  Using the inclusive photon spectrum based on a data sample collected at the
$J/\psi$ peak with the KEDR detector at the VEPP-4M $e^+e^-$ collider, we
measured the rate of the radiative decay $J/\psi\to\gamma\eta_{\rm c}$ as well
as $\eta_{\rm c}$ mass and width. Taking into account an asymmetric photon
lineshape we obtained $\Gamma^0_{\gamma\eta_{\rm c}}=2.98\pm0.18
\phantom{|}^{+0.15}_{-0.33}$ keV, $M_{\eta_{\rm c}} = 2983.5 \pm 1.4
\phantom{|}^{+1.6}_{-3.6}$ MeV/$c^2$, $\Gamma_{\eta_{\rm c}} = 27.2 \pm 3.1
\phantom{|}^{+5.4}_{-2.6}$ MeV.
