The first two transient supersoft X-ray sources in M 31 globular clusters and the connection to classical novae

M. Henze, W. Pietsch, F. Haberl, G. Sala, R. Quimby, M. Hernanz, M. Della Valle, P. Milne, G. G. Williams, V. Burwitz, J. Greiner, H. Stiele, D. H. Hartmann, A. K.H. Kong, K. Hornoch

Research output: Contribution to journalArticlepeer-review

25 Scopus citations


Context. Classical novae (CNe) have been found to represent the major class of supersoft X-ray sources (SSSs) in our neighbour galaxy M 31. Aims. We determine the properties and evolution of the two first SSSs ever discovered in the M 31 globular cluster (GC) system. Methods. We have used XMM-Newton, Chandra and. Swift observations of the centre region of M 31 to discover both SSSs and to determine their X-ray light curves and spectra. We performed detailed analysis of XMM-Newton EPIC PN spectra of the source in Bol 111 (SS1) using blackbody and NLTE white dwarf (WD) atmosphere models. For the SSS in Bol 194 (SS2) we used optical monitoring data to search for an optical counterpart. Results. Both GC X-ray sources were classified, as SSS. We identify SS1 with the CN M31N 2007-06b recently discovered in the M 31 GC Bol 111. For SS2 we did not find evidence for a recent nova outburst and can only provide useful constraints on the time of the outburst of a hypothetical nova. Conclusions. The only known CN in a M 31 GC can be identified with the first SSS found in a M 31 GC. We discuss the impact of our observations on the nova rate for the M 31 GC system.

Original languageEnglish (US)
Pages (from-to)769-779
Number of pages11
JournalAstronomy and astrophysics
Issue number2
StatePublished - Jun 2009


  • - Globular clusters, individual. Bol 194 -
  • - Novae
  • - Stars, individual: Nova m31n 2007
  • -06b globular clusters, individual, bol 111
  • Cataclysmic variables
  • Galaxies, individual, m 31
  • X-rays, galaxies

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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