//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22884 SUBJECT: GRB 180703B: Fermi-LAT detection DATE: 18/07/04 02:35:47 GMT FROM: Judith Racusin at GSFC J. L. Racusin (NASA/GSFC), M. Crnogorčević (UMD), A. Barker (George Washington), G. Vianello (Stanford), M. Axelsson (KTH and Stockholm University) report on behalf of the Fermi-LAT team: At 22:46:51.32 UTC on July 03, 2018 Fermi-LAT detected high-energy emission from GRB 180703B, which was also detected by Fermi-GBM (trigger 552350816 / 180703949). The best LAT on-ground location is found to be RA, Dec = 96.92, -29.88 (J2000) with an error radius of 0.4 deg (90% containment, statistical error only). This was 30 deg from the LAT boresight at the time of the trigger. The data from the Fermi-LAT show a significant increase in the event rate that is spatially and temporally correlated with the trigger with high significance. The highest-energy photon is a ~1 GeV event which is observed 35 seconds after the GBM trigger. A Swift ToO has been requested for this burst. The Fermi-LAT point of contact for this burst is Judith Racusin (judith.racusin@nasa.gov). The Fermi-LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22888 SUBJECT: GRB 180703B: CALET Gamma-Ray Burst Monitor detection DATE: 18/07/04 09:24:53 GMT FROM: Valentin Pal'shin at AGU I. Takahashi (IPMU), 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), Y. Asaoka, 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 Fermi-LAT GRB 180703B (Racusin et al. GCN Circ. 22884) triggered the CALET Gamma-ray Burst Monitor (CGBM) at 22:46:51.183 UTC on 3 July 2018. The burst signal was seen by all CGBM detectors. The burst light curve shows two short pulses which start at T+0.1 sec, peaks at T+1.4 sec and ends at T+2.1 sec. The T90 and the T50 durations measured by the SGM data are 1.4 +- 0.2 sec and 0.4 +- 0.1 sec (40-1000 keV), respectively. Despite its very high brightness the burst spectrum is soft with almost no emission seen in the CGBM data above ~500 keV. So, this is a very bright, short, and soft GRB. The follow-up observations of this interesting event is highly encouraged. The ground processed light curve is available at http://cgbm.calet.jp/cgbm_trigger/ground/1214693124/ The CALET data used in this analysis are provided by the Waseda CALET Operation Center located at the Waseda University. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22897 SUBJECT: GRB 180703B: Fermi GBM detection DATE: 18/07/04 17:00:32 GMT FROM: Suraj Poolakkil at UAH S.Poolakkil and C. Meegan (both UAH) report on behalf of the Fermi GBM Team: "At 22:46:51.32 UT on 03 July 2018, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 180703B (trigger 552350816/ 180703949), which was also detected by the Fermi LAT (Racusin et al. 2018, GCN 22884). The GBM on-ground location is consistent with the LAT position. The angle from the Fermi LAT boresight at the GBM trigger time is 31 degrees. The GBM light curve shows two peaks with a duration (T90) of about 1.6 s (50-300 keV). The time-averaged spectrum from T0-0.1 s to T0+2.4 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.79 +/- 0.03 and the cutoff energy, parameterized as Epeak, is 138 +/- 3 keV. The event fluence (10-1000 keV) in this time interval is (8.281 +/- 0.119)E-06 erg/cm^2. The 64-ms peak photon flux measured starting from T0+1.21 s in the 10-1000 keV band is 103.9 +/- 2.92 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: 22908 SUBJECT: IPN Triangulation of GRB 180703B DATE: 18/07/06 05:14:31 GMT FROM: Anna Kozlova at Ioffe Institute K. Hurley, on behalf of the IPN, I. G. Mitrofanov, D. Golovin, M. L. Litvak, and A. B. Sanin, on behalf of the HEND-Odyssey GRB team, A. Kozlova, S. Golenetskii, R. Aptekar, D. Frederiks, D. Svinkin, and T. Cline on behalf of the Konus-Wind team, A. Goldstein, M. S. Briggs, and C. Wilson-Hodge on behalf of the Fermi GBM team, A. von Kienlin, X. Zhang, A. Rau, V. Savchenko, E. Bozzo, and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team, S. Barthelmy, J. Cummings, H. Krimm, and D. Palmer, on behalf of the Swift-BAT team, and W. Boynton, C. Fellows, K. Harshman, H. Enos, and R. Starr, on behalf of the GRS-Odyssey GRB team, report: The short duration GRB 180703B (Fermi-LAT detection: Racusin et al., GCN Circ. 22884; CGBM detection: Takahasi et al., GCN Circ. 22888; Fermi-GBM detection: Poolakkil and Meegan, GCN Circ. 22897) was detected by Fermi (GBM trigger 552350816), Konus-Wind, INTEGRAL (SPI-ACS), Mars-Odyssey (HEND), CALET (CGBM), and Swift (BAT), at about 82009 s UT (22:46:49). The burst was outside the coded field of view of the BAT. We have triangulated it to a Konus-HEND annulus centered at RA(2000)=132.436 deg (08h 49m 45s) Dec(2000)=+22.998 deg (+22d 59' 54"), whose radius is 62.605 +/- 0.326 deg (3 sigma). The LAT position reported by Racusin et al. (GCN Circ. 22884) is consistent with the annulus. The annulus combined with the LAT (90 % containment, statistical-only) error circle gives the following error box: --------------------------------------------- RA(2000), deg Dec(2000), deg --------------------------------------------- Center: 97.0594 -29.7187 Corners: 96.9223 -29.8774 97.2925 -30.1165 97.1962 -29.5599 96.5548 -29.6361 --------------------------------------------- The error box area is 894.7 sq. arcmin (a factor of 2 smaller than that of the LAT error circle). This box may be improved. A triangulation map is posted at http://www.ioffe.ru/LEA/GRBs/GRB180703_T82008/IPN //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22914 SUBJECT: Konus-Wind observation of GRB 180703B DATE: 18/07/06 11:56:57 GMT FROM: Dmitry Frederiks at Ioffe Institute D. Frederiks, S. Golenetskii, R.Aptekar, A. Kozlova, A.Lysenko, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report: GRB 180703B (IPN Triangulation: Hurley et al., GCN 22908; Fermi-LAT detection: Racusin et al., GCN 22884; Fermi-GBM detection: Poolakkil & Meegan, GCN 22897) triggered Konus-Wind at T0=82008.633 s UT (22:46:48.633) The burst light curve shows two prominent peaks, with a total duration of ~2.0 s. The emission in the main peak is seen up to ~2 MeV. As observed by Konus-Wind, the burst had a fluence of (6.4 ± 0.4)x10^-6 erg/cm2 and a 64-ms peak energy flux, measured from T0+1.088, of (1.60 ± 0.09)x10^-5 erg/cm2 (both in the 20 keV - 10 MeV energy range). The time-integrated spectrum (measured from T0 to T0+8.448 s) is best fit in the 20 keV - 2 MeV range by a cutoff power-law (CPL) function with the following model parameters: the photon index alpha = -0.74(-0.18,+0.19), and the peak energy Ep = 131(-9,+11) keV, chi2 = 55/57 dof. Fitting this spectrum with the GRB (Band) function yields the same alpha and Ep, and only an upper limit on beta (<-3.3). The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB180703_T82008/ All the quoted errors are estimated at the 90% confidence level. All the presented results are preliminary. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22932 SUBJECT: GRB 180703B: further analysis of CGBM data DATE: 18/07/09 14:07:10 GMT FROM: Takanori Sakamoto at AGU V. Pal'shin, Y. Kawakubo, A. Yoshida, T. Sakamoto, S. Sugita, 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), 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: Using the CALET Gamma-ray Burst Monitor (CGBM) event data we report further analysis of the bright, short-duration, soft spectrum GRB 180703B (Fermi-LAT detection: Racusin et al. GCN Circ. 22884; CGBM detection: Takahashi et al. GCN Circ. 22888; Fermi-GBM detection: Poolakkil and Meegan GCN Circ. 22897; IPN localization: Hurley et al. GCN Circ. 22908; Konus-Wind observation: Frederiks et al. GCN Circ. 22914). Using a 16-ms binned light curve of the sum of HXM1 and HXM2 detectors, the estimated spectral lag for the 25-50 keV to 100-300 keV bands is 43 ± 30 ms (68% CL). This value is more consistent with lags of long rather than short GRBs. We also obtained more precise estimates of T90 and T50 using the SGM 16-ms lc: 1.44 s +- 0.10 s and 0.34 +- 0.06 sec (40-1000 keV), respectively. The time-averaged spectrum of the burst (measured by the SGM from T0+0.032 sec to T0+1.856 sec, where T0=22:46:51.183 UTC) is best fit in the 30-1000 keV range by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = -0.83(-0.32, +0.36) and Ep = 143(-13, +15) keV (chi2 = 62/59 dof). The resulting fluence in this energy range is 5.98(-0.43, +0.46)x10^-6 erg/cm2. The quoted errors are at 90% CL. All the quoted values are preliminary. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 23058 SUBJECT: GRB 180703B: CALET CAL gamma-ray analysis DATE: 18/07/30 09:44:28 GMT FROM: Takanori Sakamoto at AGU K. Yoshikawa, Y. Asaoka (Waseda U), N. Cannady (LSU), 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), 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: Using the CALET CALorimeter (CAL) data, we report GeV gamma-ray search analysis associated to GRB 180703B (Racusin et al. GCN Circ. 22884; Takahashi et al. GCN Circ. 22888; Poolakkil and Meegan GCN Circ. 22897; Hurley et al. GCN Circ. 22908; Frederiks et al. GCN Circ. 22914). The CAL was operating in low energy trigger mode at the trigger time of the CALET Gamma-ray Burst Monitor (CGBM). We have searched for gamma-ray events in the 1-10 GeV band from -60 sec to +60 sec from the CGBM trigger time using the Fermi-LAT position (Racusin et al. GCN Circ. 22884) and found no candidates. The 90% upper limit of CAL is 1.5e-6 erg/cm2/s (1-10 GeV) assuming a power-law spectrum of a photon index of -2. All the quoted values are preliminary.