Speaker
Description
Blazars exhibit strong variability across multiwavelength observations and multiple timescales. We present a systematic study of the X-ray spectral and timing variability of the TeV blazar PKS 2155-304 using Chandra and NuSTAR observations spanning 25 years (1999-2024). Timing analysis and flux distribution studies reveal moderate variability in most light curves and variable power spectral indices across the observational time. Hardness-ratio plots indicate that while many observations show limited spectral evolution with flux, some exhibit significant hardness changes correlated with brightness. We modeled the X-ray spectra with power-law, broken power-law, log-parabola, and bremsstrahlung plus power-law functions. The bremsstrahlung plus power-law model provides the best description for the majority of observations, suggesting the coexistence of thermal and non-thermal components in the X-ray emission. Additionally, we performed joint spectral fitting to Chandra and NuSTAR data during flares around MJD 56405-564056. These findings highlight the complex variability of PKS 2155-304 and provide new constraints on the relativistic jet’s non-thermal processes and possible thermal contributions to blazar emission.
