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PREDNASAJUCI / LECTURER :
Ivan L. Andronov

Odessa National Maritime University

NAZOV / TITLE :
Space Laboratory to Study Accretion in Magnetic Cataclysmic Variables: The Case
 of Exotic Newly-Discovered Polar OTJ 071126+440405 

ABSTRAKT / ABSTRACT :

Self-consistent mathematical model of the exotic object OTJ 071126+440405= CSS
 081231:071126+440405 is discussed. The system was discovered as a polar at the
 New year night 31.12.2008/01.01.2009 by D.Denisenko (VSNET Circ), and we have
 initiated an international campaign of photometric and polarimetric observations
 of this object (totally ~80 runs in Ukraine, Korea, Slovakia, Finland, USA). This
 work is a part of the "Inter-Longitude Astronomy" (ILA) project on monitoring of
 variable stars of different classes (Andronov et al., 2003). Results of this
 campaign will be published separately (Andronov et al., 2009). Here we present
 the geometrical and physical model of the system. In an addition to the usual
 assumption that cataclysmic variables contain a Roche-lobe filling red dwarf and
 an accreting white dwarf, we propose an interpretation of three types of the
 brightness minima, as the eclipses by the red dwarf, white dwarf and the
 accretion column itself (self-eclipse). In the low luminosity state, when the
 accretion rate is suggested to vanish, a "quiescence" is observed at the light
 curve, i.e. the optical flux comes from the illuminated secondary star and the
 non-accreting side of the white dwarf. When the accretion column becomes visible,
 the light curve exhibits a `hump" interrupted by the main eclipse by the red
 dwarf. In the "intermediate" luminosity state, the brightness increases at all
 phases, however, the main hump shifts to smaller phases and an additional minimum
 (self-eclipse) is observed. In this state, the emitting accreting region becomes
 larger, and is not significantly eclipsed by the white dwarf. The phase
 difference between the preliminary and main eclipses is smaller than in the high
 luminosity state, what is interpreted by the dependence of the
 position of the thread point, where magnetic field of the white dwarf captures the (initially
 ballistic) accretion stream. At the high state, the thread point approaches the
 cross-section of the ballistic stream with the magnetic axis, whereas at the
 intermediate state, the thread point may lie from 70% to 100% of the distance
 between the white dwarf and the inner Lagrangian point. As the ballistic
 trajectory nearly coincides with the magnetic field lines near the inner
 Lagrangian point, this argues for an "energetically optimal" orientation of the
 magnetic axis. As the system is of ~20 mag at minimum, no spectral observations
 were made to determine parameters of the red dwarf. From the statistical
 relationship, the mass of the red dwarf is estimated to be ~0.165 solar masses,
 for the white dwarf (from eclipse duration) - from 0.5 to 1.76 solar masses. As
 the system resembles ER UMa in some characteristics, the lower value may be
 assumed. The inclination of the system and other physical parameters are
 estimated. The object is an excellent laboratory to study multiple physical
 processes in the magnetic systems.