(cba:news) august stars

Joe Patterson jop at astro.columbia.edu
Wed Aug 15 09:54:31 EDT 2007

Dear CBAers,

Many apologies for my long silence.  It has been an arduous summer, 
mostly from my father's long illness and eventual death.  The head is 
starting to clear now, and I look forward to getting back to minding the 
CBA store.

Several campaigns have reached successful conclusions.  I've succeeded 
in tying down all 25 years of V1223 Sgr timings with a simple 
constant-Pdot ephemeris, and that means we can leave this star alone for 
at least a few years... and publish the result simply and promptly.
Likewise, we've covered V1494 Aql during the last five years, and have 
excellently covered the change in orbital waveform (which changes 
year-to-year, but no faster).  That's another one scheduled for rapid 
and simple publication.

It's also time to end the V533 Her campaign.  That one is still puzzling 
me... but it needs to step aside for bigger fish to fry.

In the north, there are now two dwarf novae urgently needing a 
time-series photometry campaign.  V1006 Cyg and MN Dra.  Both appear to 
have orbital periods roughly in the period gap, and superhump 
measurements will nicely test our understanding of what happens in this 
Porb region, which is still so dimly understood.  Pick one and observe 
it for a few weeks!  MN Dra gets very faint in quiescence, but we'll try 
to pick up any slack with large-scope data if needed.  V1006 Cyg you 
might be able to track all the way to quiescence.

The third important northern star now is RX1803+40, a little-studied DQ 
Her star.  Good backup for the two erupters.  A second-priority backup 
is V Sge, whixh is a good target for poor nights, since at 11.5 it's 
mighty forgiving.

No major erupters in the south right now.  The V1432 Aql campaign is 
worth continuing; we want to measure the synchronization rate of this 
"asynchronous AM Her".  In principle we need ~50 days to make the 
measurement - the beat between Porb and Prot.  In practice, probably ~35 
d will suffice to pin down the phase.

I recommend two new stars in Indus.  EC2117-54 is a nice CV eclipser 
about which nothing has yet been published.  Another season of data, and 
let's us do it.  And CD Ind, a local and fairly famous AM Her star.  We 
want to carry out brief campaigns on many AM Hers to test limits of 
synchronization.  Most AM Hers are forgotten once they are declared 
synchronized, though the data certifying that sometimes only spans a 
couple of weeks.  With CBA levels of patience, we can apply much more 
stringent tests.  Who knows, we may find that small amounts of 
asynchronism are actually common among these stars!

And finally there's Oph = RX1730-05.  Still trying to time that 128 s 

That's a pretty wholesale revamping of the CBA sky.  Have a great ol' 
time observing these stars!


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