Gamma-ray Burst 191218A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

• none

• GCN/BACODINE POSITION NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Wed 18 Dec 19 02:43:03 UT
  NOTICE_TYPE:     Swift-BAT GRB Position
  TRIGGER_NUM:     944916,   Seg_Num: 0
  GRB_RA:          301.078d {+20h 04m 19s} (J2000),
                   301.414d {+20h 05m 39s} (current),
                   300.234d {+20h 00m 56s} (1950)
  GRB_DEC:         -40.274d {-40d 16' 25"} (J2000),
                   -40.216d {-40d 12' 58"} (current),
                   -40.416d {-40d 24' 56"} (1950)
  GRB_ERROR:       3.00 [arcmin radius, statistical only]
  GRB_INTEN:       4619 [cnts]    Image_Peak=152 [image_cnts]
  TRIGGER_DUR:     1.024 [sec] 
  TRIGGER_INDEX:   155     E_range: 50-350 keV
  BKG_INTEN:       16354 [cnts]
  BKG_TIME:        9751.89 SOD {02:42:31.89} UT
  BKG_DUR:         8 [sec]
  GRB_DATE:        18835 TJD;   352 DOY;   19/12/18
  GRB_TIME:        9763.86 SOD {02:42:43.86} UT
  GRB_PHI:         -139.25 [deg]
  GRB_THETA:        50.32 [deg]
  SOLN_STATUS:     0x3
  RATE_SIGNIF:     51.86 [sigma]
  IMAGE_SIGNIF:    8.88 [sigma]
  MERIT_PARAMS:     +1  +0  +0  +0  +3  -1 -100  +0 -82  +0 
  SUN_POSTN:       265.50d {+17h 42m 00s}  -23.37d {-23d 22' 17"}
  SUN_DIST:         34.53 [deg]   Sun_angle= -2.4 [hr] (East of Sun)
  MOON_POSTN:      164.66d {+10h 58m 38s}  +11.63d {+11d 37' 56"}
  MOON_DIST:       132.45 [deg]
  MOON_ILLUM:      63 [%]
  GAL_COORDS:        0.16,-30.47 [deg] galactic lon,lat of the burst (or transient)
  ECL_COORDS:      294.69,-19.46 [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 = 217.38,17.24 [deg].  
  

• red DSS finding chart ps-file
  
  
• GCN NOTICE
  

  TITLE:          GCN/INTEGRAL NOTICE
  NOTICE_DATE:    Wed 18 Dec 19 02:44:06 UT
  NOTICE_TYPE:    INTEGRAL SPI ACS Trigger
  TRIGGER_NUM:    8462,   Sub_Num: 0
  GRB_INTEN:      9.54 [sigma]   
  GRB_TIME:       9760.97 SOD {02:42:40.97} UT
  GRB_DATE:       18835 TJD;   352 DOY;   19/12/18 
  COMMENTS:       INTEGRAL SPI_ACS GRB Trigger.
  COMMENTS:       Time_Scale=2.0000 and Time_Error=1.0000. 
  COMMENTS:
  COMMENTS:       NOTE: This SPIACS event is temporally(3.0<100sec) coincident with the SWIFT_BAT event (trignum=944916).
  COMMENTS:
  COMMENTS:       The SPIACS lightcurve can be found at:
  COMMENTS:       ftp://isdcarc.unige.ch/arc/FTP/ibas/spiacs/2019-12/2019-12-18T02-42-40.7796-05329-19344-0.lc
  

• GCN NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Wed 18 Dec 19 02:46:42 UT
  NOTICE_TYPE:     Swift-BAT GRB Lightcurve
  TRIGGER_NUM:     944916,   Seg_Num: 0
  GRB_RA:          301.078d {+20h 04m 19s} (J2000),
                   301.414d {+20h 05m 39s} (current),
                   300.234d {+20h 00m 56s} (1950)
  GRB_DEC:         -40.274d {-40d 16' 25"} (J2000),
                   -40.216d {-40d 12' 58"} (current),
                   -40.416d {-40d 24' 56"} (1950)
  GRB_DATE:        18835 TJD;   352 DOY;   19/12/18
  GRB_TIME:        9763.86 SOD {02:42:43.86} UT
  TRIGGER_INDEX:   155
  GRB_PHI:         -139.25 [deg]
  GRB_THETA:        50.32 [deg]
  DELTA_TIME:      -75.00 [sec]
  TRIGGER_DUR:     1.024 [sec] 
  SOLN_STATUS:     0x3
  RATE_SIGNIF:     51.86 [sigma]
  IMAGE_SIGNIF:    8.88 [sigma]
  LC_URL:          sw00944916000msb.lc
  SUN_POSTN:       265.50d {+17h 42m 00s}  -23.37d {-23d 22' 17"}
  SUN_DIST:         34.53 [deg]   Sun_angle= -2.4 [hr] (East of Sun)
  MOON_POSTN:      164.69d {+10h 58m 47s}  +11.62d {+11d 37' 11"}
  MOON_DIST:       132.42 [deg]
  MOON_ILLUM:      62 [%]
  GAL_COORDS:        0.16,-30.47 [deg] galactic lon,lat of the burst (or transient)
  ECL_COORDS:      294.69,-19.46 [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 = 217.38,17.24 [deg].  
  

  
• GCN Circular #26480
  E. Troja (NASA/GSFC/UMCP), N. J. Klingler (PSU), A. Y. Lien (GSFC/UMBC), M. J. Moss (GWU), K. L. Page (U Leicester), D. M. Palmer (LANL), M. H. Siegel (PSU) and A. Tohuvavohu (U Toronto) report on behalf of the Neil Gehrels Swift Observatory Team:
  At 02:42:43 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 191218A (trigger=944916). Swift did not slew to this burst due to a Sun constraint. The BAT on-board calculated location is RA, Dec 301.078, -40.274 which is

     RA(J2000) = 20h 04m 19s
     Dec(J2000) = -40d 16' 25"
  

  with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a double-peaked structure with a duration of about 60 sec. The peak count rate was ~4000 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 12:12 UT on 2020 February 27. 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/)
• GCN Circular #26482
  R. Gaikwad, S.Gupta, V. Sharma, A. Vibhute and D. Bhattacharya (IUCAA), V. Bhalerao (IIT-B), A. R. Rao (TIFR) and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration:
  Analysis of AstroSat CZTI data showed the detection of a GRB 191218A, which was also detected by Swift (Troja E. et al., GCN #26480).
  The source was clearly detected in the 40-200 keV energy range. The light curve shows multiple peaks of emission with the strongest peak at 2019-12-18 02:42:43.0 UT. The measured peak count rate associated with the burst is 348 cts/s above the background in the combined data of four quadrants, with a total of 3669 cts. The local mean background count rate was 507 cts/s. Using cumulative rates, we measure a T90 of 51.03 s.
  It was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range.
  CZTI GRB detections are reported regularly on the payload site at http://astrosat.iucaa.in/czti/?q=grb. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, ISAC, IUCAA, SAC and PRL. The Indian Space Research Organisation funded, managed and facilitated the project.
• GCN Circular #26495
  C. B. Markwardt (GSFC), S. D. Barthelmy (GSFC), J. R. Cummings (CPI), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (GSFC/UMBC), D. M. Palmer (LANL), T. Sakamoto (AGU), M. Stamatikos (OSU), E. Troja (GSFC/UMD), 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 191218A (trigger #944916) (Troja et al., GCN Circ. 26480). The BAT ground-calculated position is RA, Dec = 301.070, -40.277 deg which is

     RA(J2000)  =  20h 04m 16.7s
     Dec(J2000) = -40d 16' 38.8"
  

  with an uncertainty of 1.4 arcmin, (radius, sys+stat, 90% containment). The partial coding was 9%.
  The mask weighted light curve shows two peaks at ~T+4 s and ~T+45 s. The overall structure starts at ~T-2 s and lasts till ~T+58 s. T90 (15-350 keV) is 44.67 +- 0.73 sec (estimated error including systematics).
  The time-averaged spectrum from T-0.23 to T+46.03 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.12 +- 0.10. The fluence in the 15-150 keV band is 7.8 +- 0.4 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+0.66 sec in the 15-150 keV band is 6.3 +- 0.9 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/944916/BA/
• GCN Circular #26506
  A. Ridnaia, S. Golenetskii, R. Aptekar, D. Frederiks, M. Ulanov, D. Svinkin, A. Tsvetkova, A. Lysenko, and T. Cline on behalf of the Konus-Wind team, report:
  The long-duration GRB 191218A (Swift-BAT trigger #944916: Troja et al., GCN 26480; Markwardt et al., GCN 26495; AstroSat CZTI detection: Gaikwad et al., GCN 26482) triggered Konus-Wind at T0=9758.735 s UT (02:42:38.735).
  The burst light curve shows a double-peaked structure which starts at ~T0-0.5 s and has a total duration of ~78.8 s. The emission is seen up to ~4 MeV.
  As observed by Konus-Wind, the burst had a fluence of 3.92(-0.37,+0.45)x10^-5 erg/cm2, and a 64-ms peak flux, measured from T0+1.440 s, of 4.08(-1.07,+1.07)x10^-6 erg/cm2/s (both in the 20 keV - 10 MeV energy range).
  The time-averaged spectrum of the burst (measured from T0 to T0+81.664 s) is best fit in the 20 keV - 4 MeV range by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = -0.76(-0.18,+0.20) and Ep = 330(-44,+61) keV (chi2 = 54/69 dof). Fitting by a GRB (Band) model yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -2.2 (chi2 = 53/68 dof).
  The spectrum near the maximum count rate (measured from T0+0.256 to T0+7.936 s) is best fit in the 20 keV - 4 MeV range by a power law with exponential cutoff model with alpha = -0.27(-0.15,+0.17) and Ep = 322(-24,+28) keV (chi2 = 74/69 dof). Fitting by a GRB (Band) model yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -2.7 (chi2 = 73/68 dof).
  The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB191218_T09758/
  All the quoted errors are at the 90% confidence level. All the quoted values are preliminary.