Pulsars, transients and relativistic astrophysics

Abstract:

Recently, we have identified a small number of extended radio sources that consist of two double-lobed radio sources, which axe well aligned and centered on a common nucleus. We have called these 'Double-double radio galaxies' (DDRGs). The observed structures strongly suggest interrupted central activity as the origin of these sources. We have developed a model based on this assumption with which we are able to explain several observed properties. Since the inner structures of the DDRGs advance inside the cocoon originally formed by the outer lobes, these allow us to probe the cocoon medium. Our results indicate that the cocoon density must be higher than has been assumed in earlier models.

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.