PREPRINT

# Constraints on axionlike particles from a combined analysis of three flaring $\mathit{\text{Fermi}}$ flat-spectrum radio quasars

James Davies, Manuel Meyer, Garret Cotter

Submitted on 7 November 2022

## Abstract

Many theories beyond the Standard Model of particle physics predict the existence of axionlike particles (ALPs) that mix with photons in the presence of a magnetic field. Searching for the effects of ALP-photon mixing in gamma-ray observations of blazars has provided some of the strongest constraints on ALP parameter space so far. Previously, only individual sources have been analysed. We perform a combined analysis on $\mathit{\text{Fermi}}$ Large Area Telescope data of three bright, flaring flat-spectrum radio quasars, with the blazar jets themselves as the dominant mixing region. For the first time, we include a full treatment of photon-photon dispersion within the jet, and account for the uncertainty in our B-field model by leaving the field strength free in the fitting. Overall, we find no evidence for ALPs, but are able to exclude the ALP parameters ${m}_{a}\lesssim 200$ neV and ${g}_{a\gamma }\gtrsim 5×{10}^{-12}$ GeV${}^{-1}$ with 95\% confidence.

## Preprint

Comment: 18 pages, 14 figures; submitted to Physical Review D

Subjects: Astrophysics - High Energy Astrophysical Phenomena; High Energy Physics - Phenomenology