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DO Draconis

DO Draconis is a DQ Herculis star or Intermediate Polar.  It's a cataclysmic variable with a magnetic white dwarf.  The term intermediate is used to describe white dwarf stars whose magnetic field strengths are a few million Gauss -- enormous by terrestrial standards, but low among the classes of white dwarfs with magnetic fields strong enough to affect the accretion process.  In the IPs, the accretion stream from the secondary can still form a disk far out from the white dwarf, but the inner accretion disk is disrupted by the white dwarf magnetic field.  Inside the magnetic radius, the accretion stream is funnelled down the magnetic field lines onto the white dwarf surface.  In true polars the accretion stream is completely controlled by the magnetic field.  Matter flows from the Roche lobe of the secondary down the magnetic field lines and directly onto the white dwarf.  Both the IPs and polars are strong emitters of hard X-rays and may emit gamma rays, although the latter have not been conclusively detected.

DO Dra shows some similarities with the dwarf novae as well, undergoing very occasional rapid outbursts lasting a few days at most.  But for the most part, the long-term light curve is characterized by rapid nightly variations and longer-term quiescent variations.

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Prepared By: Matthew Templeton
AAVSO 49 Bay State Rd. Cambridge, MA 02138 617-354-0484