//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 23257 SUBJECT: GRB 180923A: MAXI/GSC detection DATE: 18/09/23 06:57:35 GMT FROM: Motoko Suzuki at RIKEN W. Maruyama, H. Negoro (Nihon U.), M. Serino (AGU), M. Nakajima, A. Sakamaki (Nihon U.), T. Mihara, S. Nakahira, F. Yatabe, Y. Takao, M. Matsuoka (RIKEN), T. Sakamoto, S. Sugita, Y. Kawakubo, T. Hashimoto, A. Yoshida (AGU), N. Kawai, M. Sugizaki, Y. Tachibana, K. Morita (Tokyo Tech), S. Ueno, H. Tomida, M. Ishikawa, Y. Sugawara, N. Isobe, R. Shimomukai (JAXA), Y. Ueda, A. Tanimoto, T. Morita, S. Yamada (Kyoto U.), Y. Tsuboi, W. Iwakiri, R. Sasaki, H. Kawai, T. Sato (Chuo U.), H. Tsunemi, T. Yoneyama, K. Asakura, S. Ide (Osaka U.), M. Yamauchi, K. Hidaka, S. Iwahori (Miyazaki U.), T. Kawamuro (NAOJ), K. Yamaoka (Nagoya U.), M. Shidatsu (Ehime U.) report on behalf of the MAXI team: The MAXI/GSC nova alert system triggered a bright uncatalogued X-ray transient source at 2018-09-23T04:08:25 UT . We obtain the source position at (R.A., Dec) = (38.304 deg, 6.301 deg) = (02 33 12, +06 18 03) (J2000) with a rectangular error box with the following corners: (R.A., Dec) = (37.429, 7.302) deg = (02 29 42, +07 18 07) (J2000) (R.A., Dec) = (37.165, 6.998) deg = (02 28 39, +06 59 52) (J2000) (R.A., Dec) = (39.010, 5.456) deg = (02 36 02, +05 27 21) (J2000) (R.A., Dec) = (39.274, 5.760) deg = (02 37 05, +05 45 35) (J2000) . There is an additional systematic uncertainty of 0.1 deg (90% containment radius). The X-ray flux averaged over the scan was 162 +- 26 mCrab (4.0-10.0keV, 1 sigma error). There was no significant excess flux in the previous transit at UT 02:35 and in the next transit at 05:41 UT with an upper limit of 20 mCrab for each. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 23258 SUBJECT: GRB 180923A: MASTER inspection MAXI/GSC error box DATE: 18/09/23 08:38:06 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, E. Gorbovskoy, D. Vlasenko, N.Tiurina, V.Kornilov, A.Kuznetsov, V.Chazov, I. Gorbunov, D.Zimnukhov, D.Kuvshinov, P.Balanutsa, V.Vladimirov, Lomonosov Moscow State University,SAI A. Tlatov, V.Senik, D. Dormidontov Kislovodsk Solar Station of the Pulkovo Observatory D. Buckley, South African Astronomical Observatory (SAAO) R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres The Instituto de Astrofisica de Canarias (IAC) R. Podesta, F. Podesta, C. Lopez, C.Francile Observatorio Astronomico Felix Aguilar (OAFA) H.Levato, Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE) O. Gres, N.M.Budnev , Yu.Ishmuhametova Irkutsk State University (ISU) A. Gabovich, V. Yurkov, Yu. Sergienko Blagoveschensk Educational State University (BSPU) MASTER-OAFA robotic telescope (MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Argentina (OAFA observatory of San Juan National University) was starting survey on the MAXI GRB180923.17 error-box (ra=02 33 12 dec=+06 18 02 r=1) 2777 sec after notice time and 7954 sec after trigger time at 2018-09-23 06:21:04 UT. The 5-sigma upper limit on our first (60s exposure) set is about 17.9 mag No OT detected. The galacitc latitude b = 0 deg. The observations made on zenit distance = 39 deg.The moon (97 % bright part) is 42 deg. above the horizon. The distance between moon and object is 59 The sun altitude is -48.6 deg. The object can be observed till sunrise at 2018-09-23 10:25:33 . The cover map is availavle at http://observ.pereplet.ru/images/GRB180923A_cover_map.png Only for MASTER-team: The OT candidate available here https://200.123.254.238:49004//master2/trans.php?wh=transients.coord2000@%27%3C%2838.3d%2C6.30056d%29%2C2d%3E%27%3A%3Ascircle+and+transients.datetime%3E%3D%272018-09-23+04%3A08%3A30%27&class=9&t2=MAXI+GRB180923.17+optical+counterpart+candidate The full information about this GRB180923.17 available here https://200.123.254.238:49004//master2/grb.php?not=2018-09-23+05%3A34%3A46.484065&sat=MAXI&gcrd=%2838.3d%2C6.30056d%29&eb=1&trig=2018-09-23+04%3A08%3A30&n=GRB180923.17 The message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 23259 SUBJECT: GRB 180923A: CALET Gamma-Ray Burst Monitor detection DATE: 18/09/24 00:10:40 GMT FROM: Valentin Pal'shin at AGU A. V. Penacchioni, 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), 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), P. S. Marrocchesi (U of Siena) and the CALET collaboration: The MAXI GRB 180923A (Maruyama et al., GCN Circ. 23257) was detected in ground analysis of the CALET Gamma-ray Burst Monitor (CGBM) data near the MAXI/GSC trigger time at T0=04:08:25 UT on 23 September 2018. The burst signal was seen by all CGBM detectors. The burst light curve shows a multi-peaked structure which starts at T-18 sec and ends at T+107 sec. The T90 and the T50 durations measured by the SGM data are 122 +- 15 sec and 95 +- 58 sec (40-1000 keV), respectively. The significant emission is seen only below ~100 keV. The ground processed light curve is available at http://cgbm.calet.jp/cgbm_trigger/ground/1221710834/ The CALET data used in this analysis are provided by the Waseda CALET Operation Center located at the Waseda University. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 23269 SUBJECT: Konus-Wind observation of GRB 180923A DATE: 18/09/25 15:02:50 GMT FROM: Anna Kozlova at Ioffe Institute A.Kozlova, S. Golenetskii, R.Aptekar, D. Frederiks, M. Ulanov, D. Svinkin, A. Tsvetkova, A.Lysenko, and T. Cline on behalf of the Konus-Wind team, report: The long-duration GRB 180923A localized by MAXI/GSC (Maruyama et al., GCN 23257) and observed by CALET (GBM: Penacchioni et al., GCN 23259) was detected by Konus-Wind (KW) in the waiting mode. The burst light curve shows two episodes, started at ~T0(MAXI)-19 s with a total duration of ~ 127 s. As observed by KW, the burst had a fluence of 5.42(-0.65,+1.26)x10^-6 erg/cm2 and a 2.944-s peak flux, measured from ~T0(MAXI)+93.3 s, of 3.47(-0.92,+1.15)x10^-7 erg/cm2/s (both in the 20 - 1000 keV energy range). Modeling the KW 3-channel time-integrated spectrum (from ~T0(MAXI)-18.6 s to ~T0(MAXI)+108 s) by a simple power-law model yields a power law index of -2.2(-0.2,+0.2), chi2=0.2/1 dof. The KW light curve of this burst is available at http://www.ioffe.rssi.ru/LEA/GRBs/GRB180923A All the quoted errors are estimated at the 1 sigma confidence level. All the presented results are preliminary.