TITLE: GCN CIRCULAR NUMBER: 21265 SUBJECT: GRB 170626B: The first GRB detected by the Insight-HXMT X-ray Telescope (revised) DATE: 17/06/26 16:16:06 GMT (revised submission 17/06/27 05:32:06 UT) FROM: Shaolin Xiong at IHEP C. Z. Liu, X. Ma, J. Y. Liao, 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), X. B. Li, S. L. Xiong, C. K. Li, Y. Huang, Y. P. Chen, M. Y. Ge, M. Gao (IHEP), T. P. Li (IHEP/THU), G. Li, M. S. Li, H. W. Liu, F. J. Lu, L. M. Song, W. H. Tao, H. Y. Wang, Y. H. Wang, X. Y. Wen, M. Wu, H. Xu, Y. P. Xu, C. M. Zhang, F. Zhang, J. Zhang, T. Zhang, S. N. Zhang (IHEP), report on behalf of the Insight-HXMT team: The Insight-HXMT (Hard X-ray Modulation Telescope) satellite, was launched successfully on June 15, 2017. As one of the three instruments onboard the Insight-HXMT, the High Energy x-ray telescope (HE) consists of 18 detector modules with a total area of about 5000 cm2. Each HE module is made of a NaI(Tl)/CsI(Na) PHOSWICH detector. The CsI detectors can work as a GRB monitor in the energy range of 40 keV to ~1000 keV in the normal operation mode, or 200 keV to ~3 MeV in the GRB operation mode, with a large effective area up to about 2000 cm2 on average and a FoV covering nearly the whole sky unblocked by the Earth. During the commissioning phase, at 2017-06-26T00:57:55.800 (T0), Insight-HXMT detected the GRB 170626B (trig ID: HEB170626040) in a routine search of the data, which was also observed by the CALET (trig# 1182473374) and the Konus-Wind (trig time: 2017-06-26T00:58:02.21). After comparing the measurements with CALET and Konus-Wind, we conclude that this is the first confirmed GRB discovered by the Insight-HXMT Telescope! The Insight-HXMT light curve mainly consists of two pulses with a duration (T90) of 6.5 s measured from T0+1.26 s. The 1-second peak rate, measured from T0+5.0 s, is 4624.5 cnts/sec. The total counts from this burst is 13919 counts. All measurements above are made with the CsI detectors in the energy range of about 80-840 keV. Please note that this is the deposited energy, rather than the incident photon energy. URL_LC: http://www.hxmt.org/images/GRB/HEB170626040_lc.jpg The Insight localization of this GRB gives (J2000): RA: 241.69 [deg] DEC: -54.13 [deg] Err: 10 [deg] The statistical error is about 2 deg, however, the systematic error should dominate at the commissioning phase since the calibration is sill ongoing. We estimate the total error of location is about 10 deg, as indicated with the red circle in the following location map. URL_LOC: http://www.hxmt.org/images/GRB/HEB170626040_loc.jpg 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 this telescope could be found at: http://www.hxmt.org/index.php/enhome . [GCN OPS NOTE(27jun17): Per author's request, this is a revised version of the original GCN 21265 circular. The "localization" and "statistical error" paragraphs were added.] ///////////////////////////Original Distribution/////////////////////// TITLE: GCN CIRCULAR NUMBER: 21265 SUBJECT: GRB 170626B: The first GRB detected by the Insight-HXMT X-ray Telescope DATE: 17/06/26 16:16:06 GMT FROM: Shaolin Xiong at IHEP C. Z. Liu, X. Ma, J. Y. Liao, 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), X. B. Li, S. L. Xiong, C. K. Li, Y. Huang, Y. P. Chen, M. Y. Ge, M. Gao (IHEP), T. P. Li (IHEP/THU), G. Li, M. S. Li, H. W. Liu, F. J. Lu, L. M. Song, W. H. Tao, H. Y. Wang, Y. H. Wang, X. Y. Wen, M. Wu, H. Xu, Y. P. Xu, C. M. Zhang, F. Zhang, J. Zhang, T. Zhang, S. N. Zhang (IHEP), report on behalf of the Insight-HXMT team: The Insight-HXMT (Hard X-ray Modulation Telescope) satellite, was launched successfully on June 15, 2017. As one of the three instruments onboard the Insight-HXMT, the High Energy x-ray telescope (HE) consists of 18 detector modules with a total area of about 5000 cm2. Each HE module is made of a NaI(Tl)/CsI(Na) PHOSWICH detector. The CsI detectors can work as a GRB monitor in the energy range of 40 keV to ~1000 keV in the normal operation mode, or 200 keV to ~3 MeV in the GRB operation mode, with a large effective area up to about 2000 cm2 on average and a FoV covering nearly the whole sky unblocked by the Earth. During the commissioning phase, at 2017-06-26T00:57:55.816 (T0), Insight-HXMT detected the GRB 170626B (trig ID: HEB170626040) in a routine search of the data, which was also observed by the CALET (trig# 1182473374) and the Konus-Wind (trig time: 2017-06-26T00:58:02.21). After comparing the measurements with CALET and Konus-Wind, we conclude that this is the first confirmed GRB discovered by the Insight-HXMT Telescope! The Insight-HXMT light curve mainly consists of two pulses with a duration (T90) of 6.3 s measured from T0+2.51 s. The 1-second peak rate, measured from T0+6.5 s, is 4426.9 cnts/sec. The total counts from this burst is 13784 counts. All measurements above are made with the CsI detectors in the energy range of about 80-840 keV. Please note that this is the deposited energy, rather than the incident photon energy. URL_LC: http://newshxmt.ihep.ac.cn/images/GRB/HEB170626040_lc.jpg 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 this telescope could be found at: http://newshxmt.ihep.ac.cn/index.php/enhome .