Discovery of a Be/X-ray pulsar binary and associated supernova remnant in the Wing of the SMC

TL;DR

This paper reports the discovery of a new slow-rotating Be/X-ray pulsar binary in the SMC, associated with a supernova remnant, providing insights into supernova remnants and pulsar evolution.

Contribution

It presents the first evidence of a supernova remnant linked to a Be/X-ray binary in the SMC, with detailed multi-wavelength observations and age estimation.

Findings

Discovered a 1062 s X-ray pulsar in the SMC Wing.

Identified the optical counterpart as a Be star with spectral type B0-0.5(III)e+.

Detected a shell nebula likely to be a supernova remnant with an age of 20,000 to 40,000 years.

Abstract

We report on a new Be/X-ray pulsar binary located in the Wing of the Small Magellanic Cloud (SMC). The strong pulsed X-ray source was discovered with the Chandra and XMM-Newton X-ray observatories. The X-ray pulse period of 1062 s is consistently determined from both Chandra and XMM-Newton observations, revealing one of the slowest rotating X-ray pulsars known in the SMC. The optical counterpart of the X-ray source is the emission-line star 2dFS 3831. Its B0-0.5(III)e+ spectral type is determined from VLT-FLAMES and 2dF optical spectroscopy, establishing the system as a Be/X-ray binary (Be-XRB). The hard X-ray spectrum is well fitted by a power-law with additional thermal and blackbody components, the latter reminiscent of persistent Be-XRBs. This system is the first evidence of a recent supernova in the low density surroundings of NGC 602. We detect a shell nebula around 2dFS 3831 in H-alpha and [O III] images and conclude that it is most likely a supernova remnant. If it is linked to the supernova explosion that created this new X-ray pulsar, its kinematic age of (2-4)x10^4 yr provides a constraint on the age of the pulsar.