A Flare in the Jet of Pictor A

TL;DR

This paper reports the discovery of a transient X-ray flare in the Pictor A jet, challenging existing models of jet emission due to its rapid variability over a large spatial scale.

Contribution

It presents the first observation of a short-term X-ray flare in a large-scale astrophysical jet, suggesting localized regions with enhanced magnetic fields.

Findings

Detected a flare that faded between 2000 and 2002

The flare was not present in 2009 observations

Variability implies small, magnetically enhanced sub-volumes within the jet

Abstract

A Chandra X-ray imaging observation of the jet in Pictor A showed a feature that appears to be a flare that faded between 2000 and 2002. The feature was not detected in a follow-up observation in 2009. The jet itself is over 150 kpc long and a kpc wide, so finding year-long variability is surprising. Assuming a synchrotron origin of the observed high-energy photons and a minimum energy condition for the outflow, the synchrotron loss time of the X-ray emitting electrons is of order 1200 yr, which is much longer than the observed variability timescale. This leads to the possibility that the variable X-ray emission arises from a very small sub-volume of the jet, characterized by magnetic field that is substantially larger than the average over the jet.