XMM-Newton observations of the low-mass X-ray binary XB1832-330 in the galactic globular cluster NGC 6652

TL;DR

This study used XMM-Newton observations to analyze the low-energy absorption and neon abundance in the ultracompact low-mass X-ray binary XB1832-330 within NGC 6652, finding no anomalous neon enrichment.

Contribution

First high-resolution spectral analysis of XB1832-330 showing no evidence of neon enrichment, and identification of additional faint sources in the field.

Findings

Ne/O ratios consistent with interstellar medium values

No evidence of neon-rich material near the binary

Detection of 46 faint sources in the field

Abstract

We report on two XMM-Newton observations performed in 2006 of the luminous low-mass X-ray binary XB1832-330 which is located in the galactic globular cluster NGC 6652 and is probably an ultracompact binary (orbital period less than 1 hour). The aim of these observations is to investigate the low-energy absorption towards NGC6652 and in particular to search for Ne-rich material local to the binary, which has been suggested as a possible spectral signature of Neon rich degenerate companions. XMM-Newton observed the source twice, in 2006 September and October. High resolution spectroscopy with the RGS was used to estimate the ratio of the neutral neon to oxygen column densities to search for an anomalous Ne abundance in this X-ray binary. We find no evidence for anomalous Ne/O ratios, finding Ne/O=0.18+/-0.06 and Ne/O=0.17+/-0.03 (1 sigma uncertainties), in the two observations, respectively. These values are consistent with that in the interstellar medium. Timing analysis of EPIC data suggests possible periodicities at 9170+/-235 s and 18616 +/- 531 s, which need confirmation. A by-product of these observations consists of the spatial analysis of the source field, which resulted in the detection of 46 faint sources within the EPIC field of view, which are not present in the Second XMM-Newton Serendipitous Source Catalogue. All these faint sources are likely foreground objects. We performed the first high spectral resolution observations of XB1832-33, a probable ultracompact binary, without finding any evidence for an anomalous Ne abundance.