Speaker
Description
PKS 2155-304 is a nearby high‑synchrotron‑peaked (HSP) BL Lac blazar at redshift z ≈ 0.116, and a benchmark source for studying multiwavelength variability in relativistic jets. In this work, we present a time‑dependent modeling study of its spectral energy distributions (SEDs) across the electromagnetic spectrum, using data from H.E.S.S. (very‑high‑energy gamma rays, 2003-2016), Fermi‑LAT (high‑energy gamma rays), Swift‑XRT and UVOT (X‑ray to UV), SMARTS (optical to near‑infrared), Steward Observatory (all covering the period from August 5, 2008, MJD 54683, to December 31, 2018, MJD 58483). This long‑baseline coverage enables a detailed view of its quiescent states, multiwavelength flares, and orphan‑flare episodes.
We construct time‑resolved SEDs at multiple epochs and apply the time‑dependent leptonic diffusive shock acceleration and radiation transfer model in which the relativistic electron population evolves according to injection, acceleration, and radiative cooling. By varying physical parameters such as magnetic field strength, Doppler factor, electron injection rate, and emission‑zone size, we investigate how different activity states - quiescence, gamma‑ray‑dominant, X‑ray‑dominant, and optical‑UV‑dominant flares - emerge from changes in the underlying jet physics. The modeling allows us to derive characteristic acceleration and cooling time‑scales and to assess the degree to which a single emission zone can account for the observed broadband variability.
Our time‑dependent modeling can reproduce the general spectral shapes and flux evolution of PKS 2155-304 across the various wavelength regimes over MJD 54683-58483. The analysis highlights PKS 2155-304 as an excellent benchmark for constraining jet dynamics through time‑resolved SED modeling, and provides a baseline for interpreting future observations with next‑generation facilities such as the Cherenkov Telescope Array and the MAGIC telescope.