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Paper: Evolution of X-ray Emission from Young, Massive Stellar Clusters
Volume: 367, Massive Stars in Interactive Binaries
Page: 637
Authors: Oskinova, L.M.
Abstract: The evolution of young, massive stellar clusters is modeled in order to explain the striking difference observed in the levels of X-ray emission among clusters of different age. It is shown that the level and character of soft (0.2-10 keV) X-ray emission change drastically with cluster age and are tightly linked with stellar evolution. Assuming an instantaneous burst of star formation and a standard initial mass function, the total X-ray luminosity of all low-mass stars (0.1 − 3M) is higher than the total luminosity of the cluster’s high-mass stars (8 − 100M). At the same time, massive stars are the brightest X-ray point sources, although they become much dimmer when they evolve to the Wolf-Rayet (WR) star phase. Emission from a supernova remnant may be a dominant X-ray source in an old enough cluster, but only for a relatively short time of a few thousand years. The diffuse X-ray emission originates from the intracluster wind heated by the kinetic energy of stellar winds and supernova explosions. When massive stars reach theWR phase, the level of diffuse emission rises due to the powerful WR stellar winds. Subsequent SN explosions pump the level of diffuse emission even higher. The clusters older then ≈ 2Myr may have no bright stellar point sources, but a relatively high level of diffuse emission. The above scenario provides a plausible explanation for the X-ray observations of the Arches and the Quintuplet cluster in the Galaxy, as well as of a sample of LMC clusters.
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