(cba:news) stars for mid-June

Joe Patterson jop at astro.columbia.edu
Sun Jun 15 13:45:09 EDT 2008

Dear CBAers,

The Junebugs are out, olde whiteface is back, and it's time to roll the 
target stars.

1. GW Lib has been a treasure trove! I've learned a lot about the 
mysterious 2.1 hr variation:

* it's actually a 4.2 hr signal;
* it's a poor clock, wandering in phase over a few days;
* its amplitude is highly variable on a timescale of a few days, and
   possibly varies in (anti)sync with the amplitude of the 20 min

And the star shows a rich pulsation spectrum - not much correlated with 
the signals present prior to the outburst.

It's a great star and beautifully placed for all australites, except a 
few days (like now) each month.  I'm sure it will continue to be very 
rewarding for at least another month.

2. Late in these southern winter nights, V1432 Aql and CD Ind are very 
attractive targets.  These are 2 of the 5 known "BY Cam stars", in which 
a slowly rotating white dwarf gradually synchronizes with the orbit. 
We're in a privileged position to watch this synchronization - so let's 
do it!

As for northern targets:

1. Delete MV Lyr.  I'm still not sure if the orbital signal showed up in 
the last month's coverage.  If so, it was too weak to do much with. 
I'll finish the analysis when I get back from Italy.  But for the rest 
of 08, let's ditch it.

2. SDSS1627+12.  Nice dwarf nova outburst, nicely covered.  Seems to be 
back down though... so that seems to be the end.

3. V2491 Cyg.  Worth a try... but Bob Koff got 5 straight nights, and no 
periodic signals appeared.  This star is apparently not yet inclined to 
yield its secrets.  Maybe in the (northern) fall, or next year.

4. GW Lib.  If you're decently southern and not too bothered by 
moonlight, please do this star.  The USA especially fills in the ZA-NZ 
gap, and global coverage is VERY DESIRABLE to track these complex 
signals.  If you explicitly show airmass (in a third column, say), then 
I can make an airmass correction - up to about 2.8 airmasses.  (Beyond 
2.8 airmasses, I wouldn't recommend going; I susually say 2.2, but I'm 
greedy here.)

5. RX1813+61 = Dra.  Very handsome negative superhumper, nicely placed 
in the sky.

Plus two equatorial stars:  RX1730-05 and V1494 Aql.  The former has a 
very fast periodic signal; see if you can 20 s time resolution or 
better.  The latter has a 3.5 hr wave that looks different every year, 
as the hot white dwarf cools. Let's find out what it looks like this year!

I'm off to Italy for about 10 days.  I hope to find some email 
connectivity;  the chance of reading email is probably good... the 
chance of replying (except maybe in monosyllables) not quite as good. 
But this is a good menu - and Jonathan can handle any CBA biz.


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