Diffuse Axion Background
arXiv:2402.00100
Abstract
Relativistic axions can be readily produced in a broad variety of transient sources, such as axion star bosenova explosions, supernovae or even evaporating primordial black holes. We develop a general framework describing the resulting persistent diffuse axion background (DB) due to accumulated axions from historic transient events. We derive strong constraints on the DB flux from light axions emitted from sources with energies considering the non-observation of excess photons associated with axion-photon coupling from experiments, including COMPTEL, NuSTAR, XMM-Newton, INTEGRAL, EGRET and Fermi. Future searches in experiments such as SKA, JWST, XRISM, Vera C. Rubin Observatory, AMEGO/e-ASTROGAM will allow probing DB and associated axion-photon couplings with unprecedented sensitivity covering a wide range of possible source energies as low as eV and multiple decades in axion masses. We highlight the differences between astrophysical and dark sector sources of DB. Further, we discuss complementarity with direct detection as well as prospects for other DB searches. Our analysis demonstrates that DB can act as a promising probe of populations of axion emission sources as well as emission mechanisms.
56 pages, 19 figures. Updated with additional references and new sources of relativistic axion emission