GRB 180723A

W. Ishizaki (ICRR), A. Yoshida, T. Sakamoto, V. Pal'shin, S. Sugita,
Y. Kawakubo, A. Tezuka, S. Matsukawa, H. Onozawa, T. Ito,
H. Morita, Y. Sone (AGU), K. Yamaoka (Nagoya U), S. Nakahira (RIKEN),
I. Takahashi (IPMU), Y. Asaoka, S. Ozawa, S. Torii (Waseda U),
Y. Shimizu, T. Tamura (Kanagawa U), M. L. Cherry (LSU),
S. Ricciarini (U of Florence), A. V. Penacchioni, P. S. Marrocchesi (U of Siena)
and the CALET collaboration:

The long GRB 180723A (Fermi-GBM trigger #554062193) triggered the CALET
Gamma-ray Burst Monitor (CGBM) at 18:09:45.493 UTC on 23 July 2018.
This GRB is also clearly seen by the publicly available INTEGRAL
SPI-ACS light curve.  The burst signal was seen by all CGBM detectors.

The burst light curve shows a FRED-like pulse which starts
at T+2.4 sec, peaks at T+4.9 sec, and ends at T+14.5 sec.
The T90 and the T50 durations measured by the SGM data are
10.0 +- 1.3 sec and 4.3 +- 0.7 sec (40-1000 keV), respectively.

The ground processed light curve is available at

http://cgbm.calet.jp/cgbm_trigger/ground/1216404464/

The CALET data used in this analysis are provided by
the Waseda CALET Operation Center located at the Waseda University.

S.Poolakkil and C. Meegan (both UAH) report on
behalf of the Fermi GBM Team:

"At 18:09:48.16 UT on 23 July 2018, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 180723A (trigger 554062193/ 180723757).

The on-ground calculated location, using the GBM trigger
data, is RA = 7.84, DEC = -66.11, with an uncertainty
of 1 degree (radius, 1-sigma containment,
statistical only; there is additionally a systematic
error which we have characterized as a core-plus-tail model, with 90% of
GRBs having a 3.7 deg error and a small tail suffering a larger than 10 deg
systematic error. [Connaughton et al. 2015, ApJS, 216, 32] ).

The angle from the Fermi LAT boresight
at the GBM trigger time is 132 degrees.

The GBM light curve consists of a single bright peak
with a duration (T90) of about 19.71 s (50-300 keV).
The time-averaged spectrum from T0-2.05 s to T0+31.74 s is
best fit by a power-law function with an exponential
high-energy cutoff. The power law index is -1.22 +/- 0.02 and
the cutoff energy, parameterized as Epeak, is 178 +/- 5 keV.

The event fluence (10-1000 keV) in this time interval is
(4.616 +/- 0.057)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+3.39 s in the 10-1000 keV band
is 41.2 +/- 0.81 ph/s/cm^2.

The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."

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 bright GRB 180723A, which was also detected by CALET (Ishizaki W. et al., GCN 23029
Loading...
 
 ) and Fermi-GBM (Poolakkil S. et al., GCN 23035
Loading...
 
 ).

The source was clearly detected in the 40-200 keV energy range. The light curve shows multiple peaks of emission with strongest peak at 18:09:49.50 UT. The measured peak count rate is 1123.5 cts/s above the background in combined data of four quadrants, with a total of 6717 cts. The local mean background count rate was 543.5 cts/s. Using cumulative rates, we measure a T90 of 25.3 s. In preliminary analysis, we find that 459 compton events are associated with this event.

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.