The IXPE view of GRB 221009A

Understand

We present the IXPE observation of GRB 221009A which includes upper limits on the linear polarization degree of both prompt and afterglow emission in the soft X-ray energy band.

• GRB 221009A is an exceptionally bright gamma-ray burst (GRB) that reached Earth on 2022 October 9 after travelling through the dust of the Milky Way.
• The Imaging X-ray Polarimetry Explorer (IXPE) pointed at GRB 221009A on October 11 to observe, for the first time, the 2-8 keV X-ray polarization of a GRB afterglow.
• We set an upper limit to the polarization degree of the afterglow emission of 13.8% at a 99% confidence level.