Gamma-ray Burst 141118A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

• none

• GCN Circular #17073
  K. Hurley, on behalf of the IPN,
  I. G. Mitrofanov, D. Golovin, M. L. Litvak, and A. B. Sanin, on behalf of the HEND-Odyssey GRB team,
  W. Boynton, C. Fellows, K. Harshman, H. Enos, and R. Starr, on behalf of the GRS-Odyssey GRB team,
  S. Golenetskii, R. Aptekar, V. Pal'shin, D. Frederiks, D. Svinkin, and T. Cline on behalf of the Konus-Wind team,
  D. M. Smith, J. McTiernan, R. Schwartz, W. Hajdas, and A. Zehnder, on behalf of the RHESSI GRB team,
  S. Barthelmy, J. Cummings, N. Gehrels, H. Krimm, and D. Palmer, on behalf of the Swift-BAT team,
  J. Goldsten, on behalf of the MESSENGER NS GRB team, and
  V. Connaughton, M. S. Briggs, C. Meegan, and V. Pelassa, on behalf of the Fermi GBM team, report:
  GRB 141118A has been observed by Fermi GBM, Konus-Wind, RHESSI, Swift (outside the coded field of view), Odyssey (HEND), and MESSENGER (GRNS), so far, at 58550 s (16:15:50 UT) so far. We have triangulated it to a preliminary, 3 sigma error box whose area is 2890 sq. arcmin. and whose coordinates are:

                RA(2000)                      DEC(2000)
  CENTER:  156.874 o =10 h 27 m 30 s     19.079 o= 19 o 04 ' 45 "
  CORNERS: 157.620 o =10 h 30 m 29 s     21.134 o= 21 o 08 ' 01 "
           156.676 o =10 h 26 m 42 s     19.104 o= 19 o 06 ' 15 "
           157.071 o =10 h 28 m 17 s     19.054 o= 19 o 03 ' 13 "
           155.644 o =10 h 22 m 35 s     15.768 o= 15 o 46 ' 06 "
  

  This error box may be improved. A map has been posted at ssl.berkeley.edu/ipn3/141118A. Details of this burst will be given in a forthcoming GCN Circular.
• GCN Circular #17074
  S. Golenetskii, R.Aptekar, D. Frederiks, V. Pal'shin, P. Oleynik, M. Ulanov, D. Svinkin, A. Tsvetkova, A.Lyssenko, and T. Cline on behalf of the Konus-Wind team, report:
  A long-duration GRB 141118A (IPN triangulation: Hurley et al., GCN 17073) triggered Konus-Wind at T0=58548.540 s UT (16:15:48.540).
  The KW light curve shows a single emission episode lasting from ~T0-0.5 s to ~T0+5 s. The emission in this episode is visible up to ~2 MeV.
  As observed by Konus-Wind, the burst had a fluence of 2.3(-0.5,+1.4)x10^-6 erg/cm2, and a 64-ms peak flux, measured from T0, of 1.6(-0.4,+1.0)x10^-6 erg/cm2/s (both in the 20 keV - 10 MeV energy range).
  The time-averaged spectrum (measured from T0 to T0+8.448 s) is best fit in the 20 keV - 15 MeV range by the cutoff power law with the following model parameters: the photon index alpha = -1.14(-0.67,+0.89), and the peak energy Ep = 165(-55,+198) keV, chi2 = 95/97 dof. Fitting this spectrum with the Band model yields the same values of alpha and Ep and an upper limit on beta of -2.0
  The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB141118_T58548/
  All the quoted errors are at the 90% confidence level. All the quoted values are preliminary.
• GCN Circular #17079
  L. P. Singer (Caltech), M. M. Kasliwal (Carnegie Observatories/Princeton), V. B. Bhalerao (IUCAA), and S. B. Cenko (NASA/GSFC) report on behalf of the intermediate Palomar Transient Factory (iPTF) collaboration:
  We searched for optical counterparts of GRB 141118A (GCN 17073, Hurley et al.; GCN 17074, Golenetskii et al.) using the Palomar 48-inch Oschin telescope (P48). At about 18 hours after the burst, we began imaging 20 fields spanning an area of 145 deg2, covering most of the 1-sigma statistical+systematic region of the final Fermi GBM localization (Fermi trigger 438020153 / 141118678). Based on the GBM localization, we estimate a 77% chance that these fields contain the true location of the source. Coincidentally, we estimate the same containment probability based on the IPN error box.
  Sifting through candidate variable sources using image subtraction and standard iPTF vetting procedures, we detect the optical transient iPTF14hvs, at the coordinates:

    RA(J2000)  =  10h 26m 05.29s (156.522055 deg)
    Dec(J2000) = +18d 34' 08.6"  (+18.569044 deg)
  

  This position is just inside the error box. It is also in the outskirts of the galaxy SDSS J102605.09+183411.6, which has a photoZ of ~0.1. In host- subtracted P48 photometry, we find marginal evidence that the source faded:

    +18.41 hours:  R = 19.92 +/- 0.14
    +19.06 hours:  R = 20.03 +/- 0.08
  

  Times are relative to the GBM trigger. Magnitudes are in the Mould R filter and in the AB system, calibrated with respect to point sources in SDSS as described in Ofek et al. (2012, http://dx.doi.org/10.1086/664065).
  We obtained a series of spectra of iPTF14hvs with the Gemini Multi-Object Spectrograph mounted on the 8 m Gemini North telescope beginning at 15:21 UT on 2014 Nov 11. The spectra cover the wavelength range of 3900-9200 A. Cross-correlation with a library of supernova spectra using the ``Supernova Identification'' code (SNID; Blondin and Tonry 2007, ApJ 666, 1024) indicates the source is a type Ia supernova several weeks past maximum light at z ~ 0.11. Spatially offset from the transient location we identify narrow emission lines of H-alpha, [N II], and [S II] at a common redshift of z = 0.108.
  We conclude that iPTF14hvs is not related to the GRB.
  The diagram http://www.its.caltech.edu/~lsinger/iptf/Fermi438020153.pdf shows our P48 fields and the location of the optical transient in relation to the Fermi GBM 1- and 2-sigma statistical+systematic contours and the IPN annulus.
  We thank the IPN team for promptly sharing their analysis.
• GCN Circular #17094
  P. Jenke (UAH) reports on behalf of the Fermi GBM Team:
  "At 16:15:50.31 on November 18 2014, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 141118A (trigger 438020153/141118678). The GBM on-ground location, using the Fermi GBM trigger data, is RA = 158.1, Dec = 19.8 (J2000 degrees, equivalent to 10h 32m 24s, 19d 48'), with an uncertainty of 2.2 degrees (radius, 1-sigma containment,statistical only; there is additionally a systematic error which is currently estimated to be 2 to 3 degrees). GBM's location is consistent with the IPN Triangulation (K. Hurley et al. 2014, GCN 17073).
  This GRB was also detected by Konus-Wind (Golenetskii et al. GCN 17074).
  A follow-up search of GBM's error box by iPTF produced an optical candidate, well within the GBM 1 sigma confidence region, that on further investigations turned out to be a fading SNe unrelated to the GRB (Singer et al. 2014, GCN 17079).
  The angle of the burst direction to the Fermi LAT boresight is 74 degrees.
  The GBM light curve consists of a single peak with a duration (T90) of about 4.4 s (50-300 keV). The time-averaged spectrum from T0-2.9 s to T0+3.2s is well fit by a power law function with an exponential high-energy cutoff. The power law index is -0.77 +/- 0.09 and the cutoff energy, parameterized as Epeak, is 286 +/- 34 keV. The event fluence (10-1000 keV) in this time interval is (3.3 +/- 0.2)E-06 erg/cm^2. The 1 sec peak photon flux measured starting from T0+0.0 s in the 10-1000 keV band is 6.5 +/- 0.3 ph/s/cm^2.
  The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."