Year: 2025
Type: conference-paper
Abstract: Blazars, a subclass of active galactic nuclei (AGN), are known to be bright $\gamma$-ray sources, frequently exhibiting active (flaring) periods. The blazar PKS~2155-304 is a high synchrotron-peaked BL Lac object located at redshift $z=0.116$. On 2006 July 28, an extremely remarkable outburst of VHE $\gamma$-ray emission from this blazar was reported by the H.E.S.S. experiment, with an average flux more than 10 times the low-state level. The variability timescale of this extraordinary flare was as short as approximately 200~s. In order to guarantee the transparency of the emission region for TeV photons, the fast variability demands an extremely high Doppler factor $\delta_{\rm D}>50$ of the jet within the classical one-zone model, leading to the so-called ``Doppler factor crisis''. Here we demonstrate that the stochastic dissipation model, which is a multi-blob scenario for blazars, can self-consistently explain the giant TeV flares of PKS~2155-304 and the low-state emission before and after the flares, in terms of both multi-wavelength spectral and variability characteristics. The required Doppler factor in this model can be as low as 20, which is a reasonable and typical value for blazar jets. The obtained model parameters may shed some light on the physical properties of the relativistic jet.
DOI: 10.22323/1.501.0858
Authors: Hongbin Tan, Ruoyu Liu, Markus Böttcher
Institutions: Nanjing University, North-West University
Language: English
Subfield: Nuclear and High Energy Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: hybrid
OpenAlex ID: W4414530564
FWCI:
Cites:
Cited by:
Related to: