| Name: | Surabhi Chandra |
| Affiliation: | Indian Institute of Space Science & Technology |
| Conference ID : | ASI2024_496 |
| Title : | Exploring Gamma-Ray Burst Radio Afterglow Population |
| Authors : | Chandra Surabhi1, L. Resmi1, Kiran M Jayasurya2 |
| Authors Affiliation: | 1 Indian Institute of Space Science & Technology, Thiruvananthapuram - 695547, India
2 U R Rao Satellite Centre, ISITE Campus, Bengaluru - 560037, India |
| Mode of Presentation: | Poster |
| Abstract Category : | High Energy Phenomena, Fundamental Physics and Astronomy |
| Abstract : | Gamma-Ray bursts (GRBs) are relativistic transients associated with the gravitational collapse of massive stars or coalescing compact objects. GRB Afterglows contain a wealth of information about the explosion energetics, surrounding environment, and the relativistic jet, which helps us further examine the progenitor.
Afterglow physics can be probed either by detailed multi-wavelength modelling of individual well-observed GRBs or by exploring a population of bursts in a specific wavelength. Population studies of radio afterglows have been less common due to their low detection rates. Studies by Kangas & Fruchter in 2021 have shown that radio afterglow differ in many aspects from their optical and X-ray counter-parts, often showing incompatibility with the standard fireball model. In this project, we study a population of radio afterglows and investigate their general behaviour, particularly against the theoretical expectations.
First, we generate synthetic radio lightcurves in the ambit of the standard afterglow model for a wide range of physical parameters, which include the explosion energetics, jet opening angle, and ambient medium density among others. We then compare these synthetic lightcurves with a carefully selected sample of 237 radio lightcurves from 61 GRBs observed between 1997-2022. Our preliminary results indicate that the afterglow population does not support the model where a single jet emitting non-thermal synchrotron radiation decelerates through a constant density ambient medium. The observed radio lightcurves decline at a slower rate than the simulated ones. A stratified density profile driven by the progenitor wind does better as lightcurves are flatter in this case in comparison to the constant density medium. However, for the standard parameter ranges, the shallow decay phase of the wind-medium lightcurves end and a steeper decay phase starts before the epochs of most radio observations. Additional frameworks and modifications are being explored to close the gap between observed data and standard afterglow theory.
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