Results from the XMM-Newton M31 major axis survey

Greening, L. Shaw; Barnard, R.; Tonkin, C.; Kolb, U. and Osborne, J. (2008). Results from the XMM-Newton M31 major axis survey. In: AIP Conference Proceedings, p. 325.

DOI: https://doi.org/10.1063/1.2945067

URL: http://scitation.aip.org/dbt/dbt.jsp?KEY=APCPCS&Vo...

Abstract

We present the results of a complete spectral survey of the X-ray point sources detected in five XMM-Newton observations along the major axis of M31 but avoiding the central bulge, aimed at establishing the population characteristics of X-ray sources in this galaxy. We obtained background subtracted spectra and lightcurves for each of the 335 X-ray point sources detected across the five observations from 2002. We also correlate our source list with those of earlier X-ray surveys and radio, optical and infra-red catalogues. Sources with more than 50 source counts are individually spectrally fit in order to create the most accurate luminosity functions of M31 to date. Based on the spectral fitting of these sources with a power law model, we observe a broad range of best fit photon index. From this distribution of best fit index, we present the first evidence for high mass X-ray binary systems in M31. We show the first cumulative luminosity functions created using the best fit spectral model to each source with more than 50 source counts in the disc of M31. The cumulative luminosity functions show a prominent, statistically significant flattening in the interval 37.0<~log LX [erg s-1]<~37.5. Such a feature may also be present in the X-ray populations of several other galaxies, but at a much lower statistical significance.

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