The peculiar new state of the blazar PKS 1510-089

TL;DR

This study reports a significant change in the optical and gamma-ray emissions of blazar PKS 1510-089 since July 2021, with a notable decrease in optical flux and polarization, while X-ray and VHE gamma-ray fluxes remained steady, analyzed through multiwavelength observations and SED modeling.

Contribution

The paper provides a detailed multiwavelength observational analysis and theoretical SED modeling to explain the unusual state change in PKS 1510-089.

Findings

Optical flux and polarization decreased to near zero in 2022.

High-energy gamma-ray flux remained steady despite optical changes.

X-ray and VHE gamma-ray fluxes showed no significant variation.

Abstract

Contemporaneous multiwavelength observations with H.E.S.S., SALT, Fermi-LAT, Swift, and ATOM show that the blazar PKS 1510-089 suffered a significant decrease in its optical flux, degree of optical polarization and high-energy gamma-ray (E > 100 MeV) flux since July 2021. Meanwhile, the X-ray and very-high-energy gamma-ray (E > 100 GeV) fluxes remained steady throughout 2021 and 2022. The degree of optical polarization decreased to about zero in 2022, indicating an unpolarized dominating accretion disk component in the optical-UV domain that is completely diluting the polarized electron synchrotron component. In this proceeding we will discuss, via theoretical SED modeling, possible reasons for this dramatic change in the appearance of this blazar.