Discovery of a QPO in the NGC55 ULX?

We request a long (125ks) XMM-Newton observation of the ULX in the nearby galaxy NGC55. Previous short observations have revealed several unique aspects of this ULX. The temporal behavior of the ULX suggests a QPO at 1.5mHz and a power spectrum break. Such temporal features have been observed only for three other ULXs. Moreover, the source undergoes frequent spectral transitions making it a unique ULX where characteristic temporal behavior can be studied in conjunction with spectral transitions. Such studies are crucial to understanding the differences/similarities between ULX and Galactic X-ray binaries. Furthermore, the ULX exhibits a series of strange and unexplained X-ray dips of duration ~200s, whose nature can be revealed in spectral analysis of co-added dip data.