Gamma-ray Burst 200306C

(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 22:51:20 UT
  NOTICE_TYPE:     Swift-BAT GRB Position
  TRIGGER_NUM:     960102,   Seg_Num: 0
  GRB_RA:          198.582d {+13h 14m 20s} (J2000),
                   198.833d {+13h 15m 20s} (current),
                   197.959d {+13h 11m 50s} (1950)
  GRB_DEC:         +11.255d {+11d 15' 18"} (J2000),
                   +11.149d {+11d 08' 55"} (current),
                   +11.519d {+11d 31' 10"} (1950)
  GRB_ERROR:       3.00 [arcmin radius, statistical only]
  GRB_INTEN:       10731 [cnts]    Image_Peak=262 [image_cnts]
  TRIGGER_DUR:     4.096 [sec] 
  TRIGGER_INDEX:   307     E_range: 50-350 keV
  BKG_INTEN:       83343 [cnts]
  BKG_TIME:        82183.44 SOD {22:49:43.44} UT
  BKG_DUR:         40 [sec]
  GRB_DATE:        18914 TJD;    66 DOY;   20/03/06
  GRB_TIME:        82239.06 SOD {22:50:39.06} UT
  GRB_PHI:          58.49 [deg]
  GRB_THETA:        30.63 [deg]
  SOLN_STATUS:     0x2003
  RATE_SIGNIF:     14.10 [sigma]
  IMAGE_SIGNIF:    7.35 [sigma]
  MERIT_PARAMS:     +1  +0  +0  +2  +3  -3  +0  +0 +85  +0 
  SUN_POSTN:       347.88d {+23h 11m 32s}   -5.20d {-05d 11' 53"}
  SUN_DIST:        148.81 [deg]   Sun_angle= 9.9 [hr] (West of Sun)
  MOON_POSTN:      131.36d {+08h 45m 27s}  +20.90d {+20d 53' 56"}
  MOON_DIST:        65.16 [deg]
  MOON_ILLUM:      89 [%]
  GAL_COORDS:      322.75, 73.24 [deg] galactic lon,lat of the burst (or transient)
  ECL_COORDS:      192.68, 17.66 [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:        There is a bright star (mag=5.67) 5.42 arcmin from this position.  
  COMMENTS:        This is a GRB.  
  COMMENTS:        This trigger occurred at longitude,latitude = 358.67,17.28 [deg].  
  

• red DSS finding chart ps-file
  
  
• GCN NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Fri 06 Mar 20 22:52:50 UT
  NOTICE_TYPE:     Swift-XRT Nack-Position
  TRIGGER_NUM:     960102,   Seg_Num: 0 
  POINT_RA:        198.582d {+13h 14m 20s} (J2000)
  POINT_DEC:       +11.267d {+11d 16' 03"} (J2000)
  IMG_START_DATE:  18914 TJD;    66 DOY;   20/03/06
  IMG_START_TIME:  82355.97 SOD {22:52:35.97} UT,   116.9 [sec] since BAT Trigger
  +Time
  COUNTS:          21    Min_needed= 20 
  STD_DEV:         32.76   Max_StdDev_for_Good=28.44 [arcsec]
  PH2_ITER:        3    Max_iter_allowed= 4
  ERROR_CODE:      3
  COMMENTS:        SWIFT-XRT Nack Position.
  COMMENTS:        Standard deviation too large.
  

• GCN NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Fri 06 Mar 20 22:54:24 UT
  NOTICE_TYPE:     Swift-BAT GRB Lightcurve
  TRIGGER_NUM:     960102,   Seg_Num: 0
  GRB_RA:          198.582d {+13h 14m 20s} (J2000),
                   198.833d {+13h 15m 20s} (current),
                   197.959d {+13h 11m 50s} (1950)
  GRB_DEC:         +11.255d {+11d 15' 18"} (J2000),
                   +11.149d {+11d 08' 55"} (current),
                   +11.519d {+11d 31' 10"} (1950)
  GRB_DATE:        18914 TJD;    66 DOY;   20/03/06
  GRB_TIME:        82239.06 SOD {22:50:39.06} UT
  TRIGGER_INDEX:   307
  GRB_PHI:          58.49 [deg]
  GRB_THETA:        30.63 [deg]
  DELTA_TIME:      39.00 [sec]
  TRIGGER_DUR:     4.096 [sec] 
  SOLN_STATUS:     0x2003
  RATE_SIGNIF:     14.10 [sigma]
  IMAGE_SIGNIF:    7.35 [sigma]
  LC_URL:          sw00960102000msb.lc
  SUN_POSTN:       347.89d {+23h 11m 33s}   -5.20d {-05d 11' 50"}
  SUN_DIST:        148.82 [deg]   Sun_angle= 9.9 [hr] (West of Sun)
  MOON_POSTN:      131.39d {+08h 45m 35s}  +20.89d {+20d 53' 34"}
  MOON_DIST:        65.13 [deg]
  MOON_ILLUM:      89 [%]
  GAL_COORDS:      322.75, 73.24 [deg] galactic lon,lat of the burst (or transient)
  ECL_COORDS:      192.68, 17.66 [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:        There is a bright star (mag=5.67) 5.42 arcmin from this position.  
  COMMENTS:        This is a GRB.  
  COMMENTS:        This trigger occurred at longitude,latitude = 358.67,17.28 [deg].  
  

  
• GCN NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Fri 06 Mar 20 22:57:18 UT
  NOTICE_TYPE:     Swift-UVOT Source List 
  TRIGGER_NUM:     960102,   Seg_Num: 0   
  POINT_RA:        198.582d {+13h 14m 20s} (J2000)
  POINT_DEC:       +11.267d {+11d 16' 02"} (J2000)
  POINT_ROLL:      81.293d
  IMG_START_DATE:  18914 TJD;    66 DOY;   20/03/06
  IMG_START_TIME:  82356.55 SOD {22:52:36.55} UT,   117.5 [sec] since BAT Trigger
  +Time
  FILTER:          7, U
  BKG_MEAN:        0.634
  N_STARS:         114 
  X_OFFSET:        262 [pixels]
  Y_OFFSET:        417 [pixels]
  X_MAX:           1701 [pixels]
  Y_MAX:           1856 [pixels]
  DET_THRESH:      7
  PHOTO_THRESH:    3
  SL_URL:          sw00960102000msufc0117.fits
  SUN_POSTN:       347.89d {+23h 11m 33s}   -5.20d {-05d 11' 47"}
  SUN_DIST:        148.82 [deg]   Sun_angle= 9.9 [hr] (West of Sun)
  MOON_POSTN:      131.42d {+08h 45m 42s}  +20.89d {+20d 53' 14"}  
  MOON_DIST:        65.09 [deg] 
  MOON_ILLUM:      89 [%] 
  GAL_COORDS:      322.77, 73.25 [deg] galactic lon,lat of the pointing direction
  ECL_COORDS:      192.67, 17.67 [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 22:57:39 UT
  NOTICE_TYPE:     Swift-UVOT Processed Source List
  TRIGGER_NUM:     960102,   Seg_Num: 0 
  POINT_RA:        198.582d {+13h 14m 20s} (J2000)
  POINT_DEC:       +11.267d {+11d 16' 02"} (J2000)
  POINT_ROLL:      81.293d
  IMG_START_DATE:  18914 TJD;    66 DOY;   20/03/06
  IMG_START_TIME:  82356.55 SOD {22:52:36.55} UT,   117.5 [sec] since BAT Trigger Time
  FILTER:          7, U
  BKG_MEAN:        0.634
  N_STARS:         114 
  X_OFFSET:        262 [pixels]
  Y_OFFSET:        417 [pixels]
  X_MAX:           1701 [pixels]
  Y_MAX:           1856 [pixels]
  DET_THRESH:      7
  PHOTO_THRESH:    3
  SL_URL:          sw00960102000msufc0117.fits
  SUN_POSTN:       347.89d {+23h 11m 33s}   -5.20d {-05d 11' 46"}
  SUN_DIST:        148.82 [deg]   Sun_angle= 9.9 [hr] (West of Sun)
  MOON_POSTN:      131.43d {+08h 45m 43s}  +20.89d {+20d 53' 11"}  
  MOON_DIST:        65.09 [deg] 
  MOON_ILLUM:      89 [%] 
  GAL_COORDS:      322.77, 73.25 [deg] galactic lon,lat of the pointing direction
  ECL_COORDS:      192.67, 17.67 [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 22:58:17 UT
  NOTICE_TYPE:     Swift-UVOT Image
  TRIGGER_NUM:     960102,   Seg_Num: 0
  POINT_RA:        198.582d {+13h 14m 20s} (J2000)
  POINT_DEC:       +11.267d {+11d 16' 02"} (J2000)
  ROLL:            81.293d
  IMG_START_DATE:  18914 TJD;    66 DOY;   20/03/06
  IMG_START_TIME:  82356.55 SOD {22:52:36.55} UT,   117.5 [sec] since BAT Trigger Time
  FILTER:          7, U
  EXPOSURE_ID:     605227981
  X_OFFSET:        821 [pixels]
  Y_OFFSET:        976 [pixels]
  WIDTH:           160 [pixels]
  HEIGHT:          160 [pixels]
  X_GRB_POS:       981 
  Y_GRB_POS:       1136
  BINNING_INDEX:   1
  IM_URL:          sw00960102000msuni0142.fits
  SUN_POSTN:       347.89d {+23h 11m 33s}   -5.20d {-05d 11' 46"}
  SUN_DIST:        148.82 [deg]   Sun_angle= 9.9 [hr] (West of Sun)
  MOON_POSTN:      131.44d {+08h 45m 44s}  +20.89d {+20d 53' 07"}  
  MOON_DIST:        65.08 [deg] 
  MOON_ILLUM:      89 [%] 
  GAL_COORDS:      322.77, 73.25 [deg] galactic lon,lat of the pointing direction
  ECL_COORDS:      192.67, 17.67 [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 06 Mar 20 22:58:38 UT
  NOTICE_TYPE:     Swift-UVOT Processed Image
  TRIGGER_NUM:     960102,   Seg_Num: 0 
  POINT_RA:        198.582d {+13h 14m 20s} (J2000)
  POINT_DEC:       +11.267d {+11d 16' 02"} (J2000)
  ROLL:            81.293d
  IMG_START_DATE:  18914 TJD;    66 DOY;   20/03/06
  IMG_START_TIME:  82356.55 SOD {22:52:36.55} UT,   117.5 [sec] since BAT Trigger Time
  FILTER:          7, U
  EXPOSURE_ID:     605227981
  X_OFFSET:        821 [pixels]
  Y_OFFSET:        976 [pixels]
  WIDTH:           160 [pixels]
  HEIGHT:          160 [pixels]
  X_GRB_POS:       981 
  Y_GRB_POS:       1136
  BINNING_INDEX:   1
  IM_URL:          sw00960102000msuni0142.fits
  SUN_POSTN:       347.89d {+23h 11m 33s}   -5.20d {-05d 11' 46"}
  SUN_DIST:        148.82 [deg]   Sun_angle= 9.9 [hr] (West of Sun)
  MOON_POSTN:      131.44d {+08h 45m 45s}  +20.88d {+20d 53' 04"}  
  MOON_DIST:        65.08 [deg] 
  MOON_ILLUM:      89 [%] 
  GAL_COORDS:      322.77, 73.25 [deg] galactic lon,lat of the pointing direction
  ECL_COORDS:      192.67, 17.67 [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:     Fri 06 Mar 20 22:59:44 UT
  NOTICE_TYPE:     Swift-XRT Position
  TRIGGER_NUM:     960102,   Seg_Num: 0
  GRB_RA:          198.5556d {+13h 14m 13.34s} (J2000),
                   198.8070d {+13h 15m 13.68s} (current),
                   197.9327d {+13h 11m 43.83s} (1950)
  GRB_DEC:         +11.2698d {+11d 16' 11.2"} (J2000),
                   +11.1634d {+11d 09' 48.1"} (current),
                   +11.5342d {+11d 32' 03.1"} (1950)
  GRB_ERROR:       3.5 [arcsec radius, statistical plus systematic, 90% containment]    
  GRB_INTEN:       1.00e-10 [erg/cm2/sec]
  GRB_SIGNIF:      10.00 [sigma]
  IMG_START_DATE:  18914 TJD;    66 DOY;   20/03/06
  IMG_START_TIME:  82397.00 SOD {22:53:17.00} UT,   157.9 [sec] since BAT Trigger Time
  TAM[0-3]:        100.00 100.00 100.00 100.00
  AMPLIFIER:       1
  WAVEFORM:        31
  SUN_POSTN:       347.89d {+23h 11m 33s}   -5.20d {-05d 11' 44"}
  SUN_DIST:        148.84 [deg]   Sun_angle= 9.9 [hr] (West of Sun)
  MOON_POSTN:      131.45d {+08h 45m 48s}  +20.88d {+20d 52' 57"}  
  MOON_DIST:        65.04 [deg] 
  MOON_ILLUM:      89 [%] 
  GAL_COORDS:      322.69, 73.26 [deg] galactic lon,lat of the burst
  ECL_COORDS:      192.65, 17.66 [deg] ecliptic lon,lat of the burst
  COMMENTS:        SWIFT-XRT Coordinates.
  COMMENTS:        There is a bright star (mag=5.67) 5.76 arcmin from the XRT position.       
  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 1.1% < P(seren) < 2.8%. 
  

• GCN NOTICE
  

   
  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Fri 06 Mar 20 23:00:19 UT
  NOTICE_TYPE:     Swift-UVOT Position
  TRIGGER_NUM:     960102,   Seg_Num: 0
  GRB_RA:          198.5560d {+13h 14m 13.44s} (J2000),
                   198.8074d {+13h 15m 13.78s} (current),
                   197.9331d {+13h 11m 43.93s} (1950)
  GRB_DEC:         +11.2698d {+11d 16' 11.2"} (J2000),
                   +11.1634d {+11d 09' 48.1"} (current),
                   +11.5342d {+11d 32' 03.1"} (1950)
  GRB_ERROR:       1.1 [arcsec radius, statistical only]
  GRB_MAG:         17.46 +/- 0.40 [mag]
  FILTER:          7, U 
  IMG_START_DATE:  18914 TJD;    66 DOY;   20/03/06
  IMG_START_TIME:  82353.00 SOD {22:52:33.00} UT,   113.9 [sec] since BAT Trigger Time
  SUN_POSTN:       347.89d {+23h 11m 33s}   -5.20d {-05d 11' 44"}
  SUN_DIST:        148.84 [deg]   Sun_angle= 9.9 [hr] (West of Sun)
  MOON_POSTN:      131.46d {+08h 45m 50s}  +20.88d {+20d 52' 53"}  
  MOON_DIST:        65.04 [deg] 
  MOON_ILLUM:      89 [%] 
  GAL_COORDS:      322.69, 73.26 [deg] galactic lon,lat of the burst (or transient)      
  ECL_COORDS:      192.65, 17.66 [deg] ecliptic lon,lat of the burst (or transient)      
  COMMENTS:        SWIFT UVOT Position Notice.
  COMMENTS:        This Notice was ground-generated -- not flight-generated.
  COMMENTS:        There is a bright star (mag=5.67) 5.74 arcmin from the UVOT position. 
  

• GCN Circular #27324
  V. Lipunov, E. Gorbovskoy, V.Kornilov, D.Kuvshinov, N.Tyurina, P.Balanutsa, A.Kuznetsov, D. Vlasenko, F. Balakin Lomonosov Moscow State University, Sternberg Astronomical Institute, Moscow State University
  A. Tlatov, V.Senik, A.V. Parhomenko, D. Dormidontov Kislovodsk Solar Station of the Pulkovo Observatory
  K. Ivanov, O. Gres, N.M. Budnev, S. Yazev, O. Chuvalaev, V. Poleshchuk Irkutsk State University
  V. Yurkov, A. Gabovich, Yu. Sergienko Blagoveschensk Educational State University, Blagoveschensk
  R. Podesta, Carlos Lopez and F. Podesta Observatorio Astronomico Felix Aguilar (OAFA)
  Hugo Levato Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE)
  R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres The Instituto de Astrofisica de Canarias
  D. Buckley, S. Potter, A. Kniazev, M. Kotze South African Astronomical Observatory
  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 GRB200306.95 20 sec after notice time and 63 sec after trigger time at 2020-03-06 22:51:42 UT. On our first (10s exposure) set we found 1 optical transient within Swift error-box (ra=198.579 dec=11.2547 r=0.05) brighter than 16.3.
  

   T-Tmid      Date      Time       Expt.        Ra                Dec           Mag
  ---------|---------------------|-------|-----------------|-----------------|-------
        68   2020-03-06 22:51:42      10   (13h 14m 13.43s , +11d 16m 11.4s)     14.1
  

  The 5-sigma upper limit has been about 16.3mag The message may be cited.
• GCN Circular #27325
  V. Lipunov, E. Gorbovskoy, V.Kornilov, D.Kuvshinov, N.Tyurina, P.Balanutsa, A.Kuznetsov, D. Vlasenko, F. Balakin Lomonosov Moscow State University, Sternberg Astronomical Institute, Moscow State University
  A. Tlatov, V.Senik, A.V. Parhomenko, D. Dormidontov Kislovodsk Solar Station of the Pulkovo Observatory
  K. Ivanov, O. Gres, N.M. Budnev, S. Yazev, O. Chuvalaev, V. Poleshchuk Irkutsk State University
  V. Yurkov, A. Gabovich, Yu. Sergienko Blagoveschensk Educational State University, Blagoveschensk
  R. Podesta, Carlos Lopez and F. Podesta Observatorio Astronomico Felix Aguilar (OAFA)
  Hugo Levato Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE)
  R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres The Instituto de Astrofisica de Canarias
  D. Buckley, S. Potter, A. Kniazev, M. Kotze South African Astronomical Observatory
  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 GRB200306.95 20 sec after notice time and 63 sec after trigger time at 2020-03-06 22:51:42 UT. On our first (10s exposure) set we found 1 optical transient within Swift error-box (ra=198.579 dec=11.2547 r=0.05) brighter than 16.3.

   T-Tmid      Date      Time       Expt.        Ra                Dec           Mag
  ---------|---------------------|-------|-----------------|-----------------|-------
        68   2020-03-06 22:51:42      10   (13h 14m 13.43s , +11d 16m 11.4s)     14.1
  

  The 5-sigma upper limit has been about 16.3mag The message may be cited.
• GCN Circular #27326
  J.D. Gropp (PSU), S. D. Barthelmy (GSFC), D. N. Burrows (PSU), J. A. Kennea (PSU), S. Laha (GSFC/UMBC/CRESST), A. Y. Lien (GSFC/UMBC), F. E. Marshall (NASA/GSFC), D. M. Palmer (LANL), B. Sbarufatti (PSU), M. H. Siegel (PSU) and A. Tohuvavohu (U Toronto) report on behalf of the Neil Gehrels Swift Observatory Team:
  At 22:50:39 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 200306C (trigger=960102). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 198.582, +11.255 which is

     RA(J2000) = 13h 14m 20s
     Dec(J2000) = +11d 15' 18"
  

  with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a complex structure with a duration of about 50 sec. The peak count rate was ~1800 counts/sec (15-350 keV), at ~3 sec after the trigger.
  The XRT began observing the field at 22:52:35.9 UT, 116.9 seconds after the BAT trigger. Using promptly downlinked data we find a fading, uncatalogued X-ray source located at RA, Dec 198.55562, 11.26981 which is equivalent to:

     RA(J2000)  = 13h 14m 13.35s
     Dec(J2000) = +11d 16' 11.3"
  

  with an uncertainty of 3.5 arcseconds (radius, 90% containment). This location is 107 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.
  A power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the Galactic value (1.91 x 10^20 cm^-2, Willingale et al. 2013), with an excess column of 2.8 (+2.73/-2.37) x 10^21 cm^-2 (90% confidence).
  UVOT took a finding chart exposure of 250 seconds with the U filter starting 117 seconds after the BAT trigger. There is a candidate afterglow in the list of sources generated on-board at

    RA(J2000)  =  13:14:13.44 = 198.55602
    DEC(J2000) = +11:16:11.5  =  11.26985
  

  with a 90%-confidence error radius of about 1.10 arc sec. This position is 1.4 arc sec. from the center of the XRT error circle. The estimated magnitude is 17.47. No correction has been made for the expected extinction corresponding to E(B-V) of 0.02.
  Burst Advocate for this burst is J.D. Gropp (jdg44 AT psu.edu). 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 #27327
  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 GRB200306.95 (trigger No 960102,13h 14m 19.68s , +11d 15m 18.0s, R=0.05) errorbox 18 sec after notice time and 63 sec after trigger time at 2020-03-06 22:51:42 UT, with upper limit up to 18.9 mag. The observations began at zenith distance = 32 deg. The sun altitude is -47.4 deg.
  MASTER-Tavrida robotic telescope located in Russia (Lomonosov MSU, SAI Crimea astronomical station) was pointed to the Swift GRB200306.95 errorbox 40 sec after notice time and 85 sec after trigger time at 2020-03-06 22:52:04 UT, with upper limit up to 18.9 mag. The observations began at zenith distance = 36 deg. The sun altitude is -49.3 deg.
  The galactic latitude b = 73 deg., longitude l = 324 deg.
  Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1306689
  We obtain a following upper limits.

  Tmid-T0  |          Site       |Filt.| Expt. | Limit| Comment
  _________|_____________________|_____|_______|______|________
  
        69 |   MASTER-Kislovodsk |  P- |    10 | 16.9 |        
        89 |   MASTER-Kislovodsk |  P- |    50 | 18.0 |  Coadd 
        69 |   MASTER-Kislovodsk |  P| |    10 | 16.8 |        
        89 |   MASTER-Kislovodsk |  P| |    50 | 17.9 |  Coadd 
        91 |   MASTER-Kislovodsk |  P- |    20 | 17.4 |        
        91 |   MASTER-Kislovodsk |  P| |    20 | 17.2 |        
        96 |      MASTER-Tavrida |   C |    20 | 17.5 |        
       121 |      MASTER-Tavrida |   C |    70 | 18.2 |  Coadd 
       117 |   MASTER-Kislovodsk |  P- |    20 | 17.3 |        
       117 |   MASTER-Kislovodsk |  P| |    20 | 17.2 |        
       136 |      MASTER-Tavrida |   C |    20 | 17.5 |        
       149 |   MASTER-Kislovodsk |  P- |    30 | 17.1 |        
       149 |   MASTER-Kislovodsk |  P| |    30 | 17.5 |        
       184 |   MASTER-Kislovodsk |  P| |   100 | 18.3 |  Coadd 
       181 |      MASTER-Tavrida |   C |    30 | 17.7 |        
       185 |   MASTER-Kislovodsk |  P- |    30 | 17.6 |        
       230 |   MASTER-Kislovodsk |  P- |   120 | 18.5 |  Coadd 
       185 |   MASTER-Kislovodsk |  P| |    30 | 17.5 |        
       227 |   MASTER-Kislovodsk |  P- |    40 | 17.9 |        
       227 |   MASTER-Kislovodsk |  P| |    40 | 17.6 |        
       237 |      MASTER-Tavrida |   C |    40 | 18.0 |        
       297 |      MASTER-Tavrida |   C |   160 | 18.9 |  Coadd 
       278 |   MASTER-Kislovodsk |  P- |    50 | 18.1 |        
       278 |   MASTER-Kislovodsk |  P| |    50 | 17.8 |        
       343 |   MASTER-Kislovodsk |  P| |   180 | 18.6 |  Coadd 
       302 |      MASTER-Tavrida |   C |    50 | 18.2 |        
       340 |   MASTER-Kislovodsk |  P- |    60 | 18.2 |        
       420 |   MASTER-Kislovodsk |  P- |   220 | 18.9 |  Coadd 
       340 |   MASTER-Kislovodsk |  P| |    60 | 17.9 |        
       383 |      MASTER-Tavrida |   C |    70 | 18.3 |        
       411 |   MASTER-Kislovodsk |  P- |    70 | 18.2 |        
       411 |   MASTER-Kislovodsk |  P| |    70 | 18.1 |        
       483 |      MASTER-Tavrida |   C |    90 | 18.5 |        
       498 |   MASTER-Kislovodsk |  P- |    90 | 18.2 |        
       498 |   MASTER-Kislovodsk |  P| |    90 | 18.1 |        
       605 |   MASTER-Kislovodsk |  P- |   110 | 18.2 |        
       605 |   MASTER-Kislovodsk |  P| |   110 | 18.4 |        
  

  Filter C is a clear (unfiltred) band.
  The observation and reduction will continue. The message may be cited.
• GCN NOTICE
  

   
  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Fri 06 Mar 20 23:10:19 UT
  NOTICE_TYPE:     Swift-UVOT Source List 
  TRIGGER_NUM:     960102,   Seg_Num: 0   
  POINT_RA:        198.583d {+13h 14m 20s} (J2000)
  POINT_DEC:       +11.270d {+11d 16' 10"} (J2000)
  POINT_ROLL:      81.292d
  IMG_START_DATE:  18914 TJD;    66 DOY;   20/03/06
  IMG_START_TIME:  83114.88 SOD {23:05:14.88} UT,   875.8 [sec] since BAT Trigger Time
  FILTER:          7, U
  BKG_MEAN:        0.424
  N_STARS:         105 
  X_OFFSET:        262 [pixels]
  Y_OFFSET:        417 [pixels]
  X_MAX:           1701 [pixels]
  Y_MAX:           1856 [pixels]
  DET_THRESH:      6
  PHOTO_THRESH:    2
  SL_URL:          sw00960102000msufc0875.fits
  SUN_POSTN:       347.90d {+23h 11m 35s}   -5.19d {-05d 11' 34"}
  SUN_DIST:        148.82 [deg]   Sun_angle= 9.9 [hr] (West of Sun)
  MOON_POSTN:      131.56d {+08h 46m 15s}  +20.86d {+20d 51' 42"}  
  MOON_DIST:        64.97 [deg] 
  MOON_ILLUM:      89 [%] 
  GAL_COORDS:      322.77, 73.25 [deg] galactic lon,lat of the pointing direction
  ECL_COORDS:      192.67, 17.68 [deg] ecliptic lon,lat of the pointing direction
  COMMENTS:        SWIFT-UVOT Source List.
  COMMENTS:        There is a bright star (mag=5.67) 5.42 arcmin from the BAT position.
  

• GCN NOTICE
  

    
  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Fri 06 Mar 20 23:10:44 UT
  NOTICE_TYPE:     Swift-UVOT Processed Source List
  TRIGGER_NUM:     960102,   Seg_Num: 0 
  POINT_RA:        198.583d {+13h 14m 20s} (J2000)
  POINT_DEC:       +11.270d {+11d 16' 10"} (J2000)
  POINT_ROLL:      81.292d
  IMG_START_DATE:  18914 TJD;    66 DOY;   20/03/06
  IMG_START_TIME:  83114.88 SOD {23:05:14.88} UT,   875.8 [sec] since BAT Trigger Time
  FILTER:          7, U
  BKG_MEAN:        0.424
  N_STARS:         105 
  X_OFFSET:        262 [pixels]
  Y_OFFSET:        417 [pixels]
  X_MAX:           1701 [pixels]
  Y_MAX:           1856 [pixels]
  DET_THRESH:      6
  PHOTO_THRESH:    2
  SL_URL:          sw00960102000msufc0875.fits
  SUN_POSTN:       347.90d {+23h 11m 35s}   -5.19d {-05d 11' 34"}
  SUN_DIST:        148.82 [deg]   Sun_angle= 9.9 [hr] (West of Sun)
  MOON_POSTN:      131.57d {+08h 46m 16s}  +20.86d {+20d 51' 39"}  
  MOON_DIST:        64.96 [deg] 
  MOON_ILLUM:      89 [%] 
  GAL_COORDS:      322.77, 73.25 [deg] galactic lon,lat of the pointing direction
  ECL_COORDS:      192.67, 17.68 [deg] ecliptic lon,lat of the pointing direction
  COMMENTS:        SWIFT-UVOT Processed Source List.
  COMMENTS:        All 4 attachments are included. 
  COMMENTS:        There is a bright star (mag=5.67) 5.42 arcmin from the BAT position.  
  

• GCN NOTICE
  

    
  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Fri 06 Mar 20 23:11:33 UT
  NOTICE_TYPE:     Swift-UVOT Image
  TRIGGER_NUM:     960102,   Seg_Num: 0
  POINT_RA:        198.583d {+13h 14m 20s} (J2000)
  POINT_DEC:       +11.270d {+11d 16' 10"} (J2000)
  ROLL:            81.292d
  IMG_START_DATE:  18914 TJD;    66 DOY;   20/03/06
  IMG_START_TIME:  83114.88 SOD {23:05:14.88} UT,   875.8 [sec] since BAT Trigger Time
  FILTER:          7, U
  EXPOSURE_ID:     605228739
  X_OFFSET:        821 [pixels]
  Y_OFFSET:        976 [pixels]
  WIDTH:           160 [pixels]
  HEIGHT:          160 [pixels]
  X_GRB_POS:       981 
  Y_GRB_POS:       1136
  BINNING_INDEX:   1
  IM_URL:          sw00960102000msuni0900.fits
  SUN_POSTN:       347.90d {+23h 11m 35s}   -5.19d {-05d 11' 33"}
  SUN_DIST:        148.82 [deg]   Sun_angle= 9.9 [hr] (West of Sun)
  MOON_POSTN:      131.57d {+08h 46m 18s}  +20.86d {+20d 51' 34"}  
  MOON_DIST:        64.96 [deg] 
  MOON_ILLUM:      89 [%] 
  GAL_COORDS:      322.77, 73.25 [deg] galactic lon,lat of the pointing direction
  ECL_COORDS:      192.67, 17.68 [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).
  COMMENTS:        There is a bright star (mag=5.67) 5.42 arcmin from the BAT position.
  

• GCN NOTICE
  

    
  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Fri 06 Mar 20 23:11:38 UT
  NOTICE_TYPE:     Swift-UVOT Processed Image
  TRIGGER_NUM:     960102,   Seg_Num: 0 
  POINT_RA:        198.583d {+13h 14m 20s} (J2000)
  POINT_DEC:       +11.270d {+11d 16' 10"} (J2000)
  ROLL:            81.292d
  IMG_START_DATE:  18914 TJD;    66 DOY;   20/03/06
  IMG_START_TIME:  83114.88 SOD {23:05:14.88} UT,   875.8 [sec] since BAT Trigger Time
  FILTER:          7, U
  EXPOSURE_ID:     605228739
  X_OFFSET:        821 [pixels]
  Y_OFFSET:        976 [pixels]
  WIDTH:           160 [pixels]
  HEIGHT:          160 [pixels]
  X_GRB_POS:       981 
  Y_GRB_POS:       1136
  BINNING_INDEX:   1
  IM_URL:          sw00960102000msuni0900.fits
  SUN_POSTN:       347.90d {+23h 11m 35s}   -5.19d {-05d 11' 33"}
  SUN_DIST:        148.82 [deg]   Sun_angle= 9.9 [hr] (West of Sun)
  MOON_POSTN:      131.58d {+08h 46m 18s}  +20.86d {+20d 51' 33"}  
  MOON_DIST:        64.95 [deg] 
  MOON_ILLUM:      89 [%] 
  GAL_COORDS:      322.77, 73.25 [deg] galactic lon,lat of the pointing direction
  ECL_COORDS:      192.67, 17.68 [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.
  COMMENTS:        There is a bright star (mag=5.67) 5.42 arcmin from the BAT position.
  

• GCN Circular #27328
  Martin Jelinek, 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 alert of GRB200306C (Gropp et al GCNC 27326), obtaining a series of 20 s unfiltered images starting at 22:51:39.3 UT, i.e. 60.3s post trigger.
  We clearly detect the source reported by (Gropp et al GCN 27326 and Lipunov et al GCN 27325), decaying at a rate of alpha ~ 1.4 +- 0.1. The brightness of the object was R = 14.1 the first image.
• GCN Circular #27329
  Y.-D. Hu, A. J. Castro-Tirado and E. Fernandez-Garcia (IAA-CSIC), C. Perez del Pulgar, A. Reina, A. Castellon, I. Carrasco, I. Perez-Garcia (UMA), F. Rendon (IAA-CSIC and INTA-CEDEA), on behalf of a larger collaboration, report:
  The 30cm BOOTES-1 robotic telescope at INTA-CEDEA in Huelva (Spain) automatically responded to the Swift trigger of GRB 200306C (Gropp et al., GCNC 27326). A sequence of 1-s images (clear filter) were obtained starting at 22:52:28 UT (i.e. 109s after the burst). At the UVOT position reported by Swift an optical transient is detected with R = 14.9, in agreement with the MASTER (Lipunov et al. GCNC 27324) and FRAM detections (Jelinek et al. GCNC 27328). A detailed analysis for the sequence of images which were obtained is ongoing. The magnitude is calibrated against the USNO-B1 catalog and is not corrected for Galactic extinction in the direction of the GRB.
  We thank the staff at INTA-CEDEA for its excellent support.
• GCN Circular #27332
  K. Ackley (1); K. Wiersema (2); Y.-L. Mong (1); D. K. Galloway (1); D. Steeghs (2); V.Dhillon (3); P. O'Brien (4); G. Ramsay (5); D. Pollacco (2); E. Thrane (1); S. Poshyachinda (6); R. Kotak (7); L. Nuttall (8); E. Pall\'e (9); K. Ulaczyk (2); J. Lyman (2); R. Cutter (2); A. Levan (2); T. Marsh (2); R. West (2); E. Stanway (2); B. Gompertz (2); T. Killestein (2); A. Casey (1); M. Brown (1); B. Muller (1); M. Dyer (3); J. Mullaney (3); E. Daw (3); S. Littlefair (3); J. Maund (3); L. Makrygianni (3); U. Burhanudin (3); R. Starling (4); R. Eyles (4); S. Tooke (4); S. Aukkaravittayapun (6); U. Sawangwit (6); S. Awiphan (6); D. Mkrtichian (6); P. Irawati (6); S. Mattila (7); T. Heikkil\"a (7); E. Rol (1) ((1) Monash University, (2) Warwick University, (3) University of Sheffield, (4) University of Leicester, (5) Armagh Observatory & Planetarium, (6) National Astronomical Research Institute of Thailand, (7) University of Turku, (8) University of Portsmouth, (9) Instituto de Astrofisica de Canarias)
  report on behalf of the GOTO collaboration:
  We carried out observations with the Gravitational-wave Optical Transient Observer (GOTO), in response to GRB 2000306C (Palmer et al. 2020; GCN #27326).
  We made a series of 9x60 s exposures using our wide L-band filter (400-700 nm) covering the Swift UVOT position (Palmer et al. 2020; GCN #27326), starting at 1.1 hours after the Swift BAT trigger with midtime 23:56:45 UT on 06 March 2020.
  Using a difference imaging analysis with recent survey observations of the same pointings as reference, we do not identify the detections from MASTER (Lipunov et al. GCN #27324), FRAM (Jelinek et al. GCN #27328), and BOOTES-1 (Castro-Tirado et al. GCN #27329). Our mean 5-sigma detection limit was g=19.1 mag based on PS1 catalogue calibrators.
  GOTO is operated at the La Palma observing facilities of the University of Warwick on behalf of a consortium including the University of Warwick, Monash University, Armagh Observatory, the University of Leicester, the University of Sheffield, the National Astronomical Research Institute of Thailand (NARIT) and the Instituto de Astrofisica de Canarias (IAC) (https://goto-observatory.org)
• GCN Circular #27333
  A. Moskvitin on behalf of the larger GRB follow-up team report.
  We observed the field of the GRB 200306C (Gropp et al. GCNC #27326) with the 1-m telescope of SAO RAS in BVRc filters. The observations were started in semi-automatic mode since 2 minutes after the trigger.
  We clearly detected the OT discovered by Swift/UVOT, MASTER-Net (Lipunov et al. GCNC #27324/27325/27327), FRAM-ORM (Jelinek et al. GCNC #27328), BOOTES-1 (Hu et al., GCNC #27329) with the coordinates: R. A. = 13:14:13.44, Decl. = +11:16:11.8 +/- 0".5, Epoch = 2000.0.
  Preliminary R band photometry of the OT:

  Tmid-T0, s   exp., s   Rmag +/- err
  
  151          30        15.29 +/- 0.06
  183          30        15.77 +/- 0.03
  230          30        15.97 +/- 0.12
  276          30        16.14 +/- 0.04
  388          60        16.49 +/- 0.05
  464          60        16.69 +/- 0.07
  541          60        16.99 +/- 0.04
  

  The calibration were done against nearby SDSS stars (Lupton, 2005).
• GCN Circular #27334
  L. Izzo (DARK/NBI) and D. Perley (LJMU) report:
  We observed GRB 200303C (Gropp et al. GCN 27326) with the IO:O camera mounted on the 2-m Liverpool Telescope located in La Palma, Spain. Observations started on March 7th at 01:01:49 UT (2.20 hours after the GRB trigger) and we obtained a series of 5x60s images in the griz filters.
  In our stacked i-band and z-band images we detect the afterglow at the position reported by Swift-UVOT and other telescopes (Lipunov et al. GCNC 27324, GCN 27325; Jelinek et al. GCN 27328; Hu et al., GCN 27329; Moskvitin GCN 27333) and we measure a preliminary magnitude of i(AB) = 20.7 +- 0.1 mag (median time 2.46 hr after the GRB trigger) and z(AB) = 21.0 +- 0.3 mag (median time 2.58 hr after the GRB).
  [GCN OPS NOTE(07mar20): Per author's request, in the first sentence "200303A" was changed to "200303C". Also per request, the thrid paragraph was removed as it was an accidental inclusion of a previous circular.]
• GCN Circular #27335
  D. A. Kann, M. Blazek (both HETH/IAA-CSIC), A. de Ugarte Postigo (HETH/IAA-CSIC, DARK/NBI), C. C. Thoene, J. F. Agui Fernandez (both HETH/IAA-CSIC), and V. Casanova (IAA-CSIC) report:
  We observed the optical afterglow position of GRB 200306C (Lipunov et al., GCNs #27324, #27325; Gropp et al., GCN #27326; Jelinek et al., GCN #27328; Hu et al., GCN #27329; Moskvitin, GCN #27333; Izzo & Perley, GCN #27334) with the 1.5m telescope of the Sierra Nevada Observatory, Granada, Spain, in the V filter. Observations began 46 minutes after the GRB, and we obtained 18 x 30 s images under moonlight. We also obtained four Rc images before technical problems shut down the telescope, but stray light from a nearby bright star precludes a detection.
  We detect the afterglow in a stacked image centered 0.03985 days after the GRB, at V = 19.38 +/- 0.14 mag (Vega mag).
  The afterglow magnitude was measured against six comparison stars from the GSC 2.3 catalog.
• GCN Circular #27337
  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 200306C (Gropp et al., GCN 27326) with the LCO 1-m Sinistro instrument at the Cerro Tololo Interamerican Observatory, Chile site, on March 7, from 4:50 to 5:21 UT (corresponding to 6.0 to 6.5 hours from the GRB trigger time) with the Bessel I and R filters.
  We performed a series of 5x120s exposures in I and R. We do not detect any sources in the individual frames (nor in stacked images) at the location of previous optical afterglow detections (Lipunov et al., GCN 27325, Jelinek et al., GCN 27328, Castro-Tirado et al., GCN 27329, Moskvitin et al., GCN 27333, Izzo et al., GCN 27334, Kann et al., 27335). Using the USNO-B.1 catalog as reference, we obtain the following 3-sigma upper limits:
  R > 20.56
  I > 19.65
  R.S. is funded by NSF AST grant #1831682
• GCN Circular #27338
  I.A.Steele (LJMU) reports on behalf of a larger collaboration:
  The automated system of the Liverpool 2.0m telescope, La Palma, followed up GRB200306C starting at 23:01:37 UT (i.e. approximately 11 minutes post trigger) in the r’, i’,and z’ band filters for a period of 1 hour.
  We clearly detect the afterglow reported in GCN numbers 27326, 27328, 27329, 27334 with a r’ band magnitude of 17.3 in our first frame calibrated with respect to a nearby APASS source. The afterglow continues to fade over the course of the hour.
• GCN Circular #27339
  Gu Lim (SNU), Myungshin Im (SNU), Changbom Park (KIAS), Gregory S. H. Paek (SNU) on behalf of GECKO
  We carried out a follow-up observation of the afterglow of GRB 200306C (Gropp et al GCNC 27326) using the 14-inch KCT (KIAS Chamnun Telescope) at DeepSkyChile, Chile. A series of 30x120 s exposures on SDSS i-band were obtained, starting at 04:37:13.849 UT on 06 March 2020.
  We do not detect any sources on the stacked image at the previously reported position of afterglow detections (Lipunov et al. GCN #27324, GCN #27325, Jelinek et al. GCN #27328, Castro-Tirado et al. GCN #27329, Moskvitin et al., GCN 27333, Izzo et al., GCN 27334, Kann et al., 27335). After the flux calibration using SDSS dr12 photometric catalog, 5-sigma detection limit is obtained as i > 18.40 AB magnitude.
  KIAS Chamnun Telescope (KCT) is a 0.36m telescope of the Korea Institute for Advanced Study (KIAS), recently installed at the DeepSkyChile site in Chile. "Chamnun" is a Korean word for "True Eye", meaning the eye that can see the truth. Gravitational-wave EM Counterpart Korean Observatory (GECKO) is a network of 10+ 0.5m to 1m class telescopes over the world.
• GCN Circular #27341
  P. Gokuldass (UVI), D. Morris (UVI), N. Orange (OrangeWave Innovative Science, LLC), A. Cucchiara (College of Marin), R. Strausbaugh (UVI) report:
  We observed the field of GRB200306C (Gropp et al., GCN 27326) with the 0.5m Virgin Island Robotic Telescope (VIRT) at the University of the Virgin Islands' Etelman Observatory on 03-07-2020 starting at 01:52:04 UT (T+3.0 hrs). We performed a series of exposures in R filter. The weather conditions were clear during the hours of observation and the zenith angle at the start of observations was 68 degrees and rising. We observed the Swift XRT position with a 20'x20' field of view.
  We find no new source at the position of previous optical detections (Lipunov et al., GCN 27325, Jelinek et al., GCN 27328, Castro-Tirado et al., GCN 27329, Moskvitin et al., GCN 27333, Izzo et al., GCN 27334, Kann et al., 27335) and report upper limits as follows:

  T_mid       ||Exposure     ||Filter      ||Limit
  T+3.3 hrs      ||1025s          ||R           ||18.0
  T+4.0 hrs      ||3360s          ||R           ||19.0
  

  The limits are estimated from comparison to nearby USNO B1 stars and are not corrected for Galactic extinction. The VIRT is still in the commissioning phase.
  This work is supported by NASA-MUREP-MIRO grant NNX15AP95A, NSF EiR AST Award 1901296, and NSF HBCU-UP AST Award 1831682. This message can be cited.
• GCN Circular #27342
  J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester) report on behalf of the Swift-XRT team.
  Using 1935 s of XRT Photon Counting mode data and 2 UVOT images for GRB 200306C, 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 = 198.55588, +11.26953 which is equivalent to:

  RA (J2000): 13h 14m 13.41s
  Dec (J2000): +11d 16' 10.3"
  

  with an uncertainty of 2.2 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 #27345
  K.L. Page (U. Leicester), M. Capalbi (INAF-IASFPA), M. Perri (ASDC), V. D'Elia (ASDC), D.N. Burrows (PSU), J. D. Gropp (PSU), J.A. Kennea (PSU), A.P. Beardmore (U. Leicester), P.A. Evans (U. Leicester) and J.D. Gropp report on behalf of the Swift-XRT team:
  We have analysed 6.0 ks of XRT data for GRB 200306C (Gropp et al. GCN Circ. 27326), from 101 s to 18.9 ks after the BAT trigger. The data comprise 36 s in Windowed Timing (WT) mode (the first 9 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Osborne et al. (GCN Circ. 27342).
  The late-time light curve (from T0+5.5 ks) can be modelled with a power-law decay with a decay index of alpha=2.2 (+0.4, -0.3).
  A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.56 (+0.11, -0.10). The best-fitting absorption column is 4.1 (+3.0, -2.2) x 10^20 cm^-2, consistent with the Galactic value of 1.9 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 4.2 x 10^-11 (4.4 x 10^-11) erg cm^-2 count^-1.
  A summary of the PC-mode spectrum is thus:

  Total column:	      4.1 (+3.0, -2.2) x 10^20 cm^-2
  Galactic foreground: 1.9 x 10^20 cm^-2
  Excess significance: <1.6 sigma
  Photon index:	          1.56 (+0.11, -0.10)
  

  If the light curve continues to decay with a power-law decay index of 2.2, the count rate at T+24 hours will be 4.4 x 10^-4 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.8 x 10^-14 (1.9 x 10^-14) erg cm^-2 s^-1.
  The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00960102.
  This circular is an official product of the Swift-XRT team.
• GCN Circular #27348
  D. A. Kann (HETH/IAA-CSIC), A. de Ugarte Postigo (HETH/IAA-CSIC, DARK/NBI), M. Blazek, C. C. Thoene, J. F. Agui Fernandez (all HETH/IAA-CSIC), R. Pedro Hedrosa, and E. Gallego (both CAHA) report:
  We observed the field of the afterglow of GRB 200306C (Lipunov et al., GCNs #27324, #27325; Gropp et al., GCN #27326; Jelinek et al., GCN #27328; Hu et al., GCN #27329; Moskvitin, GCN #27333; Izzo & Perley, GCN #27334; Kann et al., GCN #27335; Steele et al., GCN #27338) with the 2.2m telescope of Calar Alto equipped with CAFOS. We obtained 4 x 720 s images in the Rc band under adverse conditions (moonlight, passing clouds, bright star still there).
  Our stacked image centred at mean epoch 1.25519 d after the GRB shows no detection to a 3-sigma upper limit of Rc > 23.0 mag (AB). The magnitude limit was obtained versus SDSS stars in the field.
• GCN Circular #27352
  GRB 200306C: Swift/UVOT Detection
  J. D. Gropp (PSU) reports on behalf of the Swift/UVOT team:
  The Swift/UVOT began settled observations of the field of GRB 200306C 118 s after the BAT trigger (Gropp et al., GCN Circ. 27326).
  A fading source consistent with the positions reported by FRAM-ORM (Jelinek et al., GCN Circ. 27238), BOOTES-1 (Hu et al., GCN Circ. 27329), SAO RAS (Moskvitin et al., GCN Circ. 27333) Liverpool Telescope (Izzo et al., GCN Circ 27334) and OSN (Kann et al., GCN Circ. 27335) is detected in the initial UVOT exposures.
  The preliminary UVOT position is:

      RA  (J2000) =  13:14:13.46 = 198.55607 (deg.)
      Dec (J2000) = +11:16:11.7  =  11.26992 (deg.)
  

  with an estimated uncertainty of 0.43 arc sec. (radius, 90% confidence).
  Preliminary detections using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are:

  Filter         T_start(s)   T_stop(s)      Exp(s)           Mag
  
  u_fc           141             390               245
  16.90+-0.05
  u                899           1049               147
  18.39+-0.16
  

  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 #27353
  M. Stamatikos (OSU), S. D. Barthelmy (GSFC), J. R. Cummings (CPI), J.D. Gropp (PSU), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):
  Using the data set from T-240 to T+1065 sec from the recent telemetry downlink, we report further analysis of BAT GRB 200306C (trigger #960102) (Gropp et al., GCN Circ. 27326). The BAT ground-calculated position is RA, Dec = 198.577, 11.263 deg which is

     RA(J2000)  =  13h 14m 18.6s
     Dec(J2000) = +11d 15' 47.7"
  

  with an uncertainty of 1.3 arcmin, (radius, sys+stat, 90% containment). The partial coding was 42%.
  The mask-weighted light curve shows several overlapping pulses that start at ~T-12 s and end at ~T+50 s. T90 (15-350 keV) is 53.5 +- 12.8 sec (estimated error including systematics).
  The time-averaged spectrum from T-12.33 to T+50.70 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 0.83 +- 0.12. The fluence in the 15-150 keV band is 2.8 +- 0.2 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+3.45 sec in the 15-150 keV band is 1.3 +- 0.3 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/960102/BA/
• GCN Circular #27354
  T. Laskar (University of Bath), S. Bhandari (CSIRO), K. D. Alexander (Northwestern), E. Berger (Harvard), W. Fong (Northwestern), R. Margutti (Northwestern), C. G. Mundell (University of Bath), and P. Schady (University of Bath) report on behalf of a larger collaboration:
  "We observed GRB 200306C (Gropp et al., GCN 27326) with the Atacama Large Millimeter/Submillimeter Array (ALMA) at 97.5 GHz over two epochs:
  (i) on 2020 March 08 beginning at 05:08:54 UT (at a mean time of 0.99 d after the burst), and (ii) on 2020 March 09 beginning at 05:46:00 UT (at a mean time of 2.01 d after the burst).
  No mm-band emission is detected at the optical position (Gropp et al., GCN 27326; Moskvitin, GCN 27333) in either epoch. Preliminary 3-sigma upper limits are ~ 100 uJy and ~ 120 uJy from the individual observations and ~ 80 uJy from stacking the two epochs.
  We thank the JAO staff, AoD, P2G, and the entire ALMA team for their help with scheduling and executing these observations."