Speaker
Description
The flat-spectrum radio quasar 3C 279 is well known for its prolific emission
of rapid flares. One particular event occurred on December 20th, 2013, exhibiting
a large flux increase with a doubling time scale of a few hours, a very hard γ-ray
spectrum, and a time asymmetry with a slow decay, while no significant variations
in the optical range were detected.
We propose a novel scenario to interpret this "orphan flare", based on two
emission zones corresponding to a stationary and a fast moving plasma blob.
While the stationary blob is located within the broad-line region (BLR) and accounts
for the low-state emission, the moving blob decouples from the stationary zone,
accelerates and crosses the BLR. The high-energy flare can be attributed to the
variable external Compton emission as the blob moves through the BLR, while the
variations in the synchrotron emission remain negligible.
Our description differs from previous interpretations of this flare by not relying on any acceleration mechanisms of the electrons in the plasma blob. Instead, the flare emerges as a
consequence of the bulk motion of the blob and the geometry of the external photon fields.
