Revisiting the analysis of axion-like particles with the Fermi-LAT gamma-ray observation of NGC1275

TL;DR

This paper re-analyzes Fermi-LAT data of NGC1275 to search for axion-like particles using a spectral irregularity method, setting more stringent constraints on ALP parameters and proposing combined observations for improved limits.

Contribution

It introduces an alternative spectral irregularity method for ALP searches and provides tighter constraints than previous analyses.

Findings

No spectral oscillation detected in NGC1275

Constraints on ALP-photon coupling are improved to g_{aγ}>3×10^{-12} GeV^{-1} at 1 neV mass

Combining multiple sources can further enhance ALP exclusion limits.

Abstract

In this work, we re-analyze the Fermi-LAT observation of NGC 1275 to search for axion-like particle (ALP) effects and constrain ALP parameters. Instead of fitting the observed spectrum with ALP models, we adopt an alternative method for the analysis of this source which calculates the irregularity of the spectrum. With the newly used method, we find no spectral oscillation for the NGC 1275 and rule out couplings $g_{a\gamma}>3\times10^{-12}\,{\rm GeV^{-1}}$ around ALP mass of $m_a\sim$ 1 neV at 95\% confidence level, which is more stringent than the previous results. We also show that the constraints can be further improved by combining the observation of PKS 2155-304. We suggest that with more sources taken into account, we could obtain a much wider exclusion region.