We present the results of deep , high-resolution , multi-band optical observations of the field of the young ( \sim 5 , 000 yrs ) 16 ms X-ray pulsar PSR J0537 - 6910 performed with the Advanced Camera for Surveys ( ACS ) aboard the Hubble Space Telescope ( HST ) .
Although a few new potential counterparts have been detected within or close to the revised Chandra X-ray error circle ( \simeq 1 \arcsec ) of the pulsar , only two of them ( with magnitudes m _ { 814 W } \approx 23.9 and m _ { 814 W } \approx 24.2 ) show indications of a peculiar spectrum which could be related to optical emission from the pulsar .
This might be true also for a third , fainter , candidate detected only in one filter ( with magnitude m _ { 814 W } \approx 26.7 ) .
If either of the two brighter candidates is indeed the actual counterpart , the optical output of PSR J0537 - 6910 would make it similar to young Crab-like pulsars .
If not , it would mean that PSR J0537 - 6910 is significantly underluminous with respect to all pulsars detected in the optical .