[vsnet-alert 1378] (fwd) TT Ari switches side (CBA)

[Taichi Kato <tkato@kusastro.kyoto-u.ac.jp>]

From owner-vsnet-adm@kusastro.kyoto-u.ac.jp Fri Dec 12 07:11 JST 1997
Date: Thu, 11 Dec 1997 17:11:55 -0500 (EST)
From: Joe Patterson <jop@astro.columbia.edu>
To: vsnet-adm@kusastro.kyoto-u.ac.jp
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Subject: The Times, They Are A-Changin'
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                     TT ARI SWITCHES SIDES

     Since 1962, TT Ari has shown a photometric wave at a period near
0.133 d, about 3.5% shorter than its orbital (spectroscopic) period.
Because the period is less than Porb and wanders slightly (in the range
0.1322-0.1336 d), the signal can reasonably be called a "negative
superhump".  Its origin is still unknown.  Observation from CBA
observing stations during the last month shows that the wave has
strengthened to 0.2 mag, and the period has changed to 0.1496 d -- now
8.7% longer than Porb.

     Such turncoat behavior is very unusual among CVs.  V603 Aql did
something similar once, growing a negative superhump in 1992-1994, but
maintained its familiar positive superhump all the while.  Otherwise,
there is no precedent at all.  So it's a fine opportunity to study a
rare phenomenon in a very bright CV (V=10.8) well-placed in the evening
sky.  Who knows how long it will last?  (Rhetorical question.) We
eagerly seek help in studying the new signal through the rest of the
observing season, or however long it lasts.

     Any photoelectric or CCD observer, even with apertures as small as
15-20 cm, can effectively contribute to this campaign.  The
observations do, however, need to be in a "time-series" mode, of >3 hr
duration per night.  Most commonly, we use unfiltered differential
photometry with a CCD.  V-band would be fine too, actually better.

     Any takers out there?  We're ever on the lookout for new members,
for this or any future photometric campaign on CVs.  Especially from
exotic longitudes!  Full information on the CBA is available from our
website: www.astro.columbia.edu/~cba



Joe Patterson           Dave Harvey     Dave Skillman   Lasse Jensen
CBA-New York            CBA-Tucson      CBA-Maryland    CBA-Denmark
jop@astro.columbia.edu

Bob Fried               Darragh O'Donoghue
Braeside Observatory    South African Astronomical Observatory

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