Multiwavelength View of the Close-by GRB 190829A Sheds Light on Gamma-Ray Burst Physics
Journal article, 2022
We monitored the position of the close-by (about 370 Mpc) gamma-ray burst GRB 190829A, which originated from a massive star collapse, through very long baseline interferometry (VLBI) observations with the European VLBI Network and the Very Long Baseline Array, carrying out a total of nine observations between 9 and 117 days after the gamma-ray burst at 5 and 15 GHz, with a typical resolution of a few milliarcseconds. From a state-of-the art analysis of these data, we obtained valuable limits on the source size and expansion rate. The limits are in agreement with the size evolution entailed by a detailed modeling of the multiwavelength light curves with a forward-plus-reverse shock model, which agrees with the observations across almost 18 orders of magnitude in frequency (including the HESS data at TeV photon energies) and more than 4 orders of magnitude in time. Thanks to the multiwavelength, high-cadence coverage of the afterglow, inherent degeneracies in the afterglow model are broken to a large extent, allowing us to capture some unique physical insights; we find a low prompt emission efficiency of less than or similar to 10(-3), a low fraction of relativistic electrons in the forward shock downstream chi ( e ) < 13% (90% credible level), and a rapid decay of the magnetic field in the reverse shock downstream after the shock crossing. While our model assumes an on-axis jet, our VLBI astrometry is not sufficiently tight as to exclude any off-axis viewing angle, but we can exclude the line of sight to have been more than similar to 2 degrees away from the border of the gamma-ray-producing region based on compactness arguments.
Author
Om Sharan Salafia
Istituto nazionale di astrofisica (INAF)
National Institute for Nuclear Physics
University of Milano-Bicocca
Maria Edvige Ravasio
Istituto nazionale di astrofisica (INAF)
University of Milano-Bicocca
Jun Yang
Chalmers, Space, Earth and Environment, Onsala Space Observatory
Tao An
Guilin University of Electronic Technology
Chinese Academy of Sciences
Monica Orienti
Istituto nazionale di astrofisica (INAF)
Giancarlo Ghirlanda
National Institute for Nuclear Physics
Istituto nazionale di astrofisica (INAF)
Lara Nava
National Institute for Nuclear Physics
Istituto nazionale di astrofisica (INAF)
M. Giroletti
Istituto nazionale di astrofisica (INAF)
Prashanth Mohan
Guilin University of Electronic Technology
Riccardo Spinelli
University of Insubria
Istituto nazionale di astrofisica (INAF)
Yingkang Zhang
Chinese Academy of Sciences
Benito Marcote
Joint Institute for VLBI in Europe (JIVE)
Giuseppe Cimo
Joint Institute for VLBI in Europe (JIVE)
Xuefeng Wu
Chinese Academy of Sciences
Zhixuan Li
Chinese Academy of Sciences
Astrophysical Journal Letters
2041-8205 (ISSN) 2041-8213 (eISSN)
Vol. 931 2 L19Subject Categories
Accelerator Physics and Instrumentation
Subatomic Physics
Astronomy, Astrophysics and Cosmology
DOI
10.3847/2041-8213/ac6c28
Related datasets
Supplementary material: Multi-wavelength view of the close-by GRB~190829A sheds light on gamma-ray burst physics [dataset]
DOI: 10.5281/zenodo.6412087