Numerically Calculating the Afterglow of an Off-axis Short Gamma Ray Burst

Herminio Carrillo and Dr. Barniol DuranDept. of Physics and Astronomy, College of Natural Sciences & Mathematics

Abstract● Short gamma-ray bursts (sGRB) are among the

most energetic phenomena in the Universe. Afterglows can last for months, which allows us to follow sGRB’s extensively and use them to infer physical parameters of the explosion and its environment.

● However, given that most sGRBs are not directed straight toward us, we study the properties of sGRBs afterglows at various observer angles.

● It is imperative that we consider how the jet properties change as a function of the angle between the burst axis and the observer in order to garner relevant information on the nature of short gamma-ray bursts as a whole.

Conclusion/Future Work References

Afterglow Emission● The afterglow refers to radiation that is

seen for a certain amount of days through months.

● This prolonged emission that follows the prompt phase at lower energies such as: X-ray, ultraviolet, optical, and radio have power-law dependencies on frequency 𝜈 and time t.

● Afterglow observations allow for the identification of their home galaxies, thus allowing us to determine the distance.

Relevant Parameters

Relevant Equations

Results

The simulation models used provide good approximations of the behavior of sGRB’s when the afterglow is taken into consideration at various observer angles. The current task at hand is to build on the salient equations to model an off axis sGRB that reflects our results attained via the simulation parameters presented above, so that we may predict and understand the nature sGRB’s, the dependence of the afterglow on the various model parameters, and what they have to tell us about gravitational wave astronomy and high energy astrophysical phenomena.

Kathirgamaraju et al., 2018, “Off-axis short GRB’s from structured jets as counterparts to GW events”, Monthly Notices of the Royal Astronomical Society, Vol. 473, L121Kathirgamaraju et al. “EM counterparts of structured jets from 3D GRMHD simulations”, Monthly Notices of the Royal Astronomical Society, Vol. 484, L98Sari et al., 1988 “Spectra and light curves of gamma-ray burst afterglows” The Astrophysical Journal, Vol 497: L17-L20

Figure 1. Artist rendition of GRB time evolution NASA/Fermi “Investigating Gamma-Ray Bursts”

AcknowledgmentsWe would like to thank the National Science Foundation for the support under Grant 1816694 that made this possible.