Gamma-ray Burst 120311A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 11 Mar 12 05:33:55 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     517469,   Seg_Num: 0
GRB_RA:          273.087d {+18h 12m 21s} (J2000),
                 273.226d {+18h 12m 54s} (current),
                 272.517d {+18h 10m 04s} (1950)
GRB_DEC:         +14.275d {+14d 16' 32"} (J2000),
                 +14.279d {+14d 16' 45"} (current),
                 +14.262d {+14d 15' 43"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       1953 [cnts]    Image_Peak=220 [image_cnts]
TRIGGER_DUR:     0.256 [sec] 
TRIGGER_INDEX:   120     E_range: 15-50 keV
BKG_INTEN:       34596 [cnts]
BKG_TIME:        20008.02 SOD {05:33:28.02} UT
BKG_DUR:         8 [sec]
GRB_DATE:        15997 TJD;    71 DOY;   12/03/11
GRB_TIME:        20018.32 SOD {05:33:38.32} UT
GRB_PHI:          54.18 [deg]
GRB_THETA:        21.11 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     25.01 [sigma]
IMAGE_SIGNIF:    12.99 [sigma]
MERIT_PARAMS:     +1  +0  +0  -2  +1  +2  +0  +0 -17  +0 
SUN_POSTN:       351.78d {+23h 27m 06s}   -3.55d {-03d 32' 51"}
SUN_DIST:         79.82 [deg]   Sun_angle= 5.2 [hr] (West of Sun)
MOON_POSTN:      206.69d {+13h 46m 46s}  -14.47d {-14d 28' 07"}
MOON_DIST:        71.82 [deg]
MOON_ILLUM:      89 [%]
GAL_COORDS:       41.53, 15.00 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      273.78, 37.67 [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 = 107.14,-0.52 [deg].

red DSS finding chart ps-file
GCN Circular #13032
C. B. Markwardt (NASA/GSFC), S. D. Barthelmy (GSFC), M. M. Chester (PSU), J. R. Cummings (NASA/UMBC), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC), A. Melandri (INAF-OAB), D. M. Palmer (LANL), M. H. Siegel (PSU) and M. Stamatikos (OSU/NASA/GSFC) report on behalf of the Swift Team:
At 05:33:38 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 120311A (trigger=517469). Swift did not slew because of the Earth limb observing constraint. The BAT on-board calculated location is RA, Dec 273.087, +14.275, which is
```
   RA(J2000)  =  18h 12m 21s
   Dec(J2000) = +14d 16' 32"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows a single peak structure with a duration of about 6 sec. The peak count rate was ~5100 counts/sec (15-350 keV), at ~0 sec after the trigger.
Due to an observing constraint, Swift will not slew until T0+50.1 minutes. There will be no XRT or UVOT data until this time.
Burst Advocate for this burst is C. B. Markwardt (Craig.Markwardt AT nasa.gov). 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 NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 11 Mar 12 05:37:33 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     517469,   Seg_Num: 0
GRB_RA:          273.087d {+18h 12m 21s} (J2000),
                 273.226d {+18h 12m 54s} (current),
                 272.517d {+18h 10m 04s} (1950)
GRB_DEC:         +14.275d {+14d 16' 32"} (J2000),
                 +14.279d {+14d 16' 45"} (current),
                 +14.262d {+14d 15' 43"} (1950)
GRB_DATE:        15997 TJD;    71 DOY;   12/03/11
GRB_TIME:        20018.32 SOD {05:33:38.32} UT
TRIGGER_INDEX:   120
GRB_PHI:          54.18 [deg]
GRB_THETA:        21.11 [deg]
DELTA_TIME:      -70.00 [sec]
TRIGGER_DUR:     0.256 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     25.01 [sigma]
IMAGE_SIGNIF:    12.99 [sigma]
LC_URL:          sw00517469000msb.lc
SUN_POSTN:       351.78d {+23h 27m 07s}   -3.55d {-03d 32' 47"}
SUN_DIST:         79.82 [deg]   Sun_angle= 5.2 [hr] (West of Sun)
MOON_POSTN:      206.73d {+13h 46m 55s}  -14.48d {-14d 28' 46"}
MOON_DIST:        71.79 [deg]
MOON_ILLUM:      89 [%]
GAL_COORDS:       41.53, 15.00 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      273.78, 37.67 [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 = 107.14,-0.52 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 11 Mar 12 06:26:31 UT
NOTICE_TYPE:     Swift-XRT Nack-Position
TRIGGER_NUM:     517469,   Seg_Num: 0
POINT_RA:        273.070d {+18h 12m 17s} (J2000)
POINT_DEC:       +14.266d {+14d 15' 57"} (J2000)
IMG_START_DATE:  15997 TJD;    71 DOY;   12/03/11
IMG_START_TIME:  23179.93 SOD {06:26:19.93} UT,   3161.6 [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:     Sun 11 Mar 12 06:29:19 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     517469,   Seg_Num: 0
POINT_RA:        273.070d {+18h 12m 17s} (J2000)
POINT_DEC:       +14.266d {+14d 15' 58"} (J2000)
POINT_ROLL:      96.300d
IMG_START_DATE:  15997 TJD;    71 DOY;   12/03/11
IMG_START_TIME:  23182.38 SOD {06:26:22.38} UT,   3164.1 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.655
N_STARS:         190
X_OFFSET:        534 [pixels]
Y_OFFSET:        411 [pixels]
X_MAX:           1493 [pixels]
Y_MAX:           1370 [pixels]
DET_THRESH:      13
PHOTO_THRESH:    7
SL_URL:          sw00517469000msufc3164.fits
SUN_POSTN:       351.81d {+23h 27m 15s}   -3.53d {-03d 31' 56"}
SUN_DIST:         79.87 [deg]   Sun_angle= 5.2 [hr] (West of Sun)
MOON_POSTN:      207.25d {+13h 49m 01s}  -14.63d {-14d 38' 03"}
MOON_DIST:        71.35 [deg]
MOON_ILLUM:      89 [%]
GAL_COORDS:       41.52, 15.01 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      273.76, 37.67 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 11 Mar 12 06:29:59 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     517469,   Seg_Num: 0
POINT_RA:        273.070d {+18h 12m 17s} (J2000)
POINT_DEC:       +14.266d {+14d 15' 58"} (J2000)
POINT_ROLL:      96.300d
IMG_START_DATE:  15997 TJD;    71 DOY;   12/03/11
IMG_START_TIME:  23182.38 SOD {06:26:22.38} UT,   3164.1 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.655
N_STARS:         190
X_OFFSET:        534 [pixels]
Y_OFFSET:        411 [pixels]
X_MAX:           1493 [pixels]
Y_MAX:           1370 [pixels]
DET_THRESH:      13
PHOTO_THRESH:    7
SL_URL:          sw00517469000msufc3164.fits
SUN_POSTN:       351.81d {+23h 27m 15s}   -3.53d {-03d 31' 55"}
SUN_DIST:         79.87 [deg]   Sun_angle= 5.2 [hr] (West of Sun)
MOON_POSTN:      207.26d {+13h 49m 02s}  -14.64d {-14d 38' 10"}
MOON_DIST:        71.34 [deg]
MOON_ILLUM:      89 [%]
GAL_COORDS:       41.52, 15.01 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      273.76, 37.67 [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:     Sun 11 Mar 12 06:30:57 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     517469,   Seg_Num: 0
POINT_RA:        273.070d {+18h 12m 17s} (J2000)
POINT_DEC:       +14.266d {+14d 15' 58"} (J2000)
ROLL:            96.300d
IMG_START_DATE:  15997 TJD;    71 DOY;   12/03/11
IMG_START_TIME:  23182.38 SOD {06:26:22.38} UT,   3164.1 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     353139990
X_OFFSET:        853 [pixels]
Y_OFFSET:        730 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1013
Y_GRB_POS:       890
BINNING_INDEX:   1
IM_URL:          sw00517469000msuni3172.fits
SUN_POSTN:       351.81d {+23h 27m 15s}   -3.53d {-03d 31' 55"}
SUN_DIST:         79.87 [deg]   Sun_angle= 5.2 [hr] (West of Sun)
MOON_POSTN:      207.27d {+13h 49m 05s}  -14.64d {-14d 38' 20"}
MOON_DIST:        71.34 [deg]
MOON_ILLUM:      89 [%]
GAL_COORDS:       41.52, 15.01 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      273.76, 37.67 [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:     Sun 11 Mar 12 06:31:17 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     517469,   Seg_Num: 0
POINT_RA:        273.070d {+18h 12m 17s} (J2000)
POINT_DEC:       +14.266d {+14d 15' 58"} (J2000)
ROLL:            96.300d
IMG_START_DATE:  15997 TJD;    71 DOY;   12/03/11
IMG_START_TIME:  23182.38 SOD {06:26:22.38} UT,   3164.1 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     353139990
X_OFFSET:        853 [pixels]
Y_OFFSET:        730 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1013
Y_GRB_POS:       890
BINNING_INDEX:   1
IM_URL:          sw00517469000msuni3172.fits
SUN_POSTN:       351.81d {+23h 27m 15s}   -3.53d {-03d 31' 54"}
SUN_DIST:         79.87 [deg]   Sun_angle= 5.2 [hr] (West of Sun)
MOON_POSTN:      207.27d {+13h 49m 05s}  -14.64d {-14d 38' 24"}
MOON_DIST:        71.33 [deg]
MOON_ILLUM:      89 [%]
GAL_COORDS:       41.52, 15.01 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      273.76, 37.67 [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:     Sun 11 Mar 12 06:32:56 UT
NOTICE_TYPE:     Swift-UVOT Position
TRIGGER_NUM:     517469,   Seg_Num: 0
GRB_RA:          273.1037d {+18h 12m 24.88s} (J2000),
                 273.2427d {+18h 12m 58.25s} (current),
                 272.5336d {+18h 10m 08.07s} (1950)
GRB_DEC:         +14.2248d {+14d 13' 29.2"} (J2000),
                 +14.2286d {+14d 13' 42.8"} (current),
                 +14.2111d {+14d 12' 39.9"} (1950)
GRB_ERROR:       1.1 [arcsec radius, statistical only]
GRB_MAG:         17.86 +/- 0.40 [mag]
FILTER:          10, White
IMG_START_DATE:  15997 TJD;    71 DOY;   12/03/11
IMG_START_TIME:  23182.00 SOD {06:26:22.00} UT,   3163.7 [sec] since BAT Trigger Time
SUN_POSTN:       351.81d {+23h 27m 15s}   -3.53d {-03d 31' 53"}
SUN_DIST:         79.83 [deg]   Sun_angle= 5.2 [hr] (West of Sun)
MOON_POSTN:      207.29d {+13h 49m 09s}  -14.65d {-14d 38' 42"}
MOON_DIST:        71.34 [deg]
MOON_ILLUM:      89 [%]
GAL_COORDS:       41.49, 14.97 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      273.80, 37.62 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT UVOT Position Notice.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        Result based on srclist data.  
COMMENTS:        Notice generated automatically.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 11 Mar 12 06:35:17 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     517469,   Seg_Num: 0
GRB_RA:          273.0903d {+18h 12m 21.67s} (J2000),
                 273.2292d {+18h 12m 55.01s} (current),
                 272.5206d {+18h 10m 04.94s} (1950)
GRB_DEC:         +14.2966d {+14d 17' 47.7"} (J2000),
                 +14.3003d {+14d 18' 01.2"} (current),
                 +14.2830d {+14d 16' 58.7"} (1950)
GRB_ERROR:       4.8 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  15997 TJD;    71 DOY;   12/03/11
IMG_START_TIME:  23210.00 SOD {06:26:50.00} UT,   3191.7 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       351.82d {+23h 27m 16s}   -3.53d {-03d 31' 50"}
SUN_DIST:         79.85 [deg]   Sun_angle= 5.2 [hr] (West of Sun)
MOON_POSTN:      207.31d {+13h 49m 15s}  -14.65d {-14d 39' 07"}
MOON_DIST:        71.33 [deg]
MOON_ILLUM:      89 [%]
GAL_COORDS:       41.55, 15.01 [deg] galactic lon,lat of the burst
ECL_COORDS:      273.79, 37.70 [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 #13033
A. Melandri (INAF-OAB), C. Guidorzi (U. Ferrara), F. Virgili (LJMU), on behalf of a larger collaboration report:
"The 2-m Liverpool Telescope robotically followed up GRB 120311A (SWIFT trigger 517469, Markwardt et al., GCN 13032) 14.4 min after the GRB trigger time. The automatic "detection mode" procedure detected an uncatalogued afterglow candidate close to the XRT error circle (7 arcsec from its centroid) at:
18:12:22.166 +14:17:46.3 (J2000)
with magnitude R = 19.1 mag (vs USNOB1) 16 min after the burst.
Observations and analysis are ongoing.
GCN Circular #13034
P.A. Evans (U. Leicester), J.P. Osborne (U. Leicester), D.N. Burrows (PSU), J.A. Kennea (PSU), M. Perri (ASDC) and G. Tagliaferri (INAF-OAB) report on behalf of the Swift-XRT team:
The XRT began observing the field of GRB 120311A at 06:26:19.9 UT, 3161.6 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 273.08966, 14.29709 which is equivalent to:
```
   RA(J2000)  = 18h 12m 21.52s
   Dec(J2000) = +14d 17' 49.5"
```
with an uncertainty of 3.7 arcseconds (radius, 90% containment). This location is 80 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.
A power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the Galactic value (1.03 x 10^21 cm^-2, Kalberla et al. 2005), with an excess column of 2.5 (+2.12/-1.86) x 10^21 cm^-2 (90% confidence).
GCN Circular #13035
M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team.
Using 762 s of XRT Photon Counting mode data and 2 UVOT images for GRB 120311A, 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 = 273.09198, +14.29643 which is equivalent to:
```
RA (J2000): 18h 12m 22.08s
Dec (J2000): +14d 17' 47.2"
```
with an uncertainty of 2.6 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 #13036
P. Kubanek, M. Jelinek, J. Gorosabel (IAA-CSIC), report on behalf of a larger collaboration:
"The 1.23m CAHA telescope responded automatically to GRB 120311A (trigger=517469, Markwardt et al. GCN 13032) starting optical observations on March 11.23381 UT (~3.05 minutes after the trigger). The optical afterglow (Melandri et al. GCNC 13033) is clearly detected in two I-band frames taken before dawn at I ~ 17.3."
GCN Circular #13037
S. R. Oates (MSSL-UCL) and C. B. Markwardt (NASA/GSFC) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 120311A 3164 s after the BAT trigger (Markwardt et al., GCN Circ. 13032). No optical afterglow, consistent with the refined XRT position (Goad et al .,GCN Circ 13035) or optical position reported by the Liverpool Telescope (Melandri et al., GCN Circ 13033), is detected within 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          3164         3314          147         >16.4
white             3164        16486         2114         >16.5
v                 3321        20754         1454         >15.8
b                 4141        15574         1224         >16.4
u                 3936         5571          393         >16.3
w1                3731         5366          393         >17.7
m2                3526         5161          393         >19.0
w2                4552        17272         1850         >19.2
```
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 #13039
M. Stamatikos (OSU), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), J. Tueller (GSFC), T. N. Ukwatta (MSU) (i.e. the Swift-BAT team):
Using the data set from T-239 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 120311A (trigger #517469) (Markwardt, et al., GCN Circ. 13032). The BAT ground-calculated position is RA, Dec = 273.075, 14.297 deg which is
```
    RA(J2000)  =  18h 12m 18.1s
    Dec(J2000) = +14d 17' 49.0" 
```
with an uncertainty of 1.1 arcmin, (radius, sys+stat, 90% containment). The partial coding was 71%.
The mask-weighted light curve shows a single gradual-rise exponential-decay peak. T90 (15-350 keV) is 3.5 +- 0.8 sec (estimated error including systematics).
The time-averaged spectrum from T-1.38 to T+3.22 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.30 +- 0.15. The fluence in the 15-150 keV band is 3.0 +- 0.3 x 10^-07 erg/cm2. The 1-sec peak photon flux measured from T-0.07 sec in the 15-150 keV band is 3.2 +- 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/517469/BA/
GCN Circular #13043
A. Melandri (INAF/OAB), P. D'Avanzo (INAF/OAB) and C. B. Markwardt (NASA/GSFC) report on behalf of the Swift-XRT team:
We have analysed 15 ks of XRT data for GRB 120311A (Markwardt et al. GCN Circ. 13032), from 3.2 ks to 34.5 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 13035).
The late-time light curve (from T0+3.2 ks) can be modelled with a single power-law decay with a decay index of alpha=1.09 (+0.13,-0.12).
A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.03 (+0.27, -0.25). The best-fitting absorption column is 2.6 (+0.9, -0.8) x 10^21 cm^-2, in excess of the Galactic value of 1.0 x 10^21 cm^-2 (Kalberla et al. 2005). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 4.0 x 10^-11 (6.2 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     2.6 (+0.9, -0.8) x 10^21 cm^-2
Galactic foreground: 1.0 x 10^21 cm^-2
Excess significance: 3.2 sigma
Photon index:	     2.03 (+0.27, -0.25)
```
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00517469.
This circular is an official product of the Swift-XRT team.
GCN Circular #13048
V. Sudilovsky, T. Prinz, and J. Greiner (all MPE Garching) report on behalf of the GROND team:
We observed the field of GRB 120311A (Markwardt et al., GCN #13032) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP, 120, 405) mounted at the 2.2 m MPI/ESO telescope at La Silla Observatory (Chile). Observations centered on the BAT position started on March 11, 2012, at 08:02 UT, 2.5h after the GRB trigger. They were performed at an average seeing of 1.0", and average airmass of 1.8.
Based on a 20 minute exposure centered at 09:09 UT, the afterglow candidate reported by Melandri et al. (GCN 13033) is measured as follows (all in the AB system and calibrated against GROND zeropoints (g'r'i'z') and 2MASS (JHK)):
```
g' = 22.9 +/- 0.3 
r' = 22.5 +/- 0.1 
i' = 22.4 +/- 0.1 
z' = 22.0 +/- 0.1 
J  > 20.5 
H  > 19.6 
K  > 18.0
```
These above magnitudes have not been corrected for the Galactic extinction of E(B-V) = 0.13 towards the direction of the burst (Schlegel et al. 1998).
These magnitudes imply a fading of more than two magnitudes relative to the observations reported by Melandri et al. (GCN 13033), and thus confirm the afterglow nature of this object.
GCN Circular #13051
Paolo D'Avanzo (INAF/OAB), Bo Milvang-Jensen (DARK/NBI), Paul Vreeswijk (U. Iceland), Nial Tanvir (U. Leicester), Daniele Malesani (DARK/NBI), Paolo Goldoni (APC/U. Paris 7 and SAp/CEA), Lex Kaper (U. Amsterdam), Stefano Covino (INAF/OAB) and Johan Fynbo (DARK/NBI) report on behalf of a larger collaboration:
The optical afterglow (Melandri et al., GCN 13033) of the Swift GRB 120311A (Markwardt et al., GCN 13032; Evans et al., GCN 13034) was observed spectroscopically with VLT/X-shooter, starting on 2012 March 11.384 UT (3.65 hours after the GRB trigger). An exposure of 2400 seconds was secured, which ran well into morning twilight. The approximate X-shooter wavelength range is 0.3-2.5 micron. The seeing during the observations was about 0.8" in the optical, and the spectrum has a resulting resolving power of 5000 in the ultraviolet and near-infrared arms, and around 9000 in the optical.
The reduced spectrum shows a very weak continuum in all three arms. The very low signal-to-noise ratio prevents us from identifying any significant absorption or emission lines. From the detection of continuum flux down to roughly 3700 Angstrom we set an upper limit to the GRB 120311A redshift of approximately z < 3.
Using acquisition images preceding the spectrum, with a mid-exposure time of March 11.373 UT (3.40 hours after the GRB), we measure R = 21.57 +- 0.05 for the afterglow, assuming R=18.30 for the USNO-B1.0 star 1042-0333539 at RA = 18:12:21.82, Dec = +14:17:24.6.
We are grateful for the support of the ESO staff at Paranal, in particular that of Gabriel Brammer and Stan Stefl.
GCN Circular #13058
Simone Leonini and Paolo Rosi (Montarrenti Observatory, Siena, Italy) report:
We observed the field of GRB 120311A (Swift trigger 517469, Markwardt et al., GCN 13032) with 0.53m RC telescope + U47 detector at Montarrenti Observatory (Siena, Italy, IAU code C88).
The observations were performed in four sessions (~22 hours after the trigger):
```
from 2012-03-12 03:22:33 UT to 2012-03-12 03:23:15 UT
from 2012-03-12 04:16:03 UT to 2012-03-12 04:16:46 UT   
from 2012-03-12 04:18:09 UT to 2012-03-12 04:18:52 UT   
from 2012-03-12 04:20:16 UT to 2012-03-12 04:20:59 UT
```
Eight unfiltered images of 40s exposure were obtained. We do not detect any new point source in the coadded images (limit R~19.1, USNO-B1 catalogue) within the refined XRT error circle (Goad et al.,GCN Circ 13035) or in the afterglow candidate position reported by Melandri et al. (GCN Circ 13033). Observations were made on the twilight.
GCN Circular #13060
Vijay Kumar Bhatt, Brajesh Kumar and S.B. Pandey (ARIES, Nainital, India, on behalf of larger Indian GRB collaboration)
We imaged the field of GRB120311A (Swift trigger 517469, Markwardt et al., GCN 13032) using 1.04m and 1.3m telescopes at ARIES Nainital starting ~16 hours after the burst. Several sets of 300s exposures were taken in R_c and I_c pass-bands.
We do not detect the optical afterglow candidate (Melandri et al., GCN 13033) in our stacked images to following limits. The photometry was performed in comparison to nearby USNO-B1 stars.
```
Filter   Exposure     Limiting mag
----------------------------------
R_c      5x300s       20.0 mag

I_c      5x300s       19.5 mag
----------------------------------
```
This massage could be cited.

GCN Circular #13063
V.V.Golovnya (Main Astro Obs, Kyiv) report: We have undertaken the review of the sky area in vicinity of=20 GRB 120311A (M.R. Goad et al. GCN Circ.13035) on=20 astronegatives, collected in Ukrainian NAS Main astronomical=20 observatory plate archive (1976-1996). All the plates with=20 the possible object appearance are digitized using Microtek=20 ScanMaker 9800XL TMA and Epson Expression 10000XL flatbed=20 scanners and have been placed into Golosiiv Plate Archive=20 database DBGPA with open access to them.

 	The list of plates is given in the table:
YYYYMMDD/TimeUT	--Plates--	Exp.	LimMag	Star USNOA2=20
19840817/191914	GUA040C002619	40.1	14.50	0975-10768885
19840817/191917	GUA040D002620	40.1	14.50	0975-10768885
19860613/221841	GUA040C002948	41.7	16.20	0975-10753116
19860613/221846	GUA040D002949	41.7	15.95	0975-10751623
19870630/215915	GUA040C003102	50.5	16.20	0975-10753116
19900627/221058	GUA040C001669	19.0	16.20	0975-10753116
19900628/215100	GUA040C001976	18.0	16.20	0975-10753116
19910619/224921	GUA040C001815	18.0	14.75	0975-10758776
19910704/210331	GUA040C001818A	25.0	15.95	0975-10751623
Plates: =96the plates archive identifier of DWA (D/F=3D400/2000,=20
GUA040C, M=3D103"/mm) of the Ukrainian NAS Main Astro obs.
GUA040D (Marsden's number - 83) the plate number [1].
Exp.   - Duration of the maximum exposure (minutes).=20
LimM   - Limited V mag, derived in the 25 minutes area around=20
       the location given in M.R. Goad et al. GCN Circ.13035:=20
       RA(J2000)=3D 18h 12m 22.08s, Dec(J2000)=3D +14d 17' 47.2"
Star USNOA2 - Comparison star.

The preview images of 9 areas together with =20 the 25x25 min.of arc area from SkyMap can be found in =20 http://gua.db.ukr-vo.org/img/grb/120311A/index.html The images with full resolution are available via e-mail on=20 demand.
References:
1.L.Pakuliak DATABASE of GOLOSIIV PLATE ARCHIVE (DBGPA V2.0), http://gua.db.ukr-vo.org

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Jochen Greiner, last update: 13-Mar-2012 [Disclaimer]