  We report on the identification of the optical counterpart to Star1, the
exotic object serendipitously discovered by Deutsch et al. in the core of the
Galactic globular cluster NGC 6624. Star1 has been classified by Deutsch et al.
as either a quiescent Cataclysmic Variable or a low-mass X-ray binary. Deutsch
et al. proposed StarA as possible optical counterpart to this object. We used
high-resolution images obtained with the Hubble Space Telescope to perform a
variability analysis of the stars close to the nominal position of Star1. While
no variability was detected for StarA, we found another star, here named
COM_Star1, showing a clear sinusoidal light modulation with amplitude \Delta
m_F435W~0.7 mag and orbital period of P_orb~98 min. The shape of the light
curve is likely caused by strong irradiation by the primary heating one
hemisphere of the companion, thus suggesting a quite hot primary.

Solar and Stellar Astrophysics