(cba:news) xmm1151-62, mainly

[Joe Patterson]

Dear (mainly southern) CBAers,

   In 2010 we thought we had this guy figured out.  The star reached 
10th mag in 2008, and was a pretty strong (super?)soft X-ray source in 
2010, when it had declined to mag 13.8.  It was referred to as "Nova Cen 
2008"... and we didn't have any major gripe about that, although we 
preferred a "V Sagittae" model, based on the (likely) Porb and spectrum. 
  Here are some useful links and a finding chart:

http://www.astro.columbia.edu/~jules/XMMUJ115113.3-623730/

   Josch and Berto have been observing this star pretty often in the 
last month.  It's now down to about 15.4... and shows some waves in the 
light curve, but with no obvious period.  I'm pretty surprised by this! 
  It doesn't agree with other stars in this class, and I'm reluctant to 
let go of the idea that our 8.6 hr period in 2010 was Porb, or at least 
some important, persistent signal in it.  That would force us to 
re-think some of our ideas about V Sge - and I'm really fond of those ideas!

   So I hope that you australites out there will observe this star long 
and often in the next few weeks.  The best comparison star is the AAVSO 
star AUID 000-BJV-892, with a nominal magnitude of 11.3... and if that 
is unsuitable, then AUID 000-BJV-893, with a nominal magnitude of 11.5. 
  As usual, unfiltered is fine, but V is better, mainly because it 
minimizes differential extinction.

   An HST observation of QZ Lib = ASAS1536-08 is coming up... and, for 
all the usual reasons, observations of it are now critical.  However, 
unlike the other stars on Boris's program, this one can really use time 
series.  At 18th mag, that will be difficult - but if you have decent 
aperture and observing conditions, give it a try!

Finally, at the other end of the brightness axis, we still could use 
observations of EX Hya for another 1-2 weeks.

joe