(cba:news) novae, near and far

Joe Patterson jop at astro.columbia.edu
Sat Oct 31 06:05:26 EDT 2020

Hi CBAers,

Congrats to Tonny and Damien for spotting that amazing nova - it even 
humbles T Pyx! - in M31.  And with bright moonlight, along with so much 
contaminating starlight.

I don't hold out much hope for extracting our usual secrets - periods - 
from this star.  It did make me wonder if we can possibly get periods 
from the supersoft sources (more or less "permanent novae", since 
they're white dwarfs burning H on the surface all the time)) in the 
Magellanic Clouds.  Especially CAL 87, the prototype in the LMC.  We've 
learned a lot from our studies of such stars in the Milky Way, but 
they're very few, because of interstellar absorption in our galaxy. 
Maybe Gordon can take a crack at CAL 87...?  The main problem, of 
course, is CROWDING... and every distant star presents its own 
complicated story of meddlesome neighbors.

Meanwhile, back at the Milky Way ranch, there are plenty of novae 
inviting time-series study.  The recent guy is V392 Per.  Richard Sabo 
has been doing great work on it, but we're really hurting for European 
coverage.  There is a lot of variability in this star - especially for a 
recent nova - and periods are hard to extract amid all the noise (in the 
star!). It needs more attention from all longitudes.  At 15th magnitude 
in Perseus, it should be an easy target.  LONG time series are 
especially valuable.  This star - the only nova in history to rise from 
a previously known dwarf nova - deserves your attention!

We're also about to write something up on V Per, the 2.5 hour 
deep-eclipsing nova of 1889.  Lew Cook has been getting some great data 
on this 18.5 (diving to near 20 in eclipse) mag star.  But this too 
needs coverage at other longitudes, in order to search for variability 
on other timescales.  It also needs more North American coverage.

Similar story for V597 Pup, although it's a newcomer to our menu: 18th 
magnitude eclipsing nova (of 2007), seemingly also an intermediate 
polar.  This may become our top southern target of November-january. 
There may be an intruder star just to the south of the nova... but give 
this one a try (if Puppis is in your sky), it has promise of a great return.

Finally, there's the Gemini twins... not Castor and Pollux but DM and DN 
Gem, two decently bright and well-placed novae with essentially no 
period information known.  We've never even given them a try.  Let's see 
if we can add to humanity's sparse knowledge of these stars.

We have some new observers this year, so let me stress again the value 
of LONG observations (>4 hours if possible, or even longer).  Because 
all CVs have erratic variability, long observations give the best chance 
of overcoming that and revealing a true period - rather than one which 
is merely an accident of the observing window.  The main qualifier* is: 
avoid high airmasses (airmass 2.0 is borderline).

joe p

* But there's one circumstance where you can, and perhaps should, get 
braver.  If you're in a multi-longitude campaign and suspect that you're 
the main observer at your longitude, you can cheat to maybe 2.5 
airmasses or so.  I've learned how to correct accurately for such 
"venial sins"... and extending the longitude range of our campaigns is 
important.  Above airmass 2.5, things get pretty terrible.
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