TITLE:   GCN CIRCULAR
NUMBER:  32751
SUBJECT: GRB 221009A: HEBS detection
DATE:    22/10/14 10:09:17 GMT
FROM:    Dong Xu at NAOC/CAS  <dxu@nao.cas.cn>

J. C. Liu, Y. Q. Zhang, S. L. Xiong, C. Zheng, C. W. Wang, W. C. Xue, R. 
Qiao, W. J. Tan, D. L. Zhang, X. Q. Li, X. Y. Wen, W. X. Peng, L. M. 
Song, S. J. Zheng, D. Y. Guo, X. B. Li, X. Ma, Y. Huang, X. Y. Zhao, P. 
Wang, J. Wang, Z. Zhang, Y. Q. Du, J. Liang, Y. Q. Lu, H. Wu, W. H. Yu, 
S. Xiao, C. Cai, P. Zhang, B. Li, Z. H. An, M. Gao, K. Gong, X. J. Liu, 
Y. Q. Liu, X. L. Sun, Y. B. Xu, S. Yang, P. Y. Feng, J. Z. Wang, F. 
Zhang, G. Chen, F. J. Lu, S. N. Zhang (IHEP) report on behalf of GECAM 
and HEBS teams:

During the commissioning phase, HEBS detected the prompt emission of the
extraordinarily bright burst GRB 221009A, which was also observed by
Fermi/GBM (Lesage et al., GCN 32642, Veres et al., GCN 32636),
Swift/BAT (Dichiara et al., GCN 32632, Kennea et al., GCN 32635)
Insight-HXMT/HE (Tan et al., Atel 15660),
Fermi/LAT (Bissaldi et al. GCN 32637, Pillera et al., GCN 32658),
AGILE/MCAL (Ursi et al., GCN 32650), AGILE/GRID (Piano et al. GCN 32657),
INTEGRAL SPI/ACS (Gotz et al., GCN 32660),
Konus-Wind (Frederiks et al., GCN 32668), SIRI-2 (Mitchell et al., GCN 
32746),
and LHAASO (Huang et al., GCN 32677).

At the beginning of the burst (2022-10-09T13:17:00.050 UTC, denoted as 
T0), HEBS was in the high latitude region where the in-flight triggering 
of HEBS was disabled to eliminate false triggers caused by particle 
background. However, one gamma-ray detector (i.e. GRD01) and one charged 
particle detector (i.e. CPD02) are set to collect data normally during 
this region. The full burst of GRB 221009A prompt emission was well 
monitored by HEBS. The incident angle to GRD01 is about 70 deg during 
the prompt emission.

Despite of the extreme brightness, the GRB 221009A main burst (T0+180s 
to T0+270s) was clearly observed by HEBS without data saturation. The 
dead-time is reasonable and the pulse pileup effect is negligible for 
the low gain readout channel of GRD01.

The dead-time corrected light curves of HEBS could be found at:
http://twiki.ihep.ac.cn/pub/GECAM/GRBList/HEBS-GRB221009A.png

 From the 50 ms light curve, we note that there are complicated spiky 
structures during the main peaks. All results above are preliminary. 
Refined analysis is ongoing and will be reported later.

HEBS is an all-sky monitor for gamma-ray transients in 10 keV to 5 MeV 
aboard the Space advanced technology demonstration satellite (SATech-01) 
satellite, which is funded and built by Chinese academic of sciences, 
and was launched on July 27, 2022. Both the payload and the science 
operation of HEBS are inherited from GECAM mission (made of two 
mini-satellites, GECAM-A and GECAM-B), and thereafter HEBS is also 
called GECAM-C.