NuSTAR Bounds on Radiatively Decaying Particles from M82

Journal Article · 30 April 2025 · Physical Review Letters

DOI: https://doi.org/10.1103/PhysRevLett.134.171004 · OSTI ID:2563787

Candón, Francisco R. ; Fiorillo, Damiano F. G. ; Lucente, Giuseppe; Vitagliano, Edoardo ; Vogel, Julia K.

Axions and other putative feebly interacting particles with a mass of tens to several hundreds of keVs can be produced in stellar cores with a Lorentz boost factor $E_a/m_a\lesssim 10$ . Thus, starburst galaxies such as M82 are efficient factories of slow axions. Their decay $a\to \gamma \gamma$ would produce a large flux of x-ray photons, peaking around 100 keV and spread around the Galaxy by an angle that can be relatively large. We use observations of the Nuclear Spectroscopic Telescope Array mission to show that the absence of these features can constrain 30–500 keV axion masses into uncharted regions for axion-photon coupling of $g_{a\gamma }\sim {10}^{-10}–{10}^{-12}{\mathrm{GeV}}^{-1}$ . Our argument can be applied to other heavy feebly interacting particles and astrophysical sources that are hot enough to produce them, yet cold enough to avoid large boost factors which slow down the decay. Published by the American Physical Society 2025

• Sponsoring Organization: USDOE
• Grant/Contract Number: AC02-76SF00515
• OSTI ID: 2563787
• Journal Information: Physical Review Letters, Journal Name: Physical Review Letters Journal Issue: 17 Vol. 134; ISSN 0031-9007; ISSN PRLTAO
• Publisher: American Physical SocietyCopyright Statement
• Country of Publication: United States
• Language: English