Pulsars, transients and relativistic astrophysics

Abstract:

Chandra X-ray Observatory observations of the powerful, peculiar radio galaxy 3C 123 have resulted in an X-ray detection of the bright eastern hot-spot, with a 1-keV flux density of similar to 5 nJy. The X-ray flux and spectrum of the hot-spot axe consistent with the X-rays being inverse-Compton emission from the population of electrons responsible for the radio emission, if the magnetic fields in the hot-spot are close to their equipartition values. 3C 123 is thus the third radio galaxy to show direct evidence for equipartition in hot-spots.

Abstract:

The Chandra measurement of X-rays from the radio jet in PKS 0637-752 has implications for the source kinematics and energetics. This contribution discusses several possibilities for explaining the high X-ray output from the jet, emphasizing the impact on the assumption of equipartition between relativistic particles and fields in the jet plasma.

Abstract:

We discuss the various contributions to the jet luminosity in proton blazar models of active galactic nuclei and describe a method of estimating the jet luminosity from the observed spectral energy distribution (SED) and the fitted model parameters. We apply this to a synchrotron proton blazar (SPB) model for Markarian 501.

Abstract:

The parsec-scale radio jets of BL Lacertae objects imaged with Very Long Baseline Interferometry (VLBI) show a number of distinctive features. The most striking of these is the dominance of transverse magnetic fields on the wide range of scales probed by VLBI observations at frequencies from 43 to 5 GHz. Some compact VLBI components with transverse fields axe undoubtedly relativistic shocks, in which the transverse field has been enhanced by compression. However, there is considerable evidence that we axe also detecting the toroidal component of an underlying helical magnetic field associated with the VLBI jet.

Abstract:

In February 1997, we obtained multi-frequency polarization VLBA observations of 23 sources from a complete sample of northern BL Lac objects. Total intensity and linear polarization images of two sources (0745+241 and 0820+225) showing evidence for the presence of sheaths of longitudinal magnetic field surrounding their jets are presented. These results suggest that appreciable amounts of thermal plasma are often present on parsec scales, and that the jet magnetic field can be influenced by interaction with this surrounding medium.