(cba:news) New stars for July/August
jop at astro.columbia.edu
Mon Jul 28 07:34:42 EDT 2003
Well we're just about to push the final version of the "20 dwarf novae"
paper out the door. Most dwarf novae turn out to be pretty ordinary (of
course), and so we decided to toss our coverage of 20 of 'em into one
paper - orbital and superhump periods for each. The world should also
reckon this a merciful act. The author list was: Patterson, Thorstensen,
Kemp, Skillman, Vanmunster, Harvey, Fried, Jensen, Cook, Rea, Monard,
Velthius, McCormick, Walker, Martin, Bolt, Pavlenko, O'Donoghue, Gunn,
Novak, Masi, Garradd, Butterworth, Krajci, Foote, and Beshore. To the
coauthors, sorry we didn't consult on any of this - it seemed like an
impossible task. We'll post the thing on the website as soon as it's
accepted, and mail copies out right away. I thought the main conclusion
was pretty interesting - that the secondary stars have essentially solar
composition, and a radius 18+-6% greater than theoretical
Since the theoretical models have likely radius uncertainties of ~10% (or
more?), you can roughly say that this certifies the secondaries as
"main-sequence stars". Why is that interesting, since it has been so
stated for 30 years? Well, because throughout those 30 years, there have
been hundreds of allegations to the contrary. Often based on just one
star, and not quite appreciating the uncertainties... or on treating the
theoretical models as Holy Writ. For years we have been in the business
of making these rather precise measures of periods (orbital and
superhump), and yet I could never find a way to cash 'em in - use 'em for
a tight numerical constraint on physical variables. I think we've
learned how to do that now.
V4743 Sgr. Whoa, Nellie! What a swell star this has been! An Australite
gang has been hard at work on it - Berto Monard, Jennie McCormick, Bob
Rea, and Greg Bolt... and Tut Campbell has obtained a few nights from
Arkansas to fill in the long gap westward from South Africa to New
Zealand. This recent nova has a large sinusoidal signal at 6.69 hours,
which I take to be the orbital period, and another signal at 69.53
minutes. Union regulations require interpreting the latter as the spin
period of a magnetic white dwarf. We dunno whether this is actually true,
of course, but it will be damn fascinating to watch it change as this
bright and recent nova declines many magnitudes down to true quiescence.
Definitely worth tracking as it fades off into the western sunset.
Alon Retter has a good measure of these periods too, which he sent me a
few weeks ago. This was obtained earlier, so I imagine we'll merge the
datasets to get the best leverage on the star's behavior.
Berto has unearthed an interesting new CV from the SDSS collection -
namely SDSS J2258-0949. Berto, can you send exact coords and references?
Kind of a mystery star, wanders rapidly over a 1.5 mag range. Very nicely
positioned for all observers, decently bright (13.5-15 I believe)... and a
good target for an all-world campaign starting now!
In this dark-moon period, it would be awfully timely to cover V1974 Cyg.
Even though it was only "The Nova of the (20th) Century", I hope you won't
consider it too old-fashioned to keep tracking its odd little periodic
wiggles. At last sight a few years ago, it was nicely endowed with both
positive and negative superhumps. A greater target for northern
bigscopers (it's about 16th mag I think).
Finally a coupla items just off the presses. VW CrB went into
superoutburst; I woulda been really happy for good data on this star, but
am worried about the bad seasonal timing. Europe still has bright nights,
we still have no coverage in east Asia, and CorBor doesn't stay up long.
Anyone manage to get some good runs on this star?
I noticed that Paul Schmidtke, using Bob Fried's telescope, found LQ Peg
in a rare low state. This would be a great target for us - but only for
bigscopers. Magnitude 17 (or fainter). Give it a try!
In summary for targets:
DELETE V1141 Aql and V533 Her.
PRIMARY TARGETS are SDSS2258-09, V1974 Cyg, V4743 Sgr, LQ Peg
SECONDARY TARGETS are the pulse timers (V1223 Sgr, AO Psc, FO Aqr) and VW
As usual, this is just a rough guide. It often happens I get hot and
heavy over a star that turns out to be a dud - and miss some great ones as
a result. Trust your own instincts on this. But it definitely pays
to persist on a particular star! Aesop had it right... slow and steady
wins the race.
I'm (almost) fully moved back to NYC, I'm managing to play a lot of golf,
and the Red Sox have won two straight over the Evil Empire (aka the
Yankees). Happy, happy.
More information about the cba-public