A SPECTRAL STUDY OF 4 MILLISECOND PULSARS

Flux density measurements of four millisecond pulsars, PSR 1620 - 26, 1821 - 24, PSR 1855 + 09, and PSR 1937 + 21, have been made to determine their spectral indices in the frequency range between 425 MHz and 3 GHz. The four objects are shown to have indices that range from -1.3 to -2.6. The luminosities of these four pulsars are spread over nearly three orders of magnitude. An analytic pulse component model is developed for each object. Individual components are allowed to have different spectral indices and hence different component ratios as a function of frequency. Component separations are evaluated as a function of frequency. The analytic models are used to determine dispersion measures with a precision better than 0.01 pc cm-3 for each object.