The Complex Evolution of Gamma-Ray Burst Pulses
Abstract
Isolated Swift and BATSE gamma-ray burst (GRB) GRB pulses exhibit two distinct yet linked components. The bulk of pulsed emission comes in the form of a hard-to-soft component that can be fitted by the Norris et al. (2005) empirical pulse model. The second is a fainter, three-peaked signal overlaying the hard-to-soft component that can be fitted by an empirical wave-like function (Hakkila & Preece 2014). The two fits combine to produce GRB pulses with distinctive three-peaked shapes. The precursor peak appears on or before the pulse rise and is typically the hardest component of a pulse. The central peak is the brightest and most pronounced peak of a pulse. The decay peak occurs during the decay portion of the pulse, and converts an exponential decay into a long, soft, power-law decay. GRB pulses are dominated by hard-to-soft evolution. However, they also exhibit weaker intensity tracking behaviors that are tied to the three peaks found to varying degrees within each pulse. Hard pulses soften rapidly, but re-harden during the pulse's decay peak. Soft pulses soften slowly and re-harden during the central peak; additional hardening may occur during the decay peak. These results argue that theoretical GRB pulse models should have more than one temporally evolving spectral component in order to explain the complex observed pulse characteristics.
- Publication:
-
IAU General Assembly
- Pub Date:
- August 2015
- Bibcode:
- 2015IAUGA..2258293H