Disk diagnostics and torque mapping of X-ray pulsars: BATSE observations of A0535+262

I use results from the recent BATSE observations of the accreting X-ray pulsar A0535+262 to show the diagnostic value of simultaneous data on torque and quasi-periodic oscillations. These diagnostics yield the first evidence that inner accretion disks in X-ray pulsars are consistent with a ''middle-region'' Shakura-Sunyaev disk model and not with some other well-known disk models, irrespective of the relation between the X-ray flux I and the accretion rate M over dot. Indeed, the M over dot-I relation can be independently probed by this method, which shows that the observations are well represented by a relation of the form I proportional to M over dot (lambda) with lambda = 1 +/- 0.1. Mapping out the entire torque function by this method may also become possible in the near future.