Gamma-ray Burst 171022A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

• none

• GCN Circular #22045
  M. Palatiello (Univ & INFN Trieste), E. Bissaldi (Poiltecnico & INFN Bari), M. Axelsson (Stockholm Univ.), M. Yassine (Univ & INFN Trieste), S. Buson (NASA/GSFC) and J. Racusin (NASA/GSFC) report on behalf of the Fermi-LAT team:
  On September 22, 2017, Fermi-LAT detected high-energy emission from GRB 171022A, which was also detected by Fermi-GBM (trigger 530399665) at 21:14:20.77 UTC.
  The best LAT on-ground location is found to be
  RA, Dec 204.28, 10.98 (degrees, J2000),
  with an error radius of 0.16 deg (90% containment, statistical error only). This position was outside the LAT FoV at the time of the GBM trigger, and entered the FoV at ~T0+3000s.
  The Fermi-LAT data show a significant increase in the event rate within 12 degrees of the GBM location. More than 20 photons above 100 MeV are observed between T0+3000 s and T0+6000 s. The highest-energy photon is a 14 GeV event which is observed ~4600 seconds after the GBM trigger.
  A Swift ToO will not be performed for this GRB due to Sun constraints.
  The Fermi-LAT point of contact for this burst is Michele Palatiello (michele.palatiello@ts.infn.it).
  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 #22046
  R. Hamburg (UAH) and C. Meegan (UAH) report on behalf of the Fermi GBM Team:
  "At 21:14:20.77 UT on 22 October 2017, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 171022A (trigger 530399665 / 171022885). which was also detected by the Fermi/LAT (Palatiello et al. 2017, GCN 22045). The GBM on-ground location is consistent with the LAT position.
  The angle from the Fermi LAT boresight at the GBM trigger time is 99 degrees.
  The GBM light curve shows a multi-peaked structure with a duration (T90) of about 13 s (50-300 keV). The time-averaged spectrum from T0-0.00 s to T0+15.07 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.49 +/- 0.06 and the cutoff energy, parameterized as Epeak, is 151 +/- 5 keV.
  The event fluence (10-1000 keV) in this time interval is (8.1 +/- 0.2)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+3.23 s in the 10-1000 keV band is 8.7 +/- 0.3 ph/s/cm^2.
  The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."
• GCN Circular #22051
  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. von Kienlin, X. Zhang, A. Rau, V. Savchenko, E. Bozzo, and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team,
  V. Connaughton, M. S. Briggs, C. Meegan, V. Pelassa, and A. Goldstein, on behalf of the Fermi GBM 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 171022A (Fermi-LAT detection: Palatiello et al., GCN Circ. 22045; Fermi-GBM detection: Hamburg and Meegan, GCN Circ. 22046) was detected by Fermi (GBM trigger 530399665), Konus-Wind, INTEGRAL (SPI-ACS), and Mars-Odyssey (HEND) at about 76461 s UT (21:14:21).
  We have triangulated it to a preliminary, 3 sigma error box whose coordinates are:

    ---------------------------------------------
     RA(2000), deg                 Dec(2000), deg
    ---------------------------------------------
    Center:
     215.353 (14h 21m 25s) +12.844 (+12d 50' 37")
    Corners:
     217.045 (14h 28m 11s)  +1.841 ( +1d 50' 29")
     211.510 (14h 06m 02s) +21.802 (+21d 48' 06")
     210.607 (14h 02m 26s) +22.804 (+22d 48' 14")
     216.812 (14h 27m 15s)  +3.167 ( +3d 10' 03")
    ---------------------------------------------
  

  The error box area is 4.1 sq. deg, and its maximum dimension is 21.9 deg (the minimum one is 12.0 arcmin). The Sun distance was 16 deg.
  This box may be improved.
  The Fermi (LAT) on-ground location (RA, Dec, Rerr = 204.28, 10.98, 0.16 deg) reported in Palatiello et al. is inconsistent with the box, the minimum distance between the box and the Fermi (LAT) location is ~11 deg.
  A triangulation map is posted at http://www.ioffe.ru/LEA/GRBs/GRB171022_T76456/IPN
  The Konus-Wind time history and spectrum will be given in a forthcoming GCN Circular.
• GCN Circular #22052
  D. Frederiks, S. Golenetskii, R.Aptekar, P. Oleynik, M. Ulanov, D. Svinkin, A. Tsvetkova, A.Lysenko, A. Kozlova, and T. Cline, on behalf of the Konus-Wind team, report:
  The long GRB 171022A (Fermi-LAT detection: Palatiello et al., GCN 22045; Fermi-GBM detection: Hamburg and Meegan, GCN 22046; IPN Triangulation: Hurley et al., GCN 22051) triggered Konus-Wind at T0=3D76456.523 s UT (21:14:16.523).
  The KW light curve shows a multi-peaked emission complex with a total duration of ~15 s. A much weaker pulse is also seen in the softest KW light curve around ~T0+215 s. The emission is seen up to ~3.5 MeV.
  As observed by Konus-Wind, the burst had a fluence of (7.1 =B1 0.7)x10^-6 erg/cm2 and a 64-ms peak energy flux, measured from T0+3.328, of (2.4 =B1 0.2)x10^-6 erg/cm2 (both in the 20 keV - 10 MeV energy range).
  The time-integrated spectrum (measured from T0 to T0+16.640 s) is best fit in the 20 keV - 15 MeV range by a cutoff power-law (CPL) function with the following model parameters: the photon index alpha =3D -0.51(-0.30,+0.34), and the peak energy Ep =3D 144(-13,+17) keV, chi2 =3D 93/98 dof. Fitting this spectrum with the GRB (Band) function yields the same alpha and Ep, and an upper limit on beta of -2.7, chi2 =3D 93/97 dof.
  The spectrum near the peak count rate (measured from T0 to T0+8.448 s) is best fit in the 20 keV - 15 MeV range by the CPL function with the following model parameters: the photon index alpha =3D -0.40(-0.27,+0.30), and the peak energy Ep =3D 146(-12,+14) keV, chi2 =3D 111/98 dof. Fitting this spectrum with the GRB (Band) function yields the same alpha and Ep, and an upper limit on beta of -2.8, chi2 =3D 110/97 dof.
  The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB171022_T76456/
  All the quoted errors are estimated at the 90% confidence level. All the presented results are preliminary.
• GCN Circular #22071
  M. Palatiello (Univ & INFN Trieste), E. Bissaldi (Poiltecnico & INFN Bari), and E. Moretti (MPI Munich) report on behalf of the Fermi-LAT team:
  On October 22nd, 2017, the Fermi-LAT collaboration reported the detection of GRB 171022A (Palatiello et al., GCN #22045).
  Following the publication of the GRB IPN triangulation (Hurley et al., GCN #22051), we performed further analysis to investigate the discrepancy of the Fermi-LAT localization with respect to the region defined by the Konus Wind, Fermi-GBM and INTEGRAL annuli.
  The LAT excess reported in Palatiello et al. has a significance which is only slightly above the 5 sigma threshold. Moreover, the Fermi-LAT Point Source Catalog (3FGL, Acero et al. 2015) contains the source 3FGL J1339.0+1153 in the proximity of the position of the LAT excess. A likelihood analysis where the normalization for 3FGL J1339.0+1153 is set as a free parameter of the fit returns a marginal increase (20 +/- 15 %) in the flux of that source, tentatively associated with SDSS J133859.05+115316.7, and results in a non-detection of the excess which we previously associated with GRB 171022A. Therefore, we cannot confirm at this stage that the LAT excess is associated with GRB 171022A.
  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.