IEEE10mnd
In-depth studies of the NGC 253 ULXs with XMM–Newton: remarkable variability in ULX1, and evidence for extended coronae
Remarkably, we discovered ULX1 to be three times more variable than ULX2 in the 0.3–10 keV band, even though ULX2 is brighter. Indeed, ULX1 exhibits a power density spectrum that is consistent with ...