The magnetic geometry and radio beam of PSR 1929 + 10

PSR 1929 + 10 exhibits weak radio emission throughout most of its rotational period. To investigate the off-pulse emission, polarization measurements were conducted using the Arecibo 305-m radio telescope. Stokes parameters were obtained covering 75 percent of the pulsar period at 430 MHz and 45 percent at 1665 MHz. The emission geometry of the pulsar was derived by fitting a rotating vector model to the polarization angle swing across the pulse profile. The pulsar presents a nearly aligned geometry. Its magnetic dipole axis is tilted by 31 + or - 2 deg from the spin axis, and the minimum angle between the line of sight and the rotating dipole axis is 20 + or - 2 deg. The main pulse and interpulse are interpreted as two cuts of the line of sight across an elongated polar emission beam. The emission beam has a N-S elongation of about 5:1 at 430 MHz and about 6:1 at 1665 MHz. 15 refs