(cba:news) "Winter" stars for Dec-Jan
jop at astro.columbia.edu
Thu Nov 28 10:25:59 EST 2019
Many IPs lurking in the sky these nights. There are a few new ones to
report... plus some old ones which have now revealed or should reveal a
period change (due to the torques exerted by the accreting gas). The
latter take at least a few years to detect (white dwarfs have a decently
large moment of inertia), but we've been pounding away for a while, and
the pulses eventually start to arrive EARLY by measurable elements
("early" since most of the white dwarfs are spinning up from the torques).
So I'm preparing a history-of-period-change paper. Some well-placed
stars these days are: V418 Gem*, V902 Mon*, HT Cam*, HZ Pup*, WX Pyx*,
BG CMi, V647 Aur, V1062 Tau*, V405 Aur. I've asterisked the stars I
consider to be not yet "properly published", and therefore I guess
deserving of somewhat higher priority. But the best single measure of
priority is probably determined by the match to your individual
circumstances: brightness, time of night, quality of night, crowded
field, suitable comp, etc.
It's best to choose 1, 2, or 3 of these stars - and specialize in them.
Since the main interest here is *periods*, a clear filter is fine. A
few LONG runs are very desirable, but runs as short as 2 hours are
plenty useful too.
The only really short period here ia 4 minutes (V418 Gem - though it has
a menagerie of other periods which have never been clarified). On that
one, you need to keep the cycle time (observing + readout) below one
minute. This star has a raft of periods - fast and slow - and they've
never been adequately identified, much less understood.
Nearly all of these stars are in Koji Mukai's ("NASA's") page on
intermediate polars, and Lew Cook's re-ordering of it.
I didn't manage to make it to Las Cruces for the AAVSO meeting (been
hobbling around with a torn Achilles)... but maybe someone could write
with a summary of relevant goings-on?
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