Gamma-ray Burst 070920

(All information courtesy of the instrument teams.)

Previous IAU Circulars

• none

• GCN/BACODINE POSITION NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Thu 20 Sep 07 04:09:12 UT
  NOTICE_TYPE:     Swift-BAT GRB Position
  TRIGGER_NUM:     291614,   Seg_Num: 0
  GRB_RA:          100.932d {+06h 43m 44s} (J2000),
                   101.163d {+06h 44m 39s} (current),
                    99.436d {+06h 37m 45s} (1950)
  GRB_DEC:         +72.227d {+72d 13' 38"} (J2000),
                   +72.219d {+72d 13' 09"} (current),
                   +72.277d {+72d 16' 36"} (1950)
  GRB_ERROR:       3.00 [arcmin radius, statistical only]
  GRB_INTEN:       0 [cnts]    Image_Peak=2329 [image_cnts]
  TRIGGER_DUR:     64.000 [sec] 
  TRIGGER_INDEX:   20000     E_range: 15-50 keV
  BKG_INTEN:       0 [cnts]
  BKG_TIME:        0.00 SOD {00:00:00.00} UT
  BKG_DUR:         0 [sec]
  GRB_DATE:        14363 TJD;   263 DOY;   07/09/20
  GRB_TIME:        14413.76 SOD {04:00:13.76} UT
  GRB_PHI:         -153.50 [deg]
  GRB_THETA:        14.37 [deg]
  SOLN_STATUS:     0x13
  RATE_SIGNIF:     0.00 [sigma]
  IMAGE_SIGNIF:    10.26 [sigma]
  MERIT_PARAMS:     +1  +0  +0  +6  +1  +0  +0  +0  -9  +1 
  SUN_POSTN:       177.09d {+11h 48m 22s}   +1.26d {+01d 15' 34"}
  SUN_DIST:         84.54 [deg]   Sun_angle= 5.1 [hr] (West of Sun)
  MOON_POSTN:      272.47d {+18h 09m 52s}  -28.18d {-28d 10' 33"}
  MOON_DIST:       135.70 [deg]
  MOON_ILLUM:      55 [%]
  GAL_COORDS:      142.63, 25.16 [deg] galactic lon,lat of the burst (or transient)
  ECL_COORDS:       95.06, 48.98 [deg] ecliptic lon,lat of the burst (or transient)
  COMMENTS:        SWIFT-BAT GRB Coordinates.  
  COMMENTS:        This Notice was delayed by more than 60 sec past the end of the trigger integration interval;  
  COMMENTS:        probably due to it occurring during a Malindi downlink session.  
  COMMENTS:        This is an image trigger.  (The RATE_SIGNIF & BKG_{INTEN, TIME, DUR} are undefined.)  
  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 = 12.81,-0.29 [deg].  
  

• red DSS finding chart ps-file
  
  
• GCN NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Thu 20 Sep 07 04:09:34 UT
  NOTICE_TYPE:     Swift-BAT GRB Lightcurve
  TRIGGER_NUM:     291614,   Seg_Num: 0
  GRB_RA:          100.932d {+06h 43m 44s} (J2000),
                   101.163d {+06h 44m 39s} (current),
                    99.436d {+06h 37m 45s} (1950)
  GRB_DEC:         +72.227d {+72d 13' 38"} (J2000),
                   +72.219d {+72d 13' 09"} (current),
                   +72.277d {+72d 16' 36"} (1950)
  GRB_DATE:        14363 TJD;   263 DOY;   07/09/20
  GRB_TIME:        14413.76 SOD {04:00:13.76} UT
  TRIGGER_INDEX:   20000
  GRB_PHI:         -153.50 [deg]
  GRB_THETA:        14.37 [deg]
  DELTA_TIME:      0.00 [sec]
  TRIGGER_DUR:     64.000 [sec] 
  SOLN_STATUS:     0x13
  RATE_SIGNIF:     0.00 [sigma]
  IMAGE_SIGNIF:    10.26 [sigma]
  LC_URL:          sw00291614000msb.lc
  SUN_POSTN:       177.09d {+11h 48m 22s}   +1.26d {+01d 15' 33"}
  SUN_DIST:         84.54 [deg]   Sun_angle= 5.1 [hr] (West of Sun)
  MOON_POSTN:      272.47d {+18h 09m 53s}  -28.18d {-28d 10' 32"}
  MOON_DIST:       135.70 [deg]
  MOON_ILLUM:      55 [%]
  GAL_COORDS:      142.63, 25.16 [deg] galactic lon,lat of the burst (or transient)
  ECL_COORDS:       95.06, 48.98 [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 an image 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 = 12.81,-0.29 [deg].  
  

  
• GCN Circular #6805
  D. Grupe (PSU), N. Gehrels (NASA/GSFC), F. E. Marshall (NASA/GSFC), C. Pagani (PSU), D. M. Palmer (LANL), J. L. Racusin (PSU), G. Sato (GSFC/ISAS), M. Stamatikos (NASA/ORAU), M. C. Stroh (PSU), T. N. Ukwatta (GSFC/GWU) and L. Vetere (PSU) report on behalf of the Swift Team:
  At 04:00:13 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 070920 (trigger=291614). The BAT on-board calculated location is RA, Dec 100.932, +72.227 which is

     RA(J2000) = 06h 43m 44s
     Dec(J2000) = +72d 13' 38"
  

  with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). As is often the case with 64-second image triggers, the BAT light curve shows no obvious variation in the count rate.
  Because Swift is in the process of returning to normal operations, automatic slewing to GRBs is currently disabled. Therefore, there are no prompt XRT or UVOT observations of this burst.
  Burst Advocate for this burst is D. Grupe (grupe AT astro.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 #6806
  Klotz, A. (CESR-OMP), Boer M. (OHP), Atteia J.L. (LATT-OMP) report:
  We imaged the field of GRB 070920 detected by SWIFT (trigger 291614) with the TAROT robotic telescope (D=25cm) located at the Calern observatory, France.
  The observations started 544.7s after the GRB trigger (6.8s after the notice). The elevation of the field increased from from 57 degrees above horizon and weather conditions were excellents.
  The date of trigger : t0 = 2007-09-20T04:00:14.112
  The first image is 90.0s exposure in tracking mode: t0+544.7s to t0+634.7s : R > 18.2
  Magnitudes were estimated with the nearby USNO-B1 stars and are not corrected for galactic dust extinction.
  N.B. Galactic coordinates are lon=142.6283 lat=+25.1560 and the galactic extinction in R band is 0.3 magnitudes estimated from D. Schlegel et al. 1998ApJ...500..525S.
  This message may be cited.
• GCN Circular #6807
  L. Barbier (GSFC), S. D. Barthelmy (GSFC), J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC), D. Grupe (PSU), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), D. Palmer (LANL), T. Sakamoto (GSFC/ORAU), G. Sato (GSFC/ISAS), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC), T. Ukwatta (GWU) (i.e. the Swift-BAT team):
  Using the data set from T-119 to T+300 sec from recent telemetry downlinks, we report further analysis of BAT GRB 070920 (trigger #291614) (Grupe, et al., GCN Circ. 6805). The BAT ground-calculated position is RA, Dec = 100.968, 72.250 deg which is

     RA(J2000) =  06h 43m 52.2s 
     Dec(J2000) = 72d 14' 59" 
  

  with an uncertainty of 2.1 arcmin, (radius, sys+stat, 90% containment). The partial coding was 100%.
  The mask-weighted lightcurve shows a single peak (with structure) starting at ~T-15 sec, broadly peaking at ~T+25 sec, and ending at ~T+140 sec. T90 (15-350 keV) is 56 +- 1 sec (estimated error including systematics).
  The time-averaged spectrum from T+15.1 to T+75.0 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.69 +- 0.21. The fluence in the 15-150 keV band is 5.1 +- 0.7 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T+30.45 sec in the 15-150 keV band is 0.3 +- 0.1 ph/cm2/sec. All the quoted errors are at the 90% confidence level.
• GCN Report 83.1
  GCN_Report 83.1 has been posted: http://gcn.gsfc.nasa.gov/reports/report_83_1.pdf by D. Grupe at PSU titled: "Swift Observations of 070920A"
• GCN Circular #6854
  Galante N. (MPI/Muenchen), Garczarczyk M. (MPI/Muenchen), Gaug M. (IAC/Tenerife), Bastieri D. (U. Padova), Longo F. (INFN/Trieste) and Scapin V. (U. Udine), for the MAGIC Collaboration
  The MAGIC Imaging Atmospheric Cherenkov Telescope performed a follow-up observation of the SWIFT/BAT burst GRB070920A (GCN circular 6805, Grupe D., et al.). We received the GCN alert at T0+539s. The data taking by MAGIC started at T0+690s, 2.5 minutes after the alert income. We observed the sky positon for 36min spanning a zenith angle in the range 53-50 degrees.
  No evidence for VHE gamma-ray emission above the analysis threshold of about 250 GeV was found. A preliminary analysis, taking advantage for the first time of the fast 2GHz digitalization from the new data acquisition system, and for the hypothesis of steady emission and assumption of a differential photon spectral index of -2.5, yields the following 95% CL differential flux upper limits (inc. 30% systematic error on the efficiency):

  E(225-300 GeV)  : 7.1 x 10^(-8) erg/cm^2
  E(300-400 GeV)  : 4.6 x 10^(-8) erg/cm^2
  E(400-1000 GeV) : 2.2 x 10^(-8) erg/cm^2
  E(1-10 TeV)     : 0.53 x 10^(-8) erg/cm^2
  

  The upper limits correspond to the time period between T0+690s and T0+2490s. We can also exclude emission of a constant flux during our observation in any 100s time bin higher than:

  E(225-300 GeV)  : 1.9 x 10^(-7) erg/cm^2
  E(300-400 GeV)  : 1.0 x 10^(-7) erg/cm^2
  E(400-1000 GeV) : 2.4 x 10^(-8) erg/cm^2
  

  This message can be cited.
• GCN Circular #6921
  A.O. Jaunsen (Univ. Oslo), J. Gorosabel (IAA-CSIC), J.P.U. Fynbo, D. Malesani, J. Sollerman, Ch. Gall (DARK), T. Morel (Leuven), M.D. Stritzinger (DARK), A. Somero, J. Telting, C. Villforth (NOT), report on behalf of a larger collaboration:
  We observed the field of GRB 070920A (Grupe et al., GCN #6805) in the R band with the Nordic Optical Telescope on 2007 September 20.209-20.221 UT (1.0-1.3 hr after the GRB). Comparison images were taken on September 20.216 and again on October 15.135 UT with the same telescope, instrumentation and filter. Our images cover 96% of the revised BAT error circle(Barbier et al., GCN #6807), missing a small region at the northern boundary.
  At a mean time of 1.15 hr after the GRB, we do not detect any variable object brighter than R=24.3 (calibrated against USNO-B1.0, R1 magnitudes). There is no evidence for an associated SN on Oct. 15 down to the same limit.