Gamma-ray Burst 200228B

(All information courtesy of the instrument teams.)

Previous IAU Circulars

• none

• GCN/BACODINE POSITION NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Fri 28 Feb 20 11:15:47 UT
  NOTICE_TYPE:     Swift-BAT GRB Position
  TRIGGER_NUM:     958733,   Seg_Num: 0
  GRB_RA:          252.026d {+16h 48m 06s} (J2000),
                   252.252d {+16h 49m 00s} (current),
                   251.466d {+16h 45m 52s} (1950)
  GRB_DEC:         +16.960d {+16d 57' 37"} (J2000),
                   +16.926d {+16d 55' 33"} (current),
                   +17.047d {+17d 02' 51"} (1950)
  GRB_ERROR:       3.00 [arcmin radius, statistical only]
  GRB_INTEN:       29390 [cnts]    Image_Peak=388 [image_cnts]
  TRIGGER_DUR:     8.192 [sec] 
  TRIGGER_INDEX:   454     E_range: 15-50 keV
  BKG_INTEN:       215343 [cnts]
  BKG_TIME:        40391.48 SOD {11:13:11.48} UT
  BKG_DUR:         64 [sec]
  GRB_DATE:        18907 TJD;    59 DOY;   20/02/28
  GRB_TIME:        40481.15 SOD {11:14:41.15} UT
  GRB_PHI:         145.68 [deg]
  GRB_THETA:        39.30 [deg]
  SOLN_STATUS:     0x20000003
  RATE_SIGNIF:     9.74 [sigma]
  IMAGE_SIGNIF:    7.13 [sigma]
  MERIT_PARAMS:     +1  +0  +0  +3  +1  -3  +0  +0  +2  +0 
  SUN_POSTN:       340.90d {+22h 43m 37s}   -8.07d {-08d 04' 14"}
  SUN_DIST:         91.07 [deg]   Sun_angle= 5.9 [hr] (West of Sun)
  MOON_POSTN:       31.27d {+02h 05m 04s}   +7.84d {+07d 50' 25"}
  MOON_DIST:       132.51 [deg]
  MOON_ILLUM:      20 [%]
  GAL_COORDS:       35.45, 34.70 [deg] galactic lon,lat of the burst (or transient)
  ECL_COORDS:      247.67, 39.02 [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 = 285.53,0.93 [deg].  
  COMMENTS:           
  COMMENTS:        NOTE: This BAT event is temporally(2.0<100sec) coincident with the FERMI_GBM event (trignum=604581288).  
  

• red DSS finding chart ps-file
  
  
• GCN NOTICE
  

  TITLE:           GCN/FERMI NOTICE
  NOTICE_DATE:     Mon 03 Feb 20 20:40:02 UT
  NOTICE_TYPE:     Fermi-GBM Flight Position
  RECORD_NUM:      48
  TRIGGER_NUM:     602455182
  GRB_RA:          252.117d {+16h 48m 28s} (J2000),
                   252.481d {+16h 49m 56s} (current),
                   251.211d {+16h 44m 51s} (1950)
  GRB_DEC:         -45.150d {-45d 08' 59"} (J2000),
                   -45.184d {-45d 11' 01"} (current),
                   -45.062d {-45d 03' 44"} (1950)
  GRB_ERROR:       19.42 [deg radius, statistical plus systematic]
  GRB_INTEN:       1726 [cnts/sec]
  DATA_SIGNIF:     7.50 [sigma]
  INTEG_TIME:      0.016 [sec]
  GRB_DATE:        18882 TJD;    34 DOY;   20/02/03
  GRB_TIME:        74377.92 SOD {20:39:37.92} UT
  GRB_PHI:         309.00 [deg]
  GRB_THETA:        85.00 [deg]
  DATA_TIME_SCALE: 0.0160 [sec]
  HARD_RATIO:      2.55
  LOC_ALGORITHM:   3 (version number of)
  MOST_LIKELY:      36%  GRB
  2nd_MOST_LIKELY:  25%  SGR_1806n20
  DETECTORS:       0,0,0, 1,1,0, 0,0,0, 0,0,0, 0,0,
  SUN_POSTN:       316.94d {+21h 07m 47s}  -16.49d {-16d 29' 09"}
  SUN_DIST:         60.48 [deg]   Sun_angle= 4.3 [hr] (West of Sun)
  MOON_POSTN:       63.38d {+04h 13m 32s}  +18.33d {+18d 19' 55"}
  MOON_DIST:       152.10 [deg]
  MOON_ILLUM:      67 [%]
  GAL_COORDS:      340.24, -0.14 [deg] galactic lon,lat of the burst (or transient)
  ECL_COORDS:      256.44,-22.55 [deg] ecliptic lon,lat of the burst (or transient)
  LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2020/bn200203861/quicklook/glg_lc_medres34_bn200203861.gif
  COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
  COMMENTS:        This trigger occurred at longitude,latitude = 110.97,-24.95 [deg].  
  COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.  
  

• GCN NOTICE
  

  TITLE:           GCN/FERMI NOTICE
  NOTICE_DATE:     Mon 03 Feb 20 20:40:18 UT
  NOTICE_TYPE:     Fermi-GBM Ground Position
  RECORD_NUM:      59
  TRIGGER_NUM:     602455182
  GRB_RA:          263.200d {+17h 32m 48s} (J2000),
                   263.569d {+17h 34m 17s} (current),
                   262.283d {+17h 29m 08s} (1950)
  GRB_DEC:         -45.080d {-45d 04' 47"} (J2000),
                   -45.093d {-45d 05' 33"} (current),
                   -45.045d {-45d 02' 40"} (1950)
  GRB_ERROR:       8.92 [deg radius, statistical only]
  DATA_SIGNIF:     14.30 [sigma]
  DATA_INTERVAL:   0.016 [sec]
  GRB_DATE:        18882 TJD;    34 DOY;   20/02/03
  GRB_TIME:        74377.92 SOD {20:39:37.92} UT
  GRB_PHI:         314.00 [deg]
  GRB_THETA:        91.00 [deg]
  E_RANGE:         44.032 - 279.965 [keV]
  LOC_ALGORITHM:   4173 (Gnd S/W Version number)
  SUN_POSTN:       316.94d {+21h 07m 47s}  -16.49d {-16d 29' 09"}
  SUN_DIST:         52.78 [deg]   Sun_angle= 3.6 [hr] (West of Sun)
  MOON_POSTN:       63.39d {+04h 13m 33s}  +18.33d {+18d 19' 57"}
  MOON_DIST:       148.40 [deg]
  MOON_ILLUM:      67 [%]
  GAL_COORDS:      344.93, -6.40 [deg] galactic lon,lat of the burst (or transient)
  ECL_COORDS:      264.84,-21.76 [deg] ecliptic lon,lat of the burst (or transient)
  LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2020/bn200203861/quicklook/glg_lc_medres34_bn200203861.gif
  POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_602455182.fits
  COMMENTS:        Fermi-GBM Ground-calculated Coordinates.  
  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/SWIFT NOTICE
  NOTICE_DATE:     Fri 28 Feb 20 11:17:03 UT
  NOTICE_TYPE:     Swift-XRT Nack-Position
  TRIGGER_NUM:     958733,   Seg_Num: 0
  POINT_RA:        252.035d {+16h 48m 08s} (J2000)
  POINT_DEC:       +16.967d {+16d 58' 02"} (J2000)
  IMG_START_DATE:  18907 TJD;    59 DOY;   20/02/28
  IMG_START_TIME:  40616.81 SOD {11:16:56.81} UT,   135.7 [sec] since BAT Trigger Time
  COUNTS:          2    Min_needed= 20
  STD_DEV:         0.00   Max_StdDev_for_Good=28.44 [arcsec]
  PH2_ITER:        1    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:     Fri 28 Feb 20 11:18:46 UT
  NOTICE_TYPE:     Swift-BAT GRB Lightcurve
  TRIGGER_NUM:     958733,   Seg_Num: 0
  GRB_RA:          252.026d {+16h 48m 06s} (J2000),
                   252.252d {+16h 49m 00s} (current),
                   251.466d {+16h 45m 52s} (1950)
  GRB_DEC:         +16.960d {+16d 57' 37"} (J2000),
                   +16.926d {+16d 55' 33"} (current),
                   +17.047d {+17d 02' 51"} (1950)
  GRB_DATE:        18907 TJD;    59 DOY;   20/02/28
  GRB_TIME:        40481.15 SOD {11:14:41.15} UT
  TRIGGER_INDEX:   454
  GRB_PHI:         145.68 [deg]
  GRB_THETA:        39.30 [deg]
  DELTA_TIME:      -5.00 [sec]
  TRIGGER_DUR:     8.192 [sec] 
  SOLN_STATUS:     0x3
  RATE_SIGNIF:     9.74 [sigma]
  IMAGE_SIGNIF:    7.13 [sigma]
  LC_URL:          sw00958733000msb.lc
  SUN_POSTN:       340.91d {+22h 43m 38s}   -8.07d {-08d 04' 11"}
  SUN_DIST:         91.07 [deg]   Sun_angle= 5.9 [hr] (West of Sun)
  MOON_POSTN:       31.29d {+02h 05m 10s}   +7.85d {+07d 50' 59"}
  MOON_DIST:       132.52 [deg]
  MOON_ILLUM:      20 [%]
  GAL_COORDS:       35.45, 34.70 [deg] galactic lon,lat of the burst (or transient)
  ECL_COORDS:      247.67, 39.02 [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 = 285.53,0.93 [deg].  
  

  
• GCN NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Thu 27 Feb 20 07:32:08 UT
  NOTICE_TYPE:     Swift-UVOT Processed Source List
  TRIGGER_NUM:     958592,   Seg_Num: 0
  POINT_RA:         56.441d {+03h 45m 46s} (J2000)
  POINT_DEC:        +9.485d {+09d 29' 05"} (J2000)
  POINT_ROLL:      259.212d
  IMG_START_DATE:  18906 TJD;    58 DOY;   20/02/27
  IMG_START_TIME:  26713.17 SOD {07:25:13.17} UT,   305.2 [sec] since BAT Trigger Time
  FILTER:          7, U
  BKG_MEAN:        1.042
  N_STARS:         8
  X_OFFSET:        509 [pixels]
  Y_OFFSET:        523 [pixels]
  X_MAX:           1468 [pixels]
  Y_MAX:           1482 [pixels]
  DET_THRESH:      9
  PHOTO_THRESH:    4
  SL_URL:          sw00958592000msufc0305.fits
  SUN_POSTN:       339.82d {+22h 39m 16s}   -8.51d {-08d 30' 19"}
  SUN_DIST:         78.66 [deg]   Sun_angle= -5.1 [hr] (East of Sun)
  MOON_POSTN:       18.62d {+01h 14m 29s}   +2.55d {+02d 32' 50"}
  MOON_DIST:        38.49 [deg]
  MOON_ILLUM:      12 [%]
  GAL_COORDS:      178.14,-34.11 [deg] galactic lon,lat of the pointing direction
  ECL_COORDS:       56.37,-10.12 [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:     Fri 28 Feb 20 11:20:40 UT
  NOTICE_TYPE:     Swift-XRT Position
  TRIGGER_NUM:     958733,   Seg_Num: 0
  GRB_RA:          252.0473d {+16h 48m 11.35s} (J2000),
                   252.2730d {+16h 49m 05.51s} (current),
                   251.4878d {+16h 45m 57.06s} (1950)
  GRB_DEC:         +16.9850d {+16d 59' 05.9"} (J2000),
                   +16.9506d {+16d 57' 02.2"} (current),
                   +17.0721d {+17d 04' 19.5"} (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:  18907 TJD;    59 DOY;   20/02/28
  IMG_START_TIME:  40624.00 SOD {11:17:04.00} UT,   142.8 [sec] since BAT Trigger Time
  TAM[0-3]:        100.00 100.00 100.00 100.00
  AMPLIFIER:       1
  WAVEFORM:        31
  SUN_POSTN:       340.91d {+22h 43m 38s}   -8.07d {-08d 04' 09"}
  SUN_DIST:         91.05 [deg]   Sun_angle= 5.9 [hr] (West of Sun)
  MOON_POSTN:       31.30d {+02h 05m 13s}   +7.86d {+07d 51' 20"}
  MOON_DIST:       132.50 [deg]
  MOON_ILLUM:      20 [%]
  GAL_COORDS:       35.48, 34.69 [deg] galactic lon,lat of the burst
  ECL_COORDS:      247.69, 39.04 [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 0.11% < P(seren) < 0.58%.  
  

• GCN NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Fri 28 Feb 20 11:21:50 UT
  NOTICE_TYPE:     Swift-UVOT Processed Source List
  TRIGGER_NUM:     958733,   Seg_Num: 0
  POINT_RA:        252.035d {+16h 48m 08s} (J2000)
  POINT_DEC:       +16.967d {+16d 58' 01"} (J2000)
  POINT_ROLL:      98.037d
  IMG_START_DATE:  18907 TJD;    59 DOY;   20/02/28
  IMG_START_TIME:  40617.90 SOD {11:16:57.90} UT,   136.8 [sec] since BAT Trigger Time
  FILTER:          7, U
  BKG_MEAN:        0.706
  N_STARS:         184
  X_OFFSET:        203 [pixels]
  Y_OFFSET:        387 [pixels]
  X_MAX:           1642 [pixels]
  Y_MAX:           1826 [pixels]
  DET_THRESH:      7
  PHOTO_THRESH:    3
  SL_URL:          sw00958733000msufc0136.fits
  SUN_POSTN:       340.91d {+22h 43m 38s}   -8.07d {-08d 04' 08"}
  SUN_DIST:         91.06 [deg]   Sun_angle= 5.9 [hr] (West of Sun)
  MOON_POSTN:       31.31d {+02h 05m 15s}   +7.86d {+07d 51' 33"}
  MOON_DIST:       132.53 [deg]
  MOON_ILLUM:      20 [%]
  GAL_COORDS:       35.46, 34.70 [deg] galactic lon,lat of the pointing direction
  ECL_COORDS:      247.68, 39.02 [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:     Fri 28 Feb 20 11:22:51 UT
  NOTICE_TYPE:     Swift-UVOT Image
  TRIGGER_NUM:     958733,   Seg_Num: 0
  POINT_RA:        252.035d {+16h 48m 08s} (J2000)
  POINT_DEC:       +16.967d {+16d 58' 01"} (J2000)
  ROLL:            98.037d
  IMG_START_DATE:  18907 TJD;    59 DOY;   20/02/28
  IMG_START_TIME:  40617.90 SOD {11:16:57.90} UT,   136.8 [sec] since BAT Trigger Time
  FILTER:          7, U
  EXPOSURE_ID:     604581442
  X_OFFSET:        762 [pixels]
  Y_OFFSET:        946 [pixels]
  WIDTH:           160 [pixels]
  HEIGHT:          160 [pixels]
  X_GRB_POS:       922
  Y_GRB_POS:       1106
  BINNING_INDEX:   1
  IM_URL:          sw00958733000msuni0161.fits
  SUN_POSTN:       340.91d {+22h 43m 38s}   -8.07d {-08d 04' 07"}
  SUN_DIST:         91.06 [deg]   Sun_angle= 5.9 [hr] (West of Sun)
  MOON_POSTN:       31.32d {+02h 05m 17s}   +7.86d {+07d 51' 44"}
  MOON_DIST:       132.53 [deg]
  MOON_ILLUM:      20 [%]
  GAL_COORDS:       35.46, 34.70 [deg] galactic lon,lat of the pointing direction
  ECL_COORDS:      247.68, 39.02 [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:     Fri 28 Feb 20 11:23:09 UT
  NOTICE_TYPE:     Swift-UVOT Processed Image
  TRIGGER_NUM:     958733,   Seg_Num: 0
  POINT_RA:        252.035d {+16h 48m 08s} (J2000)
  POINT_DEC:       +16.967d {+16d 58' 01"} (J2000)
  ROLL:            98.037d
  IMG_START_DATE:  18907 TJD;    59 DOY;   20/02/28
  IMG_START_TIME:  40617.90 SOD {11:16:57.90} UT,   136.8 [sec] since BAT Trigger Time
  FILTER:          7, U
  EXPOSURE_ID:     604581442
  X_OFFSET:        762 [pixels]
  Y_OFFSET:        946 [pixels]
  WIDTH:           160 [pixels]
  HEIGHT:          160 [pixels]
  X_GRB_POS:       922
  Y_GRB_POS:       1106
  BINNING_INDEX:   1
  IM_URL:          sw00958733000msuni0161.fits
  SUN_POSTN:       340.91d {+22h 43m 38s}   -8.07d {-08d 04' 07"}
  SUN_DIST:         91.06 [deg]   Sun_angle= 5.9 [hr] (West of Sun)
  MOON_POSTN:       31.32d {+02h 05m 18s}   +7.86d {+07d 51' 47"}
  MOON_DIST:       132.54 [deg]
  MOON_ILLUM:      20 [%]
  GAL_COORDS:       35.46, 34.70 [deg] galactic lon,lat of the pointing direction
  ECL_COORDS:      247.68, 39.02 [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 #27253
  The Fermi GBM team reports the detection of a likely LONG GRB
  At 11:14:43 UT on 28 Feb 2020, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 200228B (trigger 604581288.894278 / 200228469).
  The on-ground calculated location, using the Fermi GBM trigger data, is RA = 258.4, Dec = 9.6 (J2000 degrees, equivalent to J2000 17h 13m, 9d 35'), with a statistical uncertainty of 16.7 degrees.
  The angle from the Fermi LAT boresight is 62.0 degrees.
  The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2020/bn200228469/quicklook/glg_skymap_all_bn200228469.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/bn200228469/quicklook/glg_healpix_all_bn200228469.fit
  The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2020/bn200228469/quicklook/glg_lc_medres34_bn200228469.gif
• GCN Circular #27254
  S. Laha (GSFC/UMBC/CRESST), S. D. Barthelmy (GSFC), P. A. Evans (U Leicester), C. Gronwall (PSU), J.D. Gropp (PSU) and K. L. Page (U Leicester) report on behalf of the Neil Gehrels Swift Observatory Team:
  At 11:14:41 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 200228B (trigger=958733). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 252.026, +16.960, which is

     RA(J2000)  =  16h 48m 06s
     Dec(J2000) = +16d 57' 37"
  

  with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows a single peak with a duration of about 25 sec. The peak count rate was ~2000 counts/sec (15-350 keV), at ~5 sec after the trigger.
  The XRT began observing the field at 11:16:56.8 UT, 135.7 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 252.04730, 16.98505 which is equivalent to:

     RA(J2000)  = 16h 48m 11.35s
     Dec(J2000) = +16d 59' 06.2"
  

  with an uncertainty of 5.7 arcseconds (radius, 90% containment). This location is 116 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. No spectrum from the promptly downlinked event data is yet available to determine the column density.
  UVOT data are unavailable at this time.
  Burst Advocate for this burst is S. Laha (sib.laha AT gmail.com). 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 #27256
  P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester) report on behalf of the Swift-XRT team.
  Using 87 s of XRT Photon Counting mode data and 1 UVOT images for GRB 200228B, 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 = 252.04640, +16.98523 which is equivalent to:

  RA (J2000): 16h 48m 11.14s
  Dec (J2000): +16d 59' 06.8"     
  

  with an uncertainty of 3.5 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 #27263
  WeiKang Zheng and Alexei V. Filippenko (UC Berkeley) report on behalf of the KAIT GRB team:
  The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at Lick Observatory, responded to Swift GRB 200228B (Laha et al., GCN 27254) starting at 11:21:06 UT, 395 s after the burst. Observations were performed with an automatic sequence in the clear (roughly R), V, and I filters, and the exposure time was 20 s per image. We do not detect any optical afterglow candidate within the enhanced XRT position error circle (Evans et al., GCN 27256), neither in single image, nor in the co-add images. The typical limiting magnitude of our single clear image is about 18.0 mag calibrated to the Pan-STARRS1 catalog.
• GCN Circular #27266
  E. Bissaldi (Politecnico and INFN Bari), C. Meegan (UAH), and J. Wood (NASA/MSFC) report on behalf of the Fermi GBM Team:
  "At 11:14:43.89 UT on 28 February 2020, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB 200228B (trigger 604581288 / 200228469), which was also detected by the Swift/BAT (Laha et al. 2020, GCN 27254). The GBM on-ground location is consistent with the Swift position.
  The angle from the Fermi LAT boresight at the GBM trigger time is 59 degrees.
  The GBM light curve shows a single emission episode with a duration (T90) of about 14 s (50-300 keV). The time-averaged spectrum from T0-4 s to T0+11 s is adequately fit by a power law function with an exponential high-energy cutoff. The power law index is -1.17 +/- 0.33 and the cutoff energy, parameterized as Epeak, is 76 +/- 16 keV.
  The event fluence (10-1000 keV) in this time interval is (1.30 +/- 0.18)E-07 erg/cm^2. The 1-sec peak photon flux measured starting from T0-0.3 s in the 10-1000 keV band is 1.4 +/- 0.2 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 #27267
  Margarita Pereyra (UNAM), Nat Butler (ASU), Alan M. Watson (UNAM), Alexander Kutyrev (GSFC), William H. Lee (UNAM), Michael G. Richer (UNAM), Ori Fox (STScI), J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (UVI), Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC), Jes�s Gonz�lez (UNAM), Carlos Rom�n-Z��iga (UNAM), Harvey Moseley (GSFC), John Capone (UMD), V. Zach Golkhou (U. Wash.), and Vicki Toy (UMD) report:
  We observed the field of GRB 200228B (Laha et al., GCN Circ. 27254) with the Reionization and Transients Infrared Camera (RATIR; www.ratir.org) on the 1.5m Harold Johnson Telescope at the Observatorio Astron�mico Nacional on Sierra San Pedro M�rtir from 2020/02 28.48 to 2020/02 28.53 UTC (0.27 to 1.52 hours after the BAT trigger), obtaining a total of 0.62 hours exposure in the r and i bands.
  For a source within the Swift-XRT enhanced error circle (Evans et al., GCN Circ. 27256), in comparison with the SDSS DR9 and 2MASS catalogs, we obtain the following upper limits (3-sigma):

    r > 21.48
    i > 21.40
  

  These magnitudes are in the AB system and are not corrected for Galactic extinction in the direction of the GRB.
  We thank the staff of the Observatorio Astron�mico Nacional in San Pedro M�rtir.
• GCN Circular #27268
  N. P. M. Kuin (UCL-MSSL) and S. L. Laha (GSFC/UMBC/CRESST) report on behalf of the Swift/UVOT team:
  The Swift/UVOT began settled observations of the field of GRB 200228B 137 s after the BAT trigger (Laha et al., GCN Circ. 27254). No optical afterglow consistent with the XRT position (Evans et al., GCN Circ. #27256 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
  
  u_FC               137          387          246         >20.1
  v                 4992        10685          676         >20.1
  b                 4580         6012          393         >20.6
  u                  137         5807          442         >20.4
  w1                5402         5602          197         >19.5
  m2                5197         5396          197         >19.8
  w2                4786         6218          393         >19.4
  

  The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.092 in the direction of the burst (Schlegel et al. 1998).
• GCN Circular #27269
  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),
  H.Levato (Instituto de Ciencias Astronomicas, de la Tierra y del Espacio ICATE),
  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-Kislovodsk robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the Swift GRB 200228B ( S. Laha et al., GCN 27254) errorbox 45652 sec after trigger time at 2020-02-28 23:55:33 UT, with upper limit up to 18.6 mag. The observations began at zenith distance = 51 deg. The sun altitude is -41.7 deg.
  The galactic latitude b = 34 deg., longitude l = 36 deg.
  Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1300236
  We obtain a following upper limits.

  Tmid-T0  |          Site       |Filt.| Expt. | Limit| Comment
  _________|_____________________|_____|_______|______|________
  
     45742 |   MASTER-Kislovodsk |   C |   180 | 18.4 |        
     45742 |   MASTER-Kislovodsk |   C |   180 | 18.6 |        
  Filter C is a clear (unfiltred) band. 
  

  The observation and reduction will continue. The message may be cited.
• GCN Circular #27270
  K.L. Page (U. Leicester) and S. Laha (GSFC/UMBC/CRESST) report on behalf of the Swift-XRT team:
  We have analysed 4.6 ks of XRT data for GRB 200228B (Laha et al. GCN Circ. 27254), from 143 s to 18.2 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. 27256).
  The light curve can be modelled with a power-law decay with a decay index of alpha=0.65 (+0.10, -0.12).
  A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 3.0 (+0.8, -0.7). The best-fitting absorption column is 1.6 (+0.8, -0.6) x 10^22 cm^-2, in excess of the Galactic value of 6.4 x 10^20 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.5 x 10^-11 (2.3 x 10^-10) erg cm^-2 count^-1.
  A summary of the PC-mode spectrum is thus:

  Total column:        1.6 (+0.8, -0.6) x 10^22 cm^-2
  Galactic foreground: 6.4 x 10^20 cm^-2
  Excess significance: 4.3 sigma
  Photon index:        3.0 (+0.8, -0.7)
  

  If the light curve continues to decay with a power-law decay index of 0.65, the count rate at T+24 hours will be 4.9 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.7 x 10^-13 (1.1 x 10^-12) erg cm^-2 s^-1.
  The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00958733.
  This circular is an official product of the Swift-XRT team.
• GCN Circular #27271
  D. A. Perley and A. M. Cockeram (LJMU) report:
  On 2020-02-29 UT we obtained imaging of the position of GRB 200228B (Fermi GBM team, GCN 27253; Laha et al., GCN 27254) using the 2m robotic Liverpool Telescope. We collected 3x120s of exposure time in each of the the i-band and z-band filters, beginning at 05:53:44 and ending at 06:07:33 (UTC).
  No unambiguous source is detected in either stacked image, although a possible marginal (~3-sigma) source is present close to the center of the latest enhanced XRT error circle in the z-band image. Photometry of this potential source (calibrating relative to PS1 catalog stars in the field) gives an approximate magnitude of z = 21.7 +/- 0.3.
  3-sigma limits are:

  dt(days)  filter   mag
  0.7794    i       >22.6
  0.7844    z       >21.7
  

  We additionally note that Pan-STARRS1 imaging of the field shows several faint, probably-resolved sources close to the survey detection limit inside or closely outside the XRT error circle, which could represent a possible host galaxy or host group.
  Imaging of the field is available at: http://www.astro.ljmu.ac.uk/~aridperl/grb/200228b/GRB200228B_LT_PS1.png
  (The enhanced XRT error circle is shown in cyan with the marginal "detection" highlighted in red.)
  
• GCN Circular #27272
  Rosa L. Becerra (UNAM), Alan M. Watson (UNAM), Nat Butler (ASU), Alexander Kutyrev (GSFC), William H. Lee (UNAM), Michael G. Richer (UNAM), Ori Fox (STScI), J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (UVI), Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC), Jesús González (UNAM), Carlos Román-Zúñiga (UNAM), Harvey Moseley (GSFC), John Capone (UMD), V. Zach Golkhou (U. Wash.), and Vicki Toy (UMD) report:
  We observed the field of GRB 200228B (Fermi GBM team, GCN 27253, Laha, et. al. GCN 27254) with the Reionization and Transients Infrared Camera (RATIR; www.ratir.org) on the 1.5m Harold Johnson Telescope at the Observatorio Astronómico Nacional on Sierra San Pedro Mártir from 2020/02 29.36 to 2020/02 29.53 UTC (21.40 to 25.38 hours after the BAT trigger), obtaining a total of 2.27 hours exposure in the r and i bands.
  For a source within the Swift-XRT enhanced error circle (Evans et al., GCN Circ. 27256), in comparison with the SDSS DR9 and 2MASS catalogs, we obtain the following upper limits (3-sigma):

    r > 23.19
    i > 23.11
  

  These magnitudes are in the AB system and are not corrected for Galactic extinction in the direction of the GRB.
  We thank the staff of the Observatorio Astronómico Nacional in San Pedro Mártir.
• GCN Circular #27273
  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), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):
  Using the data set from T-240 to T+297 sec from the recent telemetry downlink, we report further analysis of BAT GRB 200228B (trigger #958733) (Laha et al., GCN Circ. 27254). The BAT ground-calculated position is RA, Dec = 252.007, 16.964 deg which is

     RA(J2000)  =  16h 48m 01.8s
     Dec(J2000) = +16d 57' 50.3"
  

  with an uncertainty of 2.5 arcmin, (radius, sys+stat, 90% containment). The partial coding was 31%.
  The mask-weighted light curve shows a weak pulse that starts at ~T-1 s, peaks at ~T+2 s, and ends at ~T+7 s. T90 (15-350 keV) is 7.37 +- 1.58 sec (estimated error including systematics).
  The time-averaged spectrum from T-0.84 to T+6.97 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.27 +- 0.36. The fluence in the 15-150 keV band is 3.0 +- 0.6 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T+1.32 sec in the 15-150 keV band is 1.0 +- 0.4 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/958733/BA/
• GCN Circular #27274
  R. Strausbaugh (U. of the Virgin Islands), A. Cucchiara (U. of the Virgin Islands/College of Marin) report on behalf of a larger collaboration:
  We observed Swift GRB 200228B (Laha et al., GCN 27254) with the LCO 1-m Sinistro instrument at the McDonald Observatory, Texas, USA site, on February 29, from 10:52 to 11:42 UT (corresponding to 23.4 to 24.5 hours after the GRB trigger time) with the Bessel I and R filters.
  We performed a series of 10x120s exposures in I and R. We do not detect any uncatalouged sources in the individual frames (nor in stacked images) in the Swift error region. Using the USNO-B.1 catalog as reference, we obtain the following 3-sigma upper limits in stacked images:
  R > 22.08
  I > 20.77
  R.S. is funded by NSF AST grant #1831682
• GCN Circular #27276
  A. Pozanenko (IKI), S. Belkin (IKI), E. Klunko (ISTP), A. Kusakin (FAPHI), I. Reva (FAPHI), V. Rumyantsev (CrAO), R. Ya. Inasaridze (AbAO), E. Mazaeva (IKI), A. Volnova (IKI) report on behalf of IKI-GRB-FuN:
  We observed the field of GRB 200228B (Laha et al., GCN 27254; Fermi GBM Team, GCN 27253) with AZT-33IK 1.5-m telescope of Sayan observatory (Mondy) starting on Feb. 28 (UT) 19:24:43. We detected an optical object near the enhanced XRT position of the XRT afterglow (Evans et al., GCN 27256). The object is absent in the Pan-STARRS DR1 catalog. The coordinates of the object are (J2000) 16:48:10.88 +16:59:04.5 with uncertainty of 0.5 arcsec in both coordinates. Next we observed the filed with Zeiss-1000 1-m telescope of Tien Shan Astronomical Observatory starting on Feb. 28 (UT) 23:08:56, Abastumani starting on Feb. 29 (UT) 01:38:45, Tien Shan Astronomical Observatory starting on Feb. 29 (UT) 23:08:56, and CrAO starting on Mar. 01 (UT) 00:58:28.
  Preliminary photometry of the object and the field is following.

  Date UT start       t-T0  Filter Exp. OT Err UL(3sigma)   telescope
                           (mid, days) (s)
  2020-02-28 19:24:43 0.351  R 15*120 21.8  0.3  21.7 AZT-33IK
  2020-02-28 23:08:56 0.516  R 3480   n/d   n/d  22.3 Z-1000
  2020-02-29 01:38:45 0.616  R 46*60  n/d   n/d  21.8 AS-32
  2020-02-29 22:22:37 n/a    R 5040   n/a   n/a  n/a  Z-1000
  2020-03-01 00:58:28 1.594  R 31*120 22.05 0.09 23.8 ZTSh
  

  Photometry is based on the USNO-B2.0 nearby stars.

  USNO-B1.0    R2
  1069-0297786 18.42
  1069-0297719 18.25
  1069-0297797 14.78
  

  The finding chart is available at http://193.232.11.154/GRB200228B/GRB200228B_AZT33IK_Z1000_ZTSh_FC.png (or http://grb.iki.rssi.ru/GRB200228B/GRB200228B_AZT33IK_Z1000_ZTSh_FC.png).
  We suggest this object is a candidate in the afterglow of GRB 200228B after at least two epoch detections (see above), possible variability and absence of the bright object (R ~ 22) in the Pan-STARRS DR1.
  We did not detect any object at the position of NIR- candidate (Perley and Cockeram, GCN 27271).
  
• GCN Circular #27318
  A. Pozanenko (IKI), S. Belkin (IKI), R. Ya. Inasaridze (AbAO), E. Klunko (ISTP), A. Kusakin (FAPHI), I. Reva (FAPHI), V. Rumyantsev (CrAO), E. Mazaeva (IKI), A. Volnova (IKI) report on behalf of IKI-GRB-FuN:
  We continue observations of the OT (Pozanenko et al., GCN 27276) associated with GRB 200228B (Laha et al., GCN 27254; Fermi GBM Team, GCN 27253) with AZT-33IK 1.5-m telescope of Sayan observatory (Mondy) and AS-32 telescope of Abastumani Astrophysical observatory. The OT is well observable (see photometry below in the table) and current XRT position ( https://www.swift.ac.uk/xrt_positions/00958733/ ) coincides with position of the OT.
  Preliminary photometry of the object following.

  Date UT start       t-T0  Filter Exp. OT Err UL(3sigma)   telescope
                           (mid, days) (s)
  2020-03-03 01:36:36 3.6186   R 58*60  21.65 0.13  22.6 AS-32
  2020-03-03 21:03:33 4.4228   R 20*120 22.2  0.4   22.0 AZT-33IK
  2020-03-04 23:44:59 5.5488   R 80*60  21.93 0.17  22.6 AS-32
  

  Photometry is based on the USNO-B2.0 nearby stars used in previous observations (GCN 27276).
  The light curve in R-filter is available at http://grb.rssi.ru/GRB200228B/GRB200228B_lc_2.png
  We urge on spectroscopic and multicolor photometry to classify the OT.