//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22170 SUBJECT: GRB 171126A: Fermi GBM detection DATE: 17/11/26 18:18:29 GMT FROM: C. Michelle Hui at MSFC/Fermi-GBM C. M. Hui (NASA/MSFC) and C. Meegan (UAH) reports on behalf of the Fermi GBM Team: At 05:38:43.71 UT on 26 November 2017, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 171126A (trigger 533367528/171126235). The on-ground calculated location, using the GBM trigger data, is RA = 237.84, DEC = +46.76 (J2000 degrees, equivalent to 15h 51m, +46d 42'), with an uncertainty of 3.29 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 angle from the Fermi LAT boresight is 50 degrees. The GBM light curve shows a single bright peak followed by a secondary emission with a duration (T90) of about 1.47s (50-300 keV). The time-averaged spectrum from T0+0.0s to T0+2.08s is adequately fit by a power law function with an exponential high-energy cutoff. The power law index is -0.66 +/- 0.05 and the cutoff energy, parameterized as Epeak, is 89.36 +/- 2.52 keV. The event fluence (10-1000 keV) in this time interval is (2.074 +/- 0.042)E-06 erg/cm^2. The 64ms peak photon flux measured starting from T0+0.192s in the 10-1000 keV band is 97.21 +/- 6.07 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22176 SUBJECT: GRB 171126A: AstroSat CZTI detection DATE: 17/12/02 19:48:44 GMT FROM: Vidushi Sharma at IUCAA V. Sharma (IUCAA), V. Bhalerao (IIT-B), D. Bhattacharya (IUCAA), 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 GRB 171126A, which was also detected by Fermi-GBM (Hui C.M. et al., GCN 22170). The source was clearly detected in the 40-200 keV energy range. The light curve shows multiple peaks of emission with strongest peak at 05:38:43.810 UT. The measured peak count rate is 530.2 cts/s above the background in combined data of four quadrants, with a total of 2675 cts. The local mean background count rate was 399.8 cts/s. Using cumulative rates, we measure a T90 of 1.1 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.