(cba:news) Var Her 04, mostly
jop at astro.columbia.edu
Thu Jul 1 17:10:17 EDT 2004
Well, Mister Var Her 04 is showing, at this early stage, some grounds for
the conjectured resemblance to WZ Sge. The main outburst seems to have
ended a day ago; "echo" outbursts, if any, will support this resemblance -
but only time will tell re them. However, the power spectrum of the
superhumps (i.e. collection of frequencies in the light curve) is very
much like that of WZ Sagittae.
Most dwarf novae show only a simple power spectrum, containing the
fundamental and a few harmonics (exact integer multiples of wsh). WZ Sge
showed a much richer spectrum, with each "harmonic" containing
substructure (separated by integer multiples of W, the putative precession
frequency. The rule of thumb for these things is that each orbital
orbital harmonic (at nw) is actually a multiplet containing n+1
components, with frequencies nw-mW, where m=0,1,..., n. The m=n component
is almost always dominant, which gives superhumps their characteristic and
repeatable shape. Appreciable amplitude in other components yields
noncommensurate frequencies, and this causes recurring structure to come
and go in the lightcurve on a timescale of a few days.
CBA lightcurves are chock full of the documentary record of this structure
in superhumps, and we have dutifully reported it in a couple dozen papers.
But to this day, not a single referee has ever commented on it; not a
single reader has ever asked about it; not a single paper has ever
referenced it. Unfortunately, no one (certainly including us!) knows what
this fine-structure means. So we just report it, and hope that the day
is not far off when someone will come up with some worthy idea about what
it means. In the meantime, it's useful for one thing; assuming that the
parsing of frequencies is as described above, it can be used for deciding
what the orbital frequency is, even when the outburst light is strong. In
particular, Var Her 04 shows a very rich power spectrum seemingly
following this rule, with w=17.64(1) c/d and W=0.30(2) c/d. Among the
many components noncommensurate with wsh=w-W, the 3w component is
particularly strong. Components are seen out to the 5th harmonic,
All of this comes from the diligence of CBA photometrists: Lew Cook,
Tonny, Dave Messier, Michael Richmond, Russ Durkee, Brian Martin, Mike
Koppelman, Donn Starkey. Several others are preparing data sets for
submission, so this supply should significantly increase. Also, the star
will likely be up to more hijinks in the coming weeks, so keep a close
watch on this wonderful star!
Var Her is stealing all the thunder in the northern sky. BZ Cir is
staging a superoutburst in the southern sky, also for the first time
recorded. Data on that star would be awfully nice!
We're coming up on a very bright Moon period, and some observers may want
to start up the V603 Aql campaign. I hope. At V=11.7 and a dec of 0
degrees, I hope and trust it'll be popular with everyone!
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