//////////////////////////////////////////////////////////////////////// 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.] //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 21279 SUBJECT: IPN Triangulation of GRB 170626B DATE: 17/06/28 14:16:58 GMT FROM: Anna Kozlova at Ioffe Institute A. Kozlova, S. Golenetskii, R. Aptekar, D. Frederiks, D. Svinkin, and T. Cline on behalf of the Konus-Wind team, K. Hurley, on behalf of the IPN, S. Barthelmy, J. Cummings, H. Krimm, and D. Palmer, on behalf of the Swift-BAT team, report: The long-duration GRB 170626B was detected by Insight (HXMT), Konus-Wind, CALET (CGBM), and Swift (BAT) at about 3482 s UT (00:58:02). The burst was outside the coded field of view of the BAT. We have triangulated it to a Konus-BAT annulus centered at RA(2000)=289.789 deg (19h 19m 09s) Dec(2000)=-19.171 deg (-19d 10' 15"), whose radius is 4.975 ± 4.975 deg (3 sigma). This annulus is inconsistent with the HXMT position reported by Liu et al. (GCN 21265); also, the KW ecliptic latitude response implies the source position close to the ecliptic plane, which is ~30 deg from the HXMT localization. A triangulation map is posted at http://www.ioffe.ru/LEA/GRBs/GRB170626_T03482/IPN/ The Konus-Wind time history and spectrum will be given in a forthcoming GCN Circular. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 21280 SUBJECT: Konus-Wind observation of GRB 170626B DATE: 17/06/28 14:20:04 GMT FROM: Anna Kozlova at Ioffe Institute A. Kozlova, S. Golenetskii, R. Aptekar, D. Frederiks, P. Oleynik, M. Ulanov, D. Svinkin, A. Tsvetkova, A. Lysenko, and T. Cline on behalf of the Konus-Wind team, report: The long-duration GRB 170626B (Insight-HXMT observation: Liu et al., GCN 21265; IPN triangulation: Kozlova et al., GCN 21279) triggered Konus-Wind at T0=3482.215 s UT (00:58:02.215). The burst light curve shows a multipeaked structure started at ~T0-6.1 s with a total duration of ~16.8 s. The emission is seen up to ~10 MeV. As observed by Konus-Wind, the burst had a fluence of 4.12(-0.20,+0.22)x10^-5 erg/cm2, and a 64-ms peak flux, measured from T0+4.256 s, of 1.03(-0.18,+0.18)x10^-5 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-averaged spectrum of the burst (measured from T0 to T0+14.592 s) is best fit in the 20 keV - 10 MeV range by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = -0.59(-0.13,+0.14) and Ep = 423(-38,+45) keV (chi2 = 87/99 dof). Fitting by a GRB (Band) model yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -2.7 (chi2 = 87/98 dof) The spectrum near the maximum count rate (measured from T0+0.256 to T0+6.400 s) is best fit in the 20 keV - 10 MeV range by a power law with exponential cutoff model with alpha = -0.45(-0.11,+0.12) and Ep = 429(-30,+35) keV (chi2 = 91/92 dof). Fitting by a GRB (Band) model yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -2.8 (chi2 = 91/91 dof) The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB170626_T03482/ All the quoted errors are at the 90% confidence level. All the quoted values are preliminary. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 21282 SUBJECT: GRB 170626B CALET Gamma-Ray Burst Monitor detection DATE: 17/06/29 06:12:38 GMT FROM: Takanori Sakamoto at AGU Y. Asaoka (Waseda U), A. Yoshida, T. Sakamoto, Y. Kawakubo, M. Moriyama, Y. Yamada, A. Tezuka, S. Matsukawa (AGU), K. Yamaoka (Nagoya U), S. Nakahira (RIKEN), I. Takahashi (IPMU), S. Ozawa, S. Torii (Waseda U), Y. Shimizu, T. Tamura (Kanagawa U), W. Ishizaki (ICRR), M. L. Cherry (LSU), S. Ricciarini (U of Florence), A. V. Penacchioni, P. S. Marrocchesi (U of Siena) and the CALET collaboration: The long-duration GRB 170626B (Liu et al., GCN Circ. 21265; Konus-Wind trigger time on 00:58:02.21 UT) triggered the CALET Gamma-ray Burst Monitor (CGBM) at 00:57:56.28 on 26 June 2017. The burst signal was seen by the all CGBM instruments. The light curve of the SGM shows two overlapping peaks. The emission starts at T+1 sec, peaks at T+2.5 sec (the first peak) and T+5.5 sec (the second peak), and ends at T+10 sec. The T90 duration measured by the SGM data is 5.0 +- 0.4 sec (40-1000 keV). The light curve is available at http://cgbm.calet.jp/cgbm_trigger/flight/1182473374/ The CALET data used in this analysis are provided by the Waseda CALET Operation Center located at the Waseda University.