GRB 990123 may have radiated more than one solar mass equivalent in just its
gamma emissions. Though this may be within the upper limit of the binding
energy available from neutron stars in the Schwarzschild metric, it is
difficult to imagine a process with the required efficiency of conversion to
gamma rays. Neutron stars of ~10 solar mass are permitted in the Yilmaz metric.
A merger of two neutron stars of maximum mass could release approximately 10
solar mass equivalent binding energy.Comment: 5 pages, 1 figure, submitted to ApJ Letter