Axion parameter space. All shaded regions are excluded by one or more astrophysical probes. Specifically, the region above the blue line is excluded by the duration of the neutrino signal from SN 1987A (Raffelt 1996). The purple region is excluded by the explosion energies of Type IIP SNe (Caputo et al. 2022b), assuming a typical star with a radius of R_* = 5 × 10¹³ cm and a lower limit on the explosion energy of 0.1 foe. The grey region is constrained by measurements of the extragalactic background light (Caputo et al. 2022a), while the green region is excluded by the upper limit on the gamma-ray fluence from SN 1987A (Caputo et al. 2022a), as determined by GRS. The shaded orange region is instead in tension with X-ray observations of GW170817 event (Diamond et al. 2024). The red stars highlight points of the parameter space around which the axion’s mean free path is within ∼10¹² − 10¹⁴ cm and the energy deposition at such distances accrues to ∼0.01–0.1 foe.