  We exploit the fact that General Theory of Relativity (GTR) predicts the
existence of compact objects having surface gravitational redshift z_s <
=z_c=0.615 when the Equation of State (EOS) has the stringest general
constraint that the speed of sound c_s < = 0.57 c. This z_c can be occur if a
Neutron Star (NS) has a mass of ~2 M (solar) and radius ~8 Km, as is allowed by
most of the existing EOSs. Thus massive spherical stars can indeed collapse to
such (more compact) NSs. We have shown that the efficiency for production of
electron-positron pairs out of the annihilation of resulting
neutrino-antineutrino burst rises dramatically with the value of z_c and can
saturate to ~40%. This may explain a gamma ray burst of energy as high as ~5.
10**53 erg. By using the already existing detailed (Newtonian) calculations, it
follows that the neutrino heating driven mass loss should be negligible, and
the bulk Lorentz factor of the initial fireball could be ~1000. Most of the
existing supernova calculations also show that it is extremely difficult to
simulate the direct neutrino driven mass loss, and, the shock is not launched
if the gravitational field becomes stronger. Since the gravitation potential
well of the more compact NS is indded very deep, we do not expect additional
baryonic mass ejection. So, without invoking any exotic physics (like strange
stars) or overstretching any theory, we may explain most of the luminous GRBs
in this simple model.
