Size of the Vela pulsar's emission region at 13 centimeter wavelength

We present measurements of the size of the Vela pulsar in three gates across the pulse, from observations of the distribution of intensity. We calculate the effects on this distribution of noise in the observing system, and measure and remove it using observations of a strong continuum source. We also calculate and remove the expected effects of averaging in time and frequency. We find that effects of variations in pulsar flux density and instrumental gain, self-noise, and 1 bit digitization are undetectably small. Effects of normalization of the correlation are detectable, but do not affect the fitted size. The size of the pulsar declines from 440+/-90 km (FWHM of best-fitting Gaussian distribution) to less than 200 km across the pulse. We discuss implications of this size for theories of pulsar emission.