The power of the rings: the GRB 221009A soft X-ray emission from its dust-scattering halo

Understand

GRB 221009A is the brightest gamma-ray burst (GRB) ever detected and occurred at low Galactic latitude.

• Owing to this exceptional combination, its prompt X-ray emission could be detected for weeks in the form of expanding X-ray rings produced by scattering in Galactic dust clouds.
• We report on the analysis of 20 rings, generated by dust at distances ranging from 0.3 to 18.6 kpc, detected during two XMM-Newton observations performed about 2 and 5 days after the GRB.
• By fitting the spectra of the rings with different models for the dust composition and grain size distribution, we reconstructed the spectrum of the GRB prompt emission in the 0.7-4 keV energy range as an absorbed power law with photon index 1-1.4 and absorption in the host galaxy nHz=(4.1-5.3)E21 cm-2.