Gamma-ray Burst 120107A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

• none

• GCN Circular #12822
  Weikang Zheng and Carl Akerlof, report on behalf of the ROTSE collaboration:
  High-energy photon emission in Fermi/LAT data was found to be correlated with GBM trigger 347620337 (probably GRB 120107A). Our LAT data processing pipeline which uses the matched filter technique (Akerlof et al, 2010, ApJ, 725, L15; 2011 ApJ, 726, 22; Zheng et al. 2012, ApJ 745,72), detected the high-energy photon emission from 09:12:15 UT on Jan. 7, 2012 (MET = 347620337) as a follow-up of a routine search in GBM trigger catalogs. The GBM trigger location (Ra = 223.1, Dec = -77.96) was about 56 degree from the LAT boresight, and the zenith angle was about 106 degrees. ~7 photons above 100 MeV were detected within 50 s after the burst, with the highest energy of ~1.78 GeV at 1.18s after the burst (note that class 1 photons are not included in the pipeline analysis since it is not automatically available from LAT data server at the moment). The new GRB location estimated by the matched filter technique is Ra = 246.40, Dec = -69.93 with uncertainty ~0.5 degree, this is ~10 degrees away from the GBM trigger location.
  A likelihood analysis gives a TS value of 58.9 (duration of 50 s), and the GRB location Ra = 246.31, Dec = -69.93, which is also consistent with the location derived from the matched filter technique.
  All the pipeline results can be found in the following link, including the skymap and light curve figures: http://www.rotse.net/LAT/GBMTriggers/347620337/347620337_res.html
• GCN Circular #12823
  K. Hurley, and J. Goldsten, on behalf of the MESSENGER NS GRB team,
  S. Golenetskii, R. Aptekar, E. Mazets, V. Pal'shin, D. Frederiks, D. Svinkin, and T. Cline on behalf of the Konus-Wind team,
  V. Connaughton, M. Briggs, and C. Meegan, on behalf of the Fermi GBM 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 long GRB 120107A, seen by Fermi/GBM (trigger 347620337) and localized by Fermi/LAT (Zheng and Akerlof, GCN 12822), was also detected by Konus-Wind, Suzaku (WAM), and MESSENGER (GRNS) at about 33135 s UT (09:12:15).
  Triangulation gives a MESSENGER-GBM annulus centered at RA(2000)=268.419 deg (17h 53m 40s) Dec(2000)=3D-23.372 deg (-23d 22' 18"), whose radius is 48.611 = 0.094 deg (3 sigma); and a Konus-GBM annulus centered at RA(2000)=3D262.874 deg (17h 31m 30s) Dec(2000)=3D-24.735 deg (-24d 44' 05"), whose radius is 47.383 =B1 1.667 deg (3 sigma). These annuli intersect at grazing incidence to form a very long box (an annulus segment). The Fermi/LAT position (Zheng and Akerlof, GCN 12822) is entirely contained within the Konus-GBM annulus, and intersected by the MESSENGER-GBM annulus resulting in the IPN/LAT error box area of ~600 sq. arcmin.
  A triangulation map is posted at http://www.ioffe.ru/LEA/GRBs/GRB120107_T33132/IPN/ showing the LAT best-fit position (red star), and the IPN annuli (solid lines with centers dot-dashed).
  Follow-up observations of the LAT error box by the Swift satellite are in progress.
• GCN Circular #12824
  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 long GRB 120107A (GBM trigger 347620337; Fermi/LAT detection: Zheng and Akerlof, GCN 12822; IPN triangulation: Hurley et al., GCN 12823) triggered Konus-Wind at T0=33132.445s UT (09:12:12.445)
  The light curve shows multiple partly overlapped pulses. A total duration of the burst is ~25 s. The emission is seen up to ~2 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB120107_T33132/
  As observed by Konus-Wind the burst had a fluence of 5.5(-1.0,+1.5)x10-6 erg/cm2, and a 64-ms peak flux, measured from T0-0.128 s, of 1.2(-0.2,+0.3)x10-6 erg/cm2/s (both in the 20 keV - 2 MeV energy range).
  The time-integrated spectrum of the burst (measured from T0 to T0+24.832 s) is best fit in the 20 keV - 2 MeV range by a power law with exponential cutoff model, for which alpha = -1.38 (-0.26, +0.33), and Ep = 196(-54, +160) keV, chi2 = 82.5/58 dof.
  The spectrum at the maximum count rate (measured from T0 to T0+8.448 s) is best fit in the 20 keV - 2 MeV range by a power law with exponential cutoff model, for which alpha = -0.98 (-0.34, +0.41), and Ep = 178(-37, +72) keV, chi2 = 60.0/58 dof.
  All the quoted results are preliminary. All the quoted errors are at the 90% confidence level.
• GCN Circular #12826
  S. McBreen (UCD/MPE) reports on behalf of the Fermi GBM Team:
  "At 09:12:15.41 UT on 07 January 2012, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 120107A (trigger 347620337/120107384) which was also detected by the Fermi/LAT (Zheng and Akerlof 2012, GCN 12822).
  The GBM light curve consists of about six pulses with a duration (T90) of about 23 s (50-300 keV). The time-averaged spectrum from T0 s to T0+23 s is well fit by a Band function with Epeak = 188.90 (+24.90/-22.20) keV, alpha = -0.91 (+0.08/-0.07), and beta = -2.11 (+0.12/-0.19).
  The event fluence (10-1000 keV) in this time interval is (6.81 +/- 0.06)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+0.003 s in the 10-1000 keV band is 5.55 +/- 0.24 ph/s/cm^2.
  The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."
• GCN Circular #12828
  W. Iwakiri, M. Tashiro, Y. Terada, T. Yasuda, K. Takahara, M. Asahina, S. Kobayashi, A. Sakamoto (Saitama U.) Y. Hanabata, T. Uehara, T. Kawano, K. Takaki, M. Mizuno, M. Ohno, Y. Fukazawa (Hiroshima U.), S. Sugita (Nagoya U.), K. Yamaoka (Aoyama Gakuin U.), M. Kokubun, T. Takahashi (ISAS/JAXA), Y. E. Nakagawa (Waseda U.), N. Ohmori, M. Akiyama, M. Yamauchi (Univ. of Miyazaki), C-J. Chuang, Y. Urata, P. Tsai (NCU), K. Nakazawa, K. Makishima (Univ. of Tokyo), on behalf of the Suzaku WAM team, report:
  The long GRB 120107A (Fermi-GBM trigger 347620337; Fermi-LAT detection: Zheng & Akerlof, GCN 12822; IPN triangulation: Hurley et al., GCN 12823) triggered the Suzaku Wide-band All-sky Monitor (WAM) which covers an energy range of 50 keV - 5 MeV at 09:12:15.352 UT (=T0).
  The observed light curve shows a multi-peaked structure starting at T0-2 s and ending at T0+24 s with a duration (T90) of about 22 seconds. The fluence in 100 - 1000 keV was 3.98 (-0.31, +0.28) x 10^-6 erg/cm^2. The 1-s peak flux measured from T0 s was 1.94 (-0.37, +0.22) photons/cm^2/s in the same energy range.
  Preliminary result shows that the time-averaged spectrum from T0-2 s to T0+24 s is well fitted by a single power-law with a photon index of 2.43 (-0.23, +0.28) (chi^2/d.o.f = 20.5/25).
  All the quoted errors are at statistical 90% confidence level, in which the systematic uncertainties are not included.
  The light curves for this burst are now available at: http://www.astro.isas.jaxa.jp/suzaku/HXD-WAM/WAM-GRB/grb/trig/grb_table.html