Multi-Epoch X-ray Imaging of Globular Cluster M62 with Chandra

TL;DR

This study analyzes 144 ks of Chandra X-ray data of globular cluster M62, identifying 43 sources, classifying their types, and examining their variability and spectral properties to understand their formation and evolution.

Contribution

It provides the first detailed classification and variability analysis of X-ray sources in M62 using multi-epoch Chandra data, highlighting differences from other clusters.

Findings

43 X-ray sources detected within M62's half-light radius.

Evidence of short-term and long-term variability in multiple sources.

M62 has a higher proportion of bright X-ray sources compared to other clusters.

Abstract

Using archival spectral-imaging data with a total exposure of $\sim144$ ks obtained by {\it Chandra}, 43 X-ray sources are detected within the half-light radius of globular cluster M62 (NGC6266). Based on the X-ray colour-luminosity diagram or the positional coincidences with known sources, we have classified these sources into different groups of compact binaries including cataclysmic variable (CV), quiescent low mass X-ray binary (qLMXB), millisecond pulsar (MSP) and black hole (BH). Candidates of the X-ray counterparts of 12 CVs, 4 qLMXBs, 2 MSPs and 1 BH are identified in our analysis. The data used in our analysis consist of two frames separated by 12 years, which enable us to search for the long-term variability as well as the short-term X-ray flux variability within each observation window. Evidence for the short-term variability and long-term variability have been found in 7 and 12 sources respectively. For a number of bright sources with X-ray luminosities $L_{x}\gtrsim 10^{32}$~erg/s, we have characterized their spectral properties in further details. By comparing the X-ray population in M62 with those in several other prototypical globular clusters, we found the proportion of bright sources is larger in M62 which can possibly be a result of their active dynamical formation processes.