2003/09/26 by R. Barnard, U. Kolb, J. P. Osborne
Physics and Astronomy · #Astrophysical Phenomena and Observations #Astrophysics and Cosmic Phenomena #Pulsars and Gravitational Waves Research #astro-ph
paper · pdf · doi:10.1051/0004-6361:20031513
published as Astron.Astrophys.411:553-558,2003 · Accepted for publication in A&A, 6 pages, 5 figures
arxiv created 2003/09/26 · openalex publication_date 2003/11/14 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/31
Four XMM-Newton observations of the core of M 31, spaced at 6 month intervals, show that the brightest point X-ray source, RX J0042.6+4115, has a 0.4–10 keV luminosity of ~ 1038 erg s-1, and exhibits significant variability in intensity and X-ray spectrum over a time scale of ~100 s including hard flares; such behaviour is only observed in Z-sources and transient black hole binaries in our Galaxy. The lightcurves, X-ray spectra and hardness-intensity data from the four XMM-Newton observations all strongly suggest that it is a Z-source, bringing the total number of known Z-sources to nine.