Stellar collision time t_coll versus stellar velocity dispersion σ_∗. We have used the lower limit for the stellar density we have determined for the OHC of 1.30 × 10⁶ stars pc^-3. We have considered collisions between 1 M_⊙ stars (left panel), and 10 M_⊙ stars (right panel). We have included the case of a direct collision between “naked” stars (Eq. (A.1)) and the case with the likely presence of circumstellar disks (Eq. (A.2)) with radii 10 and 100 AU (see text).