(cba:news) Sep-Oct stars
jop at astro.columbia.edu
Sun Sep 28 21:40:24 EDT 2014
Sep 28, 2014.
Two very long campaigns continue to produce great results:
1. V1101 Aql. Now in its 75th day, with only 2 days missing, and most
days multi-longitude (Europe + USA). Very, very powerful negative
superhump, and very regular dwarf-nova outbursts (about every 16 days).
Tomas Gomez and Joe Ulowetz are still the main perpetrators, but there's
a lot of help. It has convinced me that the Z Cam stars hold deep secrets!
My notes call for "quit after the next rise to maximum" - which just
occurred. And there are some very tempting targets still reasonably
placed in the evening sky. So my advice is: quit the long time series,
but *snapshot* magnitudes will be very useful for the next 2 months (at
least). That means V or "CV" magnitudes, not merely differential
magnitudes. The idea is to watch the 16-day clock change; it changes -
2. ASASSN-14ei. 60 days and counting, and the light curves are still
beautiful. The star is a ~43 minuite binary, and probably should be
considered an AM CVn star (helium-dominated CV) until evidence proves
otherwise. Like our old friends CR Boo and V803 Cen, it seems to have a
big outburst and then numerous smaller/briefer outbursts, the latter
sometimes lasting only ~1 day. Spectacular, lengthy coverage from Gordon
Myers in Australia, plus Josch's every-night coverage from Chile, and
many early-ish nights from Berto in South Africa. All the southern
hemisphere's major landmasses chipping in (plus one smaller one: Bob Rea
has now joined the party from NZ).
Mister 14ei is now announcing itself to the world for the very first time.
It seems only fair, and responsible, to keep watching it for as long as the
star remains visible to our little scopes. Quien sabe when the next
opportunity comes? Maybe never. Keep up the great work!
And now for some others.
3. ASASSN-14gx. Another newly-discovered dwarf nova, which flashed a
8-magnitude outburst - pretty much the theoretical limit for a true
dwarf-nova outburst. That means the star is super-faint in quiescence -
hardly more than a bare white dwarf. That makes it a WZ Sge star, and it
has flashed some nice superhumps, as such stars always do. If we knew
its *orbital* period, then we could calulate its mass ratio, the most
important physics number we can get from these stars. It appears that the
early coverage, thanks to CBA and the ASSASSINs, does reveal that period.
However, we should continue for about another week, in case of echo
outbursts or other surprises. Expires October 1!
4. J0107+48. A newly-discovered SW Sex star, and a deep eclipser. Now
virtually our favorite class of CV, and lots of good coverage on th1s guy
from Enrique and Jim Jones. To my surprise, the star showed only an orbital
signal. It had its chance. Time to quit for 2014.
5. QR And. A minor celebrity, sometimes lauded - though quite incorrectly -
as "the only supersoft binary in our Galaxy". It has a 16-hour double-humped
orbital light curve, and our campaign, led by Joe U, shows that the orbital
period is rapidly changing. Success! This is a signature of the very high
mass transfer rate that powers supersoft binaries. Time to quit.
6. RX And. Jumpin' jehosaphats! A year or so ago, motivated by our
discoveries re BK Lyn, I started fiddling with the hypothesis that Z Cam
stars could show negative superhumps. Theory says no, but theory is...
well, just SOOOO 2011. RX And seemed like a good first test case, and we
- almost entirely Bob Koff - now have one full cycle of quiescence-to-outburst
data. It looks highly probable that RX And has joined the club. Now we
need to work hard to evaluate this for sure. The signal is much stronger
at quiescence, which the star has just reached (V=14.3). We *urgently* need
European coverage, but really need intensive effort from everywhere when
the star is quiescent (probably for just 1-2 more days). Also, it would be
very helpful to use a V filter on this one, because for the very long period
(4.8 hr), we need *long* time series - bringing our old nemesis, differential
extinction, into play.
7. V378 Peg and PX And. Having retired QR And and V1101 Aql, which have been
monopolizing the evening sky, I'd like to start up on V378 Peg and PX And
(actually, Enrique has already started on PX And). Both are negative
superhumpers with the "nodal" signal also present. We'd like to see if
those signals are actually (perfectly) stable; that would be a major
surprise... but the world is full of surprises.
8. CC Scl and BW Scl. The southern objects of choice in the evening sky,
in my opinion. I'm not sure if CC Scl is still accessible (because of
faintness), but our earlier work this year has certainly established as a
"hot object". In the morning sky, ASASSN-14ei for sure, and IM Eri (to start
the year's campaign).
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