  We study numerically the thermal emission of $e^+e^-$ pairs from a bare
strange star heated by energy input onto its surface; heating starts at some
moment, and is steady afterwards. The thermal luminosity in $e^+e^-$ pairs
increases to some constant value. The rise time and the steady thermal
luminosity are evaluated. Both normal and colour superconducting states of
strange quark matter are considered. The results are used to test the magnetar
model of soft gamma-ray repeaters where the bursting activity is explained by
fast decay of superstrong magnetic fields and heating of the strange star
surface. It is shown that the rise times observed in typical bursts may be
explained in this model only if strange quark matter is a superconductor with
an energy gap of more that 1 MeV.
