(cba:news) New and old DQ Hers, plus wannabes

Joe Patterson jop at astro.columbia.edu
Thu Jan 16 08:28:50 EST 2014


Dear CBAers,

Lots of clear weather in AZ, and we seem to be spending a lot of time on 
DQ Her stars and candidates.

1. HZ Pup has a great light curve, but we lack the off-longitude data to 
nail the periods down.  Also, we've stopped observing it, so time series 
from the Americas are now plenty helpful too.  Around mag 16.5.

2. PBC J0706.7+0327 (7h6m48.89s +3d24m45.0s) is a peachy candidate DQ: 
possible period near 5 minutes. Around mag 17.

3. Swift J0503.7-28 (5h3m49.2s -28d23m9s) looks promising too; not as 
swift as PBC0706, but sumpin' near 16 minutes.  Around mag 17. In 
Caelum.  I always wondered why such a miserable little constellation had 
such a regal name (heaven) - but apparently it just means "chisel".

4. V455 And.  Kinda late for Andromeda, but we're building a nice record 
of the 67/34 s oscillations, which will be ideal for a test of their 
stability.  Our run ends on Sunday.  If you can possibly resolve at 
least one of these signals (total cycle time less than 15-20 s), the 
timing data would be great.

5. The bible for these stars is Koji Mukai's page:
  http://asd.gsfc.nasa.gov/Koji.Mukai/iphome/iphome.html
I can't stress this (website) enough.  The most promising 
not-yet-credentialed stars, feasible for CBA tracking, are FS Aur, 
Paloma (0524+42) and GI Mon.  The most promising for tracking the known 
spin pulse are DW Cnc, WX Pyx, and EX Hya.  And, in general, Koji's 
website is a great place to sniff around in.

Although you might think you need long integrations to get good S/N near 
mag 17, remember that the main enterprise is period-finding, which 
depends much more on cumulative S/N.  The light curve might have an ugly 
0.1 mag noise band superimposed on it, plus intrinsic flickering 
noise... yet still easily detect a signal of 0.02 mag.  For the most 
famous periodic variable in the sky, the Crab pulsar, most integrations 
in radio/optical/X-ray light yield ZERO photons, corresponding to zero 
S/N and magnitude infinity; but in a few seconds or tens of seconds, the 
period comes roaring through.

Corinthians says that three things last forever: faith, hope, and love. 
  Love is obvious: you have to love night-sky observing and trolling for 
periodic signals, or you wouldn't be reading this.  Likewise for hope - 
why else suffer the indignities of observing?  And after some experience 
squinting at these little wiggles in light curves and pressing buttons 
on laptops, you develop some serious faith.

joe

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