X Rays from Old Neutron Stars Heated by Axion Stars

TL;DR

This paper proposes that collisions between axion stars and old neutron stars with strong magnetic fields can heat the neutron stars, causing X-ray emissions and monochromatic radiation bursts, potentially explaining some observed X-ray sources.

Contribution

It introduces a novel mechanism where axion star collisions heat neutron stars, leading to observable X-ray and monochromatic radiation signals, linking axion physics to astrophysical phenomena.

Findings

Neutron stars can reach surface temperatures of 10^5 to 10^6 K due to axion star collisions.

Such collisions can produce X-ray emissions consistent with ROSAT observations.

Monochromatic radiation bursts at frequencies related to axion mass are generated during collisions.

Abstract

We show that axionic boson stars collide with isolated old neutron stars with strong magnetic field ($>10^8$ Gauss) and causes the neutron stars to radiate X ray by heating them. Surface temperatures of such neutron stars becomes$10^5 K \sim 10^6 K$. We suggest that these are possible candidates for X ray sources observed in ROSAT Survey. We discuss a possible way of identifying such neutron stars. We also point out that the collision generates a burst of monochromatic radiations with frequency given by axion mass.