(cba:news) v1674 Her: a lesson in speed (Joe Patterson) [2021-09-07T15:57:27Z]

Hi CBAers,

I've been spending a few weeks studying the periodic signals of thiis 
ultrafast nova - Herculean in speed as well as sky location.  It's 
remarkably willing to cough up its secrets to time-series photometry. 
There are two stable signals in the light curve, at 3.67 hours and 8.36 
minutes.  At or near quiescence, no big deal; we've seen a few of these 
before in novae.  But I thought it remarkable that this behavior 
occurred 4-8 magnitudes above quiescence.  We'll need to really lean on 
the physics to understand THAT.

I didn't spend much time on the earliest phases, because our data is 
pretty sparse; the nova is so fast, and it takes a while to get a 
campaign going.

But I finally got around to studying those first ten days of outburst. 
The nova flashed on June 12, and our coverage starts June 15.  The first 
three days included data from Tonny (of course), Ken Menzies, and 
Michael Richmond.  I was astounded to see a very large amplitude signal 
seemingly in agreement with the 3.67 hr period, but definitely 180 
degrees out of phase with it.

Very provocative.  In the following ten weeks the star settled down to a 
waveform reminiscent of T Pyx and many (maybe all) supersofts. In the 
remaining 6 weeks of the observing season, let's keep up the pressure 
and be at the ready for any more surprises.  And I'll probably be 
checking for factors of -1 practically every day.

joe


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