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We present the optical and X-ray study of the ultraluminous X-ray source(ULX) NGC 5474 X-1. The X-ray spectrum taken during the bright state of thesource ($L_X \sim 2\times10^{40}$ egs/s) shows signatures of a broad absorptionline at $\simeq 8$ keV which may be a cyclotron resonant scattering feature.This implies that this system may host a neutron star with a magnetic field$\sim 10^{12}$ G. The first observation of this area with the Hubble SpaceTelescope (HST) carried out 14 months later revealed that the source was brightin the optical range as well. The subsequent observations have shown that thesource faded in both ranges (more than $2.8^m$ in the U band and by a factor of50-100 in X-rays) and has never become bright again. Deeper HST observationsmade it possible to impose constraints on the donor star spectral class andmass ($<\,7$ M$_\odot$), as well as to identify a stellar cluster of about 1Gyr, the centre of which is located at a projected distance of $\simeq 2$ pcfrom NGC 5474 X-1. The ULX can be a member of this old cluster, however, thepresence of stars with ages of $\sim10$ Myr within 300 pc around the ULX doesnot completely exclude the possibility that it is just an accidentalprojection.

NGC 5474 X-1: a neutron star ULX in an old stellar cluster?