Identification of the ULX and X4 on the WFC F555W image. (a) X4 was identified with the nucleus of a background galaxy as enclosed by a 0.5^{﹩\arcsec﹩} circle. The smaller 0.17^{﹩\arcsec﹩} circle denotes the Chandra position of X4. The line segment indicates the relative offset of 2.3^{﹩\arcsec﹩} between Chandra and HST positions. (b) The ULX was identified with a unique object labeled as "C1" through the identification of X4. Around "C1," the small error circle had a radius of 0.2^{﹩\arcsec﹩}, and the large error circle 0.5^{﹩\arcsec﹩}. The line segment indicating the offset between Chandra and HST positions was based on the identification of X4. The cross on the inner edge of the 0.5^{﹩\arcsec﹩} circle indicates the ULX position obtained through the identification of X3 as a saturated foreground star. The object to its north was a cosmic ray that only appeared in the 2003 F555W observation. Both panels show ﹩7^{\prime \prime }\times 7^{\prime \prime }﹩ regions.