| Name: | Sushmita Agarwal |
| Affiliation: | Indian Institute of Technology, Indore |
| Conference ID : | ASI2023_230 |
| Title : | Flaring activity from magnetic reconnection in BL Lac jets |
| Authors : | S. Agarwal, B. Banerjee, A. Shukla, J. Roy, S. Acharya, B. Vaidya, V. R. Chitnis,
S. M. Wagner, K. Mannheim, M. Branchesi |
| Mode of Presentation: | Poster |
| Abstract Category : | Extragalactic Astronomy |
| Abstract : | The evolution of the spectral energy distribution during flares constrains models of particle acceleration in blazar jets.
In 2020 and 2021, the archetypal blazar BL Lac gave a rare opportunity to explore spectrum variation during an extended period of intense flaring.
During its highest gamma-ray state, the measured flux (0.1-300GeV) was as high as 2.15 × 10^(-5) ph cm-2 s-1, with sub-hour scale variability.
The synchrotron hump extended into the X-ray regime up to 7.5 KeV and was accompanied by a minute-scale flare and a peak shift of the inverse-Compton hump in gamma rays.
In shock acceleration models, a Doppler factor value of more than 100 is necessary to explain the observed rapid variability, change of state, and gamma-ray peak shift. Assuming particle acceleration in mini-jets produced by magnetic reconnection during flares alleviates the constraint on the bulk Doppler factor. In such jet-in-jet theories, the unexpected alignment of a magnetic plasmoid with the direction of the line of sight causes the observed spectrum shift to higher energy (towards the TeV domain) and simultaneous fast variability. We infer a magnetic field of 0.6 G in a reconnection area at the margin of the BLR ( ~ 0.02 pc). The scenario is further supported by the log-normal flux distribution resulting from the fusion of plasmoids in the reconnection region. |
