Synchrotron sources. II. Pulsars and compact extragalactic objects

We discuss some limitation on synchrotron models for optical pulsars and compact extragalactic objects. Using the results of the previous paper, we show that several existing models for the pulsar NP 0532 are inconsistent with the measured time variations and polarization of the optical emission. We also consider whether the low-frequency falloffs in some extragalactic objects (PKS 2134+004, OQ 408, and NGC 1068) could be due to emission from particles with small pitch angles, absorption by a thermal plasma, or synchrotron self-absorption. We find that radiation by particles with small pitch angles could explain the radio emission from PKS 2134+004 and OQ 208, but this process is inconsistent with the observations of NGC 1068. The absorption interpretations cannot account for the turnover in the spectrum of PKS 2134+004. Measurements of polarization, angular structure, and X-ray flux would be helpful in evaluating these models. Subject headings: galaxies - pulsars - radio sources - synchrotron radiation