Discovery of a Pulsar Wind Nebula Candidate in the Cygnus Loop

TL;DR

This paper reports the discovery of a candidate pulsar wind nebula in the Cygnus Loop supernova remnant, based on X-ray observations, suggesting a neutron star with high velocity and characteristic emission properties.

Contribution

It presents the identification of a new pulsar wind nebula candidate in the Cygnus Loop, proposing its nature based on spectral analysis and inferred neutron star properties.

Findings

Spectral indices consistent with pulsar wind nebula

Estimated neutron star velocity ~1850 km/s

Luminosity and energy loss rate estimates

Abstract

We report on a discovery of a diffuse nebula containing a pointlike source in the southern blowout region of the Cygnus Loop supernova remnant, based on Suzaku and XMM-Newton observations. The X-ray spectra from the nebula and the pointlike source are well represented by an absorbed power-law model with photon indices of 2.2+/-0.1 and 1.6+/-0.2, respectively. The photon indices as well as the flux ratio of F_nebula/F_pointlike ~ 4 lead us to propose that the system is a pulsar wind nebula, although pulsations have not yet been detected. If we attribute its origin to the Cygnus Loop supernova, then the 0.5-8 keV luminosity of the nebula is computed to be 2.1e31 (d/540pc)^2 ergs/s, where d is the distance to the Loop. This implies a spin-down loss-energy E_dot ~ 2.6e35 (d/540pc)^2 ergs/s. The location of the neutron star candidate, ~2 degrees away from the geometric center of the Loop, implies a high transverse velocity of ~1850 (d/540pc)(t/10kyr)^{-1} km/s, assuming the currently accepted age of the Cygnus Loop.