  The gravitational wave (GW) memory from a radiating and decelerating point
mass is studied in detail. It is found that for isotropic photon emission the
memory generated from the photons is essentially the same with the memory from
the point mass that radiated the photons so that it is anti-beamed. On the
other hand, for anisotropic emission the memory from the photons may have a
non-vanishing amplitude even if it is seen with small viewing angles. In the
decelerating phases of gamma-ray burst (GRB) jets the kinetic energy of the jet
is converted into the energy of gamma-ray photons. Then it would be possible to
observe a variation in the GW memory associated with GRB jets on the timescale
of the gamma-ray emission if the emission is partially anisotropic. Such an
anisotropy in the gamma-ray emission has been suggested by the polarizations
detected in recent observations of GRBs. The GW memory from GRB jets would
provide clues to clarifying the geometry of the jets and the emission mechanism
in GRBs. Thus it will be an interesting target for the next generation
detectors of the GWs.

High Energy Astrophysical Phenomena