arXiv subjects

Rupal Basak

Publications and source records attributed to Rupal Basak.

20 records · Page 2Linked to original sources

arXiv2012

Correlation between the isotropic energy and the peak energy at zero fluence for the individual pulses of GRBs: towards an universal physical correlation for the prompt emission

We find a strong correlation between the peak energy at zero fluence ($\rm E_{peak,0}$) and the isotropic energy ($\rm E_{γ,iso}$) of the 22 pulses of 9 Gamma Ray Bursts (GRB) detected by the Fermi satellite. The correlation holds for the individual pulses of each GRB, which shows the reality of the correlation. The derived correlation (Spearman correlation coefficient, $r$, is 0.96) is much stronger compared to the correlations using $\rm E_{peak}$ (in place of $\rm E_{peak,0}$) determined from the time-integrated spectrum ($r$ = 0.8), or the time-resolved spectrum not accounting for broad pulse structures ($r$ = 0.37), or the pulse-wise spectrum ($r$ = 0.89). Though the improvement in the $\rm E_{peak}$ - $\rm E_{γ,iso}$ relation (the Amati relation) for a pulse-wise analysis is known earlier, this is the first time a parameter derived from a joint spectral and timing fit to the data is shown to improve the correlation. We suggest that $\rm E_{peak,0}$, rather than $\rm E_{peak}$, is intrinsic to a GRB pulse and a natural choice as the parameter in the pulse-wise correlation studies.

astro-ph.HE↗

arXiv2011

Measuring the pulse of GRB 090618: A Simultaneous Spectral and Timing Analysis of the Prompt Emission

We develop a new method for simultaneous timing and spectral studies of Gamma Ray Burst (GRB) prompt emission and apply it to make a pulse-wise description of the prompt emission of GRB 090618, the brightest GRB detected in the Fermi era. We exploit the large area (and sensitivity) of Swift/BAT and the wide band width of Fermi/GBM to derive the parameters for a complete spectral and timing description of the individual pulses of this GRB, based on the various empirical relations suggested in the literature. We demonstrate that this empirical model correctly describes the other observed properties of the burst like the variation of the lag with energy and the pulse width with energy. The measurements also show an indication of an increase in pulse width as a function of energy at low energies for some of the pulses, which is naturally explained as an off-shoot of some particular combination of the model parameters. We argue that these model parameters, particularly the peak energy at the beginning of the pulse, are the natural choices to be used for correlation with luminosity. The implications of these results for the use of GRBs as standard candles are briefly described.

astro-ph.HE↗