Gamma-ray Burst 170911A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

• none

• GCN NOTICE
  

  TITLE:           GCN/FERMI NOTICE
  NOTICE_DATE:     Mon 11 Sep 17 06:24:47 UT
  NOTICE_TYPE:     Fermi-GBM Flight Position
  RECORD_NUM:      47
  TRIGGER_NUM:     526803867
  GRB_RA:           30.700d {+02h 02m 48s} (J2000),
                    30.947d {+02h 03m 47s} (current),
                    30.003d {+02h 00m 01s} (1950)
  GRB_DEC:         +22.133d {+22d 07' 60"} (J2000),
                   +22.218d {+22d 13' 04"} (current),
                   +21.893d {+21d 53' 35"} (1950)
  GRB_ERROR:       27.53 [deg radius, statistical plus systematic]
  GRB_INTEN:       77 [cnts/sec]
  DATA_SIGNIF:     4.60 [sigma]
  INTEG_TIME:      2.048 [sec]
  GRB_DATE:        18007 TJD;   254 DOY;   17/09/11
  GRB_TIME:        23062.79 SOD {06:24:22.79} UT
  GRB_PHI:         198.00 [deg]
  GRB_THETA:        75.00 [deg]
  DATA_TIME_SCALE: 2.0480 [sec]
  HARD_RATIO:      0.00
  LOC_ALGORITHM:   3 (version number of)
  MOST_LIKELY:     100%  Below horizon
  2nd_MOST_LIKELY:   0%  n/a
  DETECTORS:       0,0,0, 0,0,0, 0,1,1, 0,0,0, 0,0,
  SUN_POSTN:       169.63d {+11h 18m 30s}   +4.46d {+04d 27' 46"}
  SUN_DIST:        131.59 [deg]   Sun_angle= 9.2 [hr] (West of Sun)
  MOON_POSTN:       51.24d {+03h 24m 57s}  +13.27d {+13d 16' 24"}
  MOON_DIST:        21.26 [deg]
  MOON_ILLUM:      72 [%]
  GAL_COORDS:      143.98,-37.80 [deg] galactic lon,lat of the burst (or transient)
  ECL_COORDS:       36.24,  9.07 [deg] ecliptic lon,lat of the burst (or transient)
  LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2017/bn170911267/quicklook/glg_lc_medres34_bn170911267.gif
  COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
  COMMENTS:        This trigger occurred at longitude,latitude = 67.75,7.88 [deg].  
  COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.  
  

• GCN Circular #21858
  Y. Takao (RIKEN), H. Negoro (Nihon U.), S. Ueno, H. Tomida, M. Ishikawa, Y. Sugawara, N. Isobe, R. Shimomukai (JAXA), T. Mihara, M. Sugizaki, S. Nakahira, W. Iwakiri, M. Shidatsu, M. Matsuoka (RIKEN), N. Kawai, S. Sugita, T. Yoshii, Y. Tachibana, S. Harita, Y. Muraki, K. Morita (Tokyo Tech), A. Yoshida, T. Sakamoto, M. Serino, Y. Kawakubo, Y. Kitaoka, T. Hashimoto (AGU), H. Tsunemi, T. Yoneyama (Osaka U.), M. Nakajima, T. Kawase, A. Sakamaki (Nihon U.), Y. Ueda, T. Hori, A. Tanimoto, S. Oda (Kyoto U.), Y. Tsuboi, Y. Nakamura, R. Sasaki, H. Kawai (Chuo U.), M. Yamauchi, C. Hanyu, K, Hidaka (Miyazaki U.), T. Kawamuro (NAOJ), and K. Yamaoka (Nagoya U.)
  The MAXI/GSC nova alert system triggered a bright uncatalogued X-ray transient source at 06:24:21 UT on 2017 September 11. Assuming that the source flux was constant over the transit, we obtain the source position at (R.A., Dec) = (72.100 deg, 30.914 deg) = (04 48 23, +30 54 50) (J2000) with a statistical 90% C.L. elliptical error region with long and short radii of 0.38 deg and 0.32 deg, respectively. The roll angle of long axis from the north direction is 8.0 deg counterclockwise. There is an additional systematic uncertainty of 0.1 deg (90% containment radius). The X-ray flux averaged over the scan was 119 +- 24 mCrab (4.0-10.0keV, 1 sigma error). Without the constant flux assumption, we also obtained a rectangular error box for the transient source with the following corners:

  (R.A., Dec) = (70.630, 31.515) deg = (04 42 31, +31 30 55) (J2000)
  (R.A., Dec) = (70.464, 30.944) deg = (04 41 51, +30 56 38) (J2000)
  (R.A., Dec) = (73.457, 30.459) deg = (04 53 49, +30 27 31) (J2000)
  (R.A., Dec) = (73.640, 31.026) deg = (04 54 33, +31 01 34) (J2000)
  

  There is an additional systematic uncertainty of 0.1 deg (90% containment radius).
  There was no significant excess flux in the previous transit at 04:51 and in the next transit at 07:56 with an upper limit of 20 mCrab for each.
  Fermi is likely to detected this burst (Trigger number: 526803867).
• GCN Circular #21869
  A. von Kienlin (MPE), R. Hamburg (UAH), and C. Meegan (UAH) report on behalf of the Fermi GBM Team:
  "At 06:24:22.79 UT on 11 September 2017, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 170911A (trigger 526803867 / 170911267) which was also detected by the MAXI GSC (Takao et al. 2017, GCN 21858) The GBM on-ground location is consistent with the MAXI position.
  The angle from the Fermi LAT boresight at the GBM trigger time is 43 degrees.
  The GBM light curve shows a single peak with a duration (T90) of about 20 s (50-300 keV). The time-averaged spectrum from T0-3.072 s to T0+4.096 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.2 +/- 0.2 and the cutoff energy, parameterized as Epeak, is 260 +/- 120 keV
  The event fluence (10-1000 keV) in this time interval is (9.5 +/- 1.7)E-07 erg/cm^2. The 1-sec peak photon flux measured starting from T0-1.79 s in the 10-1000 keV band is 1.96 +/- 0.17 ph/s/cm^2.
  The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."