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A sub-set of the brightest ultraluminous X-ray sources (ULXs), with X-rayluminosities well above $10^{40}$ erg s$^{-1}$, typically have energy spectrawhich can be well described as hard power-laws, and short-term variability inexcess of $\sim10\%$. This combination of properties suggests that these ULXsmay be some of the best candidates to host intermediate mass black holes(IMBHs), which would be accreting at sub-Eddington rates in the hard state seenin Galactic X-ray binaries. In this work, we present a temporal and spectralanalysis of all of the available XMM-Newton data from one such ULX, thepreviously poorly studied 2XMM J143242.1$-$440939, located in NGC 5643. Wereport that its high quality EPIC spectra can be better described by a broad,thermal component, such as an advection dominated disc or an optically thickComptonising corona. In addition, we find a hint of a marginal change in theshort-term variability which does not appear to be clearly related to thesource unabsorbed luminosity. We discuss the implications of these results,excluding the possibility that the source may be host an IMBH in a low state,and favouring an interpretation in terms of super-Eddington accretion on to ablack hole of stellar origin. The properties of NGC 5643 ULX1 allow us toassociate this source to the population of the hard/ultraluminous ULX class.

The ultraluminous X-ray source NGC 5643 ULX1: a large stellar mass black hole accreting at super-Eddington rates?