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Session 113 - Old Worn-Out Stars.
Oral session, Thursday, January 16
Piers 2/3,

[113.03] On the Dramatic Spin-up/Spin-Down Torque Transitions in BATSE Observations of X-ray Pulsars

R. Nelson, D. T. Koh, T. Prince, B. Vaughan (Caltech), L. Bildsten (Berkeley), D. Chakrabarty (MIT), M. Finger, B. Rubin, R. Wilson (NASA MSFC)

Over the last 5 years the Caltech High Energy Astrophysics group and the BATSE instrument team at NASA MSFC and UAH have collected daily pulse timing and flux measurements for roughly half of the known accreting pulsars. We have found wonderfully strange and unexpected spin behavior in nearly all the disk-fed systems, including dramatic spin-up/spin-down torque reversals on timescales of 10 days to 10 years. Such two-state torque behavior is difficult to reconcile with standard accretion torque theories. In light of this rich new dataset, I will discuss theoretical issues associated with the physics of magnetic accretion. These observations may also have important implications for the spin evolution of other disk-fed systems, such as CVs and T-Tauri stars, where magnetic fields likely play a dominant role in the transport of angular momentum.

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Program listing for Thursday