(cba:news) AL Com and competitors

Joe Patterson jop at astro.columbia.edu
Sun May 20 12:27:53 EDT 2001

Dear CBAers,                                               5/20/01

AL Com's recent jump into superoutburst made me ponder the issue of
whether to start a campaign.  Tonny's note made me realize that I should
not just ponder it but say something about it.  So here goes.

At 13th mag and as a member of a select and interesting family (the WZ Sge
stars, the most reluctant of the SU UMas), AL Com is certainly a tempting
target.  And it may well turn out that observations over the next 3
weeks will provide important new information about this class and its
superhumps.  You never know till you try.

Nevertheless, with some uncertainty I'm going to recommend not.  Here's

(1) We got very good coverage of the 1995 eruption, and I'm doubtful we
can improve on it now.  This is especially true since some of our most
established observers in the USA have been off the air for some time now,
meaning that we'll have to rely a lot on Europe where we have mainly small
telescopes and short nights.

(2) It would mean curtailing the CR Boo campaign, which I dearly hope can
continue at least until the next full moon in 2 weeks.  The continuity of
coverage is important.

(3) It would delay the other campaigns on May targets, namely HP Lib and
V849 Her.

(4) The Ouda group appears to be pouncing on the star and will probably do
a good job with it.  Of course it would be best to collaborate with them
and thereby have the basis for a better study; but until that happy day
arrives, it seems generally sensible not to compete on every interesting
CV that pops off up there.

(5) Finally - I guess this is a variant on (1) - I have some
disinclination to reobserve a dwarf nova that has once been extensively
observed in the same luminosity state.  True all the more in this case
since I expect this year's observations would be less extensive, but
also because of an astrophysical reason: that the most subtle effects
in superhumps -- especially the displaced "quasi-harmonics" -- tend to
occur in novalike variables, not dwarf novae.  Why?  Well, possibly
because dwarf-nova disks rapidly evolve, not remaining stable long
enough to permit our period-search efforts to reach high sensitivity.
In the fullness of time, I guess we'll learn what are the smarter
strategies; at present, just chalk it up as a prejudice.

  By the way, I certainly don't apply this to the enterprise of accurate
measurement of principal superhump periods!  I think that's really
important; newly discovered superhumps are golden!

  So the bottom line is that I'd like to keep the focus on CR Boo and HP
Lib, with a new campaign starting up as soon as practical on V849 Her.
But re AL Com, I'm still a very interested spectator!


By the way, I should report that the 2001 RZ LMi campaign, led and
somewhat dominated by Jeff Robertson and Tut Campbell, was extremely
successful.  It certainly appears to prove that the superhumps
really do linger throughout the interregnum between superoutbursts,
contrary to folk wisdom (and to my above dissing of dwarf novae).  Still
not clear if the superhumps actually maintain *phase* between adjacent
supermaxima, though.

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