Abstract Details
| Name: Anshika Gupta Affiliation: Aryabhatta Research Institute of Observational Sciences Conference ID: ASI2025_701 Title : The multi-wavelength evolution of GRB 190829A Authors and Co-Authors : Anshika Gupta 1,2, Ankur Ghosh 3, Kuntal Misra 1, and L. Resmi 4 Abstract Type : Poster Abstract Category : High Energy Phenomena, Fundamental Physics and Astronomy Abstract : Gamma Ray Bursts (GRBs) are one of the most energetic cosmic explosions in the Universe. A significant number of GRBs have afterglow detections in X-ray and optical bands, but for only about ∼ 30% of the GRBs, radio afterglows have been detected. The early evolution of radio afterglows (below 4 GHz) is through the optically thick regime. Therefore, the light curve peak corresponds to the transition from an optically thick to a thin regime. Hence, radio frequencies are unique in probing the evolution of the self-absorption frequency (νa), which in turn can constrain the physical parameters. The long-duration GRB 190829 (z=0.0785) was the third GRB for which the H.E.S.S. observatory detected very high energy (VHE) photons. The Gamma Ray Burst (GBM) instrument on the Fermi mission detected the burst. The Large Area Telescope (LAT) onboard Fermi also detected the high-energy photons from the GRB. Due to the vicinity of the GRB, it was observed extensively with several telescopes and thus has a rich multi-wavelength afterglow data spanning across optical, X-ray, and radio wavelengths. At low radio frequencies (below 1.4 GHz), the afterglow was detected and observed by the upgraded Giant Meterwave Radio Telescope (u-GMRT) in Khodad, NCRA, Pune. Between 400 and 1300 MHz, the afterglow was observed at several epochs, from nearly 3 days to 200 days after the burst. The afterglow was also observed at higher frequencies, like 15.5 GHz, with the Arcminute Microkelvin Imager (AMI) telescope. The presence of the reverse shock component can be observed in the AMI light curves. The rise to the peak is noticed in both the high and low-frequency radio light curves. Combining the multi-wavelength dataset, we performed the afterglow modeling, which allowed us to put constraints on the ambient medium density, collimation angle, shock microphysical parameters, and kinetic energy of the burst. |