Gamma-ray Burst 200306A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

• none

• GCN/BACODINE POSITION NOTICE
  

   
  TITLE:           GCN/SWIFT NOTICE 
  NOTICE_DATE:     Fri 06 Mar 20 00:21:26 UT 
  NOTICE_TYPE:     Swift-XRT Position 
  TRIGGER_NUM:     959917,   Seg_Num: 0 
  GRB_RA:          101.1029d {+06h 44m 24.69s} (J2000), 
                   101.1540d {+06h 44m 36.95s} (current), 
                   100.9758d {+06h 43m 54.19s} (1950) 
  GRB_DEC:         -62.0053d {-62d 00' 19.0"} (J2000), 
                   -62.0270d {-62d 01' 37.1"} (current), 
                   -61.9520d {-61d 57' 07.1"} (1950) 
  GRB_ERROR:       5.0 [arcsec radius, statistical plus systematic, 90% containment] 
  GRB_INTEN:       3.02e-09 [erg/cm2/sec] 
  GRB_SIGNIF:      10.63 [sigma] 
  IMG_START_DATE:  18914 TJD;    66 DOY;   20/03/06 
  IMG_START_TIME:  1257.15 SOD {00:20:57.15} UT 
  TAM[0-3]:        327.67 237.13 261.57 243.62 
  AMPLIFIER:       2 
  WAVEFORM:        134 
  SUN_POSTN:       347.02d {+23h 08m 04s}   -5.56d {-05d 33' 44"}
  SUN_POSTN:       347.02d {+23h 08m 04s}   -5.56d {-05d 33' 44"} 
  SUN_DIST:         96.04 [deg]   Sun_angle= -7.6 [hr] (East of Sun) 
  MOON_POSTN:      117.10d {+07h 48m 25s}  +22.88d {+22d 52' 46"} 
  MOON_DIST:        85.86 [deg] 
  MOON_ILLUM:      82 [%] 
  GAL_COORDS:      271.88,-24.55 [deg] galactic lon,lat of the burst 
  ECL_COORDS:      141.71,-83.39 [deg] ecliptic lon,lat of the burst 
  COMMENTS:        SWIFT-XRT Coordinates.   
  COMMENTS:            
  COMMENTS:        WARNING: No BAT_Position TDRSS message was received for this trigger_number!   
  COMMENTS: 
  

• GCN NOTICE
  

   
  TITLE:           GCN/SWIFT NOTICE 
  NOTICE_DATE:     Fri 06 Mar 20 00:21:35 UT 
  NOTICE_TYPE:     Swift-XRT Image 
  TRIGGER_NUM:     959917,   Seg_Num: 0 
  GRB_RA:          101.1029d {+06h 44m 24.6s} (J2000), 
                   101.1540d {+06h 44m 36.9s} (current), 
                   100.9758d {+06h 43m 54.1s} (1950) 
  GRB_DEC:         -62.0053d {-62d 00' 19.0"} (J2000), 
                   -62.0270d {-62d 01' 37.1"} (current), 
                   -61.9520d {-61d 57' 07.1"} (1950) 
  GRB_ERROR:       4.7 [arcsec, radius, statistical plus systematic] 
  GRB_INTEN:       113 [cnts] 
  IMG_START_DATE:  18914 TJD;    66 DOY;   20/03/06 
  IMG_START_TIME:  1257.15 SOD {00:20:57.15} UT 
  CENTROID_X:      281.42,  raw= 281  [pixels] 
  CENTROID_Y:      281.81,  raw= 282  [pixels] 
  ROLL:            245.98 [deg] 
  GAIN:            1 
  MODE:            3, Long Image mode 
  WAVEFORM:        134 
  EXPO_TIME:       2.50 [sec] 
  GRB_POS_XRT_Y:   -38.39 
  GRB_POS_XRT_Z:   -61.22 
  IMAGE_URL:       sw00959917000msxps_rw.img 
  SUN_POSTN:       347.02d {+23h 08m 04s}   -5.56d {-05d 33' 44"} 
  SUN_DIST:         96.04 [deg]   Sun_angle= -7.6 [hr] (East of Sun)
  SUN_POSTN:       347.02d {+23h 08m 04s}   -5.56d {-05d 33' 44"} 
  MOON_DIST:        85.86 [deg] 
  MOON_ILLUM:      82 [%] 
  GAL_COORDS:      271.88,-24.55 [deg] galactic lon,lat of the burst 
  ECL_COORDS:      141.71,-83.39 [deg] ecliptic lon,lat of the burst 
  COMMENTS:        SWIFT-XRT Image.   
  

  
• GCN NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Fri 06 Mar 20 00:21:40 UT
  NOTICE_TYPE:     Swift-XRT Processed Image
  TRIGGER_NUM:     959917,   Seg_Num: 0
  GRB_RA:          101.1029d {+06h 44m 24.6s} (J2000),
                   101.1540d {+06h 44m 36.9s} (current),
                   100.9758d {+06h 43m 54.1s} (1950)
  GRB_DEC:         -62.0053d {-62d 00' 19.0"} (J2000),
                   -62.0270d {-62d 01' 37.1"} (current),
                   -61.9520d {-61d 57' 07.1"} (1950)
  GRB_ERROR:       4.7 [arcsec, radius, statistical plus systematic]
  GRB_INTEN:       113 [cnts]
  IMG_START_DATE:  18914 TJD;    66 DOY;   20/03/06
  IMG_START_TIME:  1257.15 SOD {00:20:57.15} UT
  CENTROID_X:      281.42,  raw= 281  [pixels]
  CENTROID_Y:      281.81,  raw= 282  [pixels]
  ROLL:            245.98 [deg]
  GAIN:            1
  MODE:            3, Long Image mode
  WAVEFORM:        134
  EXPO_TIME:       2.50 [sec]
  GRB_POS_XRT_Y:   -38.39
  GRB_POS_XRT_Z:   -61.22
  IMAGE_URL:       sw00959917000msxps_rw.img
  SUN_POSTN:       347.02d {+23h 08m 04s}   -5.56d {-05d 33' 44"}
  SUN_DIST:         96.04 [deg]   Sun_angle= -7.6 [hr] (East of Sun)
  MOON_POSTN:      117.11d {+07h 48m 26s}  +22.88d {+22d 52' 45"}
  MOON_DIST:        85.86 [deg]
  MOON_ILLUM:      82 [%]
  GAL_COORDS:      271.88,-24.55 [deg] galactic lon,lat of the burst
  ECL_COORDS:      141.71,-83.39 [deg] ecliptic lon,lat of the burst
  COMMENTS:        SWIFT-XRT Processed Image.  
  

  
• GCN NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Tue 03 Mar 20 02:47:20 UT
  NOTICE_TYPE:     Swift-UVOT Processed Image
  TRIGGER_NUM:     959431,   Seg_Num: 0
  POINT_RA:        212.707d {+14h 10m 50s} (J2000)
  POINT_DEC:       +51.362d {+51d 21' 44"} (J2000)
  ROLL:            59.203d
  IMG_START_DATE:  18911 TJD;    63 DOY;   20/03/03
  IMG_START_TIME:  9605.94 SOD {02:40:05.94} UT,   308.5 [sec] since BAT Trigger Time
  FILTER:          7, U
  EXPOSURE_ID:     604896030
  X_OFFSET:        844 [pixels]
  Y_OFFSET:        905 [pixels]
  WIDTH:           160 [pixels]
  HEIGHT:          160 [pixels]
  X_GRB_POS:       1004
  Y_GRB_POS:       1065
  BINNING_INDEX:   1
  IM_URL:          sw00959431000msuni0333.fits
  SUN_POSTN:       344.32d {+22h 57m 17s}   -6.68d {-06d 40' 53"}
  SUN_DIST:        120.13 [deg]   Sun_angle= 8.8 [hr] (West of Sun)
  MOON_POSTN:       75.22d {+05h 00m 53s}  +21.10d {+21d 06' 15"}
  MOON_DIST:        98.66 [deg]
  MOON_ILLUM:      53 [%]
  GAL_COORDS:       96.55, 61.51 [deg] galactic lon,lat of the pointing direction
  ECL_COORDS:      179.87, 58.31 [deg] ecliptic lon,lat of the pointing direction
  COMMENTS:        SWIFT-UVOT Processed Image.  
  COMMENTS:        The GRB Position came from the XRT Position Command.  
  COMMENTS:        The image has 2x2 binning (compression).  
  COMMENTS:        All 4 attachments are included.  
  

  
• GCN NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Fri 06 Mar 20 00:23:59 UT
  NOTICE_TYPE:     Swift-UVOT Source List
  TRIGGER_NUM:     959917,   Seg_Num: 0
  POINT_RA:        101.145d {+06h 44m 35s} (J2000)
  POINT_DEC:       -62.009d {-62d 00' 33"} (J2000)
  POINT_ROLL:      245.977d
  IMG_START_DATE:  18914 TJD;    66 DOY;   20/03/06
  IMG_START_TIME:  1265.43 SOD {00:21:05.43} UT
  FILTER:          10, White
  BKG_MEAN:        1.539
  N_STARS:         82
  X_OFFSET:        456 [pixels]
  Y_OFFSET:        512 [pixels]
  X_MAX:           1415 [pixels]
  Y_MAX:           1471 [pixels]
  DET_THRESH:      10
  PHOTO_THRESH:    5
  SL_URL:          sw00959917000msufc605146865.fits
  SUN_POSTN:       347.02d {+23h 08m 04s}   -5.56d {-05d 33' 42"}
  SUN_DIST:         96.06 [deg]   Sun_angle= -7.6 [hr] (East of Sun)
  MOON_POSTN:      117.13d {+07h 48m 31s}  +22.88d {+22d 52' 37"}
  MOON_DIST:        85.86 [deg]
  MOON_ILLUM:      82 [%]
  GAL_COORDS:      271.89,-24.53 [deg] galactic lon,lat of the pointing direction
  ECL_COORDS:      141.86,-83.38 [deg] ecliptic lon,lat of the pointing direction
  COMMENTS:        SWIFT-UVOT Source List.  
  

  
• GCN NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Fri 06 Mar 20 00:26:23 UT
  NOTICE_TYPE:     Swift-UVOT Processed Image
  TRIGGER_NUM:     959917,   Seg_Num: 0
  POINT_RA:        101.145d {+06h 44m 35s} (J2000)
  POINT_DEC:       -62.009d {-62d 00' 33"} (J2000)
  ROLL:            245.977d
  IMG_START_DATE:  18914 TJD;    66 DOY;   20/03/06
  IMG_START_TIME:  1265.43 SOD {00:21:05.43} UT
  FILTER:          10, White
  EXPOSURE_ID:     605146889
  X_OFFSET:        933 [pixels]
  Y_OFFSET:        869 [pixels]
  WIDTH:           160 [pixels]
  HEIGHT:          160 [pixels]
  X_GRB_POS:       1093
  Y_GRB_POS:       1029
  BINNING_INDEX:   1
  IM_URL:          sw00959917000msuni605146890.fits
  SUN_POSTN:       347.02d {+23h 08m 04s}   -5.56d {-05d 33' 39"}
  SUN_DIST:         96.06 [deg]   Sun_angle= -7.6 [hr] (East of Sun)
  MOON_POSTN:      117.16d {+07h 48m 37s}  +22.87d {+22d 52' 28"}
  MOON_DIST:        85.86 [deg]
  MOON_ILLUM:      82 [%]
  GAL_COORDS:      271.89,-24.53 [deg] galactic lon,lat of the pointing direction
  ECL_COORDS:      141.86,-83.38 [deg] ecliptic lon,lat of the pointing direction
  COMMENTS:        SWIFT-UVOT Processed Image.  
  COMMENTS:        The GRB Position came from the XRT Position Command.  
  COMMENTS:        The image has 2x2 binning (compression).  
  COMMENTS:        All 4 attachments are included.  
  

  
• GCN NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Fri 06 Mar 20 00:24:16 UT
  NOTICE_TYPE:     Swift-UVOT Processed Source List
  TRIGGER_NUM:     959917,   Seg_Num: 0
  POINT_RA:        101.145d {+06h 44m 35s} (J2000)
  POINT_DEC:       -62.009d {-62d 00' 33"} (J2000)
  POINT_ROLL:      245.977d
  IMG_START_DATE:  18914 TJD;    66 DOY;   20/03/06
  IMG_START_TIME:  1265.43 SOD {00:21:05.43} UT
  FILTER:          10, White
  BKG_MEAN:        1.539
  N_STARS:         82
  X_OFFSET:        456 [pixels]
  Y_OFFSET:        512 [pixels]
  X_MAX:           1415 [pixels]
  Y_MAX:           1471 [pixels]
  DET_THRESH:      10
  PHOTO_THRESH:    5
  SL_URL:          sw00959917000msufc605146865.fits
  SUN_POSTN:       347.02d {+23h 08m 04s}   -5.56d {-05d 33' 41"}
  SUN_DIST:         96.06 [deg]   Sun_angle= -7.6 [hr] (East of Sun)
  MOON_POSTN:      117.13d {+07h 48m 32s}  +22.88d {+22d 52' 36"}
  MOON_DIST:        85.86 [deg]
  MOON_ILLUM:      82 [%]
  GAL_COORDS:      271.89,-24.53 [deg] galactic lon,lat of the pointing direction
  ECL_COORDS:      141.86,-83.38 [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 06 Mar 20 00:26:07 UT
  NOTICE_TYPE:     Swift-UVOT Image
  TRIGGER_NUM:     959917,   Seg_Num: 0
  POINT_RA:        101.145d {+06h 44m 35s} (J2000)
  POINT_DEC:       -62.009d {-62d 00' 33"} (J2000)
  ROLL:            245.977d
  IMG_START_DATE:  18914 TJD;    66 DOY;   20/03/06
  IMG_START_TIME:  1265.43 SOD {00:21:05.43} UT
  FILTER:          10, White
  EXPOSURE_ID:     605146889
  X_OFFSET:        933 [pixels]
  Y_OFFSET:        869 [pixels]
  WIDTH:           160 [pixels]
  HEIGHT:          160 [pixels]
  X_GRB_POS:       1093
  Y_GRB_POS:       1029
  BINNING_INDEX:   1
  IM_URL:          sw00959917000msuni605146890.fits
  SUN_POSTN:       347.02d {+23h 08m 04s}   -5.56d {-05d 33' 40"}
  SUN_DIST:         96.06 [deg]   Sun_angle= -7.6 [hr] (East of Sun)
  MOON_POSTN:      117.15d {+07h 48m 37s}  +22.87d {+22d 52' 29"}
  MOON_DIST:        85.86 [deg]
  MOON_ILLUM:      82 [%]
  GAL_COORDS:      271.89,-24.53 [deg] galactic lon,lat of the pointing direction
  ECL_COORDS:      141.86,-83.38 [deg] ecliptic lon,lat of the pointing direction
  COMMENTS:        SWIFT-UVOT Image.  
  COMMENTS:        The GRB Position came from the XRT Position Command.  
  COMMENTS:        The image has 2x2 binning (compression).  
  

  
• GCN NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Fri 06 Mar 20 00:31:31 UT
  NOTICE_TYPE:     Swift-UVOT Source List
  TRIGGER_NUM:     959917,   Seg_Num: 0
  POINT_RA:        101.143d {+06h 44m 34s} (J2000)
  POINT_DEC:       -62.006d {-62d 00' 21"} (J2000)
  POINT_ROLL:      245.980d
  IMG_START_DATE:  18914 TJD;    66 DOY;   20/03/06
  IMG_START_TIME:  1477.44 SOD {00:24:37.44} UT
  FILTER:          7, U
  BKG_MEAN:        0.282
  N_STARS:         46
  X_OFFSET:        613 [pixels]
  Y_OFFSET:        549 [pixels]
  X_MAX:           1572 [pixels]
  Y_MAX:           1508 [pixels]
  DET_THRESH:      5
  PHOTO_THRESH:    2
  SL_URL:          sw00959917000msufc605147077.fits
  SUN_POSTN:       347.02d {+23h 08m 05s}   -5.56d {-05d 33' 34"}
  SUN_DIST:         96.06 [deg]   Sun_angle= -7.6 [hr] (East of Sun)
  MOON_POSTN:      117.21d {+07h 48m 50s}  +22.87d {+22d 52' 10"}
  MOON_DIST:        85.86 [deg]
  MOON_ILLUM:      82 [%]
  GAL_COORDS:      271.89,-24.53 [deg] galactic lon,lat of the pointing direction
  ECL_COORDS:      141.84,-83.37 [deg] ecliptic lon,lat of the pointing direction
  COMMENTS:        SWIFT-UVOT Source List.  
  

• GCN NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Fri 06 Mar 20 00:31:52 UT
  NOTICE_TYPE:     Swift-UVOT Image
  TRIGGER_NUM:     959917,   Seg_Num: 0
  POINT_RA:        101.143d {+06h 44m 34s} (J2000)
  POINT_DEC:       -62.006d {-62d 00' 21"} (J2000)
  ROLL:            245.980d
  IMG_START_DATE:  18914 TJD;    66 DOY;   20/03/06
  IMG_START_TIME:  1477.44 SOD {00:24:37.44} UT
  FILTER:          7, U
  EXPOSURE_ID:     605147101
  X_OFFSET:        933 [pixels]
  Y_OFFSET:        869 [pixels]
  WIDTH:           160 [pixels]
  HEIGHT:          160 [pixels]
  X_GRB_POS:       1093
  Y_GRB_POS:       1029
  BINNING_INDEX:   1
  IM_URL:          sw00959917000msuni605147102.fits
  SUN_POSTN:       347.02d {+23h 08m 05s}   -5.56d {-05d 33' 34"}
  SUN_DIST:         96.06 [deg]   Sun_angle= -7.6 [hr] (East of Sun)
  MOON_POSTN:      117.21d {+07h 48m 51s}  +22.87d {+22d 52' 09"}
  MOON_DIST:        85.86 [deg]
  MOON_ILLUM:      82 [%]
  GAL_COORDS:      271.89,-24.53 [deg] galactic lon,lat of the pointing direction
  ECL_COORDS:      141.84,-83.37 [deg] ecliptic lon,lat of the pointing direction
  COMMENTS:        SWIFT-UVOT Image.  
  COMMENTS:        The GRB Position came from the XRT Position Command.  
  COMMENTS:        The image has 2x2 binning (compression).  
  

• GCN Circular #27319
  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-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 GRB200306.01 (trigger No 959917,06h 44m 24.72s , -62d 00m 18.0s, R=0.00130556) errorbox 12 sec after notice time and 49 sec after trigger time at 2020-03-06 00:21:46 UT, with upper limit up to 18.5 mag. The observations began at zenith distance = 31 deg. The sun altitude is -17.1 deg.
  The galactic latitude b = -24 deg., longitude l = 272 deg.
  Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1305993
  We obtain a following upper limits.

  Tmid-T0  |          Site       |Filt.| Expt. | Limit| Comment
  _________|_____________________|_____|_______|______|________
  
        55 |         MASTER-OAFA |   C |    10 | 17.2 |        
        96 |         MASTER-OAFA |   C |    10 | 17.2 |        
       144 |         MASTER-OAFA |   C |    20 | 17.7 |        
       201 |         MASTER-OAFA |   C |    30 | 18.0 |        
       274 |         MASTER-OAFA |   C |    50 | 18.3 |        
       361 |         MASTER-OAFA |   C |    60 | 18.5 |        
  

  Filter C is a clear (unfiltred) band.
  The observation and reduction will continue. The message may be cited.
• GCN Circular #27320
  K. K. Simpson (PSU), D. M. Palmer (LANL) and B. Sbarufatti (PSU) report on behalf of the Neil Gehrels Swift Observatory Team:
  At 00:19:40 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 200306A (trigger= 959917). Swift slewed immediately to the burst. Due to communications outages, no BAT data is immediately available at this time, but the complete data set will be available after upcoming downlinks to the ground.
  Using promptly downlinked data we find a bright, uncatalogued X-ray source with an enhanced position: RA, Dec 101.1050, -62.0058 which is equivalent to:

     RA(J2000)  = 06h 44m 25.20s
     Dec(J2000) = -62d 00' 20.9"
  

  with an uncertainty of 3.6 arcseconds (radius, 90% containment). This position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper.
  A power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the Galactic value of 8.67 x 10^20 cm^-2 (Willingale et al. 2013).
  The initial flux in the 2.5 s image was 3.02e-09 erg cm^-2 s^-1 (0.2-10 keV).
  UVOT took a finding chart exposure of nominal 150.000 seconds with the White filter starting 85s seconds after the BAT trigger. Automatic processing failed because of connectivity issues on the ground. Further analysis will be available once the full dataset gets on the ground.
  Burst Advocate for this burst is K. K. Simpson (kira.simpson1984 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 #27321
  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 200306A (Simpson et al., GCN 27320) with the LCO 1-m Sinistro instrument at the Cerro Tololo Interamerican Observatory, Chile site, on March 6, from 1:06 to 1:46 UT (corresponding to 0.78 to 1.45 hours from the GRB trigger time) with the Bessel I and R filters.
  We performed a series of 5x240s exposures in I and R. We detect a faint source in stacked R band images within the XRT error region that is not present in USNO or 2MASS catalogs. We do not detect a source in stacked I band images. Using the USNO-B.1 catalog as reference, we obtain the following magnitude detection in R at RA,DEC=101.1054814,-62.0049360 and the following 3-sigma upper limit in I:
  R = 21.75
  I > 21.52
  R.S. is funded by NSF AST grant #1831682
• GCN Circular #27331
  J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), E. Ambrosi (INAF-IASFPA) , M. Capalbi (INAF-IASFPA), M. Perri (ASDC), B. Sbarufatti (PSU), D.N. Burrows (PSU), J. D. Gropp (PSU), A.P. Beardmore (U. Leicester) and K.K. Simpson report on behalf of the Swift-XRT team:
  We have analysed 2.1 ks of XRT data for GRB 200306A (Simpson et al. GCN Circ. 27320), from 66 s to 6.2 ks after the BAT trigger. The data comprise 186 s in Windowed Timing (WT) mode (the first 9 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode. Using 2051 s of PC mode data and 6 UVOT images, we find an enhanced XRT position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 101.10233, -62.00654 which is equivalent to:
  RA (J2000): 06h 44m 24.56s Dec(J2000): -62d 00' 23.5"
  with an uncertainty of 1.5 arcsec (radius, 90% confidence).
  The light curve can be modelled with a power-law decay with a decay index of alpha=4.05 (+/-0.21).
  A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 2.93 (+/-0.14). The best-fitting absorption column is 5.2 (+/-0.5) x 10^21 cm^-2, in excess of the Galactic value of 8.6 x 10^20 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 1.89 (+0.19, -0.18) and a best-fitting absorption column of 4.3 (+1.1, -0.9) x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 4.2 x 10^-11 (6.3 x 10^-11) erg cm^-2 count^-1.
  A summary of the PC-mode spectrum is thus:

  Total column:	      4.3 (+1.1, -0.9) x 10^21 cm^-2
  Galactic foreground: 8.6 x 10^20 cm^-2
  Excess significance: 6.0 sigma
  Photon index:	          1.89 (+0.19, -0.18)
  

  If the light curve continues to decay with a power-law decay index of 4.05, the count rate at T+24 hours will be 3.6 x 10^-11 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.5 x 10^-21 (2.3 x 10^-21) erg cm^-2 s^-1.
  The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00959917.
  This circular is an official product of the Swift-XRT team.
• GCN Circular #27340
  S. Gupta, V. Sharma, A. Vibhute and D. Bhattacharya (IUCAA), V. Bhalerao (IIT-B), A. R. Rao (TIFR) and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: Analysis of AstroSat CZTI data showed the detection of the long GRB 200306A, which was also detected by Global MASTER-Net (Lipunov V. et al., GCN #27319), Swift (Simpson K. et al., GCN #27320) and Potential LCO (Strausbaugh R. et al., GCN #27321). The source was clearly detected in the 40-200 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2020-03-06 00:19:55.46 UT. The measured peak count rate associated with the burst is 323 +/- 20.4 cts/s above the background in the combined data of four quadrants, with a total of 5603 +/- 41.2 cts. The local mean background count rate was 525 +/- 0.9 cts/s. Using cumulative rates, we measure a T90 of 33.7 +/- 0.07 s. CZTI GRB detections are reported regularly on the payload site at http://astrosat.iucaa.in/czti/?q=grb. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, ISAC, IUCAA, SAC and PRL. The Indian Space Research Organisation funded, managed and facilitated the project.
• GCN Circular #27343
  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 200306A (Gropp et al., GCN Circ. 27326) 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 2020/03 7.27 to 2020/03 7.54 UTC (7.61 to 14.01 hours after the BAT trigger), obtaining a total of 4.31 hours exposure in the r and i bands.
  For a source within the Swift-XRT error circle, in comparison with the SDSS DR9 catalog, we obtain the following 3-sigma upper limits :

    r  > 23.34
    i  > 23.71
  

  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 #27346
  T. Sakamoto (AGU), S. D. Barthelmy (GSFC), J. R. Cummings (CPI), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL), K. K. Simpson (PSU), M. Stamatikos (OSU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):
  Using the data set from T-240 to T+962 sec from the recent telemetry downlink, we report further analysis of BAT GRB 200306A (trigger #959917) (Simpson et al., GCN Circ. 27320). The BAT ground-calculated position is RA, Dec = 101.114, -62.010 deg which is

     RA(J2000)  =  06h 44m 27.3s
     Dec(J2000) = -62d 00' 34.4"
  

  with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 75%.
  The mask-weighted light curve shows a few overlapping pulses that starts at ~T-4 s and ends at ~T+50 s. The main peak occurs at ~T+20 s. T90 (15-350 keV) is 32.87 +- 1.13 sec (estimated error including systematics).
  The time-averaged spectrum from T-3.67 to T+49.95 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 1.06 +- 0.15, and Epeak of 81.6 +- 6.9 keV (chi squared 32.91 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 1.0 +- 0.02 x 10^-5 erg/cm2 and the 1-sec peak flux measured from T+20.11 sec in the 15-150 keV band is 7.0 +- 0.3 ph/cm2/sec. A fit to a simple power law gives a photon index of 1.70 +- 0.03 (chi squared 98.65 for 57 d.o.f.). 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/959917/BA/
• GCN Circular #27351
  GRB 200306A: Swift/UVOT Upper Limits
  J. D. Gropp (PSU) and K. K. Simpson (PSU) report on behalf of the Swift/UVOT team:
  The Swift/UVOT began settled observations of the field of GRB 200306A 85 s after the BAT trigger (Simpson et al., GCN Circ. 27320). No optical afterglow consistent with the optical position (Strausbaugh et al., GCN Circ. 27321) 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            85          235          147         >21.0
  white               85         6191          459         >20.7
  v                 5049        11928         1011         >20.1
  b                 4434        16845         1278         >20.5
  u                  297         5864          351         >20.1
  w1                5459         5659          197         >19.7
  m2                5254         5454          197         >19.1
  w2                4844        11087         1082         >20.3
  

  The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.10 in the direction of the burst (Schlegel et al. 1998).