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ABSTRACT  We re‐assess the  XMM–Newton  and  Swift  observations of HLX1 to examine the evidence for its identification as an intermediate‐mass black hole. We show that the X‐ray spectral and timing properties are equally consistent with an intermediate‐mass black hole in a high state or with a foreground neutron star with a luminosity ∼ a few  ×10 32  erg s −1 ∼ 10 −6  L  Edd  , located at a distance of ≈1.5–3 kpc. Contrary to previously published results, we find that the X‐ray spectral change between the two  XMM–Newton  observations of 2004 and 2008 (going from power‐law dominated to thermal dominated) is not associated with a change in the X‐ray luminosity. The thermal component becomes more dominant (and hotter) during the 2009 outburst seen by  Swift  but in a way that is consistent with either scenario.

X‐ray study of HLX1: intermediate‐mass black hole or foreground neutron star?