GRB 171223A

M. Stanbro and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:

"At 19:38:15.07 UT on 23 December 2017, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 171223A (trigger 535750700 / 171223818).

The on-ground calculated location, using the GBM trigger
data, is RA = 115.84, DEC = -33.48, with an uncertainty
of 6.59 degrees (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 trigger resulted in an Autonomous Repoint Request (ARR)
by the GBM Flight Software owing to the high peak flux
of the GRB. This ARR was accepted and the spacecraft slewed to the GBM
in-flight
location. The initial angle from the Fermi LAT boresight to
the best location is 56 degrees.

The GBM light curve consists of 1 pulse
with a duration (T90) of about 0.38 s (50-300 keV).
The time-averaged spectrum from T0-0.13 s to T0+0.32 s is
best fit by a Band function with Epeak = 1156 +/- 193 keV,
alpha = -0.67 +/- 0.07, and beta = -2.42 +/- 0.28.

The event fluence (10-1000 keV) in this time interval is
(1.98 +/- 0.06)E-06 erg/cm^2. The 64-millisec peak photon flux measured
starting from T0+0.064 s in the 10-1000 keV band
is 23.8 +/- 1.2 ph/s/cm^2.

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

X.F. Li, S. L. Xiong, X. B. Li, C. K. Li, C. Z. Liu,

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:



At 2017-12-23T19:38:15.000 (T0), Insight-HXMT/HE detected GRB 171223A 

(trigger ID: HEB171223818) in a routine search of the data, which was

also observed by Fermi/GBM(M. stanbro and C. Meegan, GCN Circ.22278
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 )


The Insight-HXMT light curve mainly consists of multiple pulses
with a duration (T90) of 0.17 s measured from T0+0.0735 s.
The 0.01s peak rate, measured from T0+0.109 s, is 38390.0 cnts/sec.
The total counts from this burst is 3198 counts.

URL_LC: http://www.hxmt.org/images/GRB/HEB171223818_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 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 short GRB 171223A, which was also detected by Fermi-GBM (Stanbro M. et al., GCN 22278
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 ) and Insight-HXMT/HE (Li Z. W. et al., GCN 22286
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 ).

The source was clearly detected in the 40-200 keV energy range. The light curve shows single peak structure with peak at 19:38:15.150 UT. The measured peak count rate is 1464.1 cts/s above the background in combined data of four quadrants, with a total of 2594 cts. The local mean background count rate was 485 cts/s. Using cumulative rates, we measure a T90 of 0.27 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.