Gamma-ray Burst 120817B

(All information courtesy of the instrument teams.)

Previous IAU Circulars

• none

• GCN Circular #13670
  S. Golenetskii, R. Aptekar, E. Mazets, V. Pal'shin, D. Frederiks, D. Svinkin, and T. Cline on behalf of the Konus-Wind team,
  
  K. Hurley, and J. Goldsten, on behalf of the MESSENGER GRNS GRB team,
  V. Connaughton, M. Briggs, and C. Meegan, 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,
  S. Barthelmy, J. Cummings, N. Gehrels, H. Krimm, and D. Palmer, on behalf of the Swift-BAT team,
  and
  K. Yamaoka, M. Ohno, Y. Hanabata, Y. Fukazawa, T. Takahashi, M. Tashiro, Y. Terada, T. Murakami, and K. Makishima on behalf of the Suzaku WAM team, report:
  The short-duration, hard, very intense GRB 120817B has been observed by Konus-Wind, Fermi (GBM: trigger 366868952), INTEGRAL (SPI-ACS), Suzaku (WAM), Swift(BAT) and MESSENGER (GRNS), so far, at about 14550 s UT (04:02:30).
  We have triangulated the burst to a preliminary, 3 sigma error box whose coordinates are:

     --------------------------------------------- 
      RA(2000), deg                 Dec(2000), deg 
     --------------------------------------------- 
     Center: 
        8.321 (00h 33m 17s) -26.514 (-26d 30' 51") 
     Corners: 
        8.445 (00h 33m 47s) -26.217 (-26d 13' 00") 
        8.468 (00h 33m 52s) -26.456 (-26d 27' 23") 
        8.196 (00h 32m 47s) -26.809 (-26d 48' 34") 
        8.174 (00h 32m 42s) -26.571 (-26d 34' 17") 
     --------------------------------------------- 
  

  The error box area is 235 sq. arcmin, and its maximum dimension is 38 arcmin (the minimum dimension is 14 arcmin).
  A Swift ToO has been requested.
  This box can be improved.
  A triangulation map is posted at http://www.ioffe.ru/LEA/GRBs/GRB120817_T14553/IPN/
  The time history and spectrum will be given in a forthcoming GCN Circular.
• GCN Circular #13671
  Shaolin Xiong (UAH) reports on behalf of the Fermi GBM Team:
  "At 04:02:29.723 UT on 17 August 2012, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 120817B (trigger 366868952 / 120817168), which was also located by IPN (S. Golenetskii et al. 2012, GCN 13670). The GBM on-ground location is consistent with the IPN position. The angle from the Fermi LAT boresight is 59 degrees.
  This burst was also independently detected by INTEGRAL SPI-ACS.
  The GBM light curve shows a single pulse with a duration (T90) of about 0.192 s (50-300 keV). The time-averaged spectrum from T0-0.032 s to T0+0.064 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.65 +/- 0.05 and the cutoff energy, parameterized as Epeak, is 1377 +/- 173 keV.
  The event fluence (10-1000 keV) in this time interval is (1.85 +/- 0.06)E-6 erg/cm^2. The 64 ms peak photon flux measured starting from T0+0.0 s in the 10-1000 keV band is 46.6 +/- 1.6 ph/s/cm^2.
  The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."
• GCN Circular #13672
  E. Berger, W. Fong (Harvard), and R. Williams (Carnegie) report:
  "We observed the IPN error region of the short GRB 120817B (GCN #13670) with the Wide-Field CCD camera mounted on the du Pont 2.5-m telescope at Las Campanas Observatory. The observations started on 2012 August 18.158 UT (23.7 hour after the burst) using the R-band filter, and covered the entire error region using two pointings with an exposure time of 900 sec per pointing. A comparison to the Digital Sky Survey reveals no new sources to the limit of the survey (R~21 mag)."
• GCN Circular #13674
  S. Golenetskii, R.Aptekar, D. Frederiks, E. Mazets, V. Pal'shin, P. Oleynik, M. Ulanov, D. Svinkin, and T. Cline on behalf of the Konus-Wind team, report:
  The short-duration hard-spectrum intense GRB 120817B (IPN localization: Golenetskii at al., GCN 13670; Fermi/GBM detection: Xiong, GCN 13671) triggered Konus-Wind at T0=14553.388s UT (04:02:33.388)
  The light curve shows a single pulse, a total duration of the burst is ~0.08 s. The emission is seen up to ~6.5 MeV.
  The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB120817_T14553/
  As observed by Konus-Wind the burst had a fluence of 4.1(-1.0,+1.1)x10-6 erg/cm2, and a 16-ms peak flux, measured from T0, of 1.2(-0.3,+0.3)x10-4 erg/cm2/s (both in the 20 keV - 10 MeV energy range).
  The spectrum of the burst (measured from T0 to T0+0.064 s) is best fit in the 20 keV - 7 MeV range by a power law with exponential cutoff model, for which alpha = -0.82 (-0.18, +0.21), and Ep = 1740(-520, +890) keV, chi2 = 7.5/12 dof.
  All the quoted results are preliminary. All the quoted errors are at the 90% confidence level.
• GCN Circular #13680
  C. Pagani (U. Leicester) reports on behalf of the Swift team:
  At 22:41:45 UT, August 17, 2012, Swift began a Target of Opportunity observation of GRB 120817B (Golenetskii et al. GCN 13670).
  We have analysed 2.8 ks of XRT data, beginning 67 ks after the GRB trigger. The data are entirely in Photon Counting mode. No new source is detected in the XRT data. The 3-sigma upper limit is 0.005 counts/sec which is 2.7e-13 erg cm^-2 s^-1 for a typical GRB spectrum.
  This circular is an official product of the Swift-XRT team.
• GCN Circular #13692
  J. R. Cummings (GSFC/UMBC), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (MSU) (i.e. the Swift-BAT team):
  At 04:02:29 on August 17, 2012, Swift-BAT triggered (BAT trigger # 531259) on the IPN burst GRB 120817B (Golenetskii et al., GCN Circ # 13670). No source was found onboard. In ground analysis of the failed-trigger event sample, a significant source was found at RA, Dec 8.310, -26.428, which is

  RA (J2000)   00h 33m 14.4s 		
  Dec (J2000)  -26d 25m 42s
  

  The estimated 90% confidence position error is 2.8 arcmin radius. This position was 5.5% coded in the BAT FOV. It is 5 arcmin from the center of the IPN triangulation, within the IPN error box.
  As seen in BAT, the burst was a single spike 0.10 +/- 0.02 seconds long.
  The time-averaged spectrum from T+0.2 to T+0.3 sec is best fit by a simple power-law model. The best-fit photon index is 0.60 +/- 0.3. The total fluence in the 15-150 keV band was (1.7 +/- 0.4) x 10^-7 ergs/cm^2. The errors quoted are at the 68% confidence level.
• GCN Circular #13700
  W. Fong, E. Berger (Harvard), D. Kelson, R. Williams (Carnegie) report:
  "We re-observed the BAT-refined location of the IPN short-duration GRB 120817B (GCNs 13670, 13692) with the Inamori-Magellan Areal Camera and Spectrograph (IMACS) mounted on the Magellan/Baade 6.5-m telescope starting on 2012 Aug 21.410 UT, 4.2 days post-burst and 3.3 days after our initial LCO/WFCCD observations (GCN 13672). We obtained 2x300-sec exposures in R-band in 0.92" seeing. Digital image subtraction with our first observations using the ISIS software package reveals no evidence for a fading optical source in or around the BAT error circle. Calculating the zeropoint using a Stetson standard star field at the same airmass, we place a 3-sigma limit of R(Vega)>23.3 mag on the optical afterglow of GRB 120817B at 23.7 hours after the burst."