Gamma-ray Burst 170329A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

• none

• GCN Circular #20942
  M. Yassine (LUPM, Montpellier) ,E. Bissaldi (Politecnico & INFN Bari), G. Vianello (Stanford), J. L. Racusin (NASA/GSFC), F. Longo (University and INFN, Trieste) and N. Omodei (Stanford) report on behalf of the Fermi-LAT team:
  At 09:17:06.94 UT on March 29, 2017, Fermi-LAT detected high-energy emission from GRB 170329A, which was also detected by Fermi-GBM (170329387/512471831).
  The best LAT on-ground location is found to be RA, Dec 356.6, 9.8 (degrees, J2000) with an error radius of 0.6 deg (90% containment, statistical error only). This was 33 deg from the LAT boresight at the time of the trigger.
  The data from the Fermi-LAT show a significant increase in the event rate that is spatially and temporally consistent with the GBM emission. More than 37 photons above 100 MeV observed within 1 ks. The highest-energy photon is a 0.8 GeV event which is observed 4 seconds after the GBM trigger.
  The Fermi-LAT point of contact for this burst is Manal Yassine (manal.yassine@lupm.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.
• GCN Circular #20943
  E.Bissaldi (Politecnico & INFN Bari), O.J.Roberts (USRA/MSFC) and C.Meegan (UAH) report on behalf of the Fermi GBM Team:
  "At 09:17:06.94 UT on 29 March 2017, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 170329A (trigger 512471831 / 170329387), which was also detected by the LAT (Yassine et al. 2017, GCN 20942) The GBM on-ground location is consistent with the LAT position.
  The angle from the Fermi LAT boresight at the GBM trigger time is 33 degrees.
  The GBM light curve consists of a bright peak with a duration (T90) of 33.5 s (50-300 keV). The time-averaged spectrum from T0+0 s to T0+33.5 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.61 +/- 0.06 and the cutoff energy, parameterized as Epeak, is 799 +/- 86 keV
  The event fluence (10-1000 keV) in this time interval is (1.45 +/- 0.04)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+1.3 s in the 10-1000 keV band is 5.2 +/- 0.2 ph/s/cm^2.
  The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."
• GCN Circular #20951
  V. Sharma(IUCAA), V. Bhalerao (IITB), D. Bhattacharya (IUCAA), A. R. Rao (TIFR) and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration:
  Analysis of AstroSat CZTI data showed clear detection of GRB170329A (Fermi GBM detection: E.Bissaldi et al., GCN Circ. 20943) in the 40-200 keV energy range. The light curve shows single peak emission with peak counts at 09:17:08.940 UT, 2 s after the Fermi trigger. The measured peak count rate is 161.1 counts/s above the background in combined data of four quadrants, with a total 879 counts. The local mean background count rate was 387.9 counts/s. Using cumulative rates, we measure a T90 of 14.1 s.
  It was clearly detected in the CsI anticoincidence detector (Veto) also in the 100-500 keV energy range.
  CZTI GRB detections are reported regularly on the payload site at http://astrosat.iucaa.in/czti/?q=grb. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, ISAC, IUCAA, SAC and PRL. The Indian Space Research Organisation funded, managed and facilitated the project.
• GCN Circular #20952
  A.Kozlova, S. Golenetskii, R. Aptekar, D. Frederiks, P. Oleynik, M. Ulanov, D. Svinkin, A. Tsvetkova, A. Lysenko, and T. Cline on behalf of the Konus-Wind team, report:
  The long-duration GRB 170329A (Fermi-LAT detection: Yassine et al., GCN 20942; Fermi-GBM detection: Bissaldi et al., GCN 20943) triggered Konus-Wind at T0=33423.095 s UT (09:17:03.095).
  The burst light curve shows a single multi-peaked pulse with a total duration of ~7 s. The emission is seen up to ~6 MeV.
  As observed by Konus-Wind, the burst had a fluence of 1.47(-0.18,+0.22)x10^-5 erg/cm2, and a 64-ms peak flux, measured from T0+0.346 s, of 4.74(-1.61,+1.66)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+8.448 s) is best fit in the 20 keV - 6 MeV range by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = -0.30(-0.25,+0.30) and Ep = 688(-109,+153) keV (chi2 = 63/81 dof). Fitting by a GRB (Band) model yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -2.3 (chi2 = 63/80 dof)
  The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB170329_T33423/
  All the quoted errors are at the 90% confidence level. All the quoted values are preliminary.