(cba:news) eclipse timings... and old novae

Joe Patterson jop at astro.columbia.edu
Sun Aug 16 18:18:00 EDT 2020

Hi CBAers,

Some general comments about target choices and observing.  As most of 
you realize, we're not doing much with dwarf novae any more.  We're 
still very solicitous about intermediate polars, and trying to 
accumulate long-term observations of all that don't pose some obvious 
practical problems (too faint, crowded field, etc.)  Koji Mukai's 
website is the go-to place for the list + lots more, and his list by RA 
is useful to figure out what's up each month:


Along with Enrique, I'll keep you apprised of which ones we recommend in 
a given season... though you might well want to adopt a specific star 
and just pound on it.  If the star is brighter than ~17.5, You can be 
99% sure you're getting the best coverage of anyone (in the world),
because real ephemeris work has fallen out of favor - professional 
astronomers just can't get the telescope time any more.

But I've gotten fascinated by a new project: tracking the evolution of 
the orbital light curve of old novae.  We've discovered the "quiescent" 
orbital light curves of T Pyx and IM Nor, and tracked their period 
changes - large! - over ~20 years.  And we have (more sparsely) done 
this for ~10 other novae.  The similarities among them are amazing... 
and this too is a project tailor-made for amateur astronomers, because 
professionals often take the view "after you've observed something once, 
why would you do it again?.

So let the word go forth: work on orbital light curves.  Around ~40 
orbits of good data will give an excellent yearly light curve.  You can 
scatter it throughout, although there is always an advantage in doing it 
in a compressed interval (say over a month or two).

The *shapes* in the orbital waveform are of great interest, but the ones 
that show eclipses (or distinct, possibly deep minima in the light 
curve) are usually of greatest interest.  That's where it's advantageous 
to use Enrique's, or Tonny's, or your own calculation of expected time 
of minimum.  It's true - the eclipse phase is the most interesting time. 
  But don't get too fine with this!!  CVs will dish out dirt if you 
start expecting  them to behave as expected.

Seasonally appropriate Stars in this category are CI Aql*, Nova Sco 
1437*, V728 Sco, V392 Per, QR And, V1494 Aql, V1974 Cyg, and V339 Del.
Asterisk means: especially these.

More on the IPs tomorrow... although Enrique's choices are ideal.

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