Bounds on ALP-Mediated Dark Matter Models from Celestial Objects

Abstract: We have studied the signals from axion-like particles (ALPs) as dark matter mediators from celestial objects such as neutron stars, brown dwarfs or white dwarfs. We consider the accumulation of dark matter inside the celestial objects using the multiscatter capturing process. The production of ALP from the dark matter annihilation can escape the celestial object and decay into gamma-rays and neutrinos before reaching the Earth. We investigate our model using gamma-ray observations from Fermi and H.E.S.S. and neutrino observations from IceCube and ANTARES. The effective Lagrangian approach allows us to place constraints on the ALP-photon and ALP-fermion couplings. In the gamma-ray channel, our results are able to rule out the existence of ALP with mass up to $\sim \mathcal{O}(10)$ GeV. On the other hand, the neutrino observations can be used to probe a higher mass range with ALP mass up to $\sim \mathcal{O}(100)$ GeV.