[vsnet-grb-info 25119] LIGO/Virgo S200224ca: Upper limits from Insight-HXMT/HE observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  27219
SUBJECT: LIGO/Virgo S200224ca: Upper limits from Insight-HXMT/HE observations
DATE:    20/02/26 08:06:44 GMT
FROM:    Qi Luo at IHEP  <luoqi at ihep.ac.cn>

Q. Luo, Y. G. Zheng, C. Cai, 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 
S200224ca event (GCN #27184). At the GW trigger time 
2020-02-24T22:22:34.406 UTC (denoted as T0), about 99.6% of the 
GW localization region was covered by the Insight-HXMT without 
occultation by 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=174.9 deg, DEC=-9.8 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:   1.4e-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:   2.2e-07 erg cm^-2
10 s:  1.7e-06 erg cm^-2

Band model 3 (alpha=-0.0, beta=-1.5, Ep=1000 keV):
1 s:   6.8e-07 erg cm^-2
10 s:  3.9e-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.