1991 .

(2 publications)

R. S. Foster, L. Fairhead, and D. C. Backer. A spectral study of four millisecond pulsars. Astrophysical Journal, 378:687-695, September 1991. [ bib | DOI | ADS link ]

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/cu cm for each object.

L. Fairhead. Astrometric analysis of timing observations of the fast pulsar PSR 1937 + 214. Astronomy Astrophysics, 241:289-296, January 1991. [ bib | ADS link ]

A new analysis of the first two years of timing data acquired on the fast pulsar PSR 1937+214 at Arecibo is presented. Parameters are evaluated with various models based on two ephemerides, two atomic time scales and two TT-TB time transformations and comparison is carried out with previously published results. We provide evidence that systematic errors induced by the model adopted are 5 to 10 times larger than the formal uncertainties calculated by the fitting procedure. One must therefore exercise great care in the reduction method when comparing results from different timing programs for precise astrometric applications.