Timing and scintillations of the millisecond pulsar 1937 + 214
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Abstract
Pulse shapes, arrival times, and interstellar scintillations of the 1.56 ms PSR 1937 + 214 pulsar are analyzed at frequencies from 0.32 to 1.4 GHz using data obtained from April 1983 to December 1985. The narrow pulse and small period of the pulsar yield arrival times that are much more precise than those of most other pulsars. Arrival time precision for the pulsar is limited at low frequencies by distortions of the pulse shape imposed by interstellar scintillations. Arrival times at all radio frequencies are affected by variations in dispersion measure and, possibly, additional variations related to variations in angle of arrival. Uncertainties in how the pulse shape varies with frequency influence estimates of dispersion measures. The interstellar scintillation and pulse broadening of the pulsar strongly constrain the spatial power spectrum of electron density variations in the ISM.