Axion emission from supernovae: a cheatsheet

Supernovae provide fascinating opportunities to study various particles and their interactions. Among these there are neutrinos, axions, and other light weakly interacting particles, which play a significant role in our understanding of fundamental physics. In this study, the focus lies on the recent advancements made in characterizing axion emission from nuclear matter within the context of supernovae. The main production mechanisms for axions coupled with nucleons, bremsstrahlung and pion-axion conversion, are extensively discussed. These findings shed light on the behavior of axions in dense and hot nuclear matter, encountered in these extreme astrophysical environments.Comment: 10 pages, 5 figures. Invited contribution based on a PhD Thesis which was awarded the Sergio Fubini prize by the Istituto Nazionale di Fisica Nucleare (INFN

Constraining MeV-scale axion-like particles with Fermi-LAT observations of SN 2023ixf

The Fermi-LAT observations of SN 2023ixf, a Type II supernova in the nearby Pinwheel Galaxy, Messier 101 (M101), presents us with an excellent opportunity to constrain MeV-scale Axion-Like Particles (ALPs). By examining the photon decay signature from heavy ALPs that could be produced in the explosion, we improve the existing constraints on the ALP-photon coupling by up to a factor of $\sim 2$ for masses $m_a \lesssim 3$ MeV, with the exact value depending mostly on plasma properties of the collapsing core. This study demonstrates the relevance of core-collapse supernovae, also beyond the Magellanic Clouds, as probes of fundamental physics.Comment: 7 pages, 2 figure

Thermal axions with multi-eV masses are possible in low-reheating scenarios

We revise cosmological mass bounds on hadronic axions in low-reheating cosmological scenarios, with a reheating temperature $T_{\rm RH}~\le 100$ MeV, in light of the latest cosmological observations. In this situation, the neutrino decoupling would be unaffected, while the thermal axion relic abundance is suppressed. Moreover, axions are colder in low-reheating temperature scenarios, so that bounds on their abundance are possibly loosened. As a consequence of these two facts, cosmological mass limits on axions are relaxed. Using state-of-the-art cosmological data and characterizing axion-pion interactions at the leading order in chiral perturbation theory, we find in the standard case an axion mass bound $m_a < 0.26$ eV. However, axions with masses $m_a \simeq 1$ eV, or heavier, would be allowed for reheating temperatures $T_{\rm RH} \lesssim 80$ MeV. Multi-eV axions would be outside the mass sensitivity of current and planned solar axion helioscopes and would demand new experimental approaches to be detected.Comment: v2: minor changes to match the version published on JCAP. 27 pages, 10 figure

Production of axion-like particles from photon conversions in large-scale solar magnetic fields

The Sun is a well-studied astrophysical source of axion-like particles (ALPs), produced mainly through the Primakoff process. Moreover, in the Sun there exist large-scale magnetic fields that catalyze an additional ALP production via a coherent conversion of thermal photons. We study this contribution to the solar ALP emissivity, typically neglected in previous investigations. Furthermore, we discuss additional bounds on the ALP-photon coupling from energy-loss arguments, and the detection perspectives of this new ALP flux at future helioscope and dark matter experiments.Comment: v2: 15 pages, 7 pdf figures. Figures improved, typos removed. Matches the version published on PR

Proto-neutron stars as cosmic factories for massive axion-like-particles

The parameter space of massive axion-like-particles (ALPs) with $m_a \sim {\mathcal O} (100)$ MeV and coupled with nucleons is largely unexplored. Here, we present new constraints in this parameter region. In doing so, we characterize the supernova emissivity of heavy ALPs from a proto-neutron star, including for the first time mass effects in both nucleon-nucleon Bremsstrahlung and pionic Compton processes. In addition, we highlight novel possibilities to probe the couplings with photons and leptons from supernova ALP decays.Comment: 13 pages, 8 figure

Heavy axion-like particles and core-collapse supernovae: constraints and impact on the explosion mechanism

Heavy axion-like particles (ALPs), with masses $m_a \gtrsim 100$ keV, coupled with photons, would be copiously produced in a supernova (SN) core via Primakoff process and photon coalescence. Using a state-of-the-art SN model, we revisit the energy-loss SN 1987A bounds on axion-photon coupling. Moreover, we point out that heavy ALPs with masses $m_a \gtrsim 100$ MeV and axion-photon coupling $g_{a\gamma} \gtrsim 4 \times 10^{-9}$ GeV$^{-1}$ would decay into photons behind the shock-wave producing a possible enhancement in the energy deposition that would boost the SN shock revival.Comment: v2 (32 pages, 21 figure): revised version. Matches the published version on JCAP. Major changes to improve the robustness of the bound. Added two Appendices on the possible constraining criteria and on the effect of the SN progenitor mass on the boun