Skip to main content
Testing. You are viewing the public testing version of GCN. For the production version, go to
New Announcement Feature, Code of Conduct, Circular Revisions. See news and announcements

GCN Circular 32754

GRB 221009A: IXPE preliminary upper limits of X-ray polarization
2022-10-14T12:58:40Z (2 years ago)
Michela Negro at CRESST/NASA-GSFC/UMBC <>
Michela Negro, Alberto Manfreda, Nicola Omodei and 
Fabio Muleri report on behalf of the IXPE Collaboration 

IXPE performed the first observation of X-ray polarization of a 
GRB afterglow in the 2 ��� 8 keV energy range.
IXPE observed GRB 221009A from 2022-10-11T23:34:28UTC to 
2022-10-14T00:45:31UTC  for an effective exposure of 100 ks. 

From a quick-look analysis of the *image-, time- and energy- averaged
low-level instrument data (prior to pipeline processing at the IXPE
SOC), we report:

Polarization degree (PD) < 11.1% upper limits are derived with 99% C.L.

These results are preliminary. The IXPE Collaboration will report 
the final results in a forthcoming publication.

The Imaging X-ray Polarimetry Explorer, commonly known as IXPE 
is a space observatory with three identical telescopes designed 
to measure the polarization of cosmic X-rays. X-ray polarimetry 
enabled by IXPE can be performed in energy-, time-, and 
angle-resolved fashions. The observatory, which was launched 
on 9 December 2021, is an international collaboration between 
NASA and the Italian Space Agency (ASI).

[Editor's note: Reformatted at the request of the submitter.]
Looking for U.S. government information and services? Visit