(cba:news) novae, near and far
jop at astro.columbia.edu
Sat Oct 31 06:05:26 EDT 2020
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
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).
* 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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