The only tidally locked planet in the Solar system i Mercury. But it is synchronously tidally locked 3:2, because of the relatively high eccentricity of its orbit, so doesn't turn the same side towards the Sun. I wonder if this is common for exoplanets?
Many discovered exoplanets are close to their star and must be tidally locked. Has any of them been determined to be synchronously tidally locked, like Mercury? Is Mercury a rare freak in this respect, or a representant of a common phenomenon?