X-ray Spectral Transitions in TeV Blazars

Blazars represent the most extreme class of active galactic nuclei, characterised by relativistic jets oriented towards Earth. Recent observations have revealed that certain blazars exhibit flux-dependent X-ray spectral transitions that reflect fundamental changes in emission mechanisms. During flaring states, X-ray spectra become characteristically soft as synchrotron radiation dominates, while quiescent states display substantially harder spectra where inverse-Compton processes dominate. Intermediate flux states reveal mixed emission signatures from both components. We present a systematic study of X-ray spectral transitions in the selected TeV-detected blazars: 1ES 1215+303, S5 0716+714, W Comae, 4C +21.35, AP Librae, B2 1420+32, OT 081, 1ES 2344+514, TXS 0506+056, BL Lacertae, OJ 287 and OP 313. We perform detailed timing and spectral analysis of the X-ray data, including fractional variability, cross-correlation analysis, and spectral variability studies. Broadband spectral energy distributions are constructed for different flux states and modelled using a one-zone leptonic model to constrain the physical parameters. This work provides the first comprehensive characterisation of X-ray spectral transitions for a sample of TeV blazars. Our results reveal systematic patterns in spectral evolution that constrain the physical conditions in relativistic jets and provide new insights into the emission mechanisms operating during different activity levels.