Gamma-ray Burst 170823A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

• none

• GCN/BACODINE POSITION NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Wed 23 Aug 17 22:17:01 UT
  NOTICE_TYPE:     Swift-BAT GRB Position
  TRIGGER_NUM:     769177,   Seg_Num: 0
  GRB_RA:          188.719d {+12h 34m 53s} (J2000),
                   188.935d {+12h 35m 44s} (current),
                   188.108d {+12h 32m 26s} (1950)
  GRB_DEC:         +35.582d {+35d 34' 55"} (J2000),
                   +35.485d {+35d 29' 06"} (current),
                   +35.857d {+35d 51' 27"} (1950)
  GRB_ERROR:       3.00 [arcmin radius, statistical only]
  GRB_INTEN:       1892 [cnts]    Image_Peak=144 [image_cnts]
  TRIGGER_DUR:     0.512 [sec] 
  TRIGGER_INDEX:   124     E_range: 25-100 keV
  BKG_INTEN:       20272 [cnts]
  BKG_TIME:        80196.42 SOD {22:16:36.42} UT
  BKG_DUR:         8 [sec]
  GRB_DATE:        17988 TJD;   235 DOY;   17/08/23
  GRB_TIME:        80208.32 SOD {22:16:48.32} UT
  GRB_PHI:         -138.08 [deg]
  GRB_THETA:        24.07 [deg]
  SOLN_STATUS:     0x3
  RATE_SIGNIF:     15.96 [sigma]
  IMAGE_SIGNIF:    9.42 [sigma]
  MERIT_PARAMS:     +1  +0  +0  -1  +2  +0 -100  +0 -76  +0 
  SUN_POSTN:       153.01d {+10h 12m 02s}  +11.13d {+11d 07' 48"}
  SUN_DIST:         40.62 [deg]   Sun_angle= -2.4 [hr] (East of Sun)
  MOON_POSTN:      179.76d {+11h 59m 03s}   +3.38d {+03d 22' 37"}
  MOON_DIST:        33.21 [deg]
  MOON_ILLUM:      6 [%]
  GAL_COORDS:      144.57, 80.84 [deg] galactic lon,lat of the burst (or transient)
  ECL_COORDS:      171.63, 35.65 [deg] ecliptic lon,lat of the burst (or transient)
  COMMENTS:        SWIFT-BAT GRB Coordinates.  
  COMMENTS:        This is a rate trigger.  
  COMMENTS:        A point_source was found.  
  COMMENTS:        This does not match any source in the on-board catalog.  
  COMMENTS:        This does not match any source in the ground catalog.  
  COMMENTS:        This is a GRB.  
  COMMENTS:        This trigger occurred at longitude,latitude = 179.14,19.97 [deg].  
  

• red DSS finding chart ps-file
  
  
• GCN NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Wed 23 Aug 17 22:20:24 UT
  NOTICE_TYPE:     Swift-BAT GRB Lightcurve
  TRIGGER_NUM:     769177,   Seg_Num: 0
  GRB_RA:          188.719d {+12h 34m 53s} (J2000),
                   188.935d {+12h 35m 44s} (current),
                   188.108d {+12h 32m 26s} (1950)
  GRB_DEC:         +35.582d {+35d 34' 55"} (J2000),
                   +35.485d {+35d 29' 06"} (current),
                   +35.857d {+35d 51' 27"} (1950)
  GRB_DATE:        17988 TJD;   235 DOY;   17/08/23
  GRB_TIME:        80208.32 SOD {22:16:48.32} UT
  TRIGGER_INDEX:   124
  GRB_PHI:         -138.08 [deg]
  GRB_THETA:        24.07 [deg]
  DELTA_TIME:      -69.00 [sec]
  TRIGGER_DUR:     0.512 [sec] 
  SOLN_STATUS:     0x3
  RATE_SIGNIF:     15.96 [sigma]
  IMAGE_SIGNIF:    9.42 [sigma]
  LC_URL:          sw00769177000msb.lc
  SUN_POSTN:       153.01d {+10h 12m 03s}  +11.13d {+11d 07' 45"}
  SUN_DIST:         40.62 [deg]   Sun_angle= -2.4 [hr] (East of Sun)
  MOON_POSTN:      179.79d {+11h 59m 10s}   +3.37d {+03d 22' 00"}
  MOON_DIST:        33.21 [deg]
  MOON_ILLUM:      6 [%]
  GAL_COORDS:      144.57, 80.84 [deg] galactic lon,lat of the burst (or transient)
  ECL_COORDS:      171.63, 35.65 [deg] ecliptic lon,lat of the burst (or transient)
  COMMENTS:        SWIFT-BAT GRB Lightcurve.  
  COMMENTS:           
  COMMENTS:        The next comments were copied from the BAT_POS Notice:  
  COMMENTS:        This is a rate trigger.  
  COMMENTS:        A point_source was found.  
  COMMENTS:        This does not match any source in the on-board catalog.  
  COMMENTS:        This does not match any source in the ground catalog.  
  COMMENTS:        This is a GRB.  
  COMMENTS:        This trigger occurred at longitude,latitude = 179.14,19.97 [deg].  
  

  
• GCN Circular #21666
  E. Troja (NASA/GSFC/UMCP), A. D'Ai (INAF-IASFPA), V. D'Elia (ASDC), K. L. Page (U Leicester) and A. Tohuvavohu (PSU) report on behalf of the Swift Team:
  At 22:16:48 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 170823A (trigger=769177). Swift did not slew due to the Sun observing constraint. The BAT on-board calculated location is RA, Dec 188.719, +35.582 which is

     RA(J2000) = 12h 34m 53s
     Dec(J2000) = +35d 34' 55"
  

  with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a complex structure with a duration of about 60 sec. The peak count rate was ~4900 counts/sec (15-350 keV), at ~11 sec after the trigger.
  Due to a Sun observing constraint, Swift cannot slew to the BAT position until 18:03 UT on 2017 October 17. There will thus be no XRT or UVOT data for this trigger before this time.
  Burst Advocate for this burst is E. Troja (eleonora.troja AT nasa.gov). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/too.html.)
• GCN Circular #21678
  M. Stamatikos (OSU), S. D. Barthelmy (GSFC), J. R. Cummings (CPI), H. A. Krimm (NSF/USRA), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU), E. Troja (NASA/GSFC/UMCP), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):
  Using the data set from T-240 to T+962 sec from the recent telemetry downlink, we report further analysis of BAT GRB 170823A (trigger #769177) (Troja et al., GCN Circ. 21666). The BAT ground-calculated position is RA, Dec = 188.713, 35.549 deg which is

    RA(J2000)  =  12h 34m 51.1s
    Dec(J2000) = +35d 32' 58.0"
  

  with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 79%.
  The mask-weighted light curve shows a multi-peaked light curve that starts at ~ T0 and ends at ~T+90 s. T90 (15-350 keV) is 69.4 +- 11.7 sec (estimated error including systematics).
  The time-averaged spectrum from T-0.36 to T+87.31 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.06 +- 0.09. The fluence in the 15-150 keV band is 2.6 +- 0.1 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+21.40 sec in the 15-150 keV band is 3.7 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90% confidence level.
  The results of the batgrbproduct analysis are available at http://gcn.gsfc.nasa.gov/notices_s/769177/BA/
• GCN Circular #21727
  Klotz A., Turpin D., Atteia J.L. (CNRS-OMP-IRAP), Boer, M., Laugier, R. (CNRS-ARTEMIS), Gendre B. (UVI - Etelman Obs.) report:
  We imaged the field of GRB 170823A detected by SWIFT (trigger 769177) with the TAROT robotic telescope (D=25cm) located at the Calern observatory, France.
  The observations started 28s after the GRB trigger (18s after the notice). The elevation of the field decreased from 3 degrees above horizon and weather conditions were very good.
  The first image is trailed with a duration of 60.0s (see the description in Klotz et al., 2006, A&A 451, L39). We do not detect any OT with a limiting magnitude of: t0+28s to t0+88s : Rlim = 15.1
  The second image is 30.0s exposure in tracking mode: t0+101s to t0+131s : Rlim = 15.1
  We co-added a series of exposures: t0+101s to t0+395s : Rlim = 16.8
  Magnitudes were estimated with the nearby USNO-B1 stars and are not corrected for galactic dust extinction.
• GCN Circular #21948
  K. P. Mooley (Hintze Fellow, Oxford), T. D. Staley, R. P. Fender (Oxford), G. E. Anderson (Curtin), T. Cantwell (Manchester), D. Titterington, S. H. Carey, J. Hickish, Y. C. Perrott, N. Razavi-Ghods, P. Scott (Cambridge), K. Grainge, A. Scaife (Manchester)
  The AMI Large Array robotically triggered on the Swift alert for GRB 170823A (Troja et al., GCN 21666) as part of the 4pisky program, and subsequent follow up observations were obtained up to 10 days post-burst. Our observations at 15 GHz on 2017 Aug 24.41, Aug 25.61 and Aug 26.58 (UT) do not reveal any radio source at the BAT location (Stamatikos et al., GCN 21678). While we are dynamic range limited due to a bright radio source in the vicinity of the GRB location, we are able to place 3sigma upper limits of 1.0 mJy, 1.1 mJy, and 0.8 mJy at the respective epochs.
  We thank the AMI staff for scheduling these observations. The AMI-GRB database is a log of all GRB follow up observations with the AMI, and is available at http://4pisky.org/ami-grb/.