A Curious Source of Extended X-ray Emission in the Outskirts of Globular Cluster GLIMPSE-C01

TL;DR

This paper reports the discovery of an unusual extended X-ray emission near globular cluster GLIMPSE-C01, exploring its possible origins as a pulsar wind nebula or a bow shock, with implications for cluster evolution.

Contribution

It presents the first detection of extended X-ray emission in the outskirts of GLIMPSE-C01 and discusses its potential as a pulsar wind nebula or bow shock, suggesting new insights into cluster gas dynamics.

Findings

Extended X-ray emission with L_X = 10^{32} ergs/s identified.

Emission most significant in the 2-5 keV band, indicating non-thermal processes.

Possible evidence of gas stripping during the cluster's galactic passage.

Abstract

We report the discovery of an unusual source of extended X-ray emission CXOU J184846.3-013040 (`The Stem') located on the outskirts of the globular cluster GLIMPSE-C01. No point-like source falls within the extended emission which has an X-ray luminosity L_X =10^{32} ergs/s and a physical size of 0.1 pc at the inferred distance to the cluster. These X-ray properties are consistent with the pulsar wind nebula (PWN) of an unseen pulsar located within the 95-percent confidence error contour of unidentified Fermi gamma-ray source 0FGL J1848.6-0138. However, we cannot exclude an alternative interpretation that postulates X-ray emission associated with a bow shock produced from the interaction of the globular cluster and interstellar gas in the Galactic plane. Analysis of the X-ray data reveals that `The Stem' is most significant in the 2-5 keV band, which suggests that the emission may be dominated by non-thermal bremsstrahlung from suprathermal electrons at the bow shock. If the bow shock interpretation is correct, these observations would provide compelling evidence that GLIMPSE-C01 is shedding its intracluster gas during a galactic passage. Such a direct detection of gas stripping would help clarify a crucial step in the evolutionary history of globular clusters. Intriguingly, the data may also accommodate a new type of X-ray source.