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We present the results of a search for optical counterparts of ultraluminousX-ray source (ULX) X-1 in the nearby galaxy NGC 2500 by using archival imagestaken with the Hubble Space Telescope ({\it HST}) Wide Field Camera(WFC3)/UVIS. Four optical sources have been identified as possible counterpartswithin the 2$\sigma$ error radius of 0.3 arcsec in the images. However, onlytwo of them were investigated as candidates for counterparts due to theirpoint-like features and their identification in various filters. These twofaint candidates have absolute magnitudes of $M_{\rm V}$ $\approx$ -3.4 and-3.7. Also possible spectral classes of them were determined as B type mainsequence stars. The ages and the masses of the candidates from Color MagnitudeDiagram (CMD) were estimated as 45 Myr and 7 $M_{\rm \odot}$, respectively. Thespectral energy distributions (SEDs) of two candidates were modeled by apower-law spectrum with a photon index ($\alpha$) $\sim$1.5. The spectra withsuch slopes could be interpreted as an evidence of reprocessing of the X-raysin the outer part of the disk that generates optical emission.

Optical Counterparts of an Ultraluminous X-Ray Source X-1 in NGC 2500