# Long-term study of the Double Pulsar J0737-3039 with XMM-Newton: spectral analysis

## TL;DR

This long-term X-ray spectral study of the Double Pulsar J0737-3039 reveals stable soft X-ray emission over five years, detects new hard X-ray emission likely from iron line, and suggests a relic disk around the pulsar.

## Contribution

First evidence of hard X-ray emission and iron line detection in a non-accreting binary pulsar system, indicating a possible relic disk.

## Key findings

- No spectral variability over 5 years despite relativistic precession.
- Detection of 5-8 keV hard X-ray excess likely due to iron emission.
- Presence of a relic disk around the pulsar suggested by iron line detection.

## Abstract

We present a long-term spectral monitoring of the unique Double Pulsar binary PSR J0737-3039 corresponding to two "Large Programs" performed by XMM-Newton in 2006 and 2011. Spectral variability of pulsar emission in soft X-rays is not evident over 5 years, despite the significant relativistic spin precession in the considered time span (about 25deg). We provide, for the first time, evidence of hard X-ray emission from the system in the 5-8 keV energy band. The standard spectral analysis was coupled to the energy dependent spatial analysis to confirm this excess, most likely ascribed to iron line emission. The Fe K-alpha emission line at 6.4-6.97 keV was previously unheard-of in non-accreting binary systems and could testify to the presence of a relic disk that survived the supernova explosions that terminated the lives of the Double Pulsar's stellar progenitors. The existence of a relic disk in this system reinforces speculation about the presence of similar structures around other peculiar classes of isolated neutron stars.