(cba:news) august stars

Joe Patterson jop at astro.columbia.edu
Sat Aug 5 04:50:36 EDT 2006

Dear CBAers,

We've gone to a new computer system here at Columbia, and some mail may 
have gotten lost from down time, overenthusiastic spam blockers, etc. So 
  please bear with us, and re-send anything critical.

Two new Sagittarius stars on the menu.  V1830 Sgr has jumped into 
(super)outburst, and is a high-priority target for as long as it stays 
bright. There are no published time series of this star - or unpublished 
either, for that matter.  Secondly, our analysis of June-July CBA 
coverage of V1223 Sgr has suggested a superhump signal in that star, 
which would be awfully important if true (because it would demonstrate 
that tidal instability is not inhibited by magnetic fields).  But our 
data is not sufficiently extensive to clinch the point - we need a 
couple of weeks coverage from all our strong southern nodes (ZA, NZ, AU) 
and perhaps something from the southern USA too.  I think there's still 
time in this observing season to carry out this study.  Sooo... despite 
my previous removal of this star from the menu, couldja put it back - 
with high priority?  The star is about 14th mag and has an obvious 13 
minute pulse as well as a possible 3.6 hr superhump signal; pretty nice 

And it's now time to turn northern telescopes on V Sge, an old CBA 
favorite which we have neglected for about a decade.  This would be a 
fine target for the bright of the Moon, which seems appropriate now.
The main interest is timing the (sometimes subtle) eclipse.  This star 
is very luminous and quite rapidly evolving; the eclipses will yield the 
RATE of evolution, and this will go far to clarify the nature of this 
class of star (more or less the supersoft binaries).

The other all-hemisphere star I wanted to press for is V1494 Aql, which 
is very well placed now if you can get this faint (about 16) with a 
bright moon lurking nearby.  One additional season to yield its 3-hour 
orbital light curve (which changes year-to-year as the star cools from 
the 1999 nova eruption) will complete our study with superb coverage
every year!

I'll write again when I find out whether this even goes out... maybe 
50-50 with the new system - and my inexperience with using it!


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