Peak Energy - Isotropic Luminosity Tracking

This figure shows the light curves, plotted in black, and the time resolved peak energies, shown in red, for various Gamma Ray Bursts observed by the FERMI satellite. Some of the Gamma Ray Bursts exhibit a hard-to-soft peak energy evolution; however, for some Gamma Ray Bursts, the peak energy follows the evolution of the light curve. This figure is from the following paper: A&A 588, A135 (2016) DOI: 10.1051/0004-6361/201527509

As an NSF EAPSI Fellow during the summer of 2017 I was in Japan at the Astrophysical Big Bang Laboratory (ABBL) in RIKEN to forge new collaborations to understand radiation transport in Gamma Ray Bursts. The ABBL website is: nagataki-lab.riken.jp.

While at RIKEN, I was also investigating the connection between the time resolved spectral peak energy and the isotropic luminosity. As shown in the figure above, for some GRBs the peak energy tracks the luminosity, while for other GRBs the peak energy just follows a hard-to-soft evolution. Up until my radiation transfer simulations, this effect has not been able to even be reproduced. Thus, due to my simulations, I have the unique opportunity to understand this seemingly erratic behavior between the peak energy and the luminosity.

In 2018 I was also accepted to participate in the NASA Fermi Summer School, where I gained alot of knowledge about the gamma ray observations that take place to produce results like what is presented in the figure above. This experience spurred lots of ideas to try to connect the observed \(E_p\) - \(L_\mathrm{iso}\) tracking to the angle dependence of the tracking that I see in my simulations. One of these ideas is exemplified below, where I conducted a very preliminary analysis of GRB 080916C to try to determine the observed angle from the jet axis. I calculated the spearman rank coefficient, \(r_s\), between \(E_p\) and \(L_\mathrm{iso}\) for the GRB and compared it to \(r_s\) measured from my 16TI simulation at different viewing angles for the GRB. In this test analysis, it seems as though GRB 080916C was observed at ~2\(^\circ\) off axis, however a more stringent, self consistent analysis that includes errors need to be done.

This figure shows the comparison between the calculated \(r_s\), between \(E_p\) and \(L_\mathrm{iso}\), for GRB 080916C and my 16TI simulation at various observer viewing angles. This suggests that GRB 080916C was observed at ~2\(^\circ\) off axis.