(cba:news) stars for august

Joe Patterson jop at astro.columbia.edu
Fri Jul 30 17:05:46 EDT 2010

Dear CBAers,

That "AM/DN" star in Centaurus has stirred up some fuss.  A quite 
fascinating spectrum is getting passed around; it shows very, very high 
excitation, proving that the star is still a very intense source of soft 
X-rays.  And that's consistent with the X-ray results too (although 
there is currently no X-ray telescope sensitive to *very* soft X-rays, 
the X-ray spectrum basically corroborates this).  I say "still" because 
the star first erupted a long time ago, I believe greater than a year.
It's very, very desirable (hey, I'm begging) to obtain an orbital light 
curve before Centaurus disappears completely into the western twilight. 
Chris Stockdale (AU) has obtained 3 nights, and Berto one short one. 
I'm hoping that combining AU/NZ data (basically Auckland to Perth) with 
ZA data will clinch the period solution.  It's a big variation, I think 
about 13.8 to 14.5... and Chris's data suggests a period around 5 hours
(but aliased - single-observer data will certainly be aliased this time 
of year).

BTW the star is at 11 51 13.06
                    -62 37 29

For northern objects, scratch V1315 Aql and V603 Aql.  The coverage was 
good, but basically verified that the stars are up to their usual tricks 
- negative and positive superhumps, respectively.  I'll bundle the new 
data in with the old... but not much promise of novelty this year.

HS1813+61 looks more promising.  This year's campaign is nowhere near as 
thorough as 5 years ago (we're not getting the looonnng nightly runs), 
but it does look like the star is *probably* sprouting negative and 
positive suoerhumps simultaneously.  That's well worth exploring - so 
leave it on the list.

The northern object I'd like to promote most heavily is WZ Sge.  It's 
now 9 years since the last eruption.  We have *never* - nor has anyone 
else - had a concerted campaign at quiescence, and everything you learn 
about WZ Sge pays off quadruply, because there is so much else known 
(including a very precise distance).  It's definitely Sagitta season, 
and at V=15 it's a reasonably easy target for most CBAers on decent 
nights (but watch out for the intruder star 12 arcsec away).

Then there's the DQ Hers, nice targets for tracking period changes.  A 
short run (2 hr or so) usually does the trick, though longer is always 
better.  I'm hoping to include 2010 data in an omnibus DQ Her paper at 
year's end.  Here are the guys:

V1223 Sgr
V2306 Cyg
V4743 Sgr
AO Psc
FO Aqr
IGR 0023+61 (Cas)

Thanks, and happy observing!


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