The Pulse of Different Angular Regions in the Fireball Framework

In the fireball framework, the pulses of the different unattached angular regions (DUARs)and the different angular regions with the lower and upper opening angle (DARs)are investigated.It is shown that 1)the rise part and the decay part of the fast rise exponential decay (FRED)pulse of the fireball come from different angular regions, and the rise part mainly comes from the angular regions close to the axis;2)the FWHM of the pulse of the fireball is mainly determined by a special region with its opening angle being about 6/(10 Γ).3)the FRED pulse comes from the spherical fireball or a jet with its opening angle larger than 6/(10 Γ).If the source of gamma-ray burst is not a spherical fireball or a jet with its opening angle not larger than 6/(10 Γ), the pulse would be not FRED pulse shape.