(cba:news) stars for october-november

Joe Patterson jop at astro.columbia.edu
Sun Oct 18 18:36:06 EDT 2015


Dear CBAers,

Time for a new (almost) slate of targets.  Some stars we're quitting on:

1. ASASSN-15po.  Beautiful coverage, but the eruption and aftermath 
appear to be over.

2. HV And.  We have enough for a very accurate measure of Porb; there's 
some evidence of a weak superhump period, but we have enough to evaluate 
that, too.

3. V592 Cas.  Good superhumps, but they've been there most years; 
despite its brightness and great sky position, we're dropping it.

4. AQ Men.  Good coverage - best-ever delineation of its orbital light 
curve.  But the superhump detected (somewhat weakly) in past years 
didn't appear.  Requires some more analysis, but not more data.
The better Men target by far is now AH Men (see below)

5. V455 And.  The various periods are under control; we can quit until 
next year.

*********

The two STRICTLY SOUTHERN targets I want to promote now are BW Scl and 
AH Men.  We've written one paper on each of them, and have assembled 
several seasons of data since then.  Never with three-continent 
coverage, though - let's try for that this year (Africa, South America, 
AU/NZ - you know who you are out there).  BW Scl is basically unique for 
its type of superhump (from the 2:1 resonance I believe).

AH Men seems to show three periods in its light curve - orbit, 
+superhump, -superhump.  That was suggested in one past year's data; I'm 
hoping that increased density of coverage will decisively confirm or 
refute that.  AH Men is plenty bright, but the last time I saw it, it 
had a contaminating star just 4 arcsec away.  You'll need to adopt some 
strategy to cope with this.  I'd have thought that using a wide aperture 
and including both stars cleanly would be the best technique... but this 
might be a subject for cba-chat.  It's pretty desirable that we all 
agree on a method, since the light curves will get spliced.

Then there's IM Eri - moderately southern at -20 degrees, but plenty 
bright (about 11.5).  It would be very nice to get a good longitude 
spread in our data.  So far, Josch Hambsch is the principal observer...
and at this brightness and non-extreme dec, I hope for 3-continent 
coverage.  Well placed in Oct-Nov.  At that brightness, a V filter might 
be advisable.

CD Ind is another.  Season's about over... but Gordon Myers is working 
on this, and may want another few runs to complete his collection for 
analysis.  Gordon?

*******

There are two new EQUATORIAL stars I want to commend:
LT Eri.  Great target, lots of fun.  Eclipses and superhumps.  Let 'er rip.
V1294 Tau.  We only observed it one season, in 2002... and appeared to 
find 3 closely spaced periods: orbital + 2 flankers, which I took to be 
the positive and negative superhump (simultaneous).  Is that really 
correct?  There are no other cases of novalikes doing that, and it would 
be great to confirm or exclude it.  I admit this is a tad greedy of me; 
none of the signals were very strong, and the light curves won't be 
suitable for sending to Mom.

And another equatorial: ES Cet.  We do this every year to lengthen the 
baseline for measuring Pdot, since that is the vital number to test the 
hypothesis of gravitational radiation as the driver.  With a period of 9 
minutes, Mom might like this one.

*********

And some strictly northern guys:

RW Tri.  Last year, for no really good reason, I asked for a campaign on 
UX UMa.  To my amazement, it showed beautiful superhumps, and our 
coverage was whatever is the next superlative beyond beautiful.  It was 
a helluva surprise.  So now I want to test some other out-of-the-blue 
novalikes which theory *also* (like UX UMa) suggests should not show 
superhumps.  It's RW Tri season, let's do that one!  Long runs please 
(and be warned, it's a deep eclipser).

BZ Cam.  Great results last year. Let's see what it does for an encore. 
  The observing season is very long for us borealites, so we might be 
able to actually stretch across the gap between seasons - if the 
superhump is stable enough.

FS Aur.  Still a mystery with two stable periods - photometric (3.5 hrs) 
and radial-velocity (1.4 hrs).  We probably won't figure this guy out, 
but we should keep trying.  We're the only hope for testing whether the 
photometric period is truly stable on very long timescales (decades).


*********

Finally, there are the DQ Hers, always in season and feasible for fairly 
short observations (2-3 hrs).  AO Psc, V647 Aur, and V1033 Cas would 
come in handy.

Back to the textbooks.  This semester's class is wearing me down!

joe
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