(cba:news) stars for june

Joe Patterson jop at astro.columbia.edu
Tue Jun 16 10:02:17 EDT 2009

Dear CBAers,

Time for some (northern) spring cleaning.  The raft of March-April AM 
CVn stars have swung too far over to the west, and the dwarf novae are a 
little quiet these days.  Here's a few tantalizing new stars which are 
well placed for observation during June nights.

V4743 Sgr.  Berto has just opened the season on this guy (now about 16.5 
I think), the remnant of N Sgr 2002.  The spate of periods that the star
showed a couple of years ago still lingers - in fact seems to have 
become a little more intricate - and this new season gives us an 
opportunity to study 'em in great detail.  A great, great target for all 
southern observers... and maybe a few intrepid northerners as well.

V442 Oph.  After many years at magnitude 14, this star apparently has 
declined to V=17, and it's vital that we obtain time-series photometry 
in this low state.  The origin of low states in these stars (the SW Sex 
stars) is still not known, and Nature doesn't offer many opportunities 
to find out, since the low states are very rare.  Get thee to a 
telescope!  At a dec of -17 degrees and transiting near local midnight, 
it's decently placed for most observers, and excellently placed for 

For flat-out northern objects, I recommend one very bright star 
(RX1643+34, mag 12.7) which still has not quite (almost, though) yielded 
to our superhump search, and which has also shown some evidence of a 
rapid period - or maybe just an oddly stable QPO.  Still some annoying 
mysteries there.  It's also DQ Her season again - ESPECIALLY if you can 
take data with around a 15 second time resolution (which will easily 
resolve its 71 second signal).


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