The X-ray luminosity of rotation-powered neutron stars

TL;DR

Recent X-ray observations of rotation-powered pulsars reveal a strong correlation between X-ray luminosity and rotational energy loss, with most emission originating from magnetospheric processes and some thermal surface emission in select pulsars.

Contribution

This paper reviews the observed X-ray emission properties of 27 pulsars, highlighting the correlation with rotational energy loss and identifying thermal components in a few cases.

Findings

X-ray luminosity correlates with rotational energy loss.

Most X-ray emission is magnetospheric in origin.

Thermal surface emission detected in a few middle-aged pulsars.

Abstract

As a result of recent observations with ROSAT and ASCA the number of rotation-powered pulsars seen at X-ray energies has increased substantially. In this paper we review the phenomenology of the observed X-ray emission properties. At present 27 pulsars are detected, representing a wide range of ages (10^3 - 7 x 10^9 yrs), magnetic field strength (10^8 - 10^13 G) and spin periods (1.6 - 530 ms). Despite these dispersions in parameters all pulsars show an X-ray luminosity closely correlated with the rotational energy loss. This suggests that most of the observed X-rays are produced by magnetospheric emission originating from the co-rotating magnetosphere. Only for three middle aged pulsars (PSR 0656+14, Geminga and PSR 1055-52) and probably for the Vela-pulsar an additional thermal component is detected which can be attributed to thermal emission from the neutron stellar surface.