Gamma-ray Burst 160612A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

• none

• GCN Circular #19531
  E. Burns (UAH), C. Meegan (UAH), and P. Jenke (UAH) report on behalf of the Fermi GBM Team:
  "At 20:12:47.55 UT on 12 June 2016, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 160612A (trigger 487455171 / 160612842).
  The on-ground calculated location, using the GBM trigger data, is RA = 350, DEC = -37 with an uncertainty of 3 degrees (radius, 1-sigma containment, statistical only; there is additionally a systematic error which we have characterized as a core-plus-tail model, with 90% of GRBs having a 3.7 deg error and a small tail suffering a larger than 10 deg systematic error. [Connaughton et al. 2015, ApJS, 216, 32] ).
  The trigger resulted in an Autonomous Repoint Request (ARR) by the GBM Flight Software owing to the high peak flux of the GRB. This ARR was accepted and the spacecraft slewed to the GBM in-flight location. The initial angle from the Fermi LAT boresight to the GBM ground location is 26 degrees.
  The GBM light curve consists of a single peak with a duration (T90) of about 0.4 s (50-300 keV). The time-averaged spectrum from T0-0.256 s to T0+0.192 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.7 +/- 0.1 and the cutoff energy, parameterized as Epeak, is 1148 +/- 291 keV
  The event fluence (10-1000 keV) in this time interval is (9.8 +/- 0.7)E-07 erg/cm^2. The 0.256-sec peak photon flux measured starting from T0-0.064 s in the 10-1000 keV band is 8.6 +/- 0.5 ph/s/cm^2.
  The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."
• GCN Circular #19535
  A. Kozlova, S. Golenetskii, R. Aptekar, D. Frederiks, D. Svinkin, and T. Cline on behalf of the Konus-Wind team,
  K. Hurley, on behalf of the IPN,
  V. Connaughton, M. S. Briggs, C. Meegan, V. Pelassa, and A. Goldstein, 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
  S. Barthelmy, J. Cummings, N. Gehrels, H. Krimm, and D. Palmer, on behalf of the Swift-BAT team, report:
  The short-duration GRB 160612A (Burns et al., GCN Circ. 19531) has been detected by Fermi (GBM), Konus-Wind, INTEGRAL (SPI-ACS), and Swift (BAT), so far, at about 72768 s UT (20:12:48). The burst was outside the coded field of view of the BAT.
  We have triangulated it to a preliminary, 3 sigma error box whose coordinates are:

   ---------------------------------------------
    RA(2000), deg                 Dec(2000), deg
   ---------------------------------------------
   Center:
    348.342 (23h 13m 22s) -25.181 (-25d 10' 51")
   Corners:
    348.982 (23h 15m 56s) -27.398 (-27d 23' 52")
    349.501 (23h 18m 00s) -27.279 (-27d 16' 45")
    347.719 (23h 10m 52s) -22.963 (-22d 57' 45")
    347.216 (23h 08m 52s) -23.074 (-23d 04' 27")
   ---------------------------------------------
  

  The error box area is 2.18 sq. deg, and its maximum dimension is 4.7 deg (the minimum one is 28 arcmin). The Sun distance was about 102 deg.
  This box may be improved.
  A triangulation map is posted at http://www.ioffe.ru/LEA/GRBs/GRB160612_T72767/IPN/
  The Konus-Wind time history and spectrum will be given in a forthcoming GCN Circular.
• GCN Circular #19536
  P. A. Evans (U. Leicester) reports on behalf of the Swift team:
  Swift has initiated a ToO observation of the Swift/BAT GRB 160612A. Automated analysis of the XRT data will be presented online at http://www.swift.ac.uk/ToO_GRBs/00020665
  Any uncatalogued X-ray sources detected in this analysis will be reported on this website and via GCN COUNTERPART notices. These are not necessarily related to the Swift/BAT event. Any X-ray source considered to be a probable afterglow candidate will be reported via a GCN Circular after manual consideration.
  Details of the XRT automated analysis methods are detailed in Evans et al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8).
  This circular is an official product of the Swift-XRT team.
• GCN Circular #19537
  A. Y. Lien (GSFC/UMBC) and D. M. Palmer (LANL) report on behalf of the Swift Team:
  At 20:12:48 UT on 2016-06-12, a number of gamma ray instruments, including Swift-BAT, detected the short-hard GRB 160612A (Burns et al., GCN Circ. 19531). BAT was slewing to a pre-planned target at that time, so it did not immediately trigger. However, ground analysis of the slew data reveals the GRB location of RA, dec = 348.364, -25.375 which is

   RA(J2000) = 23h 13m 27s
   dec(J2000) = -25d 22' 30"
  

  with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). This position is consistent with the IPN error box (Kozlova, GCN Circ 19535). The lightcurve shows a short, complex peak with a duration of T90 = 0.25 seconds and a peak count rate of ~18,000 counts/s (15-350 keV)..
  The time-averaged spectrum over the T90 interval is best fit by a simple power-law model, with a photon index of 0.74+/-0.17 and a fluence in the 15-150 keV band of 1.16 +/- 0.12 x 10^-7 erg/cm^2. All quoted errors are at the 90% confidence level
  Swift ToO observations are underway (GCN 19536).
• GCN Circular #19538
  L.M. McCauley (PSU), K.L. Page (U. Leicester), B. Mingo (U. Leicester), A.P. Beardmore (U. Leicester), V. D'Elia (ASDC), A. D'Ai (INAF-IASFPA), A. Maselli (INAF-IASFPA), J.A. Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU) and P.A. Evans (U. Leicester), S. R. Oates (U. Warwick) report on behalf of the Swift-XRT and UVOT teams:
  Swift-XRT has performed follow-up observations of the Swift/BAT-detected burst GRB 160612A (Lien et al. GCN Circ. 19537), collecting 985 s of Photon Counting (PC) mode data between T0+178.4 ks and T0+179.4 ks.
  No X-ray sources have been detected inside or close to the Swift/BAT error region. The 3-sigma upper limit in the field is 0.008 ct s^-1, corresponding to a 0.3-10 keV observed flux of 3.1e-13 erg cm^-2 s^-1 (assuming a typical GRB spectrum).
  The results of the XRT-team automatic analysis of the XRT observations, including a position-specific upper limit calculator, are available at http://www.swift.ac.uk/ToO_GRBs/00020665.
  The UVOT did not detect an afterglow within the BAT error circle, down to a magnitude of > 20.87 with an exposure of 978s in the w2 filter.
  This circular is an official product of the Swift-XRT and UVOT teams.
• GCN Circular #19539
  A. Tsvetkova, S. Golenetskii, R.Aptekar, D. Frederiks, P. Oleynik, M. Ulanov, D. Svinkin, A. Lysenko, A. Kozlova and T. Cline on behalf of the Konus-Wind team, report:
  The short-duration, hard-spectrum GRB 160612A (Fermi GBM detection: Burns, Meegan & Jenke, GCN 19531; IPN triangulation: Kozlova et al., GCN 19535; BAT detection and localization: Lien & Palmer, GCN 19537) triggered Konus-Wind at T0=72767.893 s UT (20:12:47.893).
  The burst light curve shows a single pulse with a total duration of ~0.2 s.
  As observed by Konus-Wind, the burst had a fluence of 1.02(-0.13,+0.12)x10^-6 erg/cm2 and a 16-ms peak flux, measured from T0-0.074 s, of 1.16(-0.26,+0.26)x10^-5 erg/cm2/s (both in the 20 - 1000 keV energy range).
  Since a major fraction of the burst counts was accumulated before the trigger, the spectral analysis was performed using the KW 3-channel light curve data. Modeling the 3-channel time-integrated spectrum (measured from T0-0.128 s to T0+0.064 s) by the cutoff power law yields the following model parameters: the photon index alpha=-0.54(-0.38,+0.53), and the peak energy Ep=1.46(-0.62,+8.00) MeV.
  The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB160612_T72767/
  All the quoted errors are at the 68% confidence level. All the quoted values are preliminary.