Ultraluminous X-ray sources of the starburst galaxy NGC 4631

We propose to observe the galaxy NGC 4631 for a total exposure time of90 ks. NGC 4631 is an ideal target to gain fundamental information ondifferent astrophysical processes with just one observation. The twomain aims of this proposal are: 1) to study the accretion mechanismresponsible for the peculiar soft X-ray emission of the brightultraluminous super-soft source X-1; 2) to unveil the nature of theother four known ultraluminous X-ray sources (ULXs) and newly detectedtransient ULXs. We will perform searches for fast periodicities, spectralanalyses, and studies of the long-term X-ray variability. In addition,we will study the morphology of the hot X-ray emitting halo surroundingthe galaxy to unprecedented detail.