Abstract

Poster - Splinter MeVSky   (MW-0337)

Search for Axion-like Particles from Massive Stars

Saurabh Mittal, Thomas Siegert
Universität Würzburg

Axion-like particles (ALPs) are hypothetical pseudoscalar bosons that arise in many extensions of the Standard Model and can be well-motivated dark-matter candidates. Nearby massive stars in the late stages of stellar evolution provide a promising environment for enhanced ALP production due to their high core temperatures and densities. In this work, we search for a combined signal of ALP-induced hard X-ray and soft gamma-ray emission from 18 nearby pre-supernova stars using the full public INTEGRAL/SPI 22-year database. We constructed a joint likelihood that acknowledges the uncertainties in individual stellar parameters toward a combined estimate for the two coupling constants ALP-photon and ALP-electron as a function of the ALP mass. The combined estimate of the upper limit of the product of the couplings is (0.008 - 2) x 1e-24/GeV (95% C.I.) and the ALP-photon coupling is (0.13 - 1.26) x1e-11/GeV (95% C.I.) up to a mass of 1e-11 eV for different times to core-collapse and different magnetic-field models. Our results are among the strongest limits on the ALP coupling constants in the literature. We also provide conservative limits on the product of the coupling constants of (0.27 - 1.25) 1e-24/GeV (95% C.I.) by assuming all stars but one to be in the early He-burning phase. This work shows that soft gamma-ray observations are required to efficiently probe the ALP parameter space, as well as massive-star evolution models in general.