Gamma-ray Burst 150127A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

• none

• GCN Circular #17355
  Matthew Stanbro (UAH) and A. von Kienlin (MPE) report on behalf of the Fermi GBM Team:
  "At 09:32:44.14 UT on 27 January 2015, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 150127A (trigger 444043967 / 150127398).
  The on-ground calculated location, using the GBM trigger data, is RA = 285.7, DEC = -8.4, with an uncertainty of 2.8 degrees (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 39 degrees.
  The GBM light curve consists of several episodes with a duration (T90) of about 53 s (50-300 keV). The time-averaged spectrum from T0-0.00 s to T0+51.20 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.04 +/- 0.04 and the cutoff energy, parameterized as Epeak, is 1478 +/- 225 keV.
  A Band function fits the spectrum equally well with Epeak= 1083 +/- 212 keV, alpha = -0.99 +/- 0.05 and beta = -2.21 +/- 0.23.
  The event fluence (10-1000 keV) in this time interval is (2.27 +/- 0.50)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0-0.32 s in the 10-1000 keV band is 7.78 +/- 0.33 ph/s/cm^2.
  The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."
• GCN Circular #17356
  J. L. Racusin (NASA/GSFC), G. Vianello (Stanford), and D. Kocevski (NASA/GSFC) report on behalf of the Fermi-LAT team:
  At 09:32:44 on January 27, 2015, Fermi-LAT detected emission from GRB 150127A, which was also detected by Fermi-GBM (trigger 444043967/150127398, GCN 17355).
  The GBM location was initially inside the LAT field of view at an angle of ~39 degrees to the LAT boresight. No significant excess is seen using standard analysis procedures >100 MeV.
  Using the LAT Low Energy (LLE) data selection, over 60 counts above background were detected within a 10 s interval coinciding with the time of the GBM emission. This data selection has insufficient spatial resolution to provide a reliable LAT localization. Since an excess of events were not seen using the standard analysis selection, this detection is likely due to low energy gamma-rays (below 100 MeV).
  The Fermi LAT point of contact for this burst is Judith Racusin (judith.racusin@nasa.gov).
  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 #17359
  K. Hurley and J. Goldsten, on behalf of the MESSENGER NS GRB team,
  I. G. Mitrofanov, D. Golovin, M. L. Litvak, and A. B. Sanin, on behalf of the HEND-Odyssey GRB team,
  S. Golenetskii, R. Aptekar, V. Pal'shin, D. Frederiks, D. Svinkin, and T. Cline on behalf of the Konus-Wind 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 150127A has been detected by Fermi (GBM: Stanbro and von Kienlin, GCN Circ. 17355; LAT (but not localized): Racusin et al., GCN Circ. 17356), Konus-Wind, MESSENGER (GRNS), and Mars-Odyssey (HEND), so far, at about 34364 s UT (09:32:44).
  We have triangulated it to a preliminary, 3 sigma error box whose coordinates are:

     ---------------------------------------------
      RA(2000), deg                 Dec(2000), deg
     ---------------------------------------------
     Center:
      296.953 (19h 47m 49s)  -9.416 ( -9d 24' 58")
     Corners:
      297.190 (19h 48m 46s)  -6.883 ( -6d 52' 58")
      296.956 (19h 47m 50s)  -7.457 ( -7d 27' 25")
      296.868 (19h 47m 28s) -13.764 (-13d 45' 49")
      297.021 (19h 48m 05s) -12.130 (-12d 07' 50")
     ---------------------------------------------
  

  The error box area is 1.1 sq. deg, and its maximum dimension is 6.9 deg (the minimum one is 11 arcmin). The Sun distance was 13 deg.
  This box may be improved.
  A triangulation map is posted at http://www.ioffe.ru/LEA/GRBs/GRB150127_T34360/IPN/
  The Konus-Wind time history and spectrum will be given in forthcoming GCN Circulars.