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\begin{document}
\IBVShead{5664}{9 December 2005}

\IBVStitle{TT A\lowercase{ri}: Out from the Positive Superhump State}

\IBVSauth{Andronov, I. L.$^{1}$; Burwitz, V.$^{2,3}$; Chinarova, L. L.$^{1}$; Gazeas, K.$^{4}$; Kim, Y.$^{5,6}$; \break Niarchos, P. G.$^{4}$; Ostrova, N. I.$^{1}$; Patk\'os, L.$^{7}$; Yoon, J. N.$^{5}$}

\IBVSinst{Department of Astronomy and Astronomical Observatory, Odessa National 
University, 
\\\mbox{~~~~~~~~}65-014 Odessa, Ukraine, ~e-mail: tt\_\,ari\,@\,mail.ru, 
ilandronov\,@\,{}onu.edu.ua}
\IBVSinst{Max-Planck-Institut f\"{u}r Extraterrestrische Physik, D-85741 
Garching, Germany}
\IBVSinst{Observatori Astron\`{o}mic de Mallorca, E-07144 Costitx, Spain}
\IBVSinst{Astronomical Observatory, University of Athens, Gr-15784 Athens, 
Greece}
\IBVSinst{University Observatory, Chungbuk National University, 361-763
Cheongju, Korea}
\IBVSinst{Institute for Basic Science Research, Chungbuk National
University,~361¡763, Korea}
\IBVSinst{Konkoly Observatory, P.O.Box 67, H-1525 Budapest, Hungary}

\SIMBADobj{TT Ari}
\IBVStyp{ NL }
\IBVSkey{photometry}

\IBVSabs{The nova-like variable TT Ari had shown a luminosity change with a}
\IBVSabs{drastic change of the light curve. This state is distincly different}
\IBVSabs{from both the bright "negative superhump" state and the}
\IBVSabs{"positive superhump" state known before.}


\begintext

TT Ari is one of the brightest cataclysmic variables, which was a target for 
few extensive observational campaigns (Andronov et al. 1999, Kraicheva et al. 
1999, Skillman et al. 1998, Tremko et al. 1992, 1996, Semeniuk et al. 1987). 
Before 1997, the estimates of the photometric periods ranged from 0\fday13270 
to 0\fday13298 (see the compilation by Tremko et al. 1996). In 1997, the 
photometric period has changed to a ``positive superhump'' one 
$P_{sh}=0\fday14926(3)$ (Skillman et al. 1998). Our observations showed, that 
during these years, this state continued till at least December 10, 2004. For 
example, in 2004, it showed a typical asymmetric (M$-$m=0.316$\pm$0.007) shape 
with a period $P_{sh}=0\fday14840(1),$ brightness range 10\fmm84-11\fmm03 and 
the initial epoch for maximum HJD2453242.1239(7). The shape of the light curve 
in $V$ and $R$ in 2004 was the same within accuracy estimates (sent to a 
mailing list in 2004 by Andronov, Ostrova and Burwitz [VSNET-Campaign, 1555]).

The observations obtained in the Astronomical Observatory of the Athens 
University on October 14-19, 2005, have shown that the system went out of the 
``positive superhump'' state (sent to a mailing list in 2005 by Andronov, Gazeas and Niarchos [VSNET-Campaign, 1630]). The superhumps practically disappeared, but the 
negative superhumps were not very prominent. The mean brightness for 4 nights 
was $\langle V\rangle=11\fmm21$, whereas for separate nights it varied from 
11\fmm08 (October 18) to 11\fmm28. This differs both from the mean brightness 
level at the ``positive superhump'' stage (10\fmm9, Skillman et al., 1998; 
10\fmm92 Andronov et al. 2004 [VSNET-Campaign, 1555]) and at the ``negative superhump'' 10\fmm69 
(Tremko et al., 1996). Kraicheva et al. (1999) have also noted the brightness 
difference between $V=10\fmm5$ in 1996-1997 and 11\fmm0 in 1998-1999. Despite 
small differences in the instrumental systems, the results by different authors 
showed a switch to ``positive superhumps'' with a luminosity ``drop'' by a few 
dozens per cent. Thus the current ``non-positive superhump'' state with even 
smaller luminosity is not a return to the high luminosity state observed before 
1997. Kraicheva et al. (1999) suggested 27.5 and 6.25 year cycles for the 
luminosity variations possibly caused by magnetic activity of the secondary.

Further monitoring carried out during 6 nights at the 40-cm telescope of the 
Chungbuk National University shows quasi-periodic oscillations, ``negative 
superhumps'' with variable amplitude and strong flickering. The sample light 
curves obtained on subsequent nights on Nov 8 and 9, 2005 are shown in Fig.~1 
and Fig.~2. 
Significant difference in the brightness (0\fmm35) is noticeable, as well as 
the lack of the 3-hour wave in Fig.~1.

The most prominent peak at the ``$\Lambda$''--scalegram (Andronov 2003) for the 
Athens University data corresponds to an effective period of quasi-periodic 
variations of $P_e=0\fday0095=$13.7 minutes and semi-amplitudes 0\fmm046 and 
0\fmm044 for the filters $V$ and $R$, respectively. On November 4, 2005 (filter 
$B$, Konkoly Observatory), this peak was split into three approximately equal 
ones at $0\fday007-0\fday024$ with effective semi-amplitudes 
$0\fmm062-0\fmm068$. These values are by a factor of 3 larger than that for the 
"positive superhump" state on December 10, 2004. The mean $B$ magnitude has 
dropped from 10\fmm92 to 11\fmm60.

The current luminosity is much lower than expected from a continuation of the 
long-term fit (Kraicheva et al., 1999) to the present time (the range of $B$ 
magnitudes is 10\fmm55-10\fmm80). Moreover, at the previous minimum, the 
prolonged inactive ($B\sim16\mm)$ state was observed. A similar excursion to a 
low luminosity state may not be excluded after a current deep minimum, so 
continuation of monitoring is needed.

\bigskip

{\it Acknowledgements.} This work was partly supported by the Grant OTKA 34551 
(LP), by the Ministry of Education and Science of Ukraine (ILA). VB and NIO are 
greatful to the Director of the OAM Salvador Sanchez Martinez for granting the 
observing time and partially supporting this work.


\references

Andronov, I. L., 2003, {\it ASP Conf.Ser.}, {\bf 292}, 391
\BIBCODE{2003ASPC..292..391A}

Andronov, I. L., Arai, K., Chinarova, L. L., et al., 1999, {\it AJ}, {\bf 117}, 574
%\BIBCODE{1999AJ....117..574A}

G\"otz, W., 1985, {\it IBVS}, 2823
%\BIBCODE{1985IBVS.2823....1G}

Kraicheva, Z., Stanishev, V., Genkov, V., Iliev, L., 1999, {\it A\&A}, {\bf 
351}, 607 
%\BIBCODE{1999A&A...351..607K}

Tremko, J., Andronov, I.L., Chinarova, L.L., et al., 1996, {\it A\&A}, {\bf 
312}, 121
%\BIBCODE{1996A&A...312..121T}

Semeniuk, I., Schwarzenberg-Czerny, A., Duerbeck H., et al.,
1987, {\it AcA}, {\bf 37}, 197
%\BIBCODE{1987AcA....37..197S}

Tremko, J., Andronov, I. L., Luthardt, R., et al., 1992, {\it IBVS}, 3763
%\BIBCODE{1992IBVS.3763....1T}

Skillman, D.R., Harvey, D.A., Patterson, J., et al., 1998, {\it Ap.J.}, {\bf 
503}, 67L
%\BIBCODE{1998ApJ...503L..67S}

\endreferences

\IBVSfig{9.1cm}{5664-f1.eps}{Light curve of TT Ari on November 8, 2005 in filter
R (40-cm telescope of the Chungbuk University). The comparison and check stars 
are ``c'' ($V=10\fmm99$, $B-V=0\fmm69$) and ``d'' ($V=11\fmm02$, $B-V=1\fmm15$)
(G\"otz, 1985).}
\IBVSfigKey{5664-f1.eps}{TT Ari}{light curve}

\IBVSfig{10.4cm}{5664-f2.eps}{Light curve of TT Ari on November 9, 2005 in filter
R (40-cm telescope of the Chungbuk University).}
\IBVSfigKey{5664-f2.eps}{TT Ari}{light curve}

\end{document}
