Gamma-ray Burst 060306

(All information courtesy of the instrument teams.)

Previous IAU Circulars

• none

• GCN/BACODINE POSITION NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Mon 06 Mar 06 00:49:35 UT
  NOTICE_TYPE:     Swift-BAT GRB Position
  TRIGGER_NUM:     200638,   Seg_Num: 0
  GRB_RA:           41.099d {+02h 44m 24s} (J2000),
                    41.177d {+02h 44m 42s} (current),
                    40.465d {+02h 41m 52s} (1950)
  GRB_DEC:          -2.153d {-02d 09' 10"} (J2000),
                    -2.127d {-02d 07' 37"} (current),
                    -2.364d {-02d 21' 49"} (1950)
  GRB_ERROR:       3.00 [arcmin radius, statistical only]
  GRB_INTEN:       7307 [cnts]    Image_Peak=825 [image_cnts]
  TRIGGER_DUR:     1.024 [sec] 
  TRIGGER_INDEX:   146     E_range: 25-100 keV
  BKG_INTEN:       27244 [cnts]
  BKG_TIME:        2934.94 SOD {00:48:54.94} UT
  BKG_DUR:         8 [sec]
  GRB_DATE:        13800 TJD;    65 DOY;   06/03/06
  GRB_TIME:        2950.62 SOD {00:49:10.62} UT
  GRB_PHI:         -164.27 [deg]
  GRB_THETA:        40.86 [deg]
  SOLN_STATUS:     0x3
  RATE_SIGNIF:     60.76 [sigma]
  IMAGE_SIGNIF:    19.98 [sigma]
  MERIT_PARAMS:     +1  +0  +0  +0  +2 +18  +0  +0 -58  +1 
  SUN_POSTN:       346.47d {+23h 05m 53s}   -5.79d {-05d 47' 24"}
  SUN_DIST:         54.68 [deg]   Sun_angle= -3.6 [hr] (East of Sun)
  MOON_POSTN:       62.86d {+04h 11m 26s}  +25.76d {+25d 45' 23"}
  MOON_DIST:        34.89 [deg]
  MOON_ILLUM:      42 [%]
  GAL_COORDS:      175.04,-53.19 [deg] galactic lon,lat of the burst (or transient)
  ECL_COORDS:       37.97,-17.20 [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 = 224.55,-18.86 [deg].  
  

• red DSS finding chart ps-file
  
  
• GCN NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Mon 06 Mar 06 00:51:18 UT
  NOTICE_TYPE:     Swift-XRT Image
  TRIGGER_NUM:     200638,   Seg_Num: 0
  GRB_RA:           41.0950d {+02h 44m 22.7s} (J2000),
                    41.1733d {+02h 44m 41.5s} (current),
                    40.4616d {+02h 41m 50.7s} (1950)
  GRB_DEC:          -2.1482d {-02d 08' 53.5"} (J2000),
                    -2.1223d {-02d 07' 20.2"} (current),
                    -2.3590d {-02d 21' 32.4"} (1950)
  GRB_ERROR:       5.4 [arcsec, radius, statistical plus systematic]
  GRB_INTEN:       52 [cnts]
  IMG_START_DATE:  13800 TJD;    65 DOY;   06/03/06
  IMG_START_TIME:  3038.14 SOD {00:50:38.14} UT,   87.5 [sec] since BAT Trigger Time
  CENTROID_X:      317.86,  raw= 318  [pixels]
  CENTROID_Y:      301.34,  raw= 301  [pixels]
  ROLL:            264.42 [deg]
  GAIN:            1
  MODE:            3, Long Image mode
  WAVEFORM:        134
  EXPO_TIME:       2.50 [sec]
  GRB_POS_XRT_Y:   5.98
  GRB_POS_XRT_Z:   39.05
  IMAGE_URL:       sw00200638000msxps_rw.img
  SUN_POSTN:       346.47d {+23h 05m 53s}   -5.79d {-05d 47' 22"}
  SUN_DIST:         54.67 [deg]   Sun_angle= -3.6 [hr] (East of Sun)
  MOON_POSTN:       62.87d {+04h 11m 30s}  +25.76d {+25d 45' 36"}
  MOON_DIST:        34.90 [deg]
  MOON_ILLUM:      42 [%]
  GAL_COORDS:      175.03,-53.19 [deg] galactic lon,lat of the burst
  ECL_COORDS:       37.97,-17.20 [deg] ecliptic lon,lat of the burst
  COMMENTS:        SWIFT-XRT Image.  
  

  
• GCN NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Mon 06 Mar 06 00:51:17 UT
  NOTICE_TYPE:     Swift-XRT Position
  TRIGGER_NUM:     200638,   Seg_Num: 0
  GRB_RA:           41.0950d {+02h 44m 22.7s} (J2000),
                    41.1733d {+02h 44m 41.5s} (current),
                    40.4616d {+02h 41m 50.7s} (1950)
  GRB_DEC:          -2.1482d {-02d 08' 53.5"} (J2000),
                    -2.1223d {-02d 07' 20.2"} (current),
                    -2.3590d {-02d 21' 32.4"} (1950)
  GRB_ERROR:       5.4 [arcsec radius, statistical plus systematic, 90% containment]
  GRB_INTEN:       1.19e-09 [erg/cm2/sec]
  GRB_SIGNIF:      7.21 [sigma]
  IMG_START_DATE:  13800 TJD;    65 DOY;   06/03/06
  IMG_START_TIME:  3038.14 SOD {00:50:38.14} UT,   87.5 [sec] since BAT Trigger Time
  TAM[0-3]:        327.65 237.21 261.30 243.08
  AMPLIFIER:       2
  WAVEFORM:        134
  SUN_POSTN:       346.47d {+23h 05m 53s}   -5.79d {-05d 47' 22"}
  SUN_DIST:         54.67 [deg]   Sun_angle= -3.6 [hr] (East of Sun)
  MOON_POSTN:       62.87d {+04h 11m 30s}  +25.76d {+25d 45' 36"}
  MOON_DIST:        34.90 [deg]
  MOON_ILLUM:      42 [%]
  GAL_COORDS:      175.03,-53.19 [deg] galactic lon,lat of the burst
  ECL_COORDS:       37.97,-17.20 [deg] ecliptic lon,lat of the burst
  COMMENTS:        SWIFT-XRT Coordinates.  
  

• GCN NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Mon 06 Mar 06 00:52:12 UT
  NOTICE_TYPE:     Swift-XRT Processed Image
  TRIGGER_NUM:     200638,   Seg_Num: 0
  GRB_RA:           41.0950d {+02h 44m 22.7s} (J2000),
                    41.1733d {+02h 44m 41.5s} (current),
                    40.4616d {+02h 41m 50.7s} (1950)
  GRB_DEC:          -2.1482d {-02d 08' 53.5"} (J2000),
                    -2.1223d {-02d 07' 20.2"} (current),
                    -2.3590d {-02d 21' 32.4"} (1950)
  GRB_ERROR:       5.4 [arcsec, radius, statistical plus systematic]
  GRB_INTEN:       52 [cnts]
  IMG_START_DATE:  13800 TJD;    65 DOY;   06/03/06
  IMG_START_TIME:  3038.14 SOD {00:50:38.14} UT,   87.5 [sec] since BAT Trigger Time
  CENTROID_X:      317.86,  raw= 318  [pixels]
  CENTROID_Y:      301.34,  raw= 301  [pixels]
  ROLL:            264.42 [deg]
  GAIN:            1
  MODE:            3, Long Image mode
  WAVEFORM:        134
  EXPO_TIME:       2.50 [sec]
  GRB_POS_XRT_Y:   5.98
  GRB_POS_XRT_Z:   39.05
  IMAGE_URL:       sw00200638000msxps_rw.img
  SUN_POSTN:       346.47d {+23h 05m 54s}   -5.79d {-05d 47' 21"}
  SUN_DIST:         54.67 [deg]   Sun_angle= -3.6 [hr] (East of Sun)
  MOON_POSTN:       62.88d {+04h 11m 32s}  +25.76d {+25d 45' 43"}
  MOON_DIST:        34.91 [deg]
  MOON_ILLUM:      42 [%]
  GAL_COORDS:      175.03,-53.19 [deg] galactic lon,lat of the burst
  ECL_COORDS:       37.97,-17.20 [deg] ecliptic lon,lat of the burst
  COMMENTS:        SWIFT-XRT Processed Image.  
  

  
• GCN NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Mon 06 Mar 06 00:52:56 UT
  NOTICE_TYPE:     Swift-BAT GRB Lightcurve
  TRIGGER_NUM:     200638,   Seg_Num: 0
  GRB_RA:           41.099d {+02h 44m 24s} (J2000),
                    41.177d {+02h 44m 42s} (current),
                    40.465d {+02h 41m 52s} (1950)
  GRB_DEC:          -2.153d {-02d 09' 10"} (J2000),
                    -2.127d {-02d 07' 37"} (current),
                    -2.364d {-02d 21' 49"} (1950)
  GRB_DATE:        13800 TJD;    65 DOY;   06/03/06
  GRB_TIME:        2950.62 SOD {00:49:10.62} UT
  TRIGGER_INDEX:   146
  GRB_PHI:         -164.27 [deg]
  GRB_THETA:        40.86 [deg]
  DELTA_TIME:      32.00 [sec]
  TRIGGER_DUR:     1.024 [sec] 
  SOLN_STATUS:     0x3
  RATE_SIGNIF:     60.76 [sigma]
  IMAGE_SIGNIF:    19.98 [sigma]
  LC_URL:          sw00200638000msb.lc
  SUN_POSTN:       346.47d {+23h 05m 54s}   -5.79d {-05d 47' 21"}
  SUN_DIST:         54.68 [deg]   Sun_angle= -3.6 [hr] (East of Sun)
  MOON_POSTN:       62.89d {+04h 11m 34s}  +25.76d {+25d 45' 48"}
  MOON_DIST:        34.92 [deg]
  MOON_ILLUM:      42 [%]
  GAL_COORDS:      175.04,-53.19 [deg] galactic lon,lat of the burst (or transient)
  ECL_COORDS:       37.97,-17.20 [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 = 224.55,-18.86 [deg].  
  

  
• GCN NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Mon 06 Mar 06 00:55:49 UT
  NOTICE_TYPE:     Swift-UVOT Source List
  TRIGGER_NUM:     200638,   Seg_Num: 0
  POINT_RA:         41.084d {+02h 44m 20s} (J2000)
  POINT_DEC:        -2.148d {-02d 08' 52"} (J2000)
  POINT_ROLL:      264.425d
  IMG_START_DATE:  13800 TJD;    65 DOY;   06/03/06
  IMG_START_TIME:  3042.15 SOD {00:50:42.15} UT,   91.5 [sec] since BAT Trigger Time
  FILTER:          3, V
  BKG_MEAN:        1.605
  N_STARS:         17
  X_OFFSET:        394 [pixels]
  Y_OFFSET:        570 [pixels]
  X_MAX:           1353 [pixels]
  Y_MAX:           1529 [pixels]
  DET_THRESH:      11
  PHOTO_THRESH:    5
  SL_URL:          sw00200638000msufc0091.fits
  SUN_POSTN:       346.48d {+23h 05m 54s}   -5.79d {-05d 47' 18"}
  SUN_DIST:         54.66 [deg]   Sun_angle= -3.6 [hr] (East of Sun)
  MOON_POSTN:       62.92d {+04h 11m 41s}  +25.77d {+25d 46' 10"}
  MOON_DIST:        34.94 [deg]
  MOON_ILLUM:      42 [%]
  GAL_COORDS:      175.02,-53.20 [deg] galactic lon,lat of the pointing direction
  ECL_COORDS:       37.96,-17.19 [deg] ecliptic lon,lat of the pointing direction
  COMMENTS:        SWIFT-UVOT Source List.  
  

• GCN NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Mon 06 Mar 06 00:56:56 UT
  NOTICE_TYPE:     Swift-UVOT Processed Source List
  TRIGGER_NUM:     200638,   Seg_Num: 0
  POINT_RA:         41.084d {+02h 44m 20s} (J2000)
  POINT_DEC:        -2.148d {-02d 08' 52"} (J2000)
  POINT_ROLL:      264.425d
  IMG_START_DATE:  13800 TJD;    65 DOY;   06/03/06
  IMG_START_TIME:  3042.15 SOD {00:50:42.15} UT,   91.5 [sec] since BAT Trigger Time
  FILTER:          3, V
  BKG_MEAN:        1.605
  N_STARS:         17
  X_OFFSET:        394 [pixels]
  Y_OFFSET:        570 [pixels]
  X_MAX:           1353 [pixels]
  Y_MAX:           1529 [pixels]
  DET_THRESH:      11
  PHOTO_THRESH:    5
  SL_URL:          sw00200638000msufc0091.fits
  SUN_POSTN:       346.48d {+23h 05m 54s}   -5.79d {-05d 47' 17"}
  SUN_DIST:         54.66 [deg]   Sun_angle= -3.6 [hr] (East of Sun)
  MOON_POSTN:       62.93d {+04h 11m 43s}  +25.77d {+25d 46' 18"}
  MOON_DIST:        34.95 [deg]
  MOON_ILLUM:      42 [%]
  GAL_COORDS:      175.02,-53.20 [deg] galactic lon,lat of the pointing direction
  ECL_COORDS:       37.96,-17.19 [deg] ecliptic lon,lat of the pointing direction
  COMMENTS:        SWIFT-UVOT Processed Source List.  
  COMMENTS:        All 4 attachments are included.  
  

  
• GCN NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Mon 06 Mar 06 00:57:13 UT
  NOTICE_TYPE:     Swift-UVOT Image
  TRIGGER_NUM:     200638,   Seg_Num: 0
  POINT_RA:         41.084d {+02h 44m 20s} (J2000)
  POINT_DEC:        -2.148d {-02d 08' 52"} (J2000)
  ROLL:            264.425d
  IMG_START_DATE:  13800 TJD;    65 DOY;   06/03/06
  IMG_START_TIME:  3042.15 SOD {00:50:42.15} UT,   91.5 [sec] since BAT Trigger Time
  FILTER:          3, V
  EXPOSURE_ID:     163299043
  X_OFFSET:        714 [pixels]
  Y_OFFSET:        890 [pixels]
  WIDTH:           160 [pixels]
  HEIGHT:          160 [pixels]
  X_GRB_POS:       874
  Y_GRB_POS:       1050
  BINNING_INDEX:   1
  IM_URL:          sw00200638000msuni0091.fits
  SUN_POSTN:       346.48d {+23h 05m 54s}   -5.79d {-05d 47' 17"}
  SUN_DIST:         54.66 [deg]   Sun_angle= -3.6 [hr] (East of Sun)
  MOON_POSTN:       62.93d {+04h 11m 44s}  +25.77d {+25d 46' 20"}
  MOON_DIST:        34.95 [deg]
  MOON_ILLUM:      42 [%]
  GAL_COORDS:      175.02,-53.20 [deg] galactic lon,lat of the pointing direction
  ECL_COORDS:       37.96,-17.19 [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:     Mon 06 Mar 06 00:58:11 UT
  NOTICE_TYPE:     Swift-UVOT Processed Image
  TRIGGER_NUM:     200638,   Seg_Num: 0
  POINT_RA:         41.084d {+02h 44m 20s} (J2000)
  POINT_DEC:        -2.148d {-02d 08' 52"} (J2000)
  ROLL:            264.425d
  IMG_START_DATE:  13800 TJD;    65 DOY;   06/03/06
  IMG_START_TIME:  3042.15 SOD {00:50:42.15} UT,   91.5 [sec] since BAT Trigger Time
  FILTER:          3, V
  EXPOSURE_ID:     163299043
  X_OFFSET:        714 [pixels]
  Y_OFFSET:        890 [pixels]
  WIDTH:           160 [pixels]
  HEIGHT:          160 [pixels]
  X_GRB_POS:       874
  Y_GRB_POS:       1050
  BINNING_INDEX:   1
  IM_URL:          sw00200638000msuni0091.fits
  SUN_POSTN:       346.48d {+23h 05m 54s}   -5.79d {-05d 47' 16"}
  SUN_DIST:         54.66 [deg]   Sun_angle= -3.6 [hr] (East of Sun)
  MOON_POSTN:       62.94d {+04h 11m 46s}  +25.77d {+25d 46' 27"}
  MOON_DIST:        34.96 [deg]
  MOON_ILLUM:      42 [%]
  GAL_COORDS:      175.02,-53.20 [deg] galactic lon,lat of the pointing direction
  ECL_COORDS:       37.96,-17.19 [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:        If you have elected to receive attachments:  
  COMMENTS:        The uvot_catalog_image.fits.gz file does not exist; skipping the attachment.  
  

  
• GCN Circular #4848
  L. Angelini (GSFC), S. Barthelmy (GSFC), D. Burrows (PSU), M. Chester (PSU), J. Cummings (GSFC/ORAU), N. Gehrels (GSFC), M. Goad (U Leicester), H. Krimm (GSFC/USRA), F. Marshall (GSFC), D. Palmer (LANL) on behalf of the Swift team:
  At 00:49:10 UT, Swift-BAT triggered and located GRB 060306 (trigger=200638). The spacecraft slewed immediately. The BAT on-board calculated location is RA,Dec 41.099d,-2.153d {02h 44m 24s,-02d 09' 10"} (J2000), with an uncertainty of 3 arcmin (radius, 90% containment, stat+sys). The BAT light curve shows a multi-peak structure with a total duration of 30 sec. The peak count rate was ~8000 counts/sec (15-350 keV), at ~1 seconds after the trigger.
  The XRT began observing the field at 00:50:38 UT (88 sec after the trigger). The XRT found a bright, fading, uncataloged X-ray source at

  RA(J2000)  = 2h 44m 22.7s
  Dec(J2000) = -2d 8' 54"
  

  with an estimated uncertainty of 5.4" (90% radius). This position is 24 arcseconds from the BAT position. The initial flux is 1.2E-9 ergs/cm2/sec.
  UVOT took a finding chart exposure of 200 seconds with the V filter starting 93 seconds after the BAT trigger. No afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of the XRT error circle. The 3-sigma upper limit is 18.4 mag. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. The list of sources is typically complete to about 18.0 mag. No correction has been made for the expected extinction of about 0.1 magnitudes.
  We are currently in the Malindi downlink gap, and so we will not receive the complete data set for another 6 hours.
• GCN Circular #4849
  M. Nysewander, A. Foster, A. LaCluyze, D. Reichart, J. A. Crain, K. Ivarsen, J. Haislip, J. Kirschbrown, C. MacLeod, and A. Trotter report on behalf of the UNC team of the FUN GRB Collaboration:
  Skynet observed the localization of GRB 060306 (Angelini et al., GCN 4848) with one of the 16-inch PROMPT telescopes at CTIO beginning 49 sec after the burst (25 sec after notification).
  No new source is found, to i' > 17.4 mag at 7.5 min after the burst and r' > 16.8 mag at 9.3 min after the burst (3 sigma; calibrated to five USNO-B1.0 and NOMAD stars, respectively, using the transformation equations of Smith et al. 2002.)
  PROMPT is currently being built and commissioned.
• GCN Circular #4850
  K.L. Page, M.R. Goad (U. Leicester) and L. Angelini (GSFC) report on behalf of the Swift-XRT team:
  The XRT began observing the field of GRB 060306 88 seconds after the BAT trigger. Analysing the first 5 orbits of data, the following refined position was obtained:

  RA(J2000) =  02h 44m 23.0s
  Dec(J2000)= -02d 08' 52.8"
  

  with an estimated uncertainty of 3.9 arcsec (90% containment). This is 4.7 arcsec from the XRT position given in GCN 4848 (Angelini et al.), and 21.3 arcsec from the BAT position reported in the same circular.
  The light-curve shows a steep initial decay, with alpha ~3.4, breaking to a slope of ~0.6 at ~210 seconds after the trigger time.
  The WT spectrum (96-173 seconds after the trigger) can be fitted with a power-law of Gamma = 2.1 +/- 0.3, with NH ~4 x 10^21 cm^-2 (in addition to the estimated Galactic value of 3.6 x 10^20 cm^-2). There is no evidence for spectral evolution across the break in the light-curve. The observed (unabsorbed) flux over 0.3-10 keV for the WT spectrum is 2.24 x 10^-10 (3.90 x 10^-10) erg cm^-2 s^-1.
  Assuming the current decay of alpha ~0.6 continues, the estimated count rate at 24 hours is 0.02 ct s^-1, corresponding to an observed (unabsorbed) flux of 1.3 x 10^-12 (2.9 x 10^-12) erg cm^-2 s^-1.
  This circular is an official product of the Swift-XRT team.
• GCN Circular #4851
  D. Hullinger (BYU-Idaho), L. Angelini (GSFC), L. Barbier (GSFC), S. Barthelmy (GSFC), J. Cummings (GSFC/ORAU), E. Fenimore (LANL), N. Gehrels (GSFC), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/ORAU), G. Sato (ISAS), J. Tueller (GSFC), on behalf of the Swift-BAT team:
  Using the data set from T-300 to T+300 sec from the recent telemetry downlink, we report further analysis of BAT GRB 060306 (trigger #200638) (Angelini, et al., GCN 4848). The BAT ground-calculated position is (RA,Dec) = 41.096, -2.155 deg {2h 44m 23.0s, -2d 9' 19.3"} (J2000) +- 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 50%.
  The light curve is a series of FRED-like peaks at T-1, T+1, T+27, T+43, and T+60, with similar decay constants of ~2 sec. The dominant peak is at T+1. The small peak at T+60 is soft compared to the others, which all have similar spectra. T90 (15-350 keV) is 61 +- 2 sec (estimated error including systematics).
  The time-averaged spectrum from T-1.4 to T+66.9 is well fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.85 +- 0.10. The fluence in the 15-150 keV band is 2.2 +- 0.1 x 10^-06 erg/cm2. The 1-sec peak photon flux measured from T+0.20 sec in the 15-150 keV band is 6.1 +- 0.3 ph/cm2/sec. All the quoted errors are at the 90% confidence level.
• GCN Circular #4852
  M. De Pasquale (MSSL-UCL), L. Angelini (GSFC) on the behalf of the Swift/UVOT team:
  The Swift/UVOT began observing the field of GRB 060306 at 00:50:32 UT on March 6, 2006, 79 sec after the trigger (Angelini et al. GCN 4848). No source is detected at the refined XRT position (Page et al. GCN 4850) down to the following 3 sigma upper limits:
  Filter T-range (sec since trigger) Exp (sec) 3sigma U.L. (mag)
  V 79-34440 2918 20.1
  B 460-29558 2708 20.7
  U 405-28651 2701 20.1
  UW1 351-36040 2173 20.6
  UM2 297-12199 2800 20.9
  UW2 569-7040 2040 21.0
  White 513-562 50 19.3
  Quoted magnitudes have not been corrected for extinction, E(B-V)=0.036
• GCN Circular #4854
  P.A. Price (IfA, Hawaii), T. Minezaki (IoA, Tokyo), L.L. Cowie, Y. Kakazu (IfA, Hawaii) and Y. Yoshii (IoA, Tokyo) report:
  We observed the XRT position (GCN 4850) of GRB 060306 (GCN 4848) with the robotic MAGNUM telescope + MIP dual-beam camera beginning at Mar 6.235 UTC (4.8 hours after the GRB). Images in the R, I and J bands show a source present within the XRT error circle, with R ~ 20.7 mag (based on USNO-A2.0 star at 02:44:19.08 -02:08:53.6 with R = 15.2 mag). However, this source is also present in the Digitised Sky Survey red plate at a similar flux level. The position of the source from the DSS plate is:
  02:44:22.98 -02:08:51.1 J2000
  Due to the limited time baseline, we cannot make a meaningful test for variability, and hence it is not yet clear whether or not this source is related to the GRB. If related, it would likely indicate that the GRB is at a relatively low redshift. No other sources are identified within the XRT error circle to R ~ 22 mag.
  Images of the field are shown at
  http://www.ifa.hawaii.edu/~price/magnum_grb060306.jpg
  Observers with CCD images of the source at a different epoch are invited to contact PAP to perform image subtraction.
  This message may be cited.
  
• GCN Circular #4857
  M. Nysewander, D. Reichart, A. Oliveira, P. Ugarte, and A. Alvarez report on behalf of the UNC team of the FUN GRB collaboration:
  We observed the localization of GRB 060306 (Angelini et al., GCN 4848) with the SOAR infrared imager, OSIRIS, beginning at 00:31:56 UT on March 7th, 1.0 days after the burst. We detect no new source down to a 3-sigma limiting magnitude of Ks = 18.2 based on six stars from the 2MASS catalogue.
  If one assumes minimal extinction in the Ks band and uses the extrapolated to 24 hours, unabsorbed X-ray flux of Page et al. (GCN 4850), this suggests a NIR to X-ray spectral index that is shallower than -0.7.
  The source in the XRT error circle which is also in the DSS-Red plate (as noted by Price et al., GCN 4854) is at Ks = 17.3 +/- 0.2 mag.
  SOAR is currently being commissioned.
• GCN Circular #4861
  H.-W. Chen (U Chicago), X. Fan (U Arizona), F. Hearty (Colorado), M. Bayliss (Chicago), D. Q. Lamb (U Chicago), R. McMillan (APO), B. Ketzeback (APO), J. Barentine (APO), J. Dembicky (APO), and D. York (U Chicago) report:
  "We obtained a 3x300 sec dithered exposures in Ks of the field of GRB060306 (Angelini et al., GCN 4848), using the NIC-FPS near-infrared camera on the 3.5 m telescope at the Apache Point Observatory. The observations started at 20060306.10 UT (~ 2 hrs after the initial Swift trigger) through variable clouds and under a mean seeing condition of 1 arcsec. Calibrating the final stacked image to 2MASS stars in the field gives a 5 sigma depth of Ks=20.4 over a 1 arcsec diameter aperture. Within the XRT error circle (Page et al., GCN 4850), we locate a single source at

   		RA(J2000)  = 02:44:23.0
   		Dec(J2000) = -02:08:51.2,
  

  which is also present in the DSS red plate (see also Price et al., GCN 4854, and Nysewander et al., GCN 4857). Based on the 2MASS photometry, we estimate the source brightness to be Ks=18.3 +/- 0.1 mag. Comarison with the Ks image taken a day later by Nysewander et al. (GCN4857) shows no variability of this source.
  The stacked image is available at http://lambda.uchicago.edu/public/grb/grb060306/grb060306K.fits
  NIC-FPS is currently in its commissioning phase."
• GCN Circular #5079
  GRB 060306: Further Analysis of SOAR and APO NIR Observations
  D. Q. Lamb (Chicago), M. Nysewander (UNC), F. Hearty (Colorado), H.-W. Chen (Chicago), and D. E. Reichart (UNC) report on behalf of the FUN GRB Collaboration:
  We have further analyzed the Ks-band images taken with the ARC 3.5-meter telescope using NIC-FPS, beginning 1.6 hours after the burst, and the Ks-band images taken with the SOAR 4.1-meter telescope using OSIRIS, beginning 24 hours after the burst.
  From the ARC image, we measure a limiting magnitude of Ks =3D 19.5 (3 sigma) and a magnitude of Ks =3D 17.78 =B1 0.13 mag for the source that is in the XRT error circle and in the DSS (Price et al., GCN 4854), using six 2MASS objects (five of "A" quality and one of "C" quality; Skrutskie et al. 2006, AJ, 131, 1163) in the NIC-FPS image for calibration and an aperture radius of 1.6 arcsec, as dictated by a curve of growth analysis of the source. The magnitude of Ks = 18.3 +- 0.1 originally reported by Chen et al. (GCN 4861) corresponded to an aperture radius of 1.0 arcsec, and is therefore fainter.
  From the SOAR image, we measure a limiting magnitude of Ks =3D 18.4 (3 sigma) and a magnitude of Ks =3D 17.53 =B1 0.20 for the source, using the four 2MASS objects (one of "A" quality and three of "C" quality) in=20 the OSIRIS image for calibration and an aperture radius of 1.6 arcsec, as dictated by a curve of growth analysis of the source. This result is consistent with that reported by Nysewander et al. (GCN 4857).
  The two results are consistent with a constant brightness source, and PSF-matched image subtraction provides no indication that the source brightened between the two epochs.
  The source appears to be marginally extended in the ARC image, and may be the host galaxy (Price et al., GCN 4854). Spectroscopy of the source is therefore encouraged. However, even if the source is the host galaxy, or a chance-coincidence foreground star (~1% probability), PSF-matched image subtraction of the Ks-band images does not detect the afterglow at 1.6 hours after the burst to the limiting magnitude [Ks =3D 18.4 (3 sigma)] of the SOAR image.
  If one assumes minimal extinction in the Ks-band and extrapolates the unabsorbed X-ray flux (Page et al., GCN 4850) to 1.6 hours after the burst, the resulting Ks-band to X-ray spectral index is shallower than -0.48 (3 sigma), using the limiting magnitude of the SOAR image (which is appropriate if the location of the burst is coincident with the faint source in the XRT error circle), and shallower than -0.36 (3 sigma), using the limiting magnitude of the ARC image (which is appropriate if the location of the burst is not coincident with the faint source in the XRT error circle). This suggests one or more of the following possibilities:
  1. The redshift of the burst is greater than z ~ 17, which is highly unlikely.
  2. The cooling break is blueward of the Ks-band at 1.6 hours after the burst. Given that the X-ray temporal index is ~-0.6 (Page et al., GCN 4850), the Ks-band to X-ray spectral index would be ~-0.7 (e.g., Sari, Piran, and Narayan 1998, ApJ, 497, L17) if the cooling break were instead redward of the Ks band.
  3. The afterglow is highly extinguished. Given that the source-frame N_H ~ 4 x 1021 cm^-2 (1+z)2.6 (Page et al., GCN 4850; Morrison and McCammon 1983, ApJ, 270, 119), a redshift of only z ~ 1 is needed in order to produce 3 - 4 mag of extinction in the observer-frame Ks-band, provided that dust destruction by the burst and/or its afterglow is minimal. Furthermore, a redshift of z ~ 1 yields source-frame values of N_H that are consistent with giant molecular cloud environments.
  Finally, we point out that the properties of the afterglow of this burst are reminiscent of those of GRB 051022 (Doty et al., GCN 4145; Butler et al., GCNs 4165 and 4170).
• ttp://arxiv.org/abs/1112.1700 claim z=3.5 from X-Shooter spectrum.
  Priv. comm.: U-band image contradicts this.
• Previous redshift questioned in the TOUGH project, in particular: 1205.3162 1205.3490 1205.3779 1205.4036; though no new redshift could be measured.
• arXiv:1505.06743 X-shooter redshift: 1.5585/1.5597