The Characteristics of Millisecond Pulsar Emission. I. Spectra, Pulse Shapes, and the Beaming Fraction

We have monitored a large sample of millisecond pulsars using the 100-mEffelsberg radio telescope in order to compare their radio emission propertiesto the slowly rotating population. With some notable exceptions, our findingssuggest that the two groups of objects share many common properties. Acomparison of the spectral indices between samples of normal and millisecondpulsars demonstrates that millisecond pulsar spectra are not significantlydifferent from those of normal pulsars. There is evidence, however, thatmillisecond pulsars are slightly less luminous and less efficient radioemitters compared to normal pulsars. We confirm recent suggestions that adiversity exists among the luminosities of millisecond pulsars with theisolated millisecond pulsars being less luminous than the binary millisecondpulsars. There are indications that old millisecond pulsars exhibit somewhatflatter spectra than the presumably younger ones. We present evidence thatmillisecond pulsar profiles are only marginally more complex than those foundamong the normal pulsar population. Moreover, the development of the profileswith frequency is rather slow, suggesting very compact magnetospheres. Theprofile development seems to anti-correlate with the companion mass and thespin period, again suggesting that the amount of mass transfer in a binarysystem might directly influence the emission properties. The angular radius ofradio beams of millisecond pulsars does not follow the scaling predicted from acanonical pulsar model which is applicable for normal pulsars. Instead they aresystematically smaller. The smaller inferred luminosity and narrower emissionbeams will need to be considered in future calculations of the birth-rate ofthe Galactic population.Comment: 40 pages, 14 figures, accepted for publication in Ap