We present the identification of the optical counterparts to the low-mass X-ray binaries 1A 1246 - 588 and 4U 1812 - 12 .
We determine the X-ray position of 1A 1246 - 588 from ROSAT /PSPC observations and find within the error circle a blue star with V = 19.45 , B - V = 0.22 and R - I = 0.22 which we identify as the counterpart .
Within the Chandra error circle of 4U 1812 - 12 , a single star is present which appears blue with respect to the stars in the vicinity .
It has R = 22.15 , R - I = 1.53 .
Distance estimates for both systems indicate that the optical counterparts are intrinsically faint , suggesting that they are ultra-compact X-ray binaries .
These identifications would increase the number of candidate ultra-compact X-ray binaries from 2 to 4 , whereas orbital periods are measured for only 7 systems in the Galactic disk .