Gamma-ray Burst 201218A

(All information courtesy of the instrument teams.)

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Results of Observations

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Fri 18 Dec 20 04:14:40 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      47
TRIGGER_NUM:     629957660
GRB_RA:          290.300d {+19h 21m 12s} (J2000),
                 290.532d {+19h 22m 08s} (current),
                 289.746d {+19h 18m 59s} (1950)
GRB_DEC:         +18.300d {+18d 18' 00"} (J2000),
                 +18.341d {+18d 20' 27"} (current),
                 +18.205d {+18d 12' 17"} (1950)
GRB_ERROR:       3.90 [deg radius, statistical plus systematic]
GRB_INTEN:       1607 [cnts/sec]
DATA_SIGNIF:     48.60 [sigma]
INTEG_TIME:      0.512 [sec]
GRB_DATE:        19201 TJD;   353 DOY;   20/12/18
GRB_TIME:        15255.90 SOD {04:14:15.90} UT
GRB_PHI:         340.00 [deg]
GRB_THETA:        90.00 [deg]
DATA_TIME_SCALE: 0.5120 [sec]
HARD_RATIO:      0.52
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      80%  GRB
2nd_MOST_LIKELY:  15%  Cyg X-1
DETECTORS:       0,0,0, 1,0,1, 0,0,0, 0,0,0, 0,0,
SUN_POSTN:       266.41d {+17h 45m 38s}  -23.39d {-23d 23' 40"}
SUN_DIST:         47.92 [deg]   Sun_angle= -1.6 [hr] (East of Sun)
MOON_POSTN:      316.05d {+21h 04m 13s}  -21.10d {-21d 06' 16"}
MOON_DIST:        46.70 [deg]
MOON_ILLUM:      15 [%]
GAL_COORDS:       52.55,  1.93 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      295.45, 39.96 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2020/bn201218177/quicklook/glg_lc_medres34_bn201218177.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 79.33,-22.15 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Fri 18 Dec 20 04:14:49 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      59
TRIGGER_NUM:     629957660
GRB_RA:          290.167d {+19h 20m 40s} (J2000),
                 290.399d {+19h 21m 36s} (current),
                 289.614d {+19h 18m 27s} (1950)
GRB_DEC:         +18.550d {+18d 33' 00"} (J2000),
                 +18.590d {+18d 35' 26"} (current),
                 +18.455d {+18d 27' 19"} (1950)
GRB_ERROR:       3.57 [deg radius, statistical plus systematic]
GRB_INTEN:       3248 [cnts/sec]
DATA_SIGNIF:     201.20 [sigma]
INTEG_TIME:      2.048 [sec]
GRB_DATE:        19201 TJD;   353 DOY;   20/12/18
GRB_TIME:        15255.90 SOD {04:14:15.90} UT
GRB_PHI:         340.00 [deg]
GRB_THETA:        90.00 [deg]
DATA_TIME_SCALE: 2.0480 [sec]
HARD_RATIO:      0.53
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      80%  GRB
2nd_MOST_LIKELY:  15%  Cyg X-1
DETECTORS:       0,0,0, 1,0,1, 0,0,0, 0,0,0, 0,0,
SUN_POSTN:       266.41d {+17h 45m 38s}  -23.39d {-23d 23' 40"}
SUN_DIST:         48.07 [deg]   Sun_angle= -1.6 [hr] (East of Sun)
MOON_POSTN:      316.06d {+21h 04m 13s}  -21.10d {-21d 06' 15"}
MOON_DIST:        46.98 [deg]
MOON_ILLUM:      15 [%]
GAL_COORDS:       52.71,  2.16 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      295.35, 40.23 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2020/bn201218177/quicklook/glg_lc_medres34_bn201218177.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 79.33,-22.15 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Fri 18 Dec 20 04:15:01 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      58
TRIGGER_NUM:     629957660
GRB_RA:          288.060d {+19h 12m 14s} (J2000),
                 288.280d {+19h 13m 07s} (current),
                 287.536d {+19h 10m 09s} (1950)
GRB_DEC:         +23.850d {+23d 51' 00"} (J2000),
                 +23.886d {+23d 53' 11"} (current),
                 +23.765d {+23d 45' 54"} (1950)
GRB_ERROR:       1.00 [deg radius, statistical only]
DATA_SIGNIF:     110.10 [sigma]
DATA_INTERVAL:   2.048 [sec]
GRB_DATE:        19201 TJD;   353 DOY;   20/12/18
GRB_TIME:        15255.90 SOD {04:14:15.90} UT
GRB_PHI:         343.00 [deg]
GRB_THETA:        95.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   4173 (Gnd S/W Version number)
SUN_POSTN:       266.41d {+17h 45m 38s}  -23.39d {-23d 23' 41"}
SUN_DIST:         51.83 [deg]   Sun_angle= -1.5 [hr] (East of Sun)
MOON_POSTN:      316.06d {+21h 04m 14s}  -21.10d {-21d 06' 13"}
MOON_DIST:        52.49 [deg]
MOON_ILLUM:      15 [%]
GAL_COORDS:       56.52,  6.35 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      294.00, 45.80 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2020/bn201218177/quicklook/glg_lc_medres34_bn201218177.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_629957660.fits
COMMENTS:        Fermi-GBM Ground-calculated Coordinates.  
COMMENTS:        Bright hard burst in the GBM.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        The LC_URL file will not be created/available until ~15 min after the trigger.  
COMMENTS:        The POS_MAP_URL file will not be created/available until ~1.5 min after the notice.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Fri 18 Dec 20 04:16:00 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      5
TRIGGER_NUM:     629957660
GRB_RA:          286.940d {+19h 07m 46s} (J2000),
                 287.159d {+19h 08m 38s} (current),
                 286.419d {+19h 05m 40s} (1950)
GRB_DEC:         +24.100d {+24d 06' 00"} (J2000),
                 +24.134d {+24d 08' 03"} (current),
                 +24.020d {+24d 01' 12"} (1950)
GRB_ERROR:       1.00 [deg radius, statistical only]
DATA_SIGNIF:     292.10 [sigma]
DATA_INTERVAL:   11.264 [sec]
GRB_DATE:        19201 TJD;   353 DOY;   20/12/18
GRB_TIME:        15255.90 SOD {04:14:15.90} UT
GRB_PHI:         344.00 [deg]
GRB_THETA:        95.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   41731 (Gnd S/W Version number)
SUN_POSTN:       266.41d {+17h 45m 38s}  -23.39d {-23d 23' 41"}
SUN_DIST:         51.62 [deg]   Sun_angle= -1.4 [hr] (East of Sun)
MOON_POSTN:      316.07d {+21h 04m 16s}  -21.10d {-21d 06' 05"}
MOON_DIST:        53.27 [deg]
MOON_ILLUM:      15 [%]
GAL_COORDS:       56.28,  7.38 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      292.61, 46.22 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2020/bn201218177/quicklook/glg_lc_medres34_bn201218177.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_629957660.fits
COMMENTS:        Fermi-GBM Ground-calculated Coordinates.  
COMMENTS:        This is likely a Long GRB.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        The LC_URL file will not be created/available until ~15 min after the trigger.  
COMMENTS:        The POS_MAP_URL file will not be created/available until ~1.5 min after the notice.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Fri 18 Dec 20 04:23:39 UT
NOTICE_TYPE:     Fermi-GBM Final Position
RECORD_NUM:      0
TRIGGER_NUM:     629957660
GRB_RA:          286.880d {+19h 07m 31s} (J2000),
                 287.098d {+19h 08m 24s} (current),
                 286.359d {+19h 05m 26s} (1950)
GRB_DEC:         +24.180d {+24d 10' 48"} (J2000),
                 +24.214d {+24d 12' 51"} (current),
                 +24.100d {+24d 06' 01"} (1950)
GRB_ERROR:       1.00 [deg radius, statistical only]
GRB_DATE:        19201 TJD;   353 DOY;   20/12/18
GRB_TIME:        15255.90 SOD {04:14:15.90} UT
GRB_PHI:         344.00 [deg]
GRB_THETA:        95.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   41731 (Gnd S/W Version number)
SUN_POSTN:       266.42d {+17h 45m 40s}  -23.40d {-23d 23' 41"}
SUN_DIST:         51.67 [deg]   Sun_angle= -1.4 [hr] (East of Sun)
MOON_POSTN:      316.14d {+21h 04m 34s}  -21.09d {-21d 05' 06"}
MOON_DIST:        53.39 [deg]
MOON_ILLUM:      15 [%]
GAL_COORDS:       56.33,  7.46 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      292.55, 46.31 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2020/bn201218177/quicklook/glg_lc_medres34_bn201218177.gif
LOC_URL:         http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2020/bn201218177/quicklook/glg_locplot_all_bn201218177.png
COMMENTS:        Fermi-GBM Final Position.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        The LC_URL file should be available by the time this FINAL notice is produced.  
COMMENTS:        This notice was generated completely by automated pipeline processing.  
COMMENTS:        This is likely a Long GRB.

GCN Circular #29081
The Fermi GBM team reports the detection of a likely LONG GRB
At 04:14:15 UT on 18 Dec 2020, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 201218A (trigger 629957660.899176 / 201218177).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 286.9, Dec = 24.2 (J2000 degrees, equivalent to J2000 19h 07m, 24d 11'), with a statistical uncertainty of 1.0 degrees.
The angle from the Fermi LAT boresight is 95.0 degrees.
The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2020/bn201218177/quicklook/glg_skymap_all_bn201218177.png
The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2020/bn201218177/quicklook/glg_healpix_all_bn201218177.fit
The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2020/bn201218177/quicklook/glg_lc_medres34_bn201218177.gif
GCN Circular #29083
B. Biltzinger, F. Kunzweiler, F. Berlato, J. Burgess & J. Greiner (all MPE Garching) report:
The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger 629957660 at 04:14:15 on 18 Dec. 2020 were automatically fitted for spectrum and sky location with BALROG (Burgess et al. 2018, MNRAS 476, 1427; Berlato et al. 2019, ApJ 873, 60).
The best-fit position (1 sigma statistical errors) is:
```
RA(2000.0) = 287.38+/-0.29 deg
Decl.(2000.0) = 26.80+/-0.30 deg
```
We estimate an additional systematic error of 1 deg.
Further details are available at: https://grb.mpe.mpg.de/grb/GRB201218177/
The Healpix map can be downloaded from: https://grb.mpe.mpg.de/grb/GRB201218177/healpix
The location parameters are available as JSON at: https://grb.mpe.mpg.de/grb/GRB201218177/json
GCN Circular #29087
V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva, D.Kuvshinov, D. Cheryasov (Lomonosov Moscow State University, SAI, Physics Department),
R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico Felix Aguilar OAFA),
R. Rebolo, M. Serra (The Instituto de Astrofisica de Canarias),
D. Buckley (South African Astronomical Observatory),
O.A. Gres, N.M. Budnev, O.Ershova (Irkutsk State University, API),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
V. Yurkov, A. Gabovich, Yu. Sergienko (Blagoveschensk Educational State University)
MASTER-IAC robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Spain (IAC Teide Observatory) started inspect of the Fermi GRB 201218A ( Fermi GBM team, GCN 29081) errorbox 53279 sec after notice time and 53345 sec after trigger time at 2020-12-18 19:03:21 UT, with upper limit up to 16.5 mag. Observations started at twilight. The observations began at zenith distance = 64 deg. The sun altitude is -11.5 deg.
The galactic latitude b = 7 deg., longitude l = 57 deg.
Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1505659
We obtain a following upper limits.
```
Tmid-T0  |      Date Time      |          Site       |             Coord (J2000)          |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________

   22028 | 2020-12-18 10:20:53 |             MASTER- | (19h 12m 49.70s , +21d 30m 56.1s) |   C |    60 | 15.4 |        
   23215 | 2020-12-18 10:40:41 |             MASTER- | (19h 12m 56.18s , +21d 28m 59.3s) |   C |    60 | 13.0 |        
   53435 | 2020-12-18 19:03:21 |          MASTER-IAC | (19h 01m 57.16s , +23d 55m 31.2s) |   C |   180 | 16.5 |        
```
Filter C is a clear (unfiltred) band.
The observation and reduction will continue. The message may be cited.
GCN Circular #29090
K. Hurley, on behalf of the IPN,
I. G. Mitrofanov, D. V. Golovin, A. S. Kozyrev, M. L. Litvak, and A. B. Sanin, on behalf of the HEND-Odyssey GRB team,
D. Svinkin, S. Golenetskii, R. Aptekar, D. Frederiks, A. Ridnaia, and T. Cline on behalf of the Konus-Wind team,
S. Barthelmy, J. Cummings, H. Krimm, and D. Palmer, on behalf of the Swift-BAT team,
and
W. Boynton, C. Fellows, K. Harshman, H. Enos, and R. Starr, on behalf of the GRS-Odyssey GRB team, report:
The long-duration, very bright GRB 201218A (Fermi-GBM detection: The Fermi GBM team, GCN Circ. 29081; BALROG localization: Biltzinger et al., GCN Circ. 29083) has been detected by Fermi (GBM trigger 629957660), Konus-Wind, Mars-Odyssey (HEND), and Swift (BAT), so far, at about 15256 s UT (04:14:16). The burst was outside the coded field of view of the BAT.
We have triangulated it to a preliminary, 3 sigma error box whose coordinates are:
```
  ---------------------------------------------
   RA(2000), deg                 Dec(2000), deg
  ---------------------------------------------
  Center:
   288.498 (19h 13m 59s) +28.356 (+28d 21' 23")
  Corners:
   288.470 (19h 13m 53s) +28.144 (+28d 08' 38")
   288.400 (19h 13m 36s) +28.556 (+28d 33' 23")
   288.526 (19h 14m 06s) +28.569 (+28d 34' 08")
   288.596 (19h 14m 23s) +28.156 (+28d 09' 22")
  ---------------------------------------------
```
The error box area is 168 sq. arcmin, and its maximum dimension is 26 arcmin (the minimum one is 6.7 arcmin). The Sun distance was 56 deg.
The IPN localization is consistent with, but reduces the area of, the Fermi RoboBA and BALROG localizations (GCN Circ. 29081 and 29083).
A triangulation map is posted at http://www.ioffe.ru/LEA/GRBs/GRB201218_T15255/IPN/
The Konus-Wind time history and spectrum will be given in a forthcoming GCN Circular.
GCN Circular #29095
D. Svinkin, S. Golenetskii, R. Aptekar, D. Frederiks, M. Ulanov, A. Tsvetkova, A. Lysenko, A. Ridnaia, and T. Cline on behalf of the Konus-Wind team, report:
The long-duration, very bright GRB 201218A (Fermi-GBM detection: The Fermi GBM team, GCN Circ. 29081; BALROG localization: Biltzinger et al., GCN Circ. 29083; IPN triangulation: Hurley et al., GCN Circ. 29090) triggered Konus-Wind at T0=15253.184 s UT (04:14:13.184).
The burst light curve shows a multipeaked structure which starts at ~T0-17 s and has a total duration of ~55 s, followed by a weak tail seen up to ~T0+120 s. The emission is seen up to ~5 MeV.
The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB201218_T15255
As observed by Konus-Wind, the burst had a fluence of 1.35(-0.07,+0.07)x10^-4 erg/cm2, and a 64-ms peak flux, measured from T0+8.544 s, of 2.23(-0.28,+0.29)x10^-5 erg/cm2/s (both in the 20 keV - 10 MeV energy range).
The time-averaged spectrum of the burst (measured from T0 to T0+20.736 s) is best fit in the 20 keV - 10 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.82(-0.03,+0.03), the high energy photon index beta = -3.00(-0.50,+0.27), the peak energy Ep = 472(-24,+23) keV (chi2 = 139/97 dof).
The spectrum near the maximum count rate (measured from T0+8.192 to T0+8.704 s) is best fit in the 20 keV - 10 MeV range by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = -0.72(-0.09,+0.09) and Ep = 605(-68,+80) keV (chi2 = 51/63 dof). Fitting by a GRB (Band) model yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -2.5 (chi2 = 50/62 dof).
All the quoted errors are at the 90% confidence level. All the quoted values are preliminary.

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Jochen Greiner, last update: 25-Dec-2020 [Disclaimer]