2005/08/11 by J. Robrade, J. H. M. M. Schmitt, F. Favata · 5 citations
Physics and Astronomy · #Astro and Planetary Science #Astrophysics and Star Formation Studies #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1051/0004-6361:20053314
7 pages, 11 figures, accepted by A&A
arxiv created 2005/08/11 · openalex publication_date 2005/09/30 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/30
We present first results from five XMM-Newton observations of the binary system α Centauri, which has been observed in snapshot like exposures of roughly two hours each during the last two years. In all our observations the X-ray emission of the system is dominated by α Cen B, a K1 star. The derived light curves of the individual components reveal variability on short timescales and a flare was discovered on α Cen B during one observation. A PSF fitting algorithm is applied to the event distribution to determine the brightness of each component during the observations. We perform a spectral analysis with multi-temperature models to calculate the X-ray luminosities. We investigate long term variability and possible activity cycles of both stars and find the optically brighter component α Cen A, a G2 star very similar to our Sun, to have fainted in X-rays by at least an order of magnitude during the observation program, a behaviour never observed before on α Cen A, but rather similar to the X-ray behaviour observed with XMM-Newton on HD 81809. We also compare our data with earlier spatially resolved observations performed over the last 25 years.