The International Astronomical Union has issued a notice on a new variable star in M27, originally reported by the AAVSO on August 23, 2005. This one has dimmed from 13 down to 15-17 mags in the last week - so by now it's probably only a large aperature scope object. The nature of this new variable is unknown but is suspected to be a very long period (decades) cataclysmic variable - a drawf sucking accreted material off of a late stage main-sequence star. It may be useful to check your photos of M27 taken in the last few weeks for this rare variable outburst. AAVSO Alert 325 (8/23/2005) for 1955+22C VAR VUL 05 http://www.aavso.org/publications/alerts/alert325.shtml "CCD observers are urged to look for superhumps and possible WZ Sge-signature behavior to help confirm nature of this star." AAVSO Chart (f) photo http://www.aavso.org/cgi-bin/shrinkwrap.pl?path=/charts/VUL/VAR_VUL_05/VARVU... IAUC 8591 (8/29/2005) http://cfa-www.harvard.edu/iauc/RecentIAUCs.html (registered ip addresses only)
From the AAVSO website on what a WZ Sge variable star is:
"WZ Sge and SU UMa, like all cataclysmic variables, are close binary systems consisting of a late-type star that fills its inner Lagrangian surface (stability limit for two components) and transfers material onto an accretion disk formed around the companion white dwarf." "The period of time from one superoutburst to the next is called the 'supercycle'. The supercycle lengths of the known SU Uma stars are mostly around a few hundred days, but a few systems have much shorter or much longer supercycles. The short-supercycle systems have become known as ER Uma stars, while the long-supercycle systems are called WZ Sge stars. ER Uma stars typically spend a third to half their time in superoutburst, with a supercycle of only 20-50 days. When not in superoutburst these stars show frequent 'normal' oubursts - about one every 4 days. In contrast, WZ Sge stars have supercycles that last decades, while normal outbursts are few and far between. WZ Sge itself has had a superoutburst at intervals of about 33, 32, and 23 years, and it has never been seen to undergo a normal outburst. Other WZ Sge type stars include AL Com and EG Cnc which have superoutburst intervals of approximately 20 years." http://www.aavso.org/vstar/vsots/0901.shtml - Canopus56 ____________________________________________________ Start your day with Yahoo! - make it your home page http://www.yahoo.com/r/hs