GRB 170726A

X. B. Li, J. Y. Liao, C. K. Li, S. L. Xiong, C. Z. Liu, X. F. Li,
Z. W. Li, Z. Chang, X. F. Lu, J. L. Zhao, A. M. Zhang, Y. F. Zhang,
C. L. Zou (IHEP), Y. J. Jin, Z. Zhang (THU), T. P. Li (IHEP/THU),
F. J. Lu, L. M. Song, H. Y. Wang, M. Wu, Y. P. Xu, S. N. Zhang (IHEP),
report on behalf of the Insight-HXMT team:

During the commissioning phase, at 2017-07-26T19:02:59.51 (T0),
Insight-HXMT detected GRB 170726A (trigger ID: HEB170726793)
in a routine search of the data, which was also observed by
SPI-ACS (trig time: 2017-07-26T19:02:59.51) and
Fermi/GBM (trig time: 2017-07-26T19:02:59.976).

The Insight-HXMT light curve mainly consists of multi-pulses
with a duration (T90) of 23.7 s measured from T0-5.47 s.
The 1-second peak rate, measured from T0+2 s, is 1364.9 cnts/sec.
The total counts from this burst is 10261.5 counts.

URL_LC: http://www.hxmt.org/images/GRB/HEB170726793_lc.jpg

All measurements above are made with the CsI detectors operating in the
regular mode with the energy range of about 80-800 keV (record 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 telescope.

The time-averaged spectrum from T0-8 s to T0+18 s is
adequately fit by a Power Law model with spectral index = -1.94 +/- 0.05.
The energy fluence is (7.17 +/- 0.38)E-06 erg/cm^2 in 200 - 3000 keV
in this time interval.

The analysis results presented above are preliminary;
final results will be published elsewhere.

Insight-HXMT is the first Chinese space X-ray telescope, which was funded
jointly by the China National Space Administration (CNSA) and the Chinese
Academy of Sciences (CAS). More information about it could be found at:
http://www.hxmt.org/index.php/enhome .

V. Sharma and D. Bhattacharya (IUCAA), V. Bhalerao (IIT-B), A. R. Rao (TIFR) and S. Vadawale (PRL) report on behalf of the Astrosat CZTI collaboration:

Analysis of Astrosat CZTI data showed the detection of a long-duration GRB 170726A, which was also detected by Insight-HXMT (Li et al., GCN 21366
Loading...
 
 ), SPI-ACS (trig time: 2017-07-26 19:02:59.51) and
Fermi/GBM (trig time: 2017-07-26 19:02:59.976).

The source was clearly detected in the 40-200 keV energy range. The light curve shows multiple peaks of emission with the strongest peak at 19:03:00.976 UT, ~1 s after the Insight-HXMT Trigger. The measured peak count rate is 475.9 cts/s above the background in combined data of four quadrants, with a total of 5477 cts. The local mean background count rate was 377.1 cts/s. Using cumulative rates, we measure a T90 of 39.6 s.

It was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range.

CZTI GRB detections are reported regularly on the payload site at http://astrosat.iucaa.in/czti/?q=grb. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, ISAC, IUCAA, SAC and PRL. The Indian Space Research Organisation funded, managed and facilitated the project.