[vsnet-chat 1271] TT Ari: Superhump Still Positive (Andronov)

[Daisaku Nogami <nogami>]

 From: "prof. I. L. Andronov" <ila@auriga.ta3.sk>
 Subject: TT Ari: Superhump Still Positive
 Date: Sat, 5 Sep 1998 18:28:14 +0000 (GMT)

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{\Large TT Arietis: Superhump Still Positive\\}
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\noindent I.L.~Andronov, K.A.~Antoniuk\\
Department of Astronomy, Odessa State University, Ukraine\\
astro@paco.odessa.ua\\

Results of the recent study of the nova-like variable TT Ari are
reported based on 1220 photoelectric data obtained by K.A.A. on
21/26.08.98.

The primary photometric period is found to be
$P=0.14810\pm0.00007^d,$ semiamplitude $r=0.060\pm0.0015^m.$ This period
is close to that found by Skillman et al. ({\it Ap. J. Lett.,} in press)
for the observations made last year. They have discovered a switching
from a "negative" superhump with a photometric period $P=0.1329^d$ to a
normal "positive" superhump with $P=0.14926^d\pm0.00006$ which is an
excellent agreement with a value $0.1493\pm0.0007^d$ predicted by Tremko
et al. (1996, {\it As.Ap.,} {\bf 312}, 121) based on the statistical
"$P_{superhump}$ vs $P_{orbital}$" relation by Andronov (1990, {\it
Astron. Tsirk.,} {\bf 1535}, 18). Despite a presense of some peaks at
daily aliases, no evidence for a peak at a former value $P=0.1329^d$ is
seen, thus confirming continuation of the "positive superhump" state.

The quasi-periodic oscillations have been studied by using the wavelet
analysis code for irregularly spaced data (Andronov, {\it Kinematika i
Fizika Nebesnykh Tel,} in press). The frequency value corresponding to a
weighted mean wavelet periodogram is $f=56.2$ cycles/day does not
confirm a suggestion of its secular increase. The mean amplitude is
found to be $r=0.017^m$ which is in agreement with the observations
before the "switch" of the primary photometric period.
The work is a part of the international campaign "TT Ari-98"
for spectral, photometric and polarimetric monitoring.
Results from a last "TT Ari-94" campaign are presented by
Andronov et al., A.J., in press;
JENAM'97, Thessaloniki, Greece, 1997, p. 103.

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