Suzaku Detection of Diffuse Hard X-Ray Emission outside Vela X

TL;DR

This study uses Suzaku observations to detect diffuse hard X-ray emission outside Vela X, revealing extended emission likely linked to the pulsar wind nebula and indicating distinct electron populations.

Contribution

First detection of diffuse hard X-ray emission outside Vela X with Suzaku, suggesting larger PWN extent and separate electron populations.

Findings

Hard X-ray emission extends beyond Vela X

Spectral photon index is approximately 2.4

X-ray flux decreases with distance from the pulsar

Abstract

Vela X is a large, 3x2 degrees, radio-emitting pulsar wind nebula (PWN) powered by the Vela pulsar in the Vela supernova remnant. Using four Suzaku/XIS observations pointed just outside Vela X, we find hard X-ray emission extending throughout the fields of view. The hard X-ray spectra are well represented by a power-law. The photon index is measured to be constant at Gamma~2.4, similar to that of the southern outer part of Vela X. The power-law flux decreases with increasing distance from the pulsar. These properties lead us to propose that the hard X-ray emission is associated with the Vela PWN. The larger X-ray extension found in this work strongly suggests that distinct populations relativistic electrons form the X-ray PWN and Vela X, as was recently inferred from multiwavelength spectral modeling of Vela X.