Synchrotron Lightcurves of Blazars in a Time-Dependent Synchrotron-Self Compton Cooling Scenario

Abstract

Blazars emit non-thermal radiation in all frequency bands from radio to γ-rays. Additionally, they often exhibit rapid flaring events at all frequencies with doubling time scale of the TeV and X-ray flux on the order of minutes, and such rapid flaring events are hard to explain theoretically. We explore the effect of the synchrotron-self Compton cooling, which is inherently time-dependent, leading to a rapid cooling of the electrons. Having discussed intensively the resulting effects of this cooling scenario on the spectral energy distribution of blazars in previous papers, the effects of the time-dependent approach on the synchrotron lightcurve are investigated here. Taking into account the retardation due to the finite size of the source and the source geometry, we show that the time-dependent synchrotronself Compton (SSC) cooling still has profound effects on the lightcurve compared to the usual linear (synchrotron and external Compton) cooling terms. This is most obvious if the SSC cooling takes longer than the light crossing time scale. Then in most frequency bands the variability time scale is up to an order of magnitude shorter than under linear cooling conditions. This is yet another strong indication that the time-dependent approach should be taken into account for modeling blazar flares from compact emission regions.

The Extended Flare in CTA 102 in 2016 and 2017 within a Hadronic Model through Cloud Ablation by the Relativistic Jet

“…The number of particles ablated in each slice is the integral over the density ′ ( ′ ) with respect to the slice volume d . In the case of a sphere, the volume of a slice between positions ′ and ′ + d ′ is (Zacharias & Schlickeiser 2013)…”

Cloud Ablation by a Relativistic Jet and the Extended Flare in CTA 102 in 2016 and 2017

“…The number of particles ablated in each slice is the integral over the density ′ ( ′ ) with respect to the slice volume. In the case of a sphere, the volume of a slice between positions ′ and ′ + d ′ is (Zacharias & Schlickeiser 2013)…”

A time dependent approach to model X-ray and γ–ray light curves of Mrk 421 observed during the flare in February 2010

“…Nonetheless, this will lead to the increased number of parameters and a reasonable conclusion on the physical condition responsible for the flare cannot be derived. Again, we have not considered the light travel time effects [52,53,54,55] since the flare time scale at the source frame (t of ∼ 1 day in observer frame, the corresponding time in source frame will be…”