts of the type also associated with UGSU stars have been 
detected in BZ UMa despite good observational coverage since 1972.

The current outburst began on 2007 April 10 which is about the
expected time for its next outburst. However, instead of a fast rise 
typical for BZ UMa, it has continued to slowly rise after four days and 
has already reached magnitudes brighter than normal for its other 
outbursts. Also, preliminary data analysis by M. Koppelman shows the 
possibility of superhumps emerging. It is seeming more and more likely 
that this is the long awaited first detected super outburst.

AAVSO charts can be found at:


      http://www.aavso.org/cgi-bin/searchcharts3.pl?name=0846%2B58



GW LIBRAE
Further to the note on TA E-Circular 2326, Andrew Pearce, Western 
Australia, advises that this variable has brightened considerably 
reaching magnitude 8.3v by April 14.604UT.

S. Narusawa et. al., Nishi-Harima Astronomical Observatory and others 
report on CBET 923 that low-resolution spectra of GW Lib were obtained 
on Apr. 12UT (before maximum light) with the 2.0-m NAYUTA telescope + 
MALLS (range 410-670 nm; resolution 370 at H_alpha) under hazy 
conditions.  The low-S/N spectra show absorption lines of the Balmer 
series (equivalent widths of H_alpha and H_beta are 0.6 nm and 1.13 nm 
on Apr. 12.677, and 0.5 nm and 0.8 nm on Apr. 12.758), supporting the 
classification of GW Lib as a dwarf nova.

Guy M Hurst