Magnetic field structure and accretion regimes of the asynchronous polar by Cam |
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| Authors: | E P Pavlenko |
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| Institution: | (1) Crimean Astrophysical Observatory, Ukraine |
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| Abstract: | Series of photometric CCD observations of the asynchronous polar BY Cam in a low accretion state (R = 14m–16m) were made on the K-380 telescope at the Crimean Astrophysical Observatory (CrAO) over 100 hours in the course of 31 nights
during 2004–2005. A period of P
1 = 0.137120±0.000002 days was found for the variations in the brightness, along with less significant periods of P
2 = 0.139759±0.000003 and P3 = 0.138428±0.000002 days, where P2 and P3 are obviously the orbital and rotation periods, while the dominant period P1 is the sideband period. A modulation in the brightness and an amplitude of 0.137 days in the oscillations at the orbital-rotational
beat period (synodic cycle) of 14.568±0.003 day are found for the first time. The profile of the modulation period is four
humped. This indicates that the magnetic field has a quadrupole component, which shows up well during the low brightness state.
Accretion takes place simultaneously into two or three accretion zones, but at different rates. The times of the times of
maxima for the main accretion zone vary with the phase of the beat period. Three types of variation of this sort are distinguished:
linear, discontinuous, and chaotic, which indicate changes in the accretion regimes. At synodic phases 0.25 and 0.78 the bulk
of the stream switches by 180°, and at phase 0.55, by ∼75°. At phases of 0.25–0.55 and 0.55–0.78, the O-C shift with a period
of 0.1384 days, which can be explained by a retrograde shift of the main accretion zone relative to the magnetic pole and/or
a change in the angle between the field lines and the surface of the white dwarf owing to the asynchronous rotation. For phases
of 0.78–1.25 the motion of the accretion zone is quite chaotic. It is found that synchronization of the components occurs
at a rate of less than dProt/Prot∼10−9 day/day.
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Translated from Astrofizika, Vol. 49, No. 1, pp. 121–137 (February 2006). |
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| Keywords: | stars binaries-stars individual BY Cam |
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