ANGULAR MOMENTUM LOSS MECHANISMS IN CATACLYSMIC VARIABLES BELOW THE PERIOD GAP

作者：Shao Yong^*; Li Xiang Dong

来源：Astrophysical Journal, 2012, 745(2): 165.

DOI：10.1088/0004-637X/745/2/165

• binaries: close
• novae, cataclysmic variables

Mass transfer in cataclysmic variables (CVs) is usually considered to be caused by angular momentum loss (AML) driven by magnetic braking and gravitational radiation (GR) above the period gap, and solely by GR below the period gap. The best-fit revised model of CV evolution recently presented by Knigge et al., however, indicates that the AML rate below the period gap is 2.47(+/- 0.22) times the GR rate, suggesting the existence of some other AML mechanisms. We consider several kinds of consequential AML mechanisms often invoked in the literature: isotropic wind from the accreting white dwarfs, outflows from the Lagrangian points, and the formation of a circumbinary disk. We find that neither isotropic wind from the white dwarf nor outflow from the L-1 point can explain the extra AML rate, while outflow from the L-2 point or a circumbinary disk can effectively extract the angular momentum provided that similar to(15-45)% of the transferred mass is lost from the binary. A more promising mechanism is a circumbinary disk exerting gravitational torque on the binary. In this case, the mass-loss fraction can be as low as less than or similar to 10(-3).

• 出版日期2012-2-1
• 单位南京大学