Gamma-ray Burst 120918A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

• none

• GCN/BACODINE POSITION NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Tue 18 Sep 12 11:16:31 UT
  NOTICE_TYPE:     Swift-BAT GRB Position
  TRIGGER_NUM:     534015,   Seg_Num: 0
  GRB_RA:          181.054d {+12h 04m 13s} (J2000),
                   181.218d {+12h 04m 52s} (current),
                   180.411d {+12h 01m 39s} (1950)
  GRB_DEC:         -32.758d {-32d 45' 26"} (J2000),
                   -32.828d {-32d 49' 41"} (current),
                   -32.479d {-32d 28' 44"} (1950)
  GRB_ERROR:       3.00 [arcmin radius, statistical only]
  GRB_INTEN:       4889 [cnts]    Image_Peak=231 [image_cnts]
  TRIGGER_DUR:     1.024 [sec] 
  TRIGGER_INDEX:   148     E_range: 25-100 keV
  BKG_INTEN:       28459 [cnts]
  BKG_TIME:        40558.33 SOD {11:15:58.33} UT
  BKG_DUR:         8 [sec]
  GRB_DATE:        16188 TJD;   262 DOY;   12/09/18
  GRB_TIME:        40570.62 SOD {11:16:10.62} UT
  GRB_PHI:         -91.21 [deg]
  GRB_THETA:        37.63 [deg]
  SOLN_STATUS:     0x3
  RATE_SIGNIF:     21.51 [sigma]
  IMAGE_SIGNIF:    12.04 [sigma]
  MERIT_PARAMS:     +1  +0  +0  +0  +2  +1 -100  +0 -82  +0 
  SUN_POSTN:       176.27d {+11h 45m 06s}   +1.61d {+01d 36' 49"}
  SUN_DIST:         34.76 [deg]   Sun_angle= -0.3 [hr] (East of Sun)
  MOON_POSTN:      204.79d {+13h 39m 10s}  -13.15d {-13d 08' 42"}
  MOON_DIST:        29.16 [deg]
  MOON_ILLUM:      7 [%]
  GAL_COORDS:      291.58, 29.07 [deg] galactic lon,lat of the burst (or transient)
  ECL_COORDS:      195.26,-29.36 [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 = 66.34,-18.98 [deg].  
  

• red DSS finding chart ps-file
  
  
• GCN NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Tue 18 Sep 12 11:19:56 UT
  NOTICE_TYPE:     Swift-BAT GRB Lightcurve
  TRIGGER_NUM:     534015,   Seg_Num: 0
  GRB_RA:          181.054d {+12h 04m 13s} (J2000),
                   181.218d {+12h 04m 52s} (current),
                   180.411d {+12h 01m 39s} (1950)
  GRB_DEC:         -32.758d {-32d 45' 26"} (J2000),
                   -32.828d {-32d 49' 41"} (current),
                   -32.479d {-32d 28' 44"} (1950)
  GRB_DATE:        16188 TJD;   262 DOY;   12/09/18
  GRB_TIME:        40570.62 SOD {11:16:10.62} UT
  TRIGGER_INDEX:   148
  GRB_PHI:         -91.21 [deg]
  GRB_THETA:        37.63 [deg]
  DELTA_TIME:      51.00 [sec]
  TRIGGER_DUR:     1.024 [sec] 
  SOLN_STATUS:     0x3
  RATE_SIGNIF:     21.51 [sigma]
  IMAGE_SIGNIF:    12.04 [sigma]
  LC_URL:          sw00534015000msb.lc
  SUN_POSTN:       176.28d {+11h 45m 06s}   +1.61d {+01d 36' 45"}
  SUN_DIST:         34.76 [deg]   Sun_angle= -0.3 [hr] (East of Sun)
  MOON_POSTN:      204.83d {+13h 39m 18s}  -13.16d {-13d 09' 18"}
  MOON_DIST:        29.17 [deg]
  MOON_ILLUM:      8 [%]
  GAL_COORDS:      291.58, 29.07 [deg] galactic lon,lat of the burst (or transient)
  ECL_COORDS:      195.26,-29.36 [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 = 66.34,-18.98 [deg].  
  

  
• GCN Circular #13779
  B. N. Barlow (PSU), W. H. Baumgartner (GSFC/UMBC), C. Gronwall (PSU), D. M. Palmer (LANL), M. Stamatikos (OSU/NASA/GSFC) and B.-B. Zhang (PSU) report on behalf of the Swift Team:
  At 11:16:10 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 120918A (trigger=534015). Swift could not slew to the burst because of the Sun constraint. The BAT on-board calculated location is RA, Dec 181.054, -32.758 which is

     RA(J2000) = 12h 04m 13s
     Dec(J2000) = -32d 45' 26"
  

  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 50 sec. The peak count rate was ~2500 counts/sec (15-350 keV), at ~0 sec after the trigger.
  Due to a Sun observing constraint, Swift cannot slew to the BAT position until 17:37 UT on 2012 November 15. There will thus be no XRT or UVOT data for this trigger before this time.
  Burst Advocate for this burst is B. N. Barlow (bnb2 AT psu.edu). 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 #13784
  S. D. Barthelmy (GSFC), B. N. Barlow (PSU), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (MSU) (i.e. the Swift-BAT team):
  Using the data set from T-239 to T+963 sec from recent telemetry downlinks, we report further analysis of BAT GRB 120918A (trigger #534015) (Barlow, et al., GCN Circ. 13799). The BAT ground-calculated position is RA, Dec = 181.042, -32.762 deg, which is

     RA(J2000)  =  12h 04m 10.1s 
     Dec(J2000) = -32d 45' 43.5" 
  

  with an uncertainty of 1.1 arcmin, (radius, sys+stat, 90% containment). The partial coding was 15%.
  The mask-weighted light curve shows several overlapping peaks starting at ~T-5 sec, the main peak at ~T+1 sec, and ending at ~T+40 sec. T90 (15-350 keV) is 25.1 +- 2.5 sec (estimated error including systematics).
  The time-averaged spectrum from T-2.86 to T+23.90 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 1.00 +- 0.39, and Epeak of 85.5 +- 36.3 keV (chi squared 55.6 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 3.7 +- 0.6 x 10^-6 erg/cm2 and the 1-sec peak flux measured from T-0.28 sec in the 15-150 keV band is 4.5 +- 0.5 ph/cm2/sec. A fit to a simple power law gives a photon index of 1.60 +- 0.09 (chi squared 63.5 for 57 d.o.f.). 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/534015/BA/
• GCN Report 390.1
  GCN_Report 390.1 has been posted: http://gcn.gsfc.nasa.gov/reports/report_390_1.pdf by B.N. Barlow at PSU titled: "Swift Observations of GRB 120918A"