Gamma-ray Burst 100707A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

• none

• GCN Circular #10944
  Colleen A. Wilson-Hodge (NASA/MSFC) and Suzanne Foley (MPE) report on behalf of the Fermi GBM Team:
  "At 00:46:38.99 UT on 07 July 2010, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 100707 (trigger 300156400 / 100707.032).
  The on-ground calculated location, using the GBM trigger data, is RA = 351.07, DEC = -6.57 (J2000 degrees, equivalent to 23 h 24 m, -6 d 34 '), with an uncertainty of 1 degree (radius, 1-sigma containment, statistical only; there is additionally a systematic error which is currently estimated to be 2 to 3 degrees).
  The angle from the Fermi LAT boresight is 90 degrees.
  The GBM light curve show a fast rise and exponential decay with a duration (T90) of 82+/-1 s (50-300 keV). The time-averaged spectrum from T0-0.064 s to T0+83.009 s is well fit by a power law function with an exponential high energy cutoff. The power law index is -0.91 +/- 0.02 and the cutoff energy, parameterized as Epeak, is 283 +/- 7 keV
  (C-Statistic 529.4 for 358 d.o.f.).
  The event fluence (10-1000 keV) in this time interval is (8.77 +/- 0.02)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+1.152 s in the 10-1000 keV band is 48.3 +/- 0.4 ph/s/cm^2.
  The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."
• GCN Circular #10945
  Veronique Pelassa (LPTA), Melissa Pesce-Rollins (INFN-Pisa) report on behalf of the Fermi LAT collaboration:
  The Fermi Large Area Telescope (LAT) detected emission from GRB 100707A (C. Wilson-Hodge et al, GCN 10944).
  This burst was at an angle of 90 degrees to the LAT boresight, which means that neither directional nor energy information can be obtained with the standard analysis procedures.
  Using a non-standard data selection, the LAT light curve shows a single, sharply rising pulse that has a somewhat more gradual decay, similar to the initial peak in the GBM light curve. The LAT T90 duration is <30 s. This is shorter than the GBM T90 (82+/-1 s), but the LAT may be missing a long tail at later times owing to noisier data. Over 300 counts above background were detected within a 5 s interval in coincidence with the main GBM peak. The significance of this excess was greater than 14 sigma. A preliminary study of the instrument performance at such a large inclination suggests that these events are likely to be low energy gamma-rays, with energies less than 200 MeV.
  Further analysis is ongoing.
  The Fermi LAT point of contact for this burst is Veronique Pelassa (pelassa@lpta.in2p3.fr).
  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. This message can be cited.
• GCN Circular #10947
  K. Hurley and J. Goldsten, on behalf of the MESSENGER GRNS GRB team,
  S. Golenetskii, R. Aptekar, E. Mazets, V. Pal'shin, D. Frederiks, P. Oleynik, M. Ulanov, D. Svinkin and T. Cline on behalf of the Konus-Wind team,
  V. Connaughton, M.S. Briggs, and C.A. Meegan on behalf of the Fermi GBM team, and
  K. Yamaoka, M. Ohno, Y. Fukazawa, T. Takahashi, M. Tashiro, Y. Terada, T. Murakami, K. Makishima, and Y. Hanabata on behalf of the Suzaku-WAM team, report:
  The long bright GRB 100707A, observed by Fermi/GBM at 00:46:38.99 UT (Wilson-Hodge & Foley, GCN 10944) and Fermi/LAT (Pelassa & Pesce-Rollins, GCN 10945), has also been detected by Suzaku (WAM), Konus-Wind, and MESSENGER (GRNS) so far.
  We have triangulated it to a preliminary 3 sigma error box whose coordinates are:

  -----------------------------------------------
      RA(2000), deg              Dec(2000), deg
  -----------------------------------------------
  Center:
    358.019 (23h 52m 05s)    -8.658 (-08d 39' 29")
  Corners:
    358.562 (23h 54m 15s)   -11.226 (-11d 13' 32")
    358.773 (23h 55m 05s)   -11.654 (-11d 39' 14")
    357.369 (23h 49m 29s)    -5.832 (-05d 49' 56")
    357.116 (23h 48m 28s)    -5.295 (-05d 17' 42")
  -----------------------------------------------
  

  The error box area is 0.660 sq. deg This error box may be improved.
  The GBM position (Wilson-Hodge & Foley, GCN 10944) is 7.2 deg from the center of the box.
• GCN Circular #10948
  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 very bright long GRB 100707A (Fermi/GBM trigger 300156400: Wilson-Hodge and Foley, GCN 10944; localized by IPN: Hurley et al., GCN 10947) triggered Konus-Wind at T0=2798.855s UT (00:46:38.855)
  The burst light curve consists of a single FRED pulse with a duration of ~100 s.
  The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB100707_T02798/ The periodic dips seen in the 64-ms lc are caused by the occultation of the Konus detector by other instrument on board the rotating Wind s/c.
  As observed by Konus-Wind the burst had a fluence of 8.8(+/-0.6)x10-5 erg/cm2, and a 64-ms peak flux measured from T0+1.344s of 2.4(+/- 0.2)x10-5 erg/cm2/s (both in the 20 keV - 2 MeV energy range).
  The time-integrated spectrum of the burst (from T0 to T0+102.144 s) is best fit in the 20 keV - 2 MeV range by the GRB (Band) model, for which: the low-energy photon index alpha = -0.95 (+/-0.15), the high energy photon index beta = -2.2 (-0.3, +0.2), the peak energy Ep = 264(-40, +49)keV (chi2 = 43.5/57 dof).
  The spectrum at the maximum count rate (measured from T0+1.280 to T0+1.792 s) is best fit in the 20 keV - 2 MeV range by the GRB (Band) model, for which: the low-energy photon index alpha = +0.3 (-0.3, +0.5), the high energy photon index beta = -2.4 (-0.5, +0.3), the peak energy Ep = 383(-82, +80)keV (chi2 = 53.2/57 dof).
  All the quoted results are preliminary. All the quoted errors are at the 90% confidence level.
• GCN Circular #10950
  Y. Hanabata, T. Uehara, T. Takahashi, Y. Fukazawa (Hiroshima U.) K. Yamaoka (Aoyama Gakuin U.), S. Sugita (Nagoya U.), Y. Terada, M. Tashiro, W. Iwakiri, K. Takahara, T. Yasuda (Saitama U.), M. Ohno, M. Suzuki, M. Kokubun, T. Takahashi (ISAS/JAXA), Y. E. Nakagawa, T. Tamagawa (RIKEN), N. Ohmori, A. Daikyuji, Y. Nishioka, M. Yamauchi (Univ. of Miyazaki), N. Vasquez (Tokyo Tech.), Y. Urata, H. M. Lin (NCU), T. Enoto, K. Nakazawa, K. Makishima (Univ. of Tokyo), S. Hong (Nihon U.), on behalf of the Suzaku WAM team, report:
  The long GRB 100707A (Fermi/GBM trigger #300156400; C. Wilson-Hodge et al., GCN 10944; Fermi-LAT detection; V. Pelassa et al., GCN 10945) triggered the Suzaku Wide-band All-sky Monitor (WAM) which covers an energy of 50 keV - 5 MeV at 2010-07-07 00:46:38.91 UT (T=0).
  The observed light curve shows a FRED-like peak structure lasting from T0-0.5s to T0+18.5s with T90 of about 12 seconds. The fluence in 100 - 1000 keV was 5.26 (+/-0.27) x 10^-5 erg/cm^2. The 1-s peak flux measured from T0+1.5s was 32.24 (-1.28, +1.22) photons/cm^2/s in the same energy range.
  Preliminary result shows that the time-averaged spectrum from T0-0.5s to T0+18.5s is well fitted by a single power-law with a photon index of 2.15 (-0.05, +0.06) (chi^2/d.o.f = 39.4/25).
  Due to the brightness of this burst, a 3% systematic error was added for low energy channels. In addition, there might be some calibration uncertainties in these spectral parameters because GRB photons came to the WAM detector by passing through the large Ne dewar of the X-ray micro-calorimeter (XRS). All the errors are quoted at 90% confidence level.
  The light curves for this burst wiil be available at: http://www.astro.isas.jaxa.jp/suzaku/HXD-WAM/WAM-GRB/grb/trig/grb_table.html
• 1110.4246 from 20 Oct 11
  Makoto S. Tashiro et al.: Spectral Evolutions in Gamma-Ray Burst Exponential Decays Observed with Suzaku WAM
  This paper presents a study on the spectral evolution of gamma-ray burst (GRB) prompt emissions observed with the Suzaku Wide-band All-sky Monitor (WAM). By making use of the WAM data archive, 6 bright GRBs exhibiting 7 well-separated fast-rise-exponential-decay (FRED) shaped light curves are presented and the evaluated exponential decay time constants of the energy-resolved light curves from these FRED peak light curves are shown to indicate significant spectral evolution. The energy dependence of the time constants is well described with a power-law function tau(E) ~ E^gamma, where gamma ~ -(0.34 +/- 0.12) in average, although 5 FRED peaks show consistent value of gamma = -1/2 which is expected in synchrotron or inverse-Compton cooling models. In particular, 2 of the GRBs were located with accuracy sufficient to evaluate the time-resolved spectra with precise energy response matrices. Their behavior in spectral evolution suggests two different origins of emissions. In the case of GRB081224, the derived 1-s time-resolved spectra are well described by a blackbody radiation model with a power-law component. The derived behavior of cooling is consistent with that expected from radiative cooling or expansion of the emission region. On the other hand, the other 1-s time-resolved spectra from GRB100707A is well described by a Band GRB model as well as with the thermal model. Although relative poor statistics prevent us to conclude, the energy dependence in decaying light curve is consistent with that expected in the former emission mechanism model.