Probing a X-ray signature of multiple recollimation shocks in the blazar Mrk 421
Abstract
Mrk 421, as most of the TeV high-frequency-peaked BL Lacs (HBLs), show stationary or slow motions of its VLBI radio-knots structure, in stark contrast with its known fast variability. This problem, known as "the bulk Lorentz factor crisis", can be resolved if we consider that these strings of knots are successive recollimation shocks in jets. Successive shocks predict that a unique pattern of the non-thermal emission variability should appear after each strong flare. Using the 13 years long dataset of the NASA space telescope Swift-XRT, I present the detection of such a distinct pattern at more than 3 sigma of significance against stochastic fluctuations. Then I show how this pattern can be used as an innovative way to unveil the physical properties of the Mrk 421 jet, such as the flow apparent speed, the size of jet perturbations, and the jet beaming parameters.
- Publication:
-
AAS/High Energy Astrophysics Division
- Pub Date:
- March 2019
- Bibcode:
- 2019HEAD...1710630H