AAS 199th meeting, Washington, DC, January 2002
Session 27. White Dwarfs and Neutron Stars
Oral, Monday, January 7, 2002, 10:00-11:30am, Jefferson West

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[27.05] Magnetically Driven Precession of Warped Disks and Variabilities in Accreting neutron stars

D. Lai, A. Shirakawa (Cornell Univ.)

The inner region of the accretion disk around a magnetized neutron star is subjected to magnetic torques that induce warping and precession of the disk. These torques arise from interactions between the stellar field and the induced electric currents in the disk. We carry out a global analysis of warping/precession modes in a viscous accretion disk, and show that under a wide range of conditions typical of accreting X-ray pulsars, the magnetic warping torque can overcome viscous damping and make the mode grow. The warping/precession modes are concentrated near the inner edge the disk (at the magnetosphere-disk bounary), and can give rise to variabilities or quasi-periodic oscillations (QPOs) in the X-ray/UV/optical fluxes from X-ray pulsars. We examine the observed properties of mHz QPOs in several systems (such as 4U 1626-67), and suggest that some hitherto unexplained QPOs are the results of magnetically driven disk warping/precession.

This work is supported in part by NSF grant AST 9986740.

If you would like more information about this abstract, please follow the link to http://astro.cornell.edu/faculty/dong/research.html. This link was provided by the author. When you follow it, you will leave the Web site for this meeting; to return, you should use the Back comand on your browser.

The author(s) of this abstract have provided an email address for comments about the abstract: dong@astro.cornell.edu

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