[vsnet 2113] Variations of the superhump period of V368 Peg: Monotonicity or frequency doubling?

["Ivan L. Andronov" <il-a@mail.ru>]

Variations of the superhump period of V368 Peg: 
Monotonicity or frequency doubling?

The superhumps have been detected during the superoutburst in 2000,
justifying the SU UMa subtype classification. 6 nights of the CCD
observations show the decrease of the photometric period with luminosity by
a factor of 2.3 times.
The observations were obtained by N.I.Ostrova, N.A.Katysheva and
S.Yu.Shugarov from JD 2451789.41 to 2451799.56. The time series analysis was
done using the programs by I.L.Andronov.

The models of the smooth character of this dependence vs the "smooth
variation + frequency doubling" may be suggested. However, any of these
models may not be justified or ruled out because of lack of observations at
the descending branch between the bright and faint states. Another
possibility is the gradual decrease of the period with luminosity at maximum
with a subsequent frequency doubling at some level, where the Fourier
harmonic becomes dominant over the main wave. The period ratio does not
justify the effect of precise superhump frequency doubling while changing
from the superoutburst maximum to its end. 

New observations are needed to cover the "period - luminosity" relation more
densely, with a high importance of multilongitude campaign, taking into
account a rapid decline from the superoutburst. If the frequency doubling
occurs, the brightness level should be detected, where it takes place. If
not, the parameters of the smooth variation should be obtained for further
theoretic explanation. The theoretical explanation of the photometric period
change of V368 Peg is to be proposed.

At the brightness maximum, the presence of the "shot noise" is registered.

The details may be found in the paper accepted by "Notices of the
Astronomical School" ("Vestnik Astronomicheskoj Shkoly", Ukraine). The
Internet version in English is available at
http://il-a.pochtamt.ru/V368_Peg.htm .


N.I. Ostrova^1, I.L. Andronov^1, N.A.Katysheva^2
^1 Department of Astronomy, Odessa National University, Odessa 65014
Ukraine, il-a@mail.ru, http://il-a.pochtamt.ru , http://il-a.hotbox.ru 
^2 Sternberg State Astronomical Institute, Moscow State University, Moscow
119899 Russia, nk@sai.msu.ru, http://cataclysm.sai.msu.ru

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