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GCN Circular 32691

Subject
GRB221009A: INTEGRAL detection of Hard X-ray emission up to 38 hours after trigger
Date
2022-10-11T16:05:23Z (2 years ago)
From
Volodymyr Savchenko at ISDC,U of Geneve <savchenk@in2p3.fr>
Volodymyr Savchenko (UNIGE, EPFL), Carlo Ferrigno, Enrico Bozzo (UNIGE), 
D. Gotz (CEA Paris Saclay), S. Mereghetti (INAF/IASF Milano),�� Antonio 
Martin Carrillo, Lorraine Hanlon (UCD), Elisabeth Jourdain, Jean-Pierre 
Roques (IRAP), Thomas Siegert (University of W��rzburg), Erik Kuulkers, 
Celia Sanchez (ESA)


Following the detection of the record-breaking GRB221009A by Swift/BAT 
(GCN #32632,#32635), Fermi/GBM (GCN #32636),
INTEGRAL/SPI-ACS (GCN #32660), we have performed INTEGRAL pointed 
observations of the GRB221009A location.

INTEGRAL pointed observation lasted from 2022-10-10T14:31:40 (T0 + 25.2 
hours, where T0 is 2022-10-09T13:17:00) to 2022-10-11T03:18:20 (T0 + 
38.0 hours) with a total exposure time of 30.2 ks (for ISGRI).

In the complete observation, the source is clearly detected in JEM-X1, 
JEM-X2 (3-30 keV), and ISGRI (28 - 80 keV), with S/N of 27.8, 27.3, 15.0 
respectively.

The joint JEM-X and ISGRI spectra can be satisfactorily modeled between 
3 and 80 keV with a single powerlaw of slope 2.15 +/- -0.07 (90% 
confidence) with a flux of 4.4e-10 +/- -2.1e-11 erg/cm2/s (3 - 80 keV).
This might indicate a single spectral component spanning from from hard 
X-ray to Fermi/LAT (GCN #32658).

Combination of bright Hard X-ray afterglow with gamma-ray emission was 
also found in GRB120711A (Martin-Carrillo et al. 2014 A&A 567, 84) and 
GRB130427A (Kouveliotou et al. 2013 ApJ 779L, 1K)
- in fact GRB221009A appears rather similar to GRB120711A, but at 10 
times smaller distance.

Within the relatively short JEM-X not ISGRI lightcurves, we do not 
observe any evidence for flux decrease.

Further INTEGRAL observations are scheduled between 2022-10-11 13:52:21 
and 2022-10-13 00:58:26. These observations will overlap with the 
planned observation of IXPE (GCN #32690).

We are grateful to the INTEGRAL Ground Segment team for quickly 
scheduling the observations.

Images and reduced data related to this publication can be found here: 
https://zenodo.org/record/7186289
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