Axion constraints from quiescent soft gamma-ray emission from magnetars

Abstract

Axion-like-particles (ALPs) emitted from the core of magnetars can convert to photons in the strong magnetic field of the magnetosphere. We study such emissions in the soft gamma-ray range from 300 keV to 1 MeV, where the ALP spectrum peaks and astrophysical backgrounds from resonant Compton upscattering are expected to be suppressed. Using published quiescent soft-gamma flux upper limits in 6 Magnetars obtained with CGRO COMPTEL, INTE-GRAL SPI/IBIS/ISGRI and the Fermi Gamma Ray Burst Monitor (GBM), we put limits on the ALP-photon coupling obtained from conversions, assuming that ALP emission from the core is just sub-dominant to bounds from neutrino cooling. For core temperatures of 10 9 K, the constraints on the ALP-photon coupling coming from magnetars 1E 2259+586 and J170849.0-400910 are better than the current limits obtained from the CAST experiment. We provide a detailed study of the dependence of our results on the magnetar core temperature. Our results motivate a program of studying quiescent soft gamma ray emission from magnetars in the 300 keV -1 MeV band with the Fermi -GBM.

Dark Matter In Extreme Astrophysical Environments

“…Upper limits on the product of the ALP-nucleon and ALPphoton coupling can be derived by minimally demanding that the ALP-induced emission does not exceed the actual experimentally observed emission from a target, regardless of the astrophysical background. Data from NuSTAR, INTEGRAL, and XMM-Newton has been utilized to place constraints on ALPs from a set of eight magnetars for which hard X-ray data exists [31]; published quiescent soft-gamma-ray flux upper limits obtained with CGRO, COMPTEL and INTEGRAL SPI/IBIS/ISGRI have been used to obtain constraints on ALPs from five magnetars [32]. Future experiments like AMEGO covering the "MeV gap" would place better constraints.…”

Astroparticle Physics with Compact Objects

“…In addition, these objects demonstrate high-energy activity which makes it non-trivial to disentangle possible contribution from axion-photon oscillations. Nevertheless, the observations of magnetars in the energy range 10-1000 keV allowed for putting meaningful constraints on the product of couplings g aγγ × g ann [100,101]. The most stringent constraints come from magnetar 1E 1547.0-5408: g aγγ × g ann < 4.4 × 10 −20 GeV −1 for T c = 10 9 K.…”

Astroparticle physics with compact objects

“…Also, these objects demonstrate high-energy activity which makes it non-trivial to disentangle possible contribution from axion-photon oscillations. Nevertheless, the observations of magnetars in the energy range 10-1000 keV allowed to put meaningful constraints on the product of couplings g aγγ × g ann [100,101]. The most stringent constraints come from magnetar 1E 1547.0-5408: g aγγ × g ann < 4.4 × 10 −20 GeV −1 for T c = 10 9 K.…”