Session 68 - Degenerate Stars, Pulsars.
Display session, Thursday, June 11
Atlas Ballroom,

## [68.01] Magnetospheric Geometry in Pulsar B1929+10 from Radio/X-ray Phase Alignment

A. L. Somer, D. C. Backer (UC, Berkeley), J. P. Halpern, F. Y. -H. Wang (Columbia U.)

We have conducted a study of two rotation-powered pulsars that emit at both radio and x-ray wavelengths, PSR B0531+21 and PSR B1929+10. Using absolute phase information, we have phase-aligned x-ray and radio profiles from these pulsars. Observations were done using the Green Bank 140ft telescope, and ASCA. The 0531+21 x-ray profile is sharp and lines up well with the radio profile confirming that the x-ray emission from this pulsar is magnetospheric in origin. The 1929+10 profile is approximately sinusoidal (Wang amp; Halpern, ApJ 4 82, L159) with the peak of the emission arriving 67\pm 23 degrees after the maximum in the radio emission. The controversy to which the PSR B1929+10 result adds fuel, is whether this inter"-pulsar, is an aligned" or orthogonal" rotator - describing the alignment of the magnetic axis to the rotation axis. Do the two peaks in the radio profile (the pulse and interpulse) come from a double crossing of a thin hollow cone nearly aligned with rotation axis (as in Lyne amp; Manchester, 1988, MNRAS, 234, 477; Phillips, 1990, ApJL, 361, L57; Blaskiewicz et al, 1991, ApJ 370, 643), or alternatively (as in Rankin and Rathnasree, 1998 preprint) do they come from from opposite poles of an orthogonal" rotator where the spin axis is perpendicular to the magnetic axis? The radio to x-ray alignment we find favors the former explanation: if the x-ray hot spot is the result of return currents to the surface from the outward current that generates radio emission, then in the double-crossing" model, the hot spot phase is expected to lie between the main pulse and interpulse as observed.