Gamma-ray Burst 181028A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

• none

• GCN Circular #23386
  M. Axelsson (KTH and Stockholm Univ.), D. Kocevski (NASA/MSFC), E. Bissaldi (Politecnico & INFN Bari) and M. Yassine (Univ. & INFN Trieste) report on behalf of the Fermi-LAT team:
  On October 28, 2018, Fermi-LAT detected high-energy emission from GRB 181028A, which was also detected by Fermi-GBM (trigger 562428587).
  The best LAT on-ground location is found to be
  RA, Dec = 88.9, -22.0 (J2000)
  with an error radius of 0.4 deg (90 % containment, statistical error only). This is 4.9 deg from the GBM location.
  This was 60 deg from the LAT boresight at the time of the GBM trigger: 14:09:42.53 UT.
  The data from the Fermi-LAT in the time interval 0-300s after the GBM trigger show a significant increase in the event rate that is spatially correlated with the trigger with very high significance. The highest-energy photon is a 1.7 GeV event which is observed 295 seconds after the GBM trigger.
  The Fermi-LAT point of contact for this burst is Manal Yassine (mychbib@gmail.com).
  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
• GCN Circular #23387
  E. Bissaldi (Politecnico & INFN Bari) and C. Meegan (UAH) report on behalf of the Fermi GBM Team:
  "At 14:09:42.53 UT on 28 October 2018, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 181028A (trigger 562428587/ 181028590), which was also detected by the Fermi-LAT (Axelsson et al. 2018, GCN 23386). The GBM on-ground location is consistent with the LAT position.
  The angle from the Fermi-LAT boresight at the GBM trigger time is 58 degrees.
  The GBM light curve consists of multiple peaks with a duration (T90) of about 30 s (50-300 keV). The time-averaged spectrum from T0 to T0+30 s is adequately by a power law function with an exponential high-energy cutoff. The power law index is -0.72 +/- 0.02 and the cutoff energy, parameterized as Epeak, is 326 +/- 10 keV.
  The event fluence (10-1000 keV) in this time interval is (3.35 +/- 0.05)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+26.5 s in the 10-1000 keV band is 10.3 +/- 0.3 ph/s/cm^2.
  A Band function fits the spectrum equally well with Epeak= 306 +/- 13 keV, alpha = -0.69 +/- 0.03, and beta = -2.66 +/- 0.24.
  The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."
• GCN Circular #23388
  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,
  D. Svinkin, S. Golenetskii, R. Aptekar, D. Frederiks, A. Kozlova 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,
  and
  W. Boynton, C. Fellows, K. Harshman, H. Enos, and R. Starr, on behalf of the GRS-Odyssey GRB team, report:
  The long-duration GRB 181028A (Fermi-LAT detection: Axelsson et al., GCN Circ. 23386; Fermi-GBM detection: Bissaldi et al., GCN Circ. 23387) was detected by Fermi (GBM trigger 562428587), Konus-Wind, INTEGRAL (SPI-ACS), and Mars-Odyssey (HEND), at about 50982 s UT (14:09:42).
  We have triangulated it to a preliminary, 3 sigma error box whose coordinates are:

    ---------------------------------------------
     RA(2000), deg                 Dec(2000), deg
    ---------------------------------------------
    Center:
      88.889 (05h 55m 33s) -21.163 (-21d 09' 49")
    Corners:
      89.470 (05h 57m 53s) -21.496 (-21d 29' 47")
      89.355 (05h 57m 25s) -22.345 (-22d 20' 42")
      88.311 (05h 53m 15s) -20.824 (-20d 49' 27")
      88.431 (05h 53m 43s) -19.956 (-19d 57' 23")
    ---------------------------------------------
  

  The error box area is about 1.0 sq. deg, and its maximum dimension is 2.539 deg (the minimum one is 33.12 arcmin). The Sun distance was about 114 deg.
  This box intersects the Fermi-LAT 90% CL error circle (Axelsson et al., GCN Circ. 23386) to form an error box whose area is about 4 times smaller than that of the LAT error circle.
  This box may be further improved.
  A triangulation map is posted at http://www.ioffe.ru/LEA/GRBs/GRB181028_T50984/IPN
  The Konus-Wind time history and spectrum will be given in a forthcoming GCN Circular.
• GCN Circular #23393
  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 181028A (Fermi-LAT detection: Axelsson et al., GCN Circ. 23386; Fermi-GBM observation: Bissaldi & Meegan, GCN Circ. 23387; IPN Triangulation: Hurley et al., GCN Circ. 23388) triggered Konus-Wind at T0=50984.309 s UT (14:09:44.309).
  The burst light curve shows a multipeaked structure which starts at ~T0-2 s and has a total duration of ~38 s. The emission is seen up to ~4 MeV.
  As observed by Konus-Wind, the burst had a fluence of 3.43(-0.18,+0.20)x10^-5 erg/cm2, and a 64-ms peak flux, measured from T0+26.064 s, of 4.06(-1.01,+1.03)x10^-6 erg/cm2/s (both in the 20 keV - 10 MeV energy range).
  The time-averaged spectrum of the burst (measured from T0 to T0+40.704 s) is best fit in the 20 keV - 4 MeV range by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = -0.72(-0.10,+0.11) and Ep = 286(-22,+26) keV (chi2 = 53/70 dof). Fitting by a GRB (Band) model yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -2.6 (chi2 = 53/69 dof).
  The spectrum near the maximum count rate (measured from T0+24.320 to T0+32.512 s) is best fit in the 20 keV - 4 MeV range by a power law with exponential cutoff model with alpha = -0.39(-0.23,+0.27) and Ep = 292(-37,+49) keV (chi2 = 70/70 dof). Fitting by a GRB (Band) model yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -2.1 (chi2 = 70/69 dof).
  The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB181028_T50984/
  All the quoted errors are at the 90% confidence level. All the quoted values are preliminary.
• GCN Circular #23399
  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), A. V. Penacchioni, P. S. Marrocchesi (U of Siena), and the CALET collaboration:
  The long GRB 181028A (Fermi-LAT detection: Axelsson et al., GCN Circ. 23386; Fermi-GBM observation: Bissaldi & Meegan, GCN Circ. 23387; IPN Triangulation: Hurley et al., GCN Circ. 23388; Konus-Wind observation: Kozlova et al., GCN Circ. 23393) triggered the CALET Gamma-ray Burst Monitor (CGBM) at 14:09:39.546 UTC on 28 October 2018. The burst signal was seen by all CGBM detectors.
  The burst light curve shows a multi-peaked structure which starts at T+2.6 sec, peaks at T+14.4 sec, and ends at T+32.1 sec. The T90 and the T50 durations measured by the SGM data are 25.4 +- 5.5 sec and 8.3 +- 0.9 sec (40-1000 keV), respectively.
  The ground processed light curve is available at
  http://cgbm.calet.jp/cgbm_trigger/ground/1224770949/
  The CALET data used in this analysis are provided by the Waseda CALET Operation Center located at the Waseda University.
• GCN Circular #23409
  C. Cai, C. K. Li, X. B. Li, G. Li, J. Y. Liao, S. L. Xiong, C. Z. Liu, X. F. Li, Z. W. Li, Z. Chang, J. L. Zhao, A. M. Zhang, Y. F. Zhang, X. F. Lu, C. L. Zou (IHEP), Y. J. Jin, Z. Zhang (THU), T. P. Li (IHEP/THU), F. J. Lu, L. M. Song, H. Y. Wang, M. Wu, Y. P. Xu, S. N. Zhang (IHEP), report on behalf of the Insight-HXMT team:
  At 2018-10-28T14:09:43.000 (T0), the Insight-HXMT/HE detected GRB 181028A (trigger ID: HEB181028590) in a routine search of the data, which was also triggered by Fermi/LAT (Axelsson et al.,GCN 23386); Fermi/GBM (Bissaldi et al.,GCN 23387); IPN Triangulation (Hurley et al.,GCN 23388); Konus-Wind observation (Kozlova et al., GCN 23393); CALET/GBM (A. Yoshida et al., GCN 23399).
  The Insight-HXMT/HE light curve mainly consists of multiple pulses with a duration (T90) of 23.58 s measured from T0-4.53 s. The 1-s peak rate, measured from T0+14.63 s, is 1351.0 cnts/s. The total counts from this burst is 11055.5 counts. URL_LC: http://www.hxmt.org/images/GRB/HEB181028590_lc.jpg
  All measurements above are made with the CsI detectors operating in the GRB mode with the energy range of about 200-3000 keV (record energy). Only gamma-rays with energy greater than about 200 keV can penetrate the spacecraft and leave signals in the CsI detectors installed inside of the telescope.
  Insight-HXMT is the first Chinese space X-ray telescope, which was fundedjointly by the China National Space Administration (CNSA) and the Chinese Academy of Sciences (CAS). More information could be found at: http://www.hxmt.org.