(cba:news) Classical novae and DQ Hers for July-August

Joe Patterson jop at astro.columbia.edu
Tue Jul 29 21:12:46 EDT 2014


Dear CBAers,

This one on classical novae, mostly.  Mostly the hardest/faintest 
targets, but with two advantages:
(1) they don't flop up and down, hence are suitable for long and 
sensitive observing campaigns;
(2) they have known outburst dates, hence carry information about how 
novae decline from max.

    We've been going strong on V1494 Aql (1999) and DQ Her (1934). 
Still wish to keep going - in fact accelerate - on both.  The former may 
show a superhump, and the latter may also have a third periodic signal, 
other than the 4.65 hr eclipse and the 71 s spin period.  We probably 
need just ~2 more weeks on each of them.

   Strangely, both stars have contaminating neighbors, 1.5 arcsec 
(V1494) and 4 arcsec (DQ Her) away.  You definitely need to include them 
in your aperture.  But in addition, if you get very good seeing, try to 
measure the brightness and colors of these stars.  This will be very 
hard, and you should use the nova's eclipse to minimize the nova's light 
(absolutely mandatory for DQ Her, which is normally 3.5 mag brighter 
than "DQ Her C").  I estimate the unwanted star's V mags as 18.5 (DQ) 
and 17.8 (V1494).  Though measurements in VRI are ideal, a measurement 
in your instrumental (unfiltered) system is plenty useful too.  In fact, 
"x mag fainter than the nova's average magnitude" would be a quite 
useful thing to know - we gotta know how deep these eclipses really are!

   An easy target is HR Del (1967).  Good for an intensive study over 
the next two weeks of bright sky.  If we can get good longitude 
baseline, we can evaluate the published claim of a non-orbital signal. 
I doubt that this claim is true, but worth checking.

   Now come the hard ones.

V1500 Cyg.  Really faint (18.5?), but with a 1.1 mag amplitude periodic 
signal that probably signifies the white-dwarf rotation. Deserves a 
several-months long campaign.  Enrique, can you send comp-star 
recommendations?

V4743 Sgr (2002).  I yearn for this one, with its orbit and spin 
signals.  Berto has started up a campaign - let's keep going!  i think 
it's about 16.5, but possibly some field crowding (I've never actually 
observed it)

V728 Sco and V630 Sgr.  Both eclipsers, and faint - probably beyond CBA 
scopes... but for australites feeling brave, check 'em out!  The eclipse 
offers great diagnostics, if we can only get the data.

************

And now for intermediate polars.  V4743 Sgr, definitely, but also CC Scl 
- our first stab at this fascinating star which spins, dwarf-novas, and 
superhumps... a lotta work for one little star!  In the north, the DQ 
Hers needing attention are V2306 Cyg and RX2133+51.

Finally, there's V1223 Sgr, one of the great intermediate polars.  For 
the first time ever, this year's campaign (mainly Simon Lowther and 
Peter Nelson) seems to reveal a positive superhump.  In principle, the 
CBA can get great longitude coverage for southern targets (South Africa, 
Chile, AU/NZ) - so we should be able to nail this down for sure.

Lots of rewards to be had in that summer/winter sky.  Happy observing!

joe
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