Quantum synchro-curvature masers and their application to neutron stars

TL;DR

This paper investigates the potential for synchro-curvature masers in neutron star magnetospheres using relativistic quantum mechanics, finding conditions under which maser action is feasible, especially in millisecond pulsars.

Contribution

It introduces a quantum mechanical approach to model synchro-curvature masers in neutron stars, differing from previous classical treatments.

Findings

Maser action is possible under certain neutron star parameters.

The amplification factor favors millisecond pulsars as maser sources.

Dependence of maser efficiency on magnetic field and curvature parameters is systematically analyzed.

Abstract

We explore the possibility of synchro-curvature maser in the magnetosphere of neutron stars (NSs). Unlike previous studies, we employ relativistic quantum mechanics, solving the Dirac equation for an electron in helical magnetic fields and calculating the radiative transition rates perturbatively. Assuming that the curvature of magnetic-field lines is much larger than the Larmor radius, we utilize adiabatic spinor rotations to obtain the wave functions of an electron. We classify the electron states further either by the spin operator projected on the magnetic field or by the helicity operator. We then evaluate numerically the true absorption rates accounting for the induced emission for some parameter values typical to the outer gaps of different types of NSs. We show that maser is indeed possible for a range of parameters. We will also present the dependence on those parameters systematically. We finally give a crude estimate of the amplification factor in the outer gap of NSs, which seems to favor millisecond pulsars as the host of maser emissions.