  Soft gamma repeaters (SGR) are identified as single neutron stars (NS) inside
the Galaxy, or nearby galaxies, with sporadic transient gamma radiation. A
total number of discovered SGR, including relative Anomalous X-ray pulsars
(AXP), is few tens of objects. Many of them show periodic radiation, connected
with NS rotation, with periods 2-12 s. The slow rotation is accompanied by
small rate of loss of rotational energy, which is considerably smaller than the
observed sporadic gamma ray luminosity, and is many orders less that the
luminosity during giant bursts, observed in 4 SGR. Therefore the energy source
is usually connected with annihilation of very strong NS magnetic field.
Another model is based on release of a nuclear energy stored in the NS
nonequilibrium layer. We suggest here an observational test with could
distinguish between these two models.
