(cba:news) stars for may-june

Joe Patterson jop at astro.columbia.edu
Wed May 22 07:57:14 EDT 2002

Hi Berto (and CBAers),

It's too early for me to figure out much from that stretch of light
curve... but the object sure looks interesting enough to follow!

So we have kind of a crisis in the southern morning sky these days.  V2051
Oph is still in outburst and still producing great humps and eclipses...
we have a lot invested and it would be awfully nice to keep going.  It
will surely teach us a lot about the timescale for superhump demise (which
has become a potent constraint on theories - last year's flavor said "they
die when the superoutburst dies", but one popular flavor this year
says "they last forever").

That V4641 Sgr is interesting needs no explanation.

Then there are round-the-world campaigns we want to trigger soon on V603
Aql and especially V1494 Aql.  Oh, how we love these equatorial stars!

Finally there's V803 Cen, still well placed and having not yet completed a
full supercycle.  That's what we seek - coverage of a full supercycle.  I
imagine we're around 70% of the way through it - but we dunno without
keeping the vigil.  Anyway I think it's *really* important to get
occasional potshots (few a night maybe - that's Stan Walker's pace) at
its present low light level - before resuming some normal time series
early in the next super.  That would be a good time to say goodbye.
If for example we could cover it enough to know what the outburst
repitition time is at 17th mag (i.e. the 17->14 burps), that would be
outstanding - the only dwarf nova in the sky where we can measure
recurrence time at two different brightness levels (17 and 14.5 - what a
grand experiment)!

Anyway since V4641 Sgr is bright now and the lure of the unknown is great,
I guess we should work pretty hard on it for now.  Early evening is still
good for V803, and we can keep the Aquila boys at bay for a few weeks.
So that's good. V2051 Oph will definitely suffer, and I just hope you
australites can find a way to keep its suffering minimal.  Maybe a couple
of you (Bob Rea maybe?) can keep the faith on Oph...

Looking forward to meeting many of you at Photometry 2002 in NZ in

It's simpler in the north.  The campaign on RX1643+34 is wonderful beyond
words.  I'll try though.  Captain Bob and Ed Beshore (CBA-Colorado) have
come roaring back into action, and Dave Skillman, Brian Martin, and Tonny
Vanmunster have kept up a withering barrage.  We've identified the orbital
period, the (negative) superhump period, and the wobble period (3.9 days).
All very nice.  But the most interesting thing is the 1000 s QPOs, which
everyone observing the star gets drawn to - they're very strong, very
distinct, and sometimes look pretty damn coherent.  With 42 nights of
coverage (now up to ~55), the mean power spectrum shows the basic story I
think.  The main signal is a broad QPO covering 60-110 c/day.  That's
responsible for the obvious large-amplitude flickering.  But in that
broad signal appears to be a stable peak at 82 c/day, a feature that may
enable precise timing over the 2-month campaign (jury still out on that

The bottom line I think is to go for ~1-2 more weeks on RX1643, when I'll
reevaluate.  It would be nice if one of the borealites would start up the
campaign on V795 Her though... another bright novalike with powerful
and relatively stable superhumps (which have just returned to action after
a 10-year vacation).


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