High-Amplitude, Rapid Photometric Variation of the New Polar Master OT J132104.0+560957.8
NAVAL OBSERVATORY FLAGSTAFF AZ
Pagination or Media Count:
Polars are cataclysmic variables CVs in which the magnetic field of the white dwarf WD synchronizes the WD s spin period with the orbital period of the binary see Cropper 1990 for a thorough review. In contrast to non-magnetic CVs, there is no accretion disk in a polar. Instead, as the accretion stream flows from the L1 point toward the WD, the magnetic pressure from the WD rapidly increases until it matches the stream s ram pressure. The stream then threads onto the WD s magnetic field lines, which channel the captured material onto cyclotron-emitting accretion regions near the WD s magnetic poles. Because cyclotron emission is heavily beamed, it appears brightest when the observer s line of sight is perpendicular to the field lines of the emitting material thus, changes in the viewing angle of the cyclotron-emitting region can produce dramatic photometric variability modulated at the WD s spin period e.g., Gansicke et al. 2001. A polar can undergo a precipitous drop in optical brightness if the accretion region rotates behind the limb of the WD or is eclipsed by the donor star.
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