X-ray Time Lags in TeV Blazars

TL;DR

This paper investigates X-ray time lags in TeV blazars using simulations, revealing conditions under which soft and hard lags occur and reproducing observed gamma-ray/X-ray relations.

Contribution

It introduces a simulation-based study explaining the origins of X-ray time lags and their relation to particle acceleration and cooling processes in blazars.

Findings

Soft lags occur when radiative cooling dominates flare decay.

Hard lags can arise from achromatic particle energy loss mechanisms.

The gamma-ray/X-ray quadratic relation is reproduced in certain scenarios.

Abstract

We use Monte Carlo/Fokker-Planck simulations to study the X-ray time lags. Our results show that soft lags will be observed as long as the decay of the flare is dominated by radiative cooling, even when acceleration and cooling timescales are similar. Hard lags can be produced in presence of a competitive achromatic particle energy loss mechanism if the acceleration process operates on a timescale such that particles are slowly moved towards higher energy while the flare evolves. In this type of scenario, the {\gamma} -ray/X-ray quadratic relation is also reproduced.