Emission and detectability of hadronic axions from SN 1987A

We show that axions emitted by SN 1987A, with coupling strengths to nucleons in the range 9×{}10^-7{}gaN{}1×{}10^-3, would have produced an unacceptably large signal at the Kamiokande proton-decay experiment. Axions with 10^-10{}gaN{}1.4×{}10^-6 would have altered the neutrino flux from that observed, so using results from SN 1987A alone, one may nominally rule out the entire range 10^-10{}gaN{}10^-3. Uncertainties in our estimates prevent us from categorically excluding a small window around gₐₙ{}10^-6, which could have interesting consequences for supernova theory and cosmology.