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(cba:news) "Winter" stars for Dec-Jan (Joe Patterson) [2019-11-28T15:26:07Z]


Dear CBAers,

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?

joe p

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