A possible mechanism for the formation of tilted disks in intermediate polars

    Authors

    D. V. Bisikalo; A. G. Zhilkin; P. V. Kaygorodov; V. A. Ustyugov;M. M. Montgomery

    Comments

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    Abbreviated Journal Title

    Astron. Rep.

    Keywords

    MAGNETIC CATACLYSMIC VARIABLES; CLOSE BINARY STARS; ACCRETION DISKS; 3-DIMENSIONAL SIMULATIONS; INCLINED DIPOLE; FLOW STRUCTURE; DQ HERCULIS; AE-AQUARII; PQ GEM; FIELD; Astronomy & Astrophysics

    Abstract

    Using 3D gas dynamics, we numerically simulate accretion-disk formation in typical cataclysmic variable intermediate polars with dipolar magnetic fields (B (a) = 10(5)-5 x 10(5) G) and misaligned white-dwarf magnetic and rotation axes. Our simulations confirm that a significant misalignment of the axes results in a significant misalignment of the disk to the orbital plane. However, over time, this disk tilt disappears: early in the simulation, the initial particle positions in the rarefied tilted disk are governed solely by the magnetic field of the white dwarf. Due to the increasing disk mass and hence increasing disk gas pressure, the tilted disk eventually becomes decoupled from the magnetic field. The tidal action of the donor leads to a retrograde (i.e., nodal) precession of the tilted disk's streamlines, and the disk becomes twisted. When the disk tilt is greater than 4A degrees, the incoming gas stream no longer strikes the disk rim (i.e., bright shocked region). Matter is now transported over and under the disk rim to the inner regions of the disk. Over time, the increased mass of inner parts of the disk due to the action of the colinear gas stream returns the inner-disk regions to a colinear configuration. Meanwhile, the outer regions of the tilted, twisted disk become warped. Our simulations suggest that the lifetime of an intermediate polar's tilted disk could be several tens to thousands of orbital periods.

    Journal Title

    Astronomy Reports

    Volume

    57

    Issue/Number

    5

    Publication Date

    1-1-2013

    Document Type

    Article

    Language

    English

    First Page

    327

    Last Page

    337

    WOS Identifier

    WOS:000319360000002

    ISSN

    1063-7729

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