Gamma-ray Burst 120403B

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 03 Apr 12 20:48:20 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     519256,   Seg_Num: 0
GRB_RA:           54.809d {+03h 39m 14s} (J2000),
                  51.782d {+03h 27m 08s} (current),
                  69.773d {+04h 39m 06s} (1950)
GRB_DEC:         -89.037d {-89d 02' 12"} (J2000),
                 -88.996d {-88d 59' 45"} (current),
                 -89.171d {-89d 10' 14"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       7963 [cnts]    Image_Peak=204 [image_cnts]
TRIGGER_DUR:     2.048 [sec] 
TRIGGER_INDEX:   473     E_range: 25-100 keV
BKG_INTEN:       80395 [cnts]
BKG_TIME:        73999.93 SOD {20:33:19.93} UT
BKG_DUR:         24 [sec]
GRB_DATE:        16020 TJD;    94 DOY;   12/04/03
GRB_TIME:        74036.48 SOD {20:33:56.48} UT
GRB_PHI:         -115.89 [deg]
GRB_THETA:        30.63 [deg]
SOLN_STATUS:     0x20000003
RATE_SIGNIF:     13.00 [sigma]
IMAGE_SIGNIF:    7.17 [sigma]
MERIT_PARAMS:     +1  +0  +0  +1  +2  -3  +0  +0  +8  +0 
SUN_POSTN:        13.34d {+00h 53m 23s}   +5.71d {+05d 42' 48"}
SUN_DIST:         94.93 [deg]   Sun_angle= -2.6 [hr] (East of Sun)
MOON_POSTN:      154.21d {+10h 16m 51s}   +5.24d {+05d 14' 26"}
MOON_DIST:        95.46 [deg]
MOON_ILLUM:      88 [%]
GAL_COORDS:      302.21,-27.84 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      271.44,-67.34 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT-BAT GRB Coordinates.  
COMMENTS:        This Notice was delayed by more than 60 sec past the end of the trigger integration interval;  
COMMENTS:        probably due to it occurring during a Malindi downlink session.  
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 = 16.56,13.21 [deg].  
COMMENTS:           
COMMENTS:        NOTE: This BAT event is temporally(2.0<100sec) coincident with the FERMI_GBM event (trignum=355178040).

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 03 Apr 12 20:49:01 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     519256,   Seg_Num: 0
GRB_RA:           54.809d {+03h 39m 14s} (J2000),
                  51.782d {+03h 27m 08s} (current),
                  69.773d {+04h 39m 06s} (1950)
GRB_DEC:         -89.037d {-89d 02' 12"} (J2000),
                 -88.996d {-88d 59' 45"} (current),
                 -89.171d {-89d 10' 14"} (1950)
GRB_DATE:        16020 TJD;    94 DOY;   12/04/03
GRB_TIME:        74036.48 SOD {20:33:56.48} UT
TRIGGER_INDEX:   473
GRB_PHI:         -115.89 [deg]
GRB_THETA:        30.63 [deg]
DELTA_TIME:      25.00 [sec]
TRIGGER_DUR:     2.048 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     13.00 [sigma]
IMAGE_SIGNIF:    7.17 [sigma]
LC_URL:          sw00519256000msb.lc
SUN_POSTN:        13.35d {+00h 53m 23s}   +5.71d {+05d 42' 49"}
SUN_DIST:         94.93 [deg]   Sun_angle= -2.6 [hr] (East of Sun)
MOON_POSTN:      154.22d {+10h 16m 52s}   +5.24d {+05d 14' 17"}
MOON_DIST:        95.45 [deg]
MOON_ILLUM:      88 [%]
GAL_COORDS:      302.21,-27.84 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      271.44,-67.34 [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 = 16.56,13.21 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 03 Apr 12 20:52:29 UT
NOTICE_TYPE:     Swift-XRT Nack-Position
TRIGGER_NUM:     519256,   Seg_Num: 0
POINT_RA:         53.690d {+03h 34m 46s} (J2000)
POINT_DEC:       -89.059d {-89d 03' 32"} (J2000)
IMG_START_DATE:  16020 TJD;    94 DOY;   12/04/03
IMG_START_TIME:  74944.01 SOD {20:49:04.01} UT,   907.5 [sec] since BAT Trigger Time
COUNTS:          1    Min_needed= 20
STD_DEV:         0.00   Max_StdDev_for_Good=28.44 [arcsec]
PH2_ITER:        0    Max_iter_allowed= 4
ERROR_CODE:      1
COMMENTS:        SWIFT-XRT Nack Position.  
COMMENTS:        No source found in the image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 03 Apr 12 20:54:27 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     519256,   Seg_Num: 0
POINT_RA:         53.657d {+03h 34m 38s} (J2000)
POINT_DEC:       -89.059d {-89d 03' 31"} (J2000)
POINT_ROLL:      319.726d
IMG_START_DATE:  16020 TJD;    94 DOY;   12/04/03
IMG_START_TIME:  74947.38 SOD {20:49:07.38} UT,   910.9 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.515
N_STARS:         85
X_OFFSET:        625 [pixels]
Y_OFFSET:        715 [pixels]
X_MAX:           1584 [pixels]
Y_MAX:           1674 [pixels]
DET_THRESH:      10
PHOTO_THRESH:    5
SL_URL:          sw00519256000msufc0910.fits
SUN_POSTN:        13.35d {+00h 53m 24s}   +5.71d {+05d 42' 54"}
SUN_DIST:         94.93 [deg]   Sun_angle= -2.5 [hr] (East of Sun)
MOON_POSTN:      154.27d {+10h 17m 04s}   +5.22d {+05d 13' 07"}
MOON_DIST:        95.45 [deg]
MOON_ILLUM:      88 [%]
GAL_COORDS:      302.24,-27.84 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      271.45,-67.31 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 03 Apr 12 20:54:50 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     519256,   Seg_Num: 0
POINT_RA:         53.657d {+03h 34m 38s} (J2000)
POINT_DEC:       -89.059d {-89d 03' 31"} (J2000)
POINT_ROLL:      319.726d
IMG_START_DATE:  16020 TJD;    94 DOY;   12/04/03
IMG_START_TIME:  74947.38 SOD {20:49:07.38} UT,   910.9 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.515
N_STARS:         85
X_OFFSET:        625 [pixels]
Y_OFFSET:        715 [pixels]
X_MAX:           1584 [pixels]
Y_MAX:           1674 [pixels]
DET_THRESH:      10
PHOTO_THRESH:    5
SL_URL:          sw00519256000msufc0910.fits
SUN_POSTN:        13.35d {+00h 53m 24s}   +5.72d {+05d 42' 54"}
SUN_DIST:         94.93 [deg]   Sun_angle= -2.5 [hr] (East of Sun)
MOON_POSTN:      154.27d {+10h 17m 05s}   +5.22d {+05d 13' 03"}
MOON_DIST:        95.45 [deg]
MOON_ILLUM:      88 [%]
GAL_COORDS:      302.24,-27.84 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      271.45,-67.31 [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:     Tue 03 Apr 12 20:55:57 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     519256,   Seg_Num: 0
POINT_RA:         53.657d {+03h 34m 38s} (J2000)
POINT_DEC:       -89.059d {-89d 03' 31"} (J2000)
ROLL:            319.726d
IMG_START_DATE:  16020 TJD;    94 DOY;   12/04/03
IMG_START_TIME:  74947.38 SOD {20:49:07.38} UT,   910.9 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     355178955
X_OFFSET:        944 [pixels]
Y_OFFSET:        1034 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1104
Y_GRB_POS:       1194
BINNING_INDEX:   1
IM_URL:          sw00519256000msuni0919.fits
SUN_POSTN:        13.35d {+00h 53m 24s}   +5.72d {+05d 42' 55"}
SUN_DIST:         94.93 [deg]   Sun_angle= -2.5 [hr] (East of Sun)
MOON_POSTN:      154.28d {+10h 17m 08s}   +5.21d {+05d 12' 48"}
MOON_DIST:        95.45 [deg]
MOON_ILLUM:      88 [%]
GAL_COORDS:      302.24,-27.84 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      271.45,-67.31 [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:     Tue 03 Apr 12 20:56:17 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     519256,   Seg_Num: 0
POINT_RA:         53.657d {+03h 34m 38s} (J2000)
POINT_DEC:       -89.059d {-89d 03' 31"} (J2000)
ROLL:            319.726d
IMG_START_DATE:  16020 TJD;    94 DOY;   12/04/03
IMG_START_TIME:  74947.38 SOD {20:49:07.38} UT,   910.9 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     355178955
X_OFFSET:        944 [pixels]
Y_OFFSET:        1034 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1104
Y_GRB_POS:       1194
BINNING_INDEX:   1
IM_URL:          sw00519256000msuni0919.fits
SUN_POSTN:        13.35d {+00h 53m 24s}   +5.72d {+05d 42' 56"}
SUN_DIST:         94.93 [deg]   Sun_angle= -2.5 [hr] (East of Sun)
MOON_POSTN:      154.28d {+10h 17m 08s}   +5.21d {+05d 12' 44"}
MOON_DIST:        95.44 [deg]
MOON_ILLUM:      88 [%]
GAL_COORDS:      302.24,-27.84 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      271.45,-67.31 [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:     Tue 03 Apr 12 20:59:18 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     519256,   Seg_Num: 0
GRB_RA:           55.3383d {+03h 41m 21.19s} (J2000),
                  52.3750d {+03h 29m 30.00s} (current),
                  69.8784d {+04h 39m 30.80s} (1950)
GRB_DEC:         -89.0093d {-89d 00' 33.4"} (J2000),
                 -88.9690d {-88d 58' 08.3"} (current),
                 -89.1415d {-89d 08' 29.5"} (1950)
GRB_ERROR:       3.9 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  16020 TJD;    94 DOY;   12/04/03
IMG_START_TIME:  74967.00 SOD {20:49:27.00} UT,   930.5 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:        13.35d {+00h 53m 24s}   +5.72d {+05d 42' 58"}
SUN_DIST:         94.91 [deg]   Sun_angle= -2.6 [hr] (East of Sun)
MOON_POSTN:      154.31d {+10h 17m 15s}   +5.20d {+05d 12' 05"}
MOON_DIST:        95.41 [deg]
MOON_ILLUM:      88 [%]
GAL_COORDS:      302.18,-27.86 [deg] galactic lon,lat of the burst
ECL_COORDS:      271.46,-67.37 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        TAM values, flux and significance fields are not valid.  
COMMENTS:        This position was automatically generated on the ground using  
COMMENTS:        Photon Counting data telemetered via TDRSS (SPER data).  
COMMENTS:        See http://www.swift.ac.uk/sper/docs.php for details.  
COMMENTS:        The probability that this is a serendipitous source in the  
COMMENTS:        SPER window is 1.1% < P(seren) < 2.8%.

GCN Circular #13203
V. D'Elia (ASDC), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), D. N. Burrows (PSU), S. Campana (INAF-OAB), M. M. Chester (PSU), J. A. Kennea (PSU), C. B. Markwardt (NASA/GSFC), A. Maselli (INAF-IASFPA), A. Melandri (INAF-OAB), P. T. O'Brien (U Leicester), T. Sakamoto (NASA/UMBC), C. J. Saxton (UCL-MSSL), B. Sbarufatti (INAF-OAB/PSU), M. H. Siegel (PSU), G. Stratta (ASDC), C. A. Swenson (PSU), T. N. Ukwatta (MSU) and B.-B. Zhang (PSU) report on behalf of the Swift Team:
At 20:33:56 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 120403B (trigger=519256). Because of an observing constraint, the slew to the burst was delayed by 12.9 minutes. The BAT on-board calculated location is RA, Dec 54.809, -89.037, which is
```
   RA(J2000)  =  03h 39m 14s
   Dec(J2000) = -89d 02' 12"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows several spikes with a total duration of about 10 sec. The peak count rate was ~2000 counts/sec (15-350 keV), at ~1 sec after the trigger.
The XRT began observing the field at 20:49:04.0 UT, 907.5 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 55.33838, -89.00933 which is equivalent to:
```
   RA(J2000)  = 03h 41m 21.21s
   Dec(J2000) = -89d 00' 33.6"
```
with an uncertainty of 3.9 arcseconds (radius, 90% containment). This location is 104 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 http://www.swift.ac.uk/sper. We cannot determine whether the source is fading at the present time.
A power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the Galactic value of 9.52 x 10^20 cm^-2 (Kalberla et al. 2005).
UVOT took a finding chart exposure of 150 seconds with the White filter starting 910 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. The list of sources is typically complete to about 18 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.13.
Burst Advocate for this burst is V. D'Elia (delia AT asdc.asi.it). 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/too.html.)
GCN Circular #13205
M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team.
Using 1035 s of XRT Photon Counting mode data and 1 UVOT images for GRB 120403B, 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 = 55.27631, -89.00862 which is equivalent to:
```
RA (J2000): 03h 41m 6.31s
Dec (J2000): -89d 00' 31.0"
```
with an uncertainty of 2.3 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 #13206
A. A. Breeveld (MSSL-UCL) and V. D'Elia (ASDC) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 120403B 911s after the BAT trigger (D'Elia et al., GCN Circ. 13203). No optical afterglow consistent with the XRT position (Goad et al., GCN Circ. 13205) 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           911         1061          147         >21.7
white             1190         7931          568         >22.0
v                 1068         8342          588         >20.7
b                 1166         7726          568         >21.3
u                 1141        12488          404         >21.1
w1                1117         9020          851         >21.1
m2                1092         8547          568         >20.8
w2                1216         8137          485         >21.0
```
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.13 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #13207
M. Stamatikos (OSU), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), V. D'Elia (ASDC), E. E. Fenimore (LANL), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC), D. M. Palmer (LANL), A. M. Parsons (GSFC), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), J. Tueller (GSFC), T. N. Ukwatta (GWU) (i.e. the Swift-BAT team):
Using the data set from T-240 to T+70 sec from recent telemetry downlinks, we report further analysis of BAT GRB 120403B (trigger #519256) (D'Elia, et al., GCN Circ. 13203). The BAT ground-calculated position is RA, Dec = 54.302, -89.029 deg, which is
```
   RA(J2000)  =  03h 37m 12.6s 
   Dec(J2000) = -89d 01' 45.1" 
```
with an uncertainty of 2.4 arcmin, (radius, sys+stat, 90% containment). The partial coding was 47%.
The mask-weighted light curve shows several overlapping peaks starting at ~T-5 sec and ending at ~T+10 sec. T90 (15-350 keV) is 7.3 +- 1.9 sec (estimated error including systematics).
The time-averaged spectrum from T-3.0 to T+5.3 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.79 +- 0.31. The fluence in the 15-150 keV band is 2.1 +- 0.4 x 10^-07 erg/cm2. The 1-sec peak photon flux measured from T+0.92 sec in the 15-150 keV band is 0.9 +- 0.2 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/519256/BA/
GCN Circular #13212
Rhaana Starling, Klaas Wiersema (U. Leicester), Stuart Ryder (AAO), Peter Barnes (U. Florida) and Christopher Stockdale (Marquette Univ.) report:
We began observations of the field of GRB 120403B with IRIS2 on the 4m Anglo-Australian Telescope on 2012-04-04 at 08:34:00 UT, 12 hours after the BAT trigger (D'Elia et al., GCN Circ. 13203). We performed near-infrared photometry in the Ks, H and J bands, totalling 2x9 minutes in each filter.
We do not detect any source within the UVOT-enhanced XRT error circle (Goad et al., GCN Circ. 13205) down to limiting magnitudes of
```
Ks > 19.4 mag
H  > 20.0 mag
J  > 20.9 mag.
```
Calibration was carried out using 8 2MASS field stars. No correction for Galactic extinction has been applied.
These observations were obtained under programme AAT/11B/21.
GCN Circular #13214
George Younes (USRA) reports on behalf of the Fermi GBM Team:
"At 20:33:58.49 UT on April 03, 2012, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 120403B (trigger 355178040 / 120403857) which was triggered and detected by Swift (D'Elia et al., GCN 13203). The on-ground calculated location, using the Fermi GBM trigger data is consistent with the Swift location.
The GBM light curve shows a single event with a duration (T90) of about 4 s (50-300 keV).
The time-averaged spectrum from T0-1.792 s to T0 is well fit by a power law with index -1.51 +/- 0.08. A power law with an exponential high-energy cutoff fits the spectrum equally well. The power law index is -0.9 +/- 0.3 and the cutoff energy, parameterized as Epeak, is 182 +/- 74 keV.
The event fluence (10-1000 kev) in this time interval is (4.6 +/- 0.6)E-07 erg/s-cm^2. The 1-s peak photon flux starting at T0-0.896 s in the 10-1000 keV range is 1.7 +/- 0.2 ph/s/cm^2.
The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."
GCN Circular #13215
Klotz A. (IRAP-CNRS-OMP), Gendre B. (ASDC/INAF-OAR), Boer M. (UNS-CNRS-OCA), Atteia J.L. (IRAP-CNRS-OMP) report:
We imaged the field of GRB 120403B detected by SWIFT (trigger 519256) with the TAROT robotic telescope (D=25cm) located at the European Southern Observatory, La Silla observatory, Chile.
The observations started 2.8h after the GRB trigger (the burst occured during the afternoon). The elevation of the field was 29 degrees above horizon and weather conditions were good.
We co-added a series of exposures. No optical counterpart was found. The limiting magnitude of the image is R=19.5 but the burst occured close to a R=17.2 star. So we prefer to publish a conservative value of 18.2 as the upper limit of the afterglow:
```
start   stop
2.95h   4.82h   R > 18.2
```
Magnitudes were estimated with the nearby USNO-B1 stars and are not corrected for galactic dust extinction.
This message may be cited.
GCN Circular #13223
O.M. Littlejohns (U. Leicester), A. Melandri (INAF-OAB), B. Sbarufatti (INAF-OAB/PSU), G. Stratta (ASDC), D.N. Burrows (PSU), J.A. Kennea (PSU), M.C. Stroh (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester) and V.D'Elia report on behalf of the Swift-XRT team:
We have analysed 4.5 ks of XRT data for GRB 120403B (D'Elia et al. GCN Circ. 13203), from 920 s to 8.9 ks after the BAT trigger. The data are entirely in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Goad et al. (GCN. Circ 13205).
The light curve can be modelled with a power-law decay with a decay index of alpha=0.80 (+0.15, -0.14).
A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.2 (+/-0.3). The best-fitting absorption column is 2.2 (+0.9, -0.8) x 10^21 cm^-2, in excess of the Galactic value of 9.5 x 10^20 cm^-2 (Kalberla et al. 2005). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.5 x 10^-11 (5.8 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     2.2 (+0.9, -0.8) x 10^21 cm^-2
Galactic foreground: 9.5 x 10^20 cm^-2
Excess significance: 2.5 sigma
Photon index:	     2.2 (+/-0.3)
```
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00519256.
This circular is an official product of the Swift-XRT team.
GCN Report 388.1
GCN_Report 388.1 has been posted: http://gcn.gsfc.nasa.gov/reports/report_388_1.pdf by V.DElia at ASDC titled: "Swift Observations of GRB 120403B"

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Jochen Greiner, last update: 05-Apr-2012 [Disclaimer]