Gamma-ray Burst 120908A

(All information courtesy of the instrument teams.)

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• GCN Notice
  

  TITLE:           GCN/MAXI NOTICE
  NOTICE_DATE:     Sun 09 Sep 12 09:52:40 UT
  NOTICE_TYPE:     MAXI Unknown Source Position
  EVENT_ID_NUM:    178763938
  EVENT_RA:        230.77d {+15h 23m 06s} (J2000),
                   230.96d {+15h 23m 51s} (current),
                   230.03d {+15h 20m 08s} (1950) 
  EVENT_DEC:       -25.50d {-25d 29' 41"} (J2000), 
                   -25.54d {-25d 32' 21"} (current),
                   -25.32d {-25d 19' 02"} (1950)
  EVENT_ERROR:     1.0 [deg radius, stat+sys, 90% containment]
  EVENT_FLUX:      170.0 +- 0.0 [mCrab] 
  EVENT_DATE:      16178 TJD;   252 DOY;   12/09/08
  EVENT_TIME:      81313.00 SOD {22:35:13.00} UT
  EVENT_TSCALE:    10s
  EVENT_EBAND:     Low, 2-4 keV
  SUN_POSTN:       168.15d {+11h 12m 36s}   +5.09d {+05d 05' 14"}
  SUN_DIST:         68.14 [deg]
  MOON_POSTN:       86.19d {+05h 44m 46s}  +21.03d {+21d 01' 59"}
  MOON_DIST:       147.42 [deg]
  MOON_ILLUM:      42 [%]
  GAL_COORDS:      341.02, 25.94 [deg] galactic lon,lat of the burst (or transient)
  ECL_COORDS:      234.92, -6.71 [deg] ecliptic lon,lat of the burst (or transient)      
  COMMENTS:        MAXI Unknown Source Position. GRB or unknown X-ray Transient.
  
   GCN Circular #13731 
  
  
  M. Morii (Tokyo Tech), K. Yamaoka (Waseda U.), H. Negoro (Nihon U.),
  S. Ueno, H. Tomida, S. Nakahira, M. Ishikawa (JAXA),
  T. Mihara, M. Sugizaki, M. Serino, T. Yamamoto, J. Sugimoto, M. Matsuoka (RIKEN), 
  N. Kawai, R. Usui, K. Ishikawa, T. Yoshii (Tokyo Tech),
  A. Yoshida (AGU), H. Tsunemi, M. Kimura (Osaka U.),
  M. Nakajima, M. Asada, N. Serita (Nihon U.),
  Y. Ueda, K. Hiroi, M. Shidatsu, R. Sato (Kyoto U.),
  Y. Tsuboi, M. Higa (Chuo U.),
  M. Yamauchi, Y. Nishimura, T. Hanayama, K. Yoshidome (Miyazaki U.), 
  report on behalf of the MAXI team:
  
  
  MAXI/GSC triggered a bright uncatalogued X-ray transient source at UT 2012-09-08T22:35:13.
  Assuming that the source flux was constant over the transit,
  we obtain the source position at 
  
  
  (R.A., Dec) = (230.64 deg, -25.79 deg) = (15 22 32, -25 47 42) (J2000)
  
  
  with a statistical 90% C.L. elliptical error region
  with long and short radii of 0.46 deg and 0.31 deg, respectively.
  The position angle of long axis is -30 deg.
  There is an additional systematic uncertainty of 0.1 deg (90% containment radius).
  
  
  The preliminary flux of the transient source was 78 +- 19 mCrab (4 - 10 keV).
  There was no significant detection at the transit location in the
  previous and the next orbit (92 min before and after the detection)
  with an upper limit of 20 mCrab.
  There is no known bright X-ray source at the detected position.
  
  
  Follow-up observations are encouraged.
  
   GCN Circular #13740 
  
  
  S. Immler (CRESST/GSFC/UMD), C. Pagani (U. Leicester), and
  A. A. Breeveld (MSSL-UCL) report on behalf of the Swift team:
  
  
  Swift began a Target of Opportunity observation of the MAXI/GSC
  discovered burst GRB 120908A (Morii et al. GCN 13731) at 2012-09-09
  13:41:43 UT.
  
  
  We have analyzed 3.7 ks of XRT data, starting ~54 ks after the MAXI
  trigger. The data are entirely in Photon Counting mode, centered on
  the MAXI position and partially covering the MAXI error region.
  No new source is detected in the XRT data. The 3-sigma upper limit
  is 0.004 counts/sec which is 2.4e-13 erg cm^-2 s^-1 for a typical GRB
  spectrum.
  
  
  The Swift/UVOT began settled observations of the field 54.4 ks after
  the MAXI trigger (Morii et al., GCN Circ. 13731). No optical afterglow
  consistent with the MAXI position given in that circular is detected
  in the initial UVOT exposures. Preliminary 3-sigma upper limits using
  the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc.
  1358, 373) for the initial exposures are:
  Filter         T_start(s)   T_stop(s)      Exp(s)         Mag
  
  white            54383        66117         2345         >21.7
  
  The magnitude in the table is not corrected for the Galactic
  extinction due to the reddening of E(B-V) = 0.23 in the direction of
  the burst (Schlegel et al. 1998).
  
   GCN Circular #13741 
  
  
  Sinead McGlynn (MPE/TUM)
  reports on behalf of the Fermi GBM Team:
  
  
  "At 22:31:00.02  UT on 08 September 2012, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 120908A (trigger 368836263/120908938). GBM was triggered over 4 minutes earlier than the bright X-ray source reported as a MAXI/GSC detection by Morii et al. (GCN 13731). 
  
  
  The on-ground GBM location is consistent with the MAXI/GSC reported location. As a result, and due to the presence of extended soft emission in the GBM data at the time of the MAXI/GSC detection, we associate the GBM trigger with GRB 120908A.
  
  
  The angle from the Fermi LAT boresight is 87 degrees.
  
  
  The GBM light curve consists of two spiky pulses with a duration (T90) of about 66  s (50-300 keV).
  The time-averaged spectrum from T0-5.38 s to T0+15.1 s is best fit by a power law function with an exponential
  high-energy cutoff.  The power law index is -1.21 +/- 0.11 and the cutoff energy, parameterized as Epeak, is 205.9 +/- 43.1 keV. In addition, weak longer-lived soft emission is observed close to the MAXI trigger time (200-300s post GBM trigger) up to approximately 50 keV.
  
  
  The event fluence (10-1000 keV) in this time interval is (1.7 +/- 0.2)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+6 s in the 10-1000 keV band is 2.7 +/- 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 #13742 
  
  
  Weikang Zheng and Carl Akerlof (Umich), report on behalf of the ROTSE
  collaboration:
  
  
  We analyzed Fermi/LAT data of GRB 120908A (Morii et al., GCN 13731)
  and GRB 120909A (Immler et al., GCN 13727)
  as a follow-up of routine search in Swift trigger catalogs in our LAT
  data processing pipeline using both the matched filter technique
  (Akerlof et al. 2010, ApJ, 725, L15; 2011 ApJ, 726, 22; 2012,
  arXiv:1205.3066; Zheng et al. 2012, ApJ 745,72; ApJ, 756, 64)
  and likelihood method. We do NOT detect high energy photon emission
  from both methods in the two GRBs.
  
  
  A standard data selection method is applied when extracting the LAT
  photon data with energy E > 100 MeV, and a duration of T0 - T0+47.5s
  after the trigger. A zenith angle cut of <105 degree is applied to
  all photons.
  
  
  For GRB 120908A, the burst location was about 72 degrees from the
  LAT boresight, and the zenith angle was about 64 degrees at trigger time.
  Using the likelihood method, we estimated the upper limit in LAT energy
  range (0.1 - 10 GeV) is 8.3e-09 (photons cm^-2 s^-1) by assuming a
  spectral index of -2.2.
  The pipeline result of GRB 120908A is given in the following link:
  http://www.rotse.net/LAT/SwiftTriggers/368836516/
  
  
  For GRB 120909A, the burst location was about 65 degrees from the
  LAT boresight, and the zenith angle was about 98 degrees at trigger time.
  Using the likelihood method, we estimated the upper limit in LAT energy
  range (0.1 - 10 GeV) is 2.0e-08 (photons cm^-2 s^-1) by assuming a
  spectral index of -2.2.
  The pipeline result of GRB 120909A is given in the following link:
  http://www.rotse.net/LAT/SwiftTriggers/368847726/