Journal Article

The long-term variability of the X-ray sources in M82

Yi-Kuan Chiang and Albert K. H. Kong

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 414, issue 2, pages 1329-1338
Published in print June 2011 | ISSN: 0035-8711
Published online June 2011 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2011.18466.x
The long-term variability of the X-ray sources in M82

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We investigate the long-term variability exhibited by the X-ray point sources in the starburst galaxy M82. By combining nine Chandra observations taken between 1999 and 2007, we detect 58 X-ray point sources within the D25 isophote of M82 down to a luminosity of ∼1037 erg s−1. Of these 58 sources, we identify three supernova remnant candidates and one supersoft source. 26 sources in M82 exhibit long-term (i.e. days to years) flux variability and three show long-term spectral variability. Furthermore, we classify 26 sources as variables and 10 as persistent sources. Among the total 26 variables, 17 varied by a flux ratio of >3 and six are transient candidates. By comparing with other nearby galaxies, M82 shows extremely strong long-term X-ray variability that 47 per cent of the X-ray sources are variables with a flux ratio of >3. The strong X-ray variability of M82 suggests that the population is dominated by X-ray binaries.

Keywords: galaxies: individual: M82; X-rays: binaries; X-rays: galaxies

Journal Article.  7546 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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