Applications of Fermilike energy gain mechanism for Photons in shearing plasma, (i) Limb brightening in AGN jets and (ii) Spectral lag transitions in GRBs

by Dr. Mukesh Vyas

BIU

at Astrophysics and Cosmology Seminar

Wed, 04 Dec 2024, 11:10
Sacta-Rashi Building for Physics (54), room 207

Abstract

I will discuss new applications of the Fermilike energy gain mechanism for photons where a photon scatters with shearing layers of relativistic plasma and subsequently gains energy. The population of photons finally escapes from the photosphere of the system. Using structured jets that harbour velocity shear within them in extragalactic sources, I will describe two applications of this mechanism in this talk, (I) We present a unified theory of positive and negative spectral lags observed in the Gamma-Ray Bursts (GRBs) prompt phase. In positive lags, low-energy photons lag behind high-energy photons while the trend is the opposite in negative lags where high-energy photons arrive later. The model predicts a transition from positive to negative spectral lag which is commonly observed and remains unexplained in GRBs. (II) We demonstrate that the Compton scattering of photons with shearing plasma leads to a natural explanation for well-observed phenomena of Limb brightening in the Active Galactic Nuclei (AGNs) jet bases. In this phenomenon, the limb of the jet base appears brighter compared to its central axis. Our explanation lies in the relativistic nature of the optical depth in the shearing plasma. The investigation puts forward an unconventional picture of the existance of a Compton photosphere very close to jet base in AGNs.

Created on 28-11-2024 by Zitrin, Adi (zitrin)
Updaded on 28-11-2024 by Zitrin, Adi (zitrin)