(cba:news) OY Car and CN Ori: Toys for Australites

[Joe Patterson]

Dear CBAers,

The South will rise again!

(For unAmericans, this is a motto of the U.S. South, sort of a
rallying cry if you're still grumbling about losing the Civil War.  In
our case the meaning is much less sinister, just referring to the
extraordinary stellar fireworks hiding out in Ultima Thule this
season.)

Anyway, Rod Stubbings' report indicates that OY Car has gone into
outburst (at about 12.0).  As another deep-eclipsing dwarf nova, it too
promises great rewards from extended photometric coverage of the
outburst.  Not yet clear if it's a super, but whether or not, calls for
long coverage from our southerners.  Fire at will.

Speaking of which, it's time to pull the plug, mostly, on CN Ori.
I received a fair chunk of data this year from Marc Bos, Robert Rea,
and Maria Marsh (Kiwis all), and some also from James Hannon (Yank).
Some also from Gordon in the pipeline.  No really long spliced light
curves, but enough to reach two conclusions:

1. The modulation at minimum light is very strong (~0.6 mag) and has
a period in the range 0.1628-0.1634 d.  Despite its strength, I just
could not find an acceptable phasing from year to year.  In part this
is due to the star's excessively frequent jumps into outburst
(making sparse the quiescent data set) - but even so, I really expected
to find a unique precise period from the timings, and didn't.  It's
possible that this is actually not a completely stable phenomenon.

2. During outburst, there are small waves of a similar period, but they
resist any simple attempt to connect them to the (more stable but
perhaps not infinitely so) quiescent waves.  In the one season of very
extensive coverage (1995-6), a power spectrum revealed two signals:
a 0.1629 d signal usually identified as Porb, and another at 0.171 d.
Normally this would be termed a superhump, and I've occasionally called
it that (informally - none of this is published).  But it was slightly
weaker than Porb, and a German paper from the 1980s suspected a signal
at the same period *during quiescence*.  Mighty peculiar, not quite
like anything we've seen before (though V503 Cyg fans might have a few
thoughts).

We need two more advances to lead us out of this quagmire: enough
spectroscopy to tell us the true Porb to 4 decimal places (Tim and/or
John, this is your homework), and a long photometry campaign next year
which doesn't get distracted by other celestial poppings-off.  For the
rest of this season, CN Ori is good to do IN QUIESCENCE ONLY - the
eruption data isn't useful unless we have many long runs, and that we
are giving up on.  Timings of the wave in quiescence will be very
useful, though.

For borealites, the same stars remain top-drawer: SW UMa, BY Cam, U
Gem.  DW UMa fans might want to take a peek and see where the star is
hanging out these days; it's likely to be a big-time target in March.

Happy observing.  Dave East wins the prize re 53.  It hath no factors,
hence I be in the prime of life for one more year.


             joe