| 24th of May 2022 |
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| The early afterglow of GRB 190829A |
| by Dichiara et al. |
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Gamma-ray bursts (GRBs) can be detected out to high redshifts. Low
redshift (z < 0.1) GRBs are discovered only infrequently, yet provide
an opportunity to study in detail the properties of these extreme
explosions, their progenitors and local environment. In over 15 years
of operations of NASA’s Swift mission al. 2004), the long duration GRB
190829A is the fourth closest event ever observed. As such, it is
characterized by an exquisite multiwavelength dataset spanning over
fifteen decades in energy. Similar to other nearby long GRBs, it was
followed by a bright broad-lined Type Ic supernova SN 2019oyw. One of
the most remarkable features of this GRB is that it is only the third
such example of detection of emission at very high gamma-ray energies
(> 100 GeV).
Dichiara et al. present a multi-wavelength data-set for this rare event, and include data from Swift, the MASTER global network of optical telescopes, ALMA, and ATCA. The first ATCA observation was was made 0.84 days after the GRB. The image above is the multiwavelength light curve of GRB 190829A. Optical points are re-normalized scaled by a factor of 5 for plotting purposes. The best fit temporal model of the optical and X-ray data is indicated by the dashed yellow and dashed black line, respectively. The insert shows the absolute values of the Stokes parameter Q from MASTER polarization measurements. The study of the multi-wavelength light curves and broadband spectra supports a model with at least two emission components: a bright reverse shock emission, visible at early times in the optical and X-rays and, later, in the radio band; and a forward shock component dominating at later times and lower radio frequencies. |