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GCN Circular 25547

Subject
LIGO/Virgo S190828l: Upper limits from Insight-HXMT/HE observations
Date
2019-08-29T14:01:54Z (5 years ago)
From
Qi Luo at IHEP <luoqi@ihep.ac.cn>
J. M. Yao, Y. G. Zheng, C. Cai, Q. Luo, S. Xiao, Q. B. Yi, 
Y. Huang, C. K. Li, G. Li, X. B. Li, J. Y. Liao, S. L. Xiong,
C. Z. Liu, X. F. Li, Z. W. Li, Z. Chang, A. M. Zhang, 
Y. F. Zhang, X. F. Lu, C. L. Zou (IHEP), Y. J. Jin, 
Z. Zhang (THU), T. P. Li (IHEP/THU), F. J. Lu, L. M. Song, 
M. Wu, Y. P. Xu, S. N. Zhang (IHEP), 
report on behalf of the Insight-HXMT team:

Insight-HXMT was taking data normally around the reported LIGO/Virgo 
S190828l event (GCN #25503), trigger time 2019-08-28T06:55:09.887 UTC. 
At T0, about 77% of the LIGO localization region was covered by the 
Insight-HXMT without occultationby the Earth.

Within T0 +/- 100 s, no significant excess events (SNR > 3 sigma) are 
found in a search of the Insight-HXMT/HE raw light curves.

Assuming the GW counterpart GRB with three typical GRB Band spectral 
models, two typical duration timescales (1 s, 10 s) from the center 
of the LIGO-Virgo location probability map (RA=145 deg, DEC=-50 deg), 
the 5-sigma upper-limits fluence (0.2 - 5 MeV, incident energy) are 
reported below:

Band model 1 (alpha=-1.9, beta=-3.7, Ep=70 keV):
1 s:   2.5e-07 erg cm^-2
10 s:  1.1e-06 erg cm^-2

Band model 2 (alpha=-1.0, beta=-2.3, Ep=230 keV):
1 s:   4.0e-07 erg cm^-2
10 s:  1.8e-06 erg cm^-2

Band model 3 (alpha=-0.0, beta=-1.5, Ep=1000 keV):
1 s:   8.8e-07 erg cm^-2
10 s:  2.8e-06 erg cm^-2

All measurements above are made with the CsI detectors operating in the
regular mode with the energy range of about 80-800 keV (deposited energy).
Only gamma-rays with energy greater than about 200 keV can penetrate
the spacecraft and leave signals in the CsI detectors installed inside
of the spacecraft.
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