Gamma-ray Burst 201221D

(All information courtesy of the instrument teams.)

Previous IAU Circulars

• none

• GCN/BACODINE POSITION NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Mon 21 Dec 20 23:06:55 UT
  NOTICE_TYPE:     Swift-BAT GRB Position
  TRIGGER_NUM:     1014037,   Seg_Num: 0
  GRB_RA:          171.049d {+11h 24m 12s} (J2000),
                   171.334d {+11h 25m 20s} (current),
                   170.368d {+11h 21m 28s} (1950)
  GRB_DEC:         +42.144d {+42d 08' 39"} (J2000),
                   +42.029d {+42d 01' 44"} (current),
                   +42.419d {+42d 25' 09"} (1950)
  GRB_ERROR:       3.00 [arcmin radius, statistical only]
  GRB_INTEN:       1329 [cnts]    Image_Peak=188 [image_cnts]
  TRIGGER_DUR:     0.128 [sec] 
  TRIGGER_INDEX:   32     E_range: 25-100 keV
  BKG_INTEN:       17016 [cnts]
  BKG_TIME:        83181.80 SOD {23:06:21.80} UT
  BKG_DUR:         8 [sec]
  GRB_DATE:        19204 TJD;   356 DOY;   20/12/21
  GRB_TIME:        83194.28 SOD {23:06:34.28} UT
  GRB_PHI:          70.36 [deg]
  GRB_THETA:        35.65 [deg]
  SOLN_STATUS:     0x20000003
  RATE_SIGNIF:     78.12 [sigma]
  IMAGE_SIGNIF:    13.97 [sigma]
  MERIT_PARAMS:     +1  +0  +0  -3  +2  +3  +0  +0 +37  +0 
  SUN_POSTN:       270.61d {+18h 02m 26s}  -23.43d {-23d 26' 04"}
  SUN_DIST:        112.09 [deg]   Sun_angle= 6.6 [hr] (West of Sun)
  MOON_POSTN:        2.44d {+00h 09m 45s}   -4.64d {-04d 38' 11"}
  MOON_DIST:       141.32 [deg]
  MOON_ILLUM:      50 [%]
  GAL_COORDS:      167.13, 66.73 [deg] galactic lon,lat of the burst (or transient)
  ECL_COORDS:      153.03, 34.73 [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 = 142.30,19.25 [deg].  
  COMMENTS:           
  COMMENTS:        NOTE: This BAT event is temporally(0.0<100sec) coincident with the FERMI_GBM event (trignum=630284799).  
  

• GCN NOTICE
  

  TITLE:           GCN/FERMI NOTICE
  NOTICE_DATE:     Mon 21 Dec 20 23:06:58 UT
  NOTICE_TYPE:     Fermi-GBM Flight Position
  RECORD_NUM:      46
  TRIGGER_NUM:     630284799
  GRB_RA:          167.400d {+11h 09m 36s} (J2000),
                   167.696d {+11h 10m 47s} (current),
                   166.692d {+11h 06m 46s} (1950)
  GRB_DEC:         +46.983d {+46d 58' 60"} (J2000),
                   +46.869d {+46d 52' 09"} (current),
                   +47.255d {+47d 15' 17"} (1950)
  GRB_ERROR:       3.75 [deg radius, statistical plus systematic]
  GRB_INTEN:       2118 [cnts/sec]
  DATA_SIGNIF:     26.10 [sigma]
  INTEG_TIME:      0.128 [sec]
  GRB_DATE:        19204 TJD;   356 DOY;   20/12/21
  GRB_TIME:        83194.33 SOD {23:06:34.33} UT
  GRB_PHI:         243.00 [deg]
  GRB_THETA:        85.00 [deg]
  DATA_TIME_SCALE: 0.1280 [sec]
  HARD_RATIO:      0.79
  LOC_ALGORITHM:   3 (version number of)
  MOST_LIKELY:      67%  Distant Particles
  2nd_MOST_LIKELY:  32%  GRB
  DETECTORS:       0,0,0, 0,0,0, 1,1,1, 0,0,0, 0,0,
  SUN_POSTN:       270.61d {+18h 02m 26s}  -23.43d {-23d 26' 04"}
  SUN_DIST:        115.49 [deg]   Sun_angle= 6.9 [hr] (West of Sun)
  MOON_POSTN:        2.44d {+00h 09m 45s}   -4.64d {-04d 38' 10"}
  MOON_DIST:       135.89 [deg]
  MOON_ILLUM:      50 [%]
  GAL_COORDS:      161.34, 61.84 [deg] galactic lon,lat of the burst (or transient)
  ECL_COORDS:      147.30, 37.71 [deg] ecliptic lon,lat of the burst (or transient)
  LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2020/bn201221963/quicklook/glg_lc_medres34_bn201221963.gif
  COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
  COMMENTS:        This trigger occurred at longitude,latitude = 247.92,22.88 [deg].  
  COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.  
  COMMENTS:           
  COMMENTS:        NOTE: This GBM event is temporally(0.0<100sec) coincident with the SWIFT_BAT event (trignum=1014037).  
  

  
• GCN NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Mon 21 Dec 20 23:08:07 UT
  NOTICE_TYPE:     Swift-XRT Nack-Position
  TRIGGER_NUM:     1014037,   Seg_Num: 0
  POINT_RA:        171.088d {+11h 24m 21s} (J2000)
  POINT_DEC:       +42.138d {+42d 08' 17"} (J2000)
  IMG_START_DATE:  19204 TJD;   356 DOY;   20/12/21
  IMG_START_TIME:  83281.72 SOD {23:08:01.72} UT,   87.4 [sec] since BAT Trigger Time
  COUNTS:          1    Min_needed= 20
  STD_DEV:         0.00   Max_StdDev_for_Good=28.44 [arcsec]
  PH2_ITER:        0    Max_iter_allowed= 4
  ERROR_CODE:      1
  COMMENTS:        SWIFT-XRT Nack Position.  
  COMMENTS:        No source found in the image.  
  

• GCN NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Mon 21 Dec 20 23:10:08 UT
  NOTICE_TYPE:     Swift-BAT GRB Lightcurve
  TRIGGER_NUM:     1014037,   Seg_Num: 0
  GRB_RA:          171.049d {+11h 24m 12s} (J2000),
                   171.334d {+11h 25m 20s} (current),
                   170.368d {+11h 21m 28s} (1950)
  GRB_DEC:         +42.144d {+42d 08' 39"} (J2000),
                   +42.029d {+42d 01' 44"} (current),
                   +42.419d {+42d 25' 09"} (1950)
  GRB_DATE:        19204 TJD;   356 DOY;   20/12/21
  GRB_TIME:        83194.28 SOD {23:06:34.28} UT
  TRIGGER_INDEX:   32
  GRB_PHI:          70.36 [deg]
  GRB_THETA:        35.65 [deg]
  DELTA_TIME:      32.00 [sec]
  TRIGGER_DUR:     0.128 [sec] 
  SOLN_STATUS:     0x3
  RATE_SIGNIF:     78.12 [sigma]
  IMAGE_SIGNIF:    13.97 [sigma]
  LC_URL:          sw01014037000msb.lc
  SUN_POSTN:       270.61d {+18h 02m 27s}  -23.43d {-23d 26' 04"}
  SUN_DIST:        112.09 [deg]   Sun_angle= 6.6 [hr] (West of Sun)
  MOON_POSTN:        2.46d {+00h 09m 51s}   -4.63d {-04d 37' 31"}
  MOON_DIST:       141.30 [deg]
  MOON_ILLUM:      50 [%]
  GAL_COORDS:      167.13, 66.73 [deg] galactic lon,lat of the burst (or transient)
  ECL_COORDS:      153.03, 34.73 [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 = 142.30,19.25 [deg].  
  

  
• GCN NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Mon 21 Dec 20 23:10:53 UT
  NOTICE_TYPE:     Swift-UVOT Source List
  TRIGGER_NUM:     1014037,   Seg_Num: 0
  POINT_RA:        171.088d {+11h 24m 21s} (J2000)
  POINT_DEC:       +42.138d {+42d 08' 17"} (J2000)
  POINT_ROLL:      102.045d
  IMG_START_DATE:  19204 TJD;   356 DOY;   20/12/21
  IMG_START_TIME:  83286.66 SOD {23:08:06.66} UT,   92.4 [sec] since BAT Trigger Time
  FILTER:          10, White
  BKG_MEAN:        3.766
  N_STARS:         11
  X_OFFSET:        284 [pixels]
  Y_OFFSET:        669 [pixels]
  X_MAX:           1243 [pixels]
  Y_MAX:           1628 [pixels]
  DET_THRESH:      16
  PHOTO_THRESH:    9
  SL_URL:          sw01014037000msufc0092.fits
  SUN_POSTN:       270.61d {+18h 02m 27s}  -23.43d {-23d 26' 04"}
  SUN_DIST:        112.07 [deg]   Sun_angle= 6.6 [hr] (West of Sun)
  MOON_POSTN:        2.47d {+00h 09m 52s}   -4.62d {-04d 37' 21"}
  MOON_DIST:       141.31 [deg]
  MOON_ILLUM:      50 [%]
  GAL_COORDS:      167.10, 66.75 [deg] galactic lon,lat of the pointing direction
  ECL_COORDS:      153.06, 34.74 [deg] ecliptic lon,lat of the pointing direction
  COMMENTS:        SWIFT-UVOT Source List.  
  

• GCN NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Mon 21 Dec 20 23:11:09 UT
  NOTICE_TYPE:     Swift-UVOT Processed Source List
  TRIGGER_NUM:     1014037,   Seg_Num: 0
  POINT_RA:        171.088d {+11h 24m 21s} (J2000)
  POINT_DEC:       +42.138d {+42d 08' 17"} (J2000)
  POINT_ROLL:      102.045d
  IMG_START_DATE:  19204 TJD;   356 DOY;   20/12/21
  IMG_START_TIME:  83286.66 SOD {23:08:06.66} UT,   92.4 [sec] since BAT Trigger Time
  FILTER:          10, White
  BKG_MEAN:        3.766
  N_STARS:         11
  X_OFFSET:        284 [pixels]
  Y_OFFSET:        669 [pixels]
  X_MAX:           1243 [pixels]
  Y_MAX:           1628 [pixels]
  DET_THRESH:      16
  PHOTO_THRESH:    9
  SL_URL:          sw01014037000msufc0092.fits
  SUN_POSTN:       270.61d {+18h 02m 27s}  -23.43d {-23d 26' 04"}
  SUN_DIST:        112.07 [deg]   Sun_angle= 6.6 [hr] (West of Sun)
  MOON_POSTN:        2.47d {+00h 09m 53s}   -4.62d {-04d 37' 18"}
  MOON_DIST:       141.31 [deg]
  MOON_ILLUM:      50 [%]
  GAL_COORDS:      167.10, 66.75 [deg] galactic lon,lat of the pointing direction
  ECL_COORDS:      153.06, 34.74 [deg] ecliptic lon,lat of the pointing direction
  COMMENTS:        SWIFT-UVOT Processed Source List.  
  COMMENTS:        All 4 attachments are included.  
  

  
• GCN NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Mon 21 Dec 20 23:11:41 UT
  NOTICE_TYPE:     Swift-XRT Position
  TRIGGER_NUM:     1014037,   Seg_Num: 0
  GRB_RA:          171.0587d {+11h 24m 14.08s} (J2000),
                   171.3436d {+11h 25m 22.45s} (current),
                   170.3774d {+11h 21m 30.56s} (1950)
  GRB_DEC:         +42.1433d {+42d 08' 35.8"} (J2000),
                   +42.0279d {+42d 01' 40.4"} (current),
                   +42.4181d {+42d 25' 05.0"} (1950)
  GRB_ERROR:       5.7 [arcsec radius, statistical plus systematic, 90% containment]
  GRB_INTEN:       1.00e-10 [erg/cm2/sec]
  GRB_SIGNIF:      10.00 [sigma]
  IMG_START_DATE:  19204 TJD;   356 DOY;   20/12/21
  IMG_START_TIME:  83298.00 SOD {23:08:18.00} UT,   103.7 [sec] since BAT Trigger Time
  TAM[0-3]:        100.00 100.00 100.00 100.00
  AMPLIFIER:       1
  WAVEFORM:        31
  SUN_POSTN:       270.61d {+18h 02m 27s}  -23.43d {-23d 26' 04"}
  SUN_DIST:        112.09 [deg]   Sun_angle= 6.6 [hr] (West of Sun)
  MOON_POSTN:        2.47d {+00h 09m 54s}   -4.62d {-04d 37' 11"}
  MOON_DIST:       141.30 [deg]
  MOON_ILLUM:      50 [%]
  GAL_COORDS:      167.12, 66.73 [deg] galactic lon,lat of the burst
  ECL_COORDS:      153.04, 34.73 [deg] ecliptic lon,lat of the burst
  COMMENTS:        SWIFT-XRT Coordinates.  
  COMMENTS:        This Notice was ground-generated -- not flight-generated.  
  COMMENTS:        TAM values, flux and significance fields are not valid.  
  COMMENTS:        This position was automatically generated on the ground using  
  COMMENTS:        Photon Counting data telemetered via TDRSS (SPER data).  
  COMMENTS:        See http://www.swift.ac.uk/sper/docs.php for details.  
  COMMENTS:        The probability that this is a serendipitous source in the  
  COMMENTS:        SPER window is 0.58% < P(seren) < 1.1%.  
  

• GCN NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Mon 21 Dec 20 23:12:43 UT
  NOTICE_TYPE:     Swift-UVOT Image
  TRIGGER_NUM:     1014037,   Seg_Num: 0
  POINT_RA:        171.088d {+11h 24m 21s} (J2000)
  POINT_DEC:       +42.138d {+42d 08' 17"} (J2000)
  ROLL:            102.045d
  IMG_START_DATE:  19204 TJD;   356 DOY;   20/12/21
  IMG_START_TIME:  83286.66 SOD {23:08:06.66} UT,   92.4 [sec] since BAT Trigger Time
  FILTER:          10, White
  EXPOSURE_ID:     630284912
  X_OFFSET:        603 [pixels]
  Y_OFFSET:        988 [pixels]
  WIDTH:           160 [pixels]
  HEIGHT:          160 [pixels]
  X_GRB_POS:       763
  Y_GRB_POS:       1148
  BINNING_INDEX:   1
  IM_URL:          sw01014037000msuni0119.fits
  SUN_POSTN:       270.61d {+18h 02m 27s}  -23.43d {-23d 26' 04"}
  SUN_DIST:        112.07 [deg]   Sun_angle= 6.6 [hr] (West of Sun)
  MOON_POSTN:        2.48d {+00h 09m 55s}   -4.62d {-04d 36' 58"}
  MOON_DIST:       141.30 [deg]
  MOON_ILLUM:      50 [%]
  GAL_COORDS:      167.10, 66.75 [deg] galactic lon,lat of the pointing direction
  ECL_COORDS:      153.06, 34.74 [deg] ecliptic lon,lat of the pointing direction
  COMMENTS:        SWIFT-UVOT Image.  
  COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
  COMMENTS:        The image has 2x2 binning (compression).  
  

  
• GCN NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Mon 21 Dec 20 23:12:49 UT
  NOTICE_TYPE:     Swift-UVOT Processed Image
  TRIGGER_NUM:     1014037,   Seg_Num: 0
  POINT_RA:        171.088d {+11h 24m 21s} (J2000)
  POINT_DEC:       +42.138d {+42d 08' 17"} (J2000)
  ROLL:            102.045d
  IMG_START_DATE:  19204 TJD;   356 DOY;   20/12/21
  IMG_START_TIME:  83286.66 SOD {23:08:06.66} UT,   92.4 [sec] since BAT Trigger Time
  FILTER:          10, White
  EXPOSURE_ID:     630284912
  X_OFFSET:        603 [pixels]
  Y_OFFSET:        988 [pixels]
  WIDTH:           160 [pixels]
  HEIGHT:          160 [pixels]
  X_GRB_POS:       763
  Y_GRB_POS:       1148
  BINNING_INDEX:   1
  IM_URL:          sw01014037000msuni0119.fits
  SUN_POSTN:       270.61d {+18h 02m 27s}  -23.43d {-23d 26' 04"}
  SUN_DIST:        112.07 [deg]   Sun_angle= 6.6 [hr] (West of Sun)
  MOON_POSTN:        2.48d {+00h 09m 56s}   -4.62d {-04d 36' 57"}
  MOON_DIST:       141.30 [deg]
  MOON_ILLUM:      50 [%]
  GAL_COORDS:      167.10, 66.75 [deg] galactic lon,lat of the pointing direction
  ECL_COORDS:      153.06, 34.74 [deg] ecliptic lon,lat of the pointing direction
  COMMENTS:        SWIFT-UVOT Processed Image.  
  COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
  COMMENTS:        The image has 2x2 binning (compression).  
  COMMENTS:        All 4 attachments are included.  
  

  
• GCN NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Mon 21 Dec 20 23:17:57 UT
  NOTICE_TYPE:     Swift-UVOT Source List
  TRIGGER_NUM:     1014037,   Seg_Num: 0
  POINT_RA:        171.091d {+11h 24m 22s} (J2000)
  POINT_DEC:       +42.139d {+42d 08' 20"} (J2000)
  POINT_ROLL:      102.046d
  IMG_START_DATE:  19204 TJD;   356 DOY;   20/12/21
  IMG_START_TIME:  83498.90 SOD {23:11:38.90} UT,   304.6 [sec] since BAT Trigger Time
  FILTER:          7, U
  BKG_MEAN:        2.108
  N_STARS:         20
  X_OFFSET:        44 [pixels]
  Y_OFFSET:        429 [pixels]
  X_MAX:           1483 [pixels]
  Y_MAX:           1868 [pixels]
  DET_THRESH:      12
  PHOTO_THRESH:    6
  SL_URL:          sw01014037000msufc0304.fits
  SUN_POSTN:       270.62d {+18h 02m 28s}  -23.43d {-23d 26' 04"}
  SUN_DIST:        112.07 [deg]   Sun_angle= 6.6 [hr] (West of Sun)
  MOON_POSTN:        2.52d {+00h 10m 05s}   -4.60d {-04d 35' 53"}
  MOON_DIST:       141.28 [deg]
  MOON_ILLUM:      50 [%]
  GAL_COORDS:      167.10, 66.75 [deg] galactic lon,lat of the pointing direction
  ECL_COORDS:      153.06, 34.74 [deg] ecliptic lon,lat of the pointing direction
  COMMENTS:        SWIFT-UVOT Source List.  
  

• GCN NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Mon 21 Dec 20 23:18:11 UT
  NOTICE_TYPE:     Swift-UVOT Processed Source List
  TRIGGER_NUM:     1014037,   Seg_Num: 0
  POINT_RA:        171.091d {+11h 24m 22s} (J2000)
  POINT_DEC:       +42.139d {+42d 08' 20"} (J2000)
  POINT_ROLL:      102.046d
  IMG_START_DATE:  19204 TJD;   356 DOY;   20/12/21
  IMG_START_TIME:  83498.90 SOD {23:11:38.90} UT,   304.6 [sec] since BAT Trigger Time
  FILTER:          7, U
  BKG_MEAN:        2.108
  N_STARS:         20
  X_OFFSET:        44 [pixels]
  Y_OFFSET:        429 [pixels]
  X_MAX:           1483 [pixels]
  Y_MAX:           1868 [pixels]
  DET_THRESH:      12
  PHOTO_THRESH:    6
  SL_URL:          sw01014037000msufc0304.fits
  SUN_POSTN:       270.62d {+18h 02m 28s}  -23.43d {-23d 26' 04"}
  SUN_DIST:        112.07 [deg]   Sun_angle= 6.6 [hr] (West of Sun)
  MOON_POSTN:        2.52d {+00h 10m 05s}   -4.60d {-04d 35' 50"}
  MOON_DIST:       141.28 [deg]
  MOON_ILLUM:      50 [%]
  GAL_COORDS:      167.10, 66.75 [deg] galactic lon,lat of the pointing direction
  ECL_COORDS:      153.06, 34.74 [deg] ecliptic lon,lat of the pointing direction
  COMMENTS:        SWIFT-UVOT Processed Source List.  
  COMMENTS:        All 4 attachments are included.  
  

  
• GCN Circular #29112
  K. L. Page (U Leicester), S. D. Barthelmy (GSFC), J.D. Gropp (PSU), J. A. Kennea (PSU), N. J. Klingler (PSU), S. Laha (GSFC/UMBC/CRESST), A. Y. Lien (GSFC/UMBC), F. E. Marshall (NASA/GSFC), B. Sbarufatti (PSU), M. H. Siegel (PSU) and A. Tohuvavohu (U Toronto) report on behalf of the Neil Gehrels Swift Observatory Team:
  At 23:06:34 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 201221D (trigger=1014037). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 171.049, +42.144 which is

     RA(J2000) = 11h 24m 12s
     Dec(J2000) = +42d 08' 39"
  

  with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single-peaked structure with a duration of about 0.3 sec. The peak count rate was ~9000 counts/sec (15-350 keV), at ~0 sec after the trigger.
  The XRT began observing the field at 23:08:01.7 UT, 87.4 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 171.05873, 42.14332 which is equivalent to:

     RA(J2000)  = 11h 24m 14.10s
     Dec(J2000) = +42d 08' 36.0"
  

  with an uncertainty of 5.7 arcseconds (radius, 90% containment). This location is 26 arcseconds from the BAT onboard position, within the BAT error circle. This position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. We cannot determine whether the source is fading at the present time. No spectrum from the promptly downlinked event data is yet available to determine the column density.
  UVOT took a finding chart exposure of 150 seconds with the White filter starting 92 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. The list of sources is typically complete to about 18 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.02.
  Burst Advocate for this burst is K. L. Page (klp5 AT leicester.ac.uk). 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 NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Mon 21 Dec 20 23:18:20 UT
  NOTICE_TYPE:     Swift-XRT Position UPDATE
  TRIGGER_NUM:     1014037,   Seg_Num: 0
  GRB_RA:          171.0586d {+11h 24m 14.06s} (J2000),
                   171.3435d {+11h 25m 22.43s} (current),
                   170.3772d {+11h 21m 30.53s} (1950)
  GRB_DEC:         +42.1437d {+42d 08' 37.3"} (J2000),
                   +42.0283d {+42d 01' 41.9"} (current),
                   +42.4185d {+42d 25' 06.4"} (1950)
  GRB_ERROR:       4.2 [arcsec radius, statistical plus systematic, 90% containment]
  GRB_INTEN:       1.00e-10 [erg/cm2/sec]
  GRB_SIGNIF:      10.00 [sigma]
  IMG_START_DATE:  19204 TJD;   356 DOY;   20/12/21
  IMG_START_TIME:  83298.00 SOD {23:08:18.00} UT,   103.7 [sec] since BAT Trigger Time
  TAM[0-3]:        100.00 100.00 100.00 100.00
  AMPLIFIER:       1
  WAVEFORM:        31
  SUN_POSTN:       270.62d {+18h 02m 28s}  -23.43d {-23d 26' 04"}
  SUN_DIST:        112.09 [deg]   Sun_angle= 6.6 [hr] (West of Sun)
  MOON_POSTN:        2.52d {+00h 10m 06s}   -4.60d {-04d 35' 48"}
  MOON_DIST:       141.26 [deg]
  MOON_ILLUM:      50 [%]
  GAL_COORDS:      167.12, 66.73 [deg] galactic lon,lat of the burst
  ECL_COORDS:      153.04, 34.74 [deg] ecliptic lon,lat of the burst
  COMMENTS:        SWIFT-XRT Coordinates.  
  COMMENTS:        This Notice was ground-generated -- not flight-generated.  
  COMMENTS:        This is an Update Notice -- the RA,Dec values herein supersede the previous XRT_POS Notice.  
  COMMENTS:        TAM values, flux and significance fields are not valid.  
  COMMENTS:        This position was automatically generated on the ground using  
  COMMENTS:        Photon Counting data telemetered via TDRSS (SPER data).  
  COMMENTS:        See http://www.swift.ac.uk/sper/docs.php for details.  
  COMMENTS:        This position was enhanced using UVOT field astrometry.  
  COMMENTS:        The probability that this is a serendipitous source in the  
  COMMENTS:        SPER window is 0.58% < P(seren) < 1.1%.  
  

• GCN NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Mon 21 Dec 20 23:19:49 UT
  NOTICE_TYPE:     Swift-UVOT Image
  TRIGGER_NUM:     1014037,   Seg_Num: 0
  POINT_RA:        171.091d {+11h 24m 22s} (J2000)
  POINT_DEC:       +42.139d {+42d 08' 20"} (J2000)
  ROLL:            102.046d
  IMG_START_DATE:  19204 TJD;   356 DOY;   20/12/21
  IMG_START_TIME:  83498.90 SOD {23:11:38.90} UT,   304.6 [sec] since BAT Trigger Time
  FILTER:          7, U
  EXPOSURE_ID:     630285125
  X_OFFSET:        603 [pixels]
  Y_OFFSET:        988 [pixels]
  WIDTH:           160 [pixels]
  HEIGHT:          160 [pixels]
  X_GRB_POS:       763
  Y_GRB_POS:       1148
  BINNING_INDEX:   1
  IM_URL:          sw01014037000msuni0331.fits
  SUN_POSTN:       270.62d {+18h 02m 29s}  -23.43d {-23d 26' 04"}
  SUN_DIST:        112.07 [deg]   Sun_angle= 6.6 [hr] (West of Sun)
  MOON_POSTN:        2.54d {+00h 10m 08s}   -4.59d {-04d 35' 30"}
  MOON_DIST:       141.27 [deg]
  MOON_ILLUM:      50 [%]
  GAL_COORDS:      167.10, 66.75 [deg] galactic lon,lat of the pointing direction
  ECL_COORDS:      153.06, 34.74 [deg] ecliptic lon,lat of the pointing direction
  COMMENTS:        SWIFT-UVOT Image.  
  COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
  COMMENTS:        The image has 2x2 binning (compression).  
  

  
• GCN NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Mon 21 Dec 20 23:19:56 UT
  NOTICE_TYPE:     Swift-UVOT Processed Image
  TRIGGER_NUM:     1014037,   Seg_Num: 0
  POINT_RA:        171.091d {+11h 24m 22s} (J2000)
  POINT_DEC:       +42.139d {+42d 08' 20"} (J2000)
  ROLL:            102.046d
  IMG_START_DATE:  19204 TJD;   356 DOY;   20/12/21
  IMG_START_TIME:  83498.90 SOD {23:11:38.90} UT,   304.6 [sec] since BAT Trigger Time
  FILTER:          7, U
  EXPOSURE_ID:     630285125
  X_OFFSET:        603 [pixels]
  Y_OFFSET:        988 [pixels]
  WIDTH:           160 [pixels]
  HEIGHT:          160 [pixels]
  X_GRB_POS:       763
  Y_GRB_POS:       1148
  BINNING_INDEX:   1
  IM_URL:          sw01014037000msuni0331.fits
  SUN_POSTN:       270.62d {+18h 02m 29s}  -23.43d {-23d 26' 04"}
  SUN_DIST:        112.07 [deg]   Sun_angle= 6.6 [hr] (West of Sun)
  MOON_POSTN:        2.54d {+00h 10m 09s}   -4.59d {-04d 35' 28"}
  MOON_DIST:       141.27 [deg]
  MOON_ILLUM:      50 [%]
  GAL_COORDS:      167.10, 66.75 [deg] galactic lon,lat of the pointing direction
  ECL_COORDS:      153.06, 34.74 [deg] ecliptic lon,lat of the pointing direction
  COMMENTS:        SWIFT-UVOT Processed Image.  
  COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
  COMMENTS:        The image has 2x2 binning (compression).  
  COMMENTS:        All 4 attachments are included.  
  

  
• GCN Circular #29113
  P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team:
  Using promptly downlinked XRT event data for GRB 201221D, we find an enhanced XRT position of the afterglow: RA, Dec: 171.0587, 42.1438 which is equivalent to:

     RA (J2000)  = 11 24 14.09
     Dec (J2000) = +42 08 37.5
  

  with an uncertainty of 4.2 arcseconds (radius, 90% confidence). Analysis of the promptly available data is online at http://www.swift.ac.uk/sper/1014037.
  Position enhancement is is described by Goad et al. (2007, A&A, 476, 1401) and Evans et al. (2009, MNRAS, 397, 1177).
  This circular is an official product of the Swift-XRT team.
• GCN Circular #29117
  D. B. Malesani (DTU Space) and E. Knudstrup (NOT and Aarhus Univ.) report on behalf of a larger collaboration:
  We observed the field of GRB 201221D (Page et al., GCN 29112) using the Nordic Optical Telescope (NOT) equipped with the ALFOSC imaging camera. Observations were carried out using the SDSS r (3x300 s) and z (5x200 s) filters. The data were taken as soon as the target rised, so at quite high airmass (2.9 to 2.3), yielding a seeing of ~1.5".
  Inside or close to the XRT werror circle (current uncertainty 4.2": https://www.swift.ac.uk/xrt_positions/), a very faint object is detected in the stack of the r-band images. Calibrating against nearby stars from the Pan-STARRS catalog, we measure r = 23.1 +- 0.3 (AB), at a mean epoch 2020 Dec 22.032 UT (1.67 hr after the GRB). Its coordinates are:

  RA = 11:24:14.02
  Dec = +42:08:39.97
  

  No object is visible at this location in the Pan-STARRS r-band image, which has however a limiting magnitude (r ~ 23.3 AB) comparable to our measurement. Given the lack of variability and the still relatively large XRT error circle size, we cannot confirm at the present time whether this object is associated with GRB 201221D. Further observations are planned.
• GCN Circular #29118
  D. Xu (NAOC), Z.P. Zhu (NAOC, HUST), S.Y. Fu, X. Liu (NAOC), X. Gao (Urumqi No.1 Senior High School), J.Z. Liu (XAO) report:
  We observed the field of GRB 201221D (Page et al., GCN 29112) using the NEXT-0.6m optical telescope located at Nanshan, Xinjiang, China. Observations automatically started at 23:07:39 UT on 2020-12-21, i.e., 65 s after the BAT trigger. We obtained 3x40s, 4x60s and 12x90s frames in the Sloan r-filter.
  No optical source is detected in our stacked image at the XRT enhanced position (Evans et al., GCN 29113), down to a upper limit of r~21.3, calibrated with the nearby PanSTARRS field.
• GCN Circular #29119
  P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester) report on behalf of the Swift-XRT team.
  Using 651 s of XRT Photon Counting mode data and 1 UVOT images for GRB 201221D, we find an astrometrically corrected X-ray position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 171.05914, +42.14319 which is equivalent to:

  RA (J2000): 11h 24m 14.19s
  Dec (J2000): +42d 08' 35.5"
  

  with an uncertainty of 3.9 arcsec (radius, 90% confidence).
  This position may be improved as more data are received. The latest position can be viewed at http://www.swift.ac.uk/xrt_positions. Position enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans et al. (2009, MNRAS, 397, 1177).
  This circular was automatically generated, and is an official product of the Swift-XRT team.
• GCN Circular #29122
  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-OAFA robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Argentina (OAFA observatory of San Juan National University) was pointed to the Swift GRB 201221D ( K. L. Page et al., GCN 29112) errorbox 33444 sec after notice time and 33517 sec after trigger time at 2020-12-22 08:25:12 UT, with upper limit up to 17.5 mag. Observations started at twilight. The observations began at zenith distance = 75 deg. The sun altitude is -12.3 deg.
  The galactic latitude b = 67 deg., longitude l = 167 deg.
  Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1508187
  We obtain a following upper limits.

  Tmid-T0  |          Site       |Filt.| Expt. | Limit| Comment
  _________|_____________________|_____|_______|______|________
  
     33608 |         MASTER-OAFA |   C |   180 | 17.5 |        
  

  Filter C is a clear (unfiltred) band.
  The observation and reduction will continue. The message may be cited.
• GCN Circular #29124
  P.A. Evans (U. Leicester), M. Capalbi (INAF-IASFPA), M. Perri (SSDC & INAF-OAR), V. D'Elia (SSDC & INAF-OAR), J. D. Gropp (PSU), J.A. Kennea (PSU), A. Tohuvavohu (U. Toronto), J.P. Osborne (U. Leicester) and K.L. Page report on behalf of the Swift-XRT team:
  We have analysed 6.7 ks of XRT data for GRB 201221D (Page et al. GCN Circ. 29112), from 96 s to 23.5 ks after the BAT trigger. The data are entirely in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Evans et al. (GCN Circ. 29113). The source is fading with alpha >0.4.
  The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/01014037.
  This circular is an official product of the Swift-XRT team.
• GCN Circular #29125
  Martin Jelinek and Jan Strobl (ASU CAS Ondrejov, CZ), Sergey Karpov, Martin Masek, Petr Janecek, Jakub Jurysek, Jan Ebr, Ronan Cunniffe, Petr Travnicek and Michael Prouza (Institute of Physics, Prague, CZ)
  report:
  The 25cm robotic telescope FRAM-ORM at La Palma (Spain) reacted robotically to the Swift alert of GRB201221D (Page et al., GCNC 29112 and Evans et al. GCNC 29113, GCNC 29119 and 29124), obtaining a series of 20s unfiltered images starting at 23:07:11.9 UT, i.e. 37.6s post trigger.
  We do not detect any new or strongly variable source neither in single images (detection limit R>~16.9) nor in a combined 40x20s frame (mean exp time 560s post trigger, with a limit R>~18.5). While we analysed the entire 25'x25' field of view centred at the XRT localization, we did pay a special attention to the location of the candidate afterglow mentioned by Malesani & Knudstrup (GCNC 29117) with a negative outcome.
• GCN Circular #29128
  S.Dichiara (UMD, NASA-GSFC), E. Troja (UMD, NASA-GSFC), S.B. Cenko (NASA-GSFC), B. O'Connor (GWU, UMD), P. Gatkine (Caltech), J.M. Durbak (UMD), A. Kutyrev (UMD, NASA-GSFC), S. Veilleux (UMD), report on behalf of a larger collaboration:
  We observed the short GRB 201221D (Page et al., GCN 29112) using the Large Monolithic Imager (LMI) on the 4.3m Lowell Discovery Telescope (LDT) at Happy Jack, AZ. Observations started on December 22, at 09:13:28 UT (about 10.11 hours after the Swift trigger) with SDSS r, i and z filters. Observations were taken at an airmass of about 1.3 and seeing of about 0.8".
  At the position of the optical candidate counterpart (Malesani et al., GCN 29117) we detect a source in all bands with r~23.9 AB mag and i~23.7 AB mag. This is fainter than the value reported by Malesani et al. (r~23.1 at 1 hr) and may suggest that the source faded between the two epochs. However, we note that at the same position a weak source is visible in archival Pan-STARRS images, which we suggest as the putative GRB host galaxy. Our observations could be dominated by the galaxy's contribution, and further observations to determine variability are planned.
  We thank the staff of the Lowell Discovery Telescope for assistance with these observations.
• GCN Circular #29129
  A. A. Breeveld (UCL-MSSL) and K. L. Page (U. Leicester) report on behalf of the Swift/UVOT team:
  The Swift/UVOT began settled observations of the field of GRB 201221D 92 s after the BAT trigger (Page et al., GCN Circ. 29112). No optical afterglow consistent with the NOT or XRT position (Malesani et al. GCN Circ. 29117; Evans et al. GCN Circ. 29119) is detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding chart (FC) exposure and subsequent exposures are:

  Filter         T_start(s)   T_stop(s)      Exp(s)         Mag
  
  white_FC            92          242          147         >20.3
  u_FC               305          554          246         >19.3
  white             4047         4247          197         >21.0
  v                  634         4657          216         >19.2
  u                  305         5110          282         >19.4
  w1                 684         5068          216         >19.7
  m2                4663         4863          197         >19.5
  w2                4253         4453          197         >19.9
  

  The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.02 in the direction of the burst (Schlegel et al. 1998).
• GCN Circular #29130
  D. Frederiks, S. Golenetskii, R.Aptekar, A.Lysenko, A. Ridnaia, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report:
  The short GRB 201221D (Swift detection: Page et al., GCN 29112) triggered Konus-Wind (KW) at T0=83197.636 s UT (23:06:37.636).
  The burst light curve shows a single pulse with the total duration of ~1.9 s (20-1500 keV). The emission is seen up to ~1 MeV.
  The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB201221_T83197/
  As observed by Konus-Wind, the burst had a fluence of (5.3 ± 1.1)x10^-7 erg/cm^2 and a 16-ms peak energy flux, measured from T0-0.016 s, of (6.6 ± 1.3)x10^-6 erg/cm^2/s (both in the 20 keV - 10 MeV energy range).
  The spectrum of the burst (measured from T0 to T0+0.128 s) is best fit in the 20 keV - 1.5 MeV range by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = -0.95(-0.52,+0.64) and Ep = 148(-37,+86) keV (chi2 = 19/20 dof). Fitting by a GRB (Band) model yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -2.1 (chi2 =19/19 dof).
  All the quoted errors are estimated at the 90% confidence level. All the presented results are preliminary.
• GCN Circular #29132
  A. de Ugarte Postigo (HETH/IAA-CSIC, DARK/NBI), D. A. Kann (HETH/IAA-CSIC), L. Izzo (DARK/NBI), C.C. Thoene, M. Blazek, J. F. Agui Fernandez (all HETH/IAA-CSIC) and G. Lombardi (GRANTECAN, IAC) report:
  We obtained spectroscopy of the optical counterpart (Malesani et al., GCN #29117) of the short GRB 201221D (Page et al., GCN #29112) with OSIRIS at the 10.4m Gran Telescopio Canarias (Roque de los Muchachos Observatory, La Palma, Spain), starting at 1:52 UT (2.757 hr after the burst). The observation consisted of 4 x 1200 s exposures with the R1000B grism, covering the range between 3700 and 7800 Angstrom.
  The spectrum shows a weak continuum over the full spectral range. There is a prominent emission feature that we identify as the [OII] 3727/3729 doublet at a redshift of 1.046. This line happens to lie in the atmospheric A band, and therefore must be quite strong to be detectable. There are also low significance absorption featuress coincident with FeII and MgII at a similar redshift (z = 1.045). We identify this as the redshift of GRB 201221D. We note this is a high redshift for a short GRB, and it represents one of the few short GRB spectra to show afterglow absorption features.
• GCN Circular #29133
  C. D. Kilpatrick (Northwestern), D. B. Malesani (DTU Space), and W. Fong (Northwestern), report:
  “We analyzed stacked images from the PS1 Data Release 1 image archive (Flewelling et al., 2016, arXiv:1612.05243) of the location of the short-duration GRB 201221D (Page et al., GCN 29112). We detected a single source centered at:

  RA (J2000): 11:24:14.01
  Dec (J2000): +42:08:39.69
  

  in PS1 g-band, 4.6 arcseconds from the latest enhanced XRT position of GRB 201221D (Evans et al., GCN 29119). We note that this places the centroid of the candidate host galaxy just outside the enhanced XRT error circle reported by GCN 29119, which has a radius of 3.9 arcsec (90% confidence), although consistent with the real-time XRT error circle at https://www.swift.ac.uk/xrt_positions/01014037/ . Performing forced aperture photometry on this position with an aperture fixed to the FWHM size in all PS1 bands (approximately 1.1 arcseconds), we found that this source has a brightness:

  g = 23.2 +/- 0.2 mag
  r > 23.2 mag
  i > 23.3 mag
  z > 22.2 mag
  y = 22.6+/-0.2 mag
  

  All magnitudes are given in AB. We note that this source is coincident with emission identified in Malesani & Knudstrup (GCN 29117) who find a source with r = 23.1+/-0.3 mag (AB) in NOT follow up imaging. Similarly, Dichiara et al. (GCN 29128) find r=23.9 mag and i=23.7 mag (AB), all of which are consistent with our limiting magnitudes. Based on this photometry, it is fully plausible that the reported optical candidate (GCN 29117, GCN 29128) is dominated by the host galaxy. However, the detection of absorption features in the spectrum (de Ugarte Postigo et al., GCN 29132), coupled with the possible r-band fading between NOT and DCT observations (reported in GCN 29128) may indicate the presence of an optical afterglow on top of the host emission. Image subtraction will be required to test for fading, and further, deep optical observations are encouraged.
• GCN Circular #29139
  H. A. Krimm (NSF), S. D. Barthelmy (GSFC), S. Laha (GSFC/UMBC), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), K. L. Page (U Leicester), D. M. Palmer (LANL), T. Sakamoto (AGU), M. Stamatikos (OSU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):
  Using the data set from T-239 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 201221D (trigger #1014037) (Page et al., GCN Circ. 29112). The BAT ground-calculated position is RA, Dec = 171.055, 42.152 deg which is

     RA(J2000)  =  11h 24m 13.2s
     Dec(J2000) = +42d 09' 08.4"
  

  with an uncertainty of 1.3 arcmin, (radius, sys+stat, 90% containment). The partial coding was 23%.
  The mask-weighted light curve shows a single-peaked structure that starts at ~T-0.06 s, peaks at ~T+0.02 s, and ends at ~T+0.2 s. T90 (15-350 keV) is 0.16 +- 0.04 sec (estimated error including systematics).
  The time-averaged spectrum from T-0.06 to T+0.17 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.56 +- 0.13. The fluence in the 15-150 keV band is 3.9 +- 0.4 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T-0.44 sec in the 15-150 keV band is 5.6 +- 0.5 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/1014037/BA/
• GCN Circular #29140
  R. Hamburg (UAH), C. Malacaria (NASA-MSFC/USRA), and C. Meegan (UAH) report on behalf of the Fermi GBM Team:
  "At 23:06:34.33 UT on 21 December 2020, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB 201221D (trigger 630284799 / 201221963) which was also detected by the Swift/BAT and Swift/XRT (Page et al. 2020, GCN 29112) and Konus-Wind (Frederiks et al. 2020, GCN 29130). This trigger was initially classified as a particle event by the flight software, but is in fact a GRB. The GBM on-ground location is consistent with the Swift position.
  The angle from the Fermi LAT boresight at the GBM trigger time is 89 degrees.
  The GBM light curve shows a single-peaked structure with a duration (T90) of about 0.14 s (50-300 keV). The time-averaged spectrum from T0-0.064 s to T0+0.192 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.20 +/- 0.16 and the cutoff energy, parameterized as Epeak, is 108 +/- 5 keV. A Band function fits the spectrum equally well with Epeak = 98 +/- 8 keV, alpha = 0.01 +/- 0.24 and beta = -3.3 +/- 0.5.
  The event fluence (10-1000 keV) in this time interval is (1.076 +/- 0.046)E-06 erg/cm^2. The 64-ms peak photon flux measured starting from T0+0.00 s in the 10-1000 keV band is 41 +/- 2 ph/s/cm^2.
  The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html
  For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/"
• GCN Circular #29141
  Igor Andreoni (Caltech), Michael M. Coughlin (UMN) on behalf of the Global Relay of Observatories Watching Transients Happen (GROWTH) collaboration
  We used the Sinistro camera on the 1-m LCO Global Telescope Network (LCOGT, Brown et al., 2013) to observe the afterglow of short-duration GRB 201221D (Page et al., GCN #29112).
  Two sets of 300s exposures were acquired in g-r-i bands between 2020-12-22T07:57 and 2020-12-22T08:47 UTC. The observations were performed under proposal IDs TOM2020A-008 (PI Andreoni) and NOAO2020B-005 (PI Coughlin).
  We do not identify any source within 3.9 arcsec of the enhanced Swift-XRT position (Evans et al., GCN #29119). Photometric upper limits, calibrated against Pan-STARRS DR1 magnitudes (Chambers et al., 2016), were measured to be g > 22.8, r > 22.2, and i > 21.5 mag (5-sigma) after image stacking.
  The candidate optical counterpart (transient or host galaxy: Malesani et al., GCN #29117; Dichiara et al., GCN #29128; de Ugarte Postigo et al., GCN #29132; Kilpatrick et al., GCN #29133) is too faint to be detectable in our observations, which did not show any significant brightening, as expected.
  We thank the TOM Community Development Program and the TOM Toolkit Workshop organizers for the generous LCOGT time allocation. GROWTH is a worldwide collaboration comprising Caltech, USA; IPAC, USA, WIS, Israel; OKC, Sweden; JSI/UMd, USA; U Washington, USA; DESY, Germany; MOST, Taiwan; UW Milwaukee, USA; LANL USA; Tokyo Tech, Japan; IIT-B, India; IIA, India; LJMU, TTU, USyd, Australia, and SDSU, USA. GROWTH acknowledges generous support of the NSF under PIRE Grant No 1545949.
• GCN Circular #29142
  J. Rastinejad, K. Paterson, C. D. Kilpatrick, W. Fong (Northwestern) report:
  We observed the location of the Swift GRB 201221D (Page et al., GCN 29112) with the MMT and Magellan Infrared Spectrograph (MMIRS) mounted on the MMT 6.5-meter telescope on Mount Hopkins, Arizona. We obtained 25x60-sec imaging in J-band at a mid-time of 2020 December 22.36 UT (0.40 days post-burst). Within the vicinity of the XRT position (Evans et al., GCN 29113; Evans et al., GCN 29119), we detect a marginally extended source, consistent with the location of emission detected in previously reported optical follow up and archival imaging (Malesani et al., GCN 29117; Dichiara et al., GCN 29128; de Ugarte Postigo et al., GCN 29132; Kilpatrick et al., GCN 29133).
  After calibrating our stacked image to isolated stars detected in the 2MASS photometric catalog (Cutri et al., 2003, NASA/IPAC), we applied a 3 arcsecond aperture and measure a magnitude of J = 21.8 +/- 0.2 mag (AB and not corrected for Milky Way extinction).
  Further observations are planned to assess any variability of the source. We thank Ryan Howie and Joannah Hinz at the MMT for the rapid scheduling and execution of these observations.
• GCN Circular #29144
  Huang, K. (CYCU), Urata, Y. (NCU) and Petitpas, G (SAO). report:
  We observed the field of the GRB201221D (Page et al., GCN #29112) at 228 GHz using the Submillimeter Array (SMA). The observation was started at 2020 December 11:27 UT (12.3 h after the burst). There was no source at the candidate of optical afterglow (Malesani et al., GCN #29117; Dichiara et al., GCN #29128; de Ugarte Postigo et al., GCN #29132; Kilpatrick et al., GCN #29133; Rastinejad et al. GCN #29142). The preliminary limit of the observation is ~0.2 mJy (rms).
  We thank Ramprasad Rao, Mark Gurwell and staff of SMA for the scheduling and execution of observations.
• GCN Circular #29148
  Dimple (ARIES), A. Panchal (ARIES), A. Gangopadhyay (ARIES), A. Ghosh (ARIES), R. Gupta (ARIES), A. Kumar (ARIES), K. Misra (ARIES), and S. B. Pandey (ARIES) report:
  We carried out the follow-up observations of GRB 201221D (Page et al., GCN 29112) with Aries Devasthal Faint Object Spectrograph and Camera (ADFOSC) mounted on the 3.6m Devasthal Optical Telescope (DOT) at Devasthal observatory of Aryabhatta Research Institute of observational sciencES (ARIES), India. The observations were started on 2020-12-22 at 23:10:00 UT. We observed a series of 4 images with the exposure time of 900 seconds each in r-band. At the position reported by Malesani et al., (GCN 29117), we detect an uncatalogued source in r-band with a magnitude of 23.46 +- 0.09 (AB mag), calibrated with the nearby PanSTARRS field. However, we remark that this is an extended source and may contain significant host galaxy contribution. For further verification, host galaxy subtraction is highly encouraged.
  The magnitude is not corrected for the Galactic extinction in the direction of the burst.
  This circular may be cited.
• GCN Circular #29311
  A. Rossi (INAF-OAS) reports on behalf of the CIBO collaboration:
  We observed the location of the optical afterglow (Malesani et al., GCN 29117) of the short GRB 201221D (Page et al., GCN 29112) simultaneously in the J and Ks bands with the LUCI near-infrared imager and spectrograph mounted on the Large Binocular Telescope (LBT, Mt Graham, AZ, USA). Observations were obtained on 2020-12-24 at the UT midtime 11:40:00, i.e. ~2.5 days after the burst trigger, for a total of 20 min of exposure in each band.
  Inspection of the combined J and K-band images reveals a faint, extended source in both filters, for which we preliminary measure J=21.7+-0.3 (Vega system), calibrated against 2MASS field stars.
  We acknowledge the excellent support from the LBTO and LBT-INAF staff, particularly A. Cardwell, F. Cusano, and D. Paris, in obtaining these observations.
• Redshift z= 1.055 +- 0.001 from host galaxy emission ([OII])
  W.-F. Fong et al. 2022, ApJ 940, 56