Does black hole spin play a key role in the FSRQ/BL Lac dichotomy?

TL;DR

This paper investigates the role of black hole spin in the luminosity differences between FSRQs and BL Lacs, suggesting spin is a key factor in their dichotomy beyond accretion rates.

Contribution

It introduces the idea that black hole spin significantly influences the luminosity distribution differences between FSRQs and BL Lacs.

Findings

Black hole spin correlates with blazar luminosity classes.

BL Lacs are likely low-spin, slow rotators.

FSRQs tend to be high-spin, fast rotators.

Abstract

It is believed that jets emerging from blazars (Flat Spectrum Radio Quasars (FSRQs) and BL Lacs) are almost aligned to the line-of-sight. BL Lacs usually exhibit lower luminosity and harder power law spectra at gamma-ray energies than FSRQs. It was argued previously that the difference in accretion rates is mainly responsible for the large observed luminosity mismatch between them. However, when intrinsic luminosities are derived by correcting for beaming effects, this mismatch is significantly reduced. We show that spin plays an important role to reveal the dichotomy of luminosity distributions between BL Lacs and FSRQs, suggesting BL Lacs to be low luminous and slow rotators compared to FSRQs.