# 28th Texas Symposium on Relativistic Astrophysics

13-18 December 2015
International Conference Centre Geneva
Europe/Zurich timezone

## Study of GRB light curve decay indices in the afterglow phase

14 Dec 2015, 17:55
3m
Level 2, Room 7&8 (International Conference Centre Geneva)

### Level 2, Room 7&8

#### International Conference Centre Geneva

17 Rue de Varembé, 1211 Geneva
Poster

### Speaker

Mrs Roberta Del Vecchio (Astronomical Observatory of the Jagiellonian University)

### Description

In this work we study the distribution of temporal power-law decay indices, $\alpha$, in the Gamma Ray Burst (GRB) afterglow phase, fitted for a sample of $164$ long GRBs with known redshifts using a power-law form. These indices are compared to the values of characteristic afterglow luminosity, $L_a$, the time, $T_a^*$, and the analogous decay index, $\alpha_W$, derived with global light curve fitting using the Willingale et al. (2007) model. This model fitting yields similar distributions of $\alpha_W$ to the fitted $\alpha$, but for several bursts difference between these indices can be significant. Analysis of the ($\alpha$, $L_a$) distribution reveals a weak correlation of these quantities. However, we discovered a significant regular trend when studying distribution of GRB $\alpha$ values at the $L_a$, vs. $T_a^*$ (LT) plane, with a differences of the $\alpha$ parameters below and above the fitted LT correlation line (Dainotti et al. 2008). Study of the presented systematic trend may allow one for constraining the physical models for GRBs. A proposed toy model accounting for this systematics applied to the analyzed GRB distribution results in increasing the LT correlation coefficient.
Collaboration Del Vecchio Roberta, Dainotti Maria Giovanna, Ostrowski Michał

### Primary author

Mrs Roberta Del Vecchio (Astronomical Observatory of the Jagiellonian University)

### Co-authors

Dr Maria Giovanna Dainotti (Stanford University) Prof. Michał Ostrowski (Astronomical Observatory Jagiellonian University)

### Presentation Materials

 posterGinevra1.pdf posterginevra_Talk.pdf