Constraints on fall-back disks in radio pulsars and anomalous X-ray pulsars

TL;DR

This paper investigates how fall-back disks around radio pulsars and anomalous X-ray pulsars are constrained by heating from pulsar winds, showing that such disks are unlikely to influence pulsar spin-down due to large inner radius limits.

Contribution

It provides quantitative constraints on the inner radii of fall-back disks based on pulsar wind heating and near-infrared observations, challenging their potential impact on pulsar spin-down.

Findings

Inner radii of fall-back disks are too large to affect pulsar spin-down.

Pulsar wind heating constrains the presence of inner disks.

Near-infrared flux limits rule out significant fall-back disks.

Abstract

Calculations have been made of fall-back disk heating by the pulsar wind as distinct from the soft X-rays emitted by the neutron-star surface. The relation between these heating rates and measured near-infrared fluxes in the K and Ks bands places severe constraints on the inner radii of any fall-back disks that may be present in radio pulsars and in some anomalous X-ray pulsars. The lower limits found are so large that the disks concerned can have no significant effect on pulsar spin-down.