# Searching for Axion-Like Particles from Core-Collapse Supernovae with Fermi LAT's Low Energy Technique

**Authors:** Milena Crnogorčević, Regina Caputo, Manuel Meyer, Nicola Omodei, Michael Gustafsson  
**arXiv:** [2109.05790](https://arxiv.org/abs/2109.05790)  
**Date:** 2021-09-13  
**Summary page:** https://www.summarizepaper.com/en/paper/2109.05790v1/

## Key points

- Study focuses on search for axion-like particles (ALPs) produced in core-collapse supernovae (CCSNe)
- Utilizes data from the Fermi Large Area Telescope (LAT) to search for ALP spectral signatures in long gamma-ray bursts (GRBs)
- ALPs are abundantly produced during CCSNe and convert into gamma-rays in external magnetic fields
- Researchers perform sensitivity analysis to determine distances at which detection of ALP signal is possible using LAT's low-energy technique
- Distance limit ranges from approximately 0.5 to 10 Mpc, depending on sky location and CCSN progenitor mass
- Model comparison analysis of twenty-four GRBs does not show statistically significant improvement with inclusion of ALP contribution
- Statistical method used in analysis discussed, along with underlying physical assumptions
- Feasibility of setting upper limits on ALP-photon coupling explored
- Findings contribute to understanding of ALPs and their potential detection through gamma-ray observations
- Provides insights into sensitivity of LAT's low-energy technique and information for future studies on ALP properties

## Summary

This study focuses on the search for axion-like particles (ALPs) produced in core-collapse supernovae (CCSNe) and their subsequent conversion into gamma-rays. The researchers utilize data from the \textit{Fermi} Large Area Telescope (LAT) to conduct a comprehensive search for ALP spectral signatures in long gamma-ray bursts (GRBs). ALPs are hypothetical particles that are expected to be abundantly produced during CCSNe, resulting in a burst of ALPs lasting approximately 10 seconds. These ALPs then undergo conversion into gamma-rays in external magnetic fields, leading to the production of a long GRB with a characteristic spectrum peaking in the 30-100 MeV energy range. The researchers perform a data-driven sensitivity analysis to determine the distances at which detection of an ALP signal is possible using LAT's low-energy (LLE) technique. This technique allows for a larger effective area for energies down to 30 MeV compared to the standard LAT analysis. Assuming specific values for the ALP mass ($m_a \lesssim 10^{-10}$ eV) and ALP-photon coupling ($g_{a\gamma} = 5.3\times 10^{-12}$ GeV$^{-1}$), which have been considered and deduced in previous ALP searches from SN1987A, they find that the distance limit ranges from approximately 0.5 to 10 Mpc, depending on the sky location and CCSN progenitor mass. To further investigate the presence of ALP signals, the researchers select a sample of twenty-four GRBs as candidates and perform a model comparison analysis. They consider different GRB spectral models with and without an ALP signal component. However, their analysis reveals that including an ALP contribution does not result in any statistically significant improvement of the fits to the data. The study discusses the statistical method used in their analysis, as well as the underlying physical assumptions. They also explore the feasibility of setting upper limits on the ALP-photon coupling and provide an outlook on future telescopes in the context of ALP searches. Overall, this research contributes to our understanding of ALPs and their potential detection in CCSNe through gamma-ray observations. The findings provide insights into the sensitivity of LAT's LLE technique and offer valuable information for future studies aiming to detect or set constraints on ALP properties.