Gamma-ray Burst 180701A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

• none

• GCN Circular #22880
  MAXI/GSC detection of GRB 180701A/MAXI J2119-045
  W. Maruyama, H. Negoro (Nihon U.), T. Mihara, S. Nakahira, F. Yatabe, Y. Takao, M. Matsuoka (RIKEN), N. Kawai, M. Sugizaki, Y. Tachibana, K. Morita (Tokyo Tech), T. Sakamoto, M. Serino, S. Sugita, Y. Kawakubo, T. Hashimoto, A. Yoshida (AGU), M. Nakajima, A. Sakamaki (Nihon U.), 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 (Osaka U.), M. Yamauchi, K. Hidaka, S. Iwahori (Miyazaki U.), T. Kawamuro (NAOJ), K. Yamaoka (Nagoya U.), M. Shidatsu (Ehime U.)
  MAXI/GSC detected an uncatalogued short X-ray transient event at 06:47 UT on 2018 July 1. Assuming that the source flux was constant over the transit, we obtain the source position at (R.A., Dec) = (319.919 deg, -4.500 deg) = (21 19 40, -04 30 00) (J2000) with a statistical 90% C.L. elliptical error region with long and short radii of 0.36 deg and 0.32 deg, respectively. The roll angle of the long axis from the north direction is 57.0 deg counterclockwise. There is an additional systematic uncertainty of 0.1 deg (90% containment radius). The X-ray flux averaged over the scan was 74 +- 19 mCrab (4.0-10.0keV, 1 sigma error). There was no significant excess flux in the previous transit at 05:14 UT and in the next transit at 08:20 UT with an upper limit of 20 mCrab for each.
  Due to the poor statistics, we could not obtain any useful information on the energy spectrum of the source. The burst duration actually observed was about 10 seconds, which was, however, a lower limit of the duration for the event occurring at the beginning or end of the scan window. Note that, in such case, the error region to the scan direction is larger than that of the steady-flux-source case described above.
  The nature of the source is quite unknown, then we refer to the source as GRB 180701A and MAXI J2119-045.
• GCN Circular #22915
  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:
  A long GRB was detected by Konus-Wind (KW) in the waiting mode on July 1, 2018 at ~23864 s UT (06:37:44), ~600 s before the MAXI trigger (GRB 180701A; Maruyama et al., GCN 22880).
  The burst light curve shows a single pulse with a duration of ~ 12 s. Taking into account the proximity of this burst to the MAXI/GSC trigger and the consistency of the KW ecliptic latitude response with the position of GRB 180701A we suggest that KW observed the main part of GRB 180701A.
  As observed by KW, the burst had a fluence of 1.85(-0.13,+0.64)x10^-6 erg/cm2 and a 2.944-s peak flux, measured from ~T0(MAXI)-555.6 s, of 2.47(-0.75,+1.13)x10^-7 erg/cm2/s (both in the 20 keV - 10 MeV energy range).
  Modeling the KW 3-channel time-integrated spectrum (from ~T0(MAXI)-558.6 s to ~T0(MAXI)-546.8 s) by a simple power-law model yields the power law index of -2.52(-0.11,+0.25), chi2 = 1.3/1 dof.
  The KW light curve of this burst is available at http://www.ioffe.rssi.ru/LEA/GRBs/GRB180701A
  All the quoted errors are estimated at the 1 sigma confidence level. All the presented results are preliminary.
• GCN Circular #23063
  V. Pal'shin, Y. Kawakubo, T. Sakamoto, A. Yoshida, 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:
  We have performed a search of hard X-ray/gamma-ray emission from GRB 180701A/MAXI J2119-045 (Maruyama et al., GCN Circ. 22880) in the CALET Gamma-ray Burst Monitor (CGBM) data around the MAXI trigger time at T0=06:47 UT on 2018 July 1.
  The source position (RA, Dec (J2000) = 319.919 deg, -4.500 deg) at the trigger time was in the CGBM FOV at favorable angles (the off-axis angles 22.1 deg and 12.2 deg for HXM and SGM detector respectively).
  No CGBM on-board trigger occurred around T0. By using the CGBM time-history data (0.125 sec time resolution), we found no statistically significant signal between +-50 sec from T0. We estimate 7-sigma upper limit in the 30-1000 keV band as 6x10^-7 erg/cm2/s assuming a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = -1.0 and Ep = 200 keV in 1 s exposure.
  At the time of the Konus-Wind event at 06:37:44 UTC (=T0-556 sec) suggested to be the main part of GRB 180701A (Kozlova et al., GCN Circ. 22915), the position of the MAXI source was in the CGBM FoV at favorable angles (the off-axis angles 44.9 deg and 40.4 deg for HXM and SGM detector respectively). For the reported Konus-Wind spectral parameters, the estimated response in the CGBM detectors for the MAXI position would have a signal-to-noise ratio up to 15 in individual TH channel and up to 18 in combination of channels, while we do not see any hint of emission around this time. Hence, we conclude that the Konus-Wind event is likely not related to GRB 180701A/MAXI J2119-045.
  The CALET data used in this analysis are provided by the Waseda CALET Operation Center located at the Waseda University.