(cba:news) old and new targets, installment 1

Joe Patterson jop at astro.columbia.edu
Mon Sep 30 23:01:11 EDT 2013


Dear CBAers,

I've mostly finished the analysis of this year's BW Scl data. 
Throughout the observing season, the star showed a 
not-quite-coherent-but-plenty-powerful signal at 17.3 c/d, together with 
its usual orbital signal at 18.41 c/d.  The former differs from common 
superhumps because its period excess of 6.3% greatly exceeds the 
common-superhump excess of ~1.1%.  And for another reason too: because 
it's a characteristic of *minimum* light, not maximum light.  Only a few 
stars show this phenomenon, but they all seem to be pretty similar in 
their underlying structure: very low mass ratio, intrinsically faint, 
very rare eruptions (although the flagship of the class, WZ Sge, does 
not show the phenomenon).

Anyway, Berto, Josch, Gordon, and Bob Rea have been observing the star 
assiduously, and we have an extraordinary long baseline over which to 
track the phenomenon.  So it's enough!

We're also through with PX And.  This star is presently showing a 
positive superhump, as it did in our first campaign in 2000.  However, 
it's quite a bit weaker this year - not promising for us to track 
accurately.  Let's suspend for the year (at least).

Likewise for OT J0045+50.  Very nice star, but the outburst seems to be 
over.  It's possible there will be some echoes.  These are 
interesting... but not usually something *we* can learn much from, since 
time-series photometry during echoes usually shows waves of very small 
amplitude (if detectable at all).  So I'd say we're through with this star.

Likewise for V1494 Aql.  We have the orbital light curve now to high 
precision... as well as for most previous years since the 1999 nova. 
Excellent material for a study of how the orbital light curves evolve.
But we're done now.


There are two evening stars for which we had very successful 2013 
campaigns... and which we should now top off by revisiting for 7-10 more 
days.  These are V1101 Aql and V1432 Aql.  In both cases, we want to 
test for long-term coherence by counting cycles between observing 
seasons - so time series in late 2013 (now) and early 2014 (probably 
May) are the critical need.  Have at it!

Enrique has been managing RX2133+51 and ASASSN-13ck, so I'll let him 
comment on these.  The former is certainly a very mysterious star.

And now for NEW TARGETS, installment 1.

We definitely want to launch campaigns on ES Cet and VZ Scl (assuming 
the latter is in its bright state at ~15.5).  And two stars in the 
morning sky: LT Eri and "Tau2" (designation in the Downes catalog).  We 
observed Mister Tau2 quite assiduously in 2002, and found something 
quite surprising: periodic signals seemingly at nu-orb, nu-orb+eps, and 
nu-orb-2eps.  A bountiful harvest, since it would enable us to track the 
positive and negative superhumps simultaneously (which we have only done 
for one star).  But the result was not quite 100% convincing... and for 
such a 100% interesting star, I needed to reach 100% confidence.  We're 
a better network now - so let's do it.

Installment 2 coming in a day or two.

joe

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