Gamma-ray Burst 110928A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 28 Sep 11 01:52:35 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     504215,   Seg_Num: 0
GRB_RA:          257.755d {+17h 11m 01s} (J2000),
                 257.858d {+17h 11m 26s} (current),
                 257.316d {+17h 09m 16s} (1950)
GRB_DEC:         +36.570d {+36d 34' 13"} (J2000),
                 +36.556d {+36d 33' 23"} (current),
                 +36.630d {+36d 37' 49"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       25219 [cnts]    Image_Peak=349 [image_cnts]
TRIGGER_DUR:     8.192 [sec] 
TRIGGER_INDEX:   490     E_range: 50-350 keV
BKG_INTEN:       188243 [cnts]
BKG_TIME:        6600.58 SOD {01:50:00.58} UT
BKG_DUR:         64 [sec]
GRB_DATE:        15832 TJD;   271 DOY;   11/09/28
GRB_TIME:        6691.78 SOD {01:51:31.78} UT
GRB_PHI:         -21.57 [deg]
GRB_THETA:        45.33 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     8.54 [sigma]
IMAGE_SIGNIF:    7.03 [sigma]
MERIT_PARAMS:     +1  +0  +0  +3  +3  -3  +0  +0 -20  +0 
SUN_POSTN:       184.23d {+12h 16m 54s}   -1.83d {-01d 49' 43"}
SUN_DIST:         78.04 [deg]   Sun_angle= -4.9 [hr] (East of Sun)
MOON_POSTN:      190.29d {+12h 41m 09s}   -9.33d {-09d 19' 39"}
MOON_DIST:        78.12 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:       60.20, 35.10 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      250.58, 59.19 [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 = 317.83,18.45 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 28 Sep 11 01:55:11 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     504215,   Seg_Num: 0
GRB_RA:          257.755d {+17h 11m 01s} (J2000),
                 257.858d {+17h 11m 26s} (current),
                 257.316d {+17h 09m 16s} (1950)
GRB_DEC:         +36.570d {+36d 34' 13"} (J2000),
                 +36.556d {+36d 33' 23"} (current),
                 +36.630d {+36d 37' 49"} (1950)
GRB_DATE:        15832 TJD;   271 DOY;   11/09/28
GRB_TIME:        6691.78 SOD {01:51:31.78} UT
TRIGGER_INDEX:   490
GRB_PHI:         -21.57 [deg]
GRB_THETA:        45.33 [deg]
DELTA_TIME:      0.00 [sec]
TRIGGER_DUR:     8.192 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     8.54 [sigma]
IMAGE_SIGNIF:    7.03 [sigma]
LC_URL:          sw00504215000msb.lc
SUN_POSTN:       184.23d {+12h 16m 54s}   -1.83d {-01d 49' 46"}
SUN_DIST:         78.04 [deg]   Sun_angle= -4.9 [hr] (East of Sun)
MOON_POSTN:      190.31d {+12h 41m 15s}   -9.34d {-09d 20' 15"}
MOON_DIST:        78.11 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:       60.20, 35.10 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      250.58, 59.19 [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 = 317.83,18.45 [deg].

GCN Circular #12394
E. A. Hoversten (PSU), S. D. Barthelmy (GSFC), D. N. Burrows (PSU), M. M. Chester (PSU), N. Gehrels (NASA/GSFC), H. A. Krimm (CRESST/GSFC/USRA), C. B. Markwardt (NASA/GSFC), F. E. Marshall (NASA/GSFC), D. M. Palmer (LANL) and E. Sonbas (GSFC/USRA/Adiyaman Univ.) report on behalf of the Swift Team:
At 01:51:31 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 110928A (trigger=504215). Swift will slew after 52 minutes after the Earth limb constraint is avoided. The BAT on-board calculated location is RA, Dec 257.755, +36.570, which is
```
   RA(J2000)  =  17h 11m 01s
   Dec(J2000) = +36d 34' 13"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows a single FRED-like pulse with a duration of about 10 sec. The peak count rate was ~1500 counts/sec (15-350 keV), at ~0 sec after the trigger.
Due to an observing constraint, Swift will not slew until T0+52 minutes. There will be no XRT or UVOT data until this time.
Burst Advocate for this burst is E. A. Hoversten (hoversten AT astro.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/too.html.)
GCN Circular #12395
B. E. Schaefer (Louisiana State), W. Zheng (U Mich), H. Flewelling (IfA/Hawaii), report on behalf of the ROTSE collaboration:
ROTSE-IIIb, located at McDonald Observatory, Texas, responded to GRB 110928A (Swift trigger 504215; Hoversten et al., GCN 12394), producing images beginning 7.1 s after the GCN notice time. An automated response took the first image at 01:52:39.1 UT, 67.3 s after the burst, under excellent conditions. We took 10 5-sec, 10 20-sec and 10 60-sec exposures. These unfiltered images are calibrated relative to USNO A2.0 (R). Imaging is on going.
Comparison to the DSS (second epoch) reveals no new sources within the 3-sigma Swift/BAT error circle, for both single images and coadding into sets of 10; the field is not crowded. Individual images have limiting magnitudes ranging from 16.1-17.4; we set the following specific limits.
```
start UT       end UT      t_exp(s)   mlim   t_start-tGRB(s)  Coadd?
--------------------------------------------------------------------
01:52:39.1   01:52:44.1         5     16.1           67.3       N
01:52:39.1   01:54:26.8       107     17.5           67.3       Y
```
GCN Circular #12396
C. R. Klein and A. N. Morgan (U. C. Berkeley) report:
We observed the field of GRBs 110928A (Hoverston et al., GCN 12394) with the 1.3m PAIRITEL located at Mt. Hopkins, AZ. Observations began at 2011-Sep-28 02h03m59s, 12.5 minutes after the GRB. In mosaics (effective exposure time of 468s) taken simultaneously in the J, H, and Ks filters, we do not clearly detect any new sources in the BAT error circle down to the limit of the 2mass catalog.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 28 Sep 11 02:47:21 UT
NOTICE_TYPE:     Swift-XRT Nack-Position
TRIGGER_NUM:     504215,   Seg_Num: 0
POINT_RA:        257.738d {+17h 10m 57s} (J2000)
POINT_DEC:       +36.568d {+36d 34' 06"} (J2000)
IMG_START_DATE:  15832 TJD;   271 DOY;   11/09/28
IMG_START_TIME:  10029.05 SOD {02:47:09.05} UT,   3337.3 [sec] since BAT Trigger Time
COUNTS:          30    Min_needed= 20
STD_DEV:         0.00   Max_StdDev_for_Good=28.44 [arcsec]
PH2_ITER:        4    Max_iter_allowed= 4
ERROR_CODE:      2
COMMENTS:        SWIFT-XRT Nack Position.  
COMMENTS:        Algorithm did not converge; too many iterations.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 28 Sep 11 02:51:59 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     504215,   Seg_Num: 0
POINT_RA:        257.737d {+17h 10m 57s} (J2000)
POINT_DEC:       +36.569d {+36d 34' 07"} (J2000)
POINT_ROLL:      258.570d
IMG_START_DATE:  15832 TJD;   271 DOY;   11/09/28
IMG_START_TIME:  10033.75 SOD {02:47:13.75} UT,   3342.0 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        6.748
N_STARS:         37
X_OFFSET:        371 [pixels]
Y_OFFSET:        590 [pixels]
X_MAX:           1330 [pixels]
Y_MAX:           1549 [pixels]
DET_THRESH:      22
PHOTO_THRESH:    13
SL_URL:          sw00504215000msufc3341.fits
SUN_POSTN:       184.26d {+12h 17m 03s}   -1.85d {-01d 50' 41"}
SUN_DIST:         78.01 [deg]   Sun_angle= -4.9 [hr] (East of Sun)
MOON_POSTN:      190.88d {+12h 43m 31s}   -9.55d {-09d 33' 08"}
MOON_DIST:        77.81 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:       60.20, 35.11 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      250.55, 59.18 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 28 Sep 11 02:52:23 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     504215,   Seg_Num: 0
POINT_RA:        257.737d {+17h 10m 57s} (J2000)
POINT_DEC:       +36.569d {+36d 34' 07"} (J2000)
POINT_ROLL:      258.570d
IMG_START_DATE:  15832 TJD;   271 DOY;   11/09/28
IMG_START_TIME:  10033.75 SOD {02:47:13.75} UT,   3342.0 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        6.748
N_STARS:         37
X_OFFSET:        371 [pixels]
Y_OFFSET:        590 [pixels]
X_MAX:           1330 [pixels]
Y_MAX:           1549 [pixels]
DET_THRESH:      22
PHOTO_THRESH:    13
SL_URL:          sw00504215000msufc3341.fits
SUN_POSTN:       184.26d {+12h 17m 03s}   -1.85d {-01d 50' 42"}
SUN_DIST:         78.01 [deg]   Sun_angle= -4.9 [hr] (East of Sun)
MOON_POSTN:      190.88d {+12h 43m 32s}   -9.55d {-09d 33' 13"}
MOON_DIST:        77.81 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:       60.20, 35.11 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      250.55, 59.18 [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:     Wed 28 Sep 11 02:54:14 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     504215,   Seg_Num: 0
POINT_RA:        257.737d {+17h 10m 57s} (J2000)
POINT_DEC:       +36.569d {+36d 34' 07"} (J2000)
ROLL:            258.570d
IMG_START_DATE:  15832 TJD;   271 DOY;   11/09/28
IMG_START_TIME:  10033.75 SOD {02:47:13.75} UT,   3342.0 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     338870841
X_OFFSET:        690 [pixels]
Y_OFFSET:        909 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       850
Y_GRB_POS:       1069
BINNING_INDEX:   1
IM_URL:          sw00504215000msuni3349.fits
SUN_POSTN:       184.26d {+12h 17m 03s}   -1.85d {-01d 50' 43"}
SUN_DIST:         78.01 [deg]   Sun_angle= -4.9 [hr] (East of Sun)
MOON_POSTN:      190.90d {+12h 43m 36s}   -9.56d {-09d 33' 38"}
MOON_DIST:        77.80 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:       60.20, 35.11 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      250.55, 59.18 [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:     Wed 28 Sep 11 02:54:34 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     504215,   Seg_Num: 0
POINT_RA:        257.737d {+17h 10m 57s} (J2000)
POINT_DEC:       +36.569d {+36d 34' 07"} (J2000)
ROLL:            258.570d
IMG_START_DATE:  15832 TJD;   271 DOY;   11/09/28
IMG_START_TIME:  10033.75 SOD {02:47:13.75} UT,   3342.0 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     338870841
X_OFFSET:        690 [pixels]
Y_OFFSET:        909 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       850
Y_GRB_POS:       1069
BINNING_INDEX:   1
IM_URL:          sw00504215000msuni3349.fits
SUN_POSTN:       184.26d {+12h 17m 03s}   -1.85d {-01d 50' 44"}
SUN_DIST:         78.01 [deg]   Sun_angle= -4.9 [hr] (East of Sun)
MOON_POSTN:      190.90d {+12h 43m 37s}   -9.56d {-09d 33' 43"}
MOON_DIST:        77.80 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:       60.20, 35.11 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      250.55, 59.18 [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:     Wed 28 Sep 11 03:00:00 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     504215,   Seg_Num: 0
GRB_RA:          257.7336d {+17h 10m 56.06s} (J2000),
                 257.8367d {+17h 11m 20.80s} (current),
                 257.2947d {+17h 09m 10.72s} (1950)
GRB_DEC:         +36.5363d {+36d 32' 10.6"} (J2000),
                 +36.5225d {+36d 31' 20.9"} (current),
                 +36.5965d {+36d 35' 47.3"} (1950)
GRB_ERROR:       4.3 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  15832 TJD;   271 DOY;   11/09/28
IMG_START_TIME:  10048.00 SOD {02:47:28.00} UT,   3356.2 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       184.27d {+12h 17m 04s}   -1.85d {-01d 50' 49"}
SUN_DIST:         77.99 [deg]   Sun_angle= -4.9 [hr] (East of Sun)
MOON_POSTN:      190.96d {+12h 43m 50s}   -9.58d {-09d 34' 57"}
MOON_DIST:        77.75 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:       60.16, 35.11 [deg] galactic lon,lat of the burst
ECL_COORDS:      250.56, 59.15 [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 2.8% < P(seren) < 6.6%.

GCN Circular #12397
E. A. Hoversten (PSU) reports on behalf of the Swift UVOT team:
UVOT took a finding chart exposure of 150 seconds with the white filter of the field of GRB 110928A starting 3341 seconds after the BAT trigger (Hoversten et al., GCN 12394). No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers none of the XRT error circle. 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 0.03.
GCN Circular #12398
P.A. Evans (U. Leicester), J.P. Osborne (U. Leicester), D.N. Burrows (PSU), J.A. Kennea (PSU), S. Campana (INAF-OAB) and G. Cusumano (INAF-IASF PA) report on behalf of the Swift-XRT team:
The XRT began observing the field of GRB 110928A at 02:47:09.1 UT, 3337.3 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 257.73360, 36.53636 which is equivalent to:
```
   RA(J2000)  = 17h 10m 56.06s
   Dec(J2000) = +36d 32' 10.9"
```
with an uncertainty of 4.3 arcseconds (radius, 90% containment). This location is 136 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 in excess of the Galactic value (3.14 x 10^20 cm^-2, Kalberla et al. 2005), with an excess column of 2.1 (+2.44/-1.70) x 10^22 cm^-2 (90% confidence).
GCN Circular #12399
S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), E. A. Hoversten (PSU), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (GSFC/UMBC), M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (MSU) (i.e. the Swift-BAT team):
Using the data set from T-60 to T+243 sec from the recent telemetry downlink, we report further analysis of BAT GRB 110928A (trigger #504215) (Hoversten, et al., GCN Circ. 12394). The BAT ground-calculated position is RA, Dec = 257.745, 36.547 deg, which is
```
   RA(J2000)  =  17h 10m 58.7s 
   Dec(J2000) = +36d 32' 49.3" 
```
with an uncertainty of 2.3 arcmin, (radius, sys+stat, 90% containment). The partial coding was 37%.
The mask-weighted light curve shows a single FRED-like peak starting at ~T_zero and ending at ~T+30 sec. T90 (15-350 keV) is 26.7 +- 4.8 sec (estimated error including systematics).
The time-averaged spectrum from T-0.53 to T+27.88 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.09 +- 0.30. The fluence in the 15-150 keV band is 6.9 +- 1.1 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T+6.84 sec in the 15-150 keV band is 0.9 +- 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/504215/BA/
GCN Circular #12400
A. N. Morgan, C. R. Klein and J. S. Bloom (UC Berkeley) report:
We observed the field of GRB 110928A (Hoversten et al., GCN 12394) with the 1.3m PAIRITEL located at Mt. Hopkins, Arizona. Observations began at 2011-Sep-28 02h03m59s UT, ~12.5 min after the Swift trigger. In mosaics (effective exposure time of 678.6 s) taken simultaneously in the J, H, and Ks filters, we do not detect any source within the XRT error circle (Evans et al. GCN 12398).
```
post burst
t_mid (hr) exp.(hr) filt  U. Limit (3 sig)
0.36      0.19     J     > 18.2
0.36      0.19     H     > 17.5
0.36      0.19     Ks    > 15.9
```
Deeper NIR observations are underway. All magnitudes are given in the Vega system, calibrated to 2MASS. No correction for Galactic extinction has been made to the above reported values.
GCN Circular #12401
S. B. Cenko (UC Berkeley) reports on behalf of a larger collaboration:
We have imaged the field of GRB 110928A (Hoversten et al., GCN 12394) with the automated Palomar 60 inch telescope. Observations were obtained in the Sloan r', i', and z' filters beginning at 4:11 UT on 2011 September 28 (~ 2.3 hours after the Swift trigger).
We do not detect any sources within the XRT error circle (Evans et al., GCN 12398). Using nearby point sources from the Sloan Digital Sky Survey for reference, we calculate the following upper limits (AB):
```
r' > 22.1
i' > 21.6
z' > 20.3
```
We note the presence on the northern edge of the XRT error circle of one (possibly two) extended sources present in SDSS. The large size of the current X-ray localization precludes any firm association with GRB 110928A, however.
GCN Circular #12402
J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester) report on behalf of the Swift-XRT team.
Using 1477 s of XRT Photon Counting mode data and 3 UVOT images for GRB 110928A, 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 = 257.73295, +36.53571 which is equivalent to:
```
RA (J2000): 17h 10m 55.91s
Dec (J2000): +36d 32' 08.5"
```
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 #12404
C. A. Wolf (PSU), E. A. Hoversten (PSU), and K. L. Page (U Leicester) report on behalf of the Swift-XRT team:
We have analysed 12 ks of XRT data for GRB 110928A (Hoversten et al. GCN Circ. 12394), from 3.3 ks to 44.3 ks after the BAT trigger. The data was collected in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Osborne et al. (GCN. Circ 12402).
The light curve can be modelled with a power-law decay with a decay index of alpha=0.55 (+0.17, -0.19).
A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.07 (+0.34, -0.27). The best-fitting absorption column is 4.8 (+2.5, -1.7) x 10^21 cm^-2, in excess of the Galactic value of 3.1 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 4.4 x 10^-11 (8.1 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     4.8 (+2.5, -1.7) x 10^21 cm^-2
Galactic foreground: 3.1 x 10^20 cm^-2
Excess significance: 4.7 sigma
Photon index:	     2.07 (+0.34, -0.27)
```
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00504215.
This circular is an official product of the Swift-XRT team.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 28 Sep 11 20:26:19 UT
NOTICE_TYPE:     Swift-XRT Image
TRIGGER_NUM:     504307,   Seg_Num: 0
GRB_RA:          278.9302d {+18h 35m 43.2s} (J2000),
                 279.1033d {+18h 36m 24.7s} (current),
                 278.1930d {+18h 32m 46.3s} (1950)
GRB_DEC:         -19.3213d {-19d 19' 16.6"} (J2000),
                 -19.3111d {-19d 18' 39.8"} (current),
                 -19.3627d {-19d 21' 45.8"} (1950)
GRB_ERROR:       5.4 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       62 [cnts]
IMG_START_DATE:  15832 TJD;   271 DOY;   11/09/28
IMG_START_TIME:  73537.87 SOD {20:25:37.87} UT,   4097.3 [sec] since BAT Trigger Time
CENTROID_X:      292.51,  raw= 293  [pixels]
CENTROID_Y:      279.30,  raw= 279  [pixels]
ROLL:            266.66 [deg]
GAIN:            1
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   -44.08
GRB_POS_XRT_Z:   -26.35
IMAGE_URL:       sw00504307000msxps_rw.img
SUN_POSTN:       184.92d {+12h 19m 41s}   -2.13d {-02d 07' 47"}
SUN_DIST:         93.24 [deg]   Sun_angle= -6.3 [hr] (East of Sun)
MOON_POSTN:      201.54d {+13h 26m 10s}  -13.35d {-13d 21' 01"}
MOON_DIST:        74.09 [deg]
MOON_ILLUM:      3 [%]
GAL_COORDS:       13.94, -5.35 [deg] galactic lon,lat of the burst
ECL_COORDS:      278.44,  3.86 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 28 Sep 11 20:26:29 UT
NOTICE_TYPE:     Swift-XRT Processed Image
TRIGGER_NUM:     504307,   Seg_Num: 0
GRB_RA:          278.9302d {+18h 35m 43.2s} (J2000),
                 279.1033d {+18h 36m 24.7s} (current),
                 278.1930d {+18h 32m 46.3s} (1950)
GRB_DEC:         -19.3213d {-19d 19' 16.6"} (J2000),
                 -19.3111d {-19d 18' 39.8"} (current),
                 -19.3627d {-19d 21' 45.8"} (1950)
GRB_ERROR:       5.4 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       62 [cnts]
IMG_START_DATE:  15832 TJD;   271 DOY;   11/09/28
IMG_START_TIME:  73537.87 SOD {20:25:37.87} UT,   4097.3 [sec] since BAT Trigger Time
CENTROID_X:      292.51,  raw= 293  [pixels]
CENTROID_Y:      279.30,  raw= 279  [pixels]
ROLL:            266.66 [deg]
GAIN:            1
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   -44.08
GRB_POS_XRT_Z:   -26.35
IMAGE_URL:       sw00504307000msxps_rw.img
SUN_POSTN:       184.92d {+12h 19m 41s}   -2.13d {-02d 07' 47"}
SUN_DIST:         93.24 [deg]   Sun_angle= -6.3 [hr] (East of Sun)
MOON_POSTN:      201.54d {+13h 26m 10s}  -13.35d {-13d 21' 03"}
MOON_DIST:        74.09 [deg]
MOON_ILLUM:      3 [%]
GAL_COORDS:       13.94, -5.35 [deg] galactic lon,lat of the burst
ECL_COORDS:      278.44,  3.86 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Processed Image.

GCN Circular #12406
E. A. Hoversten (PSU) reports on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 110928A 3342 s after the BAT trigger (Hoversten et al., GCN Circ. 12394). No optical afterglow consistent with the XRT position (Osborne et al., GCN Circ. 12402) is detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Poole et al. 2008, MNRAS, 383, 627) for the first finding chart (FC) exposure and subsequent exposures are:
```
Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white_FC          3342         3492          147         >20.2
white             3342         4723          344         >21.0
v                 3499         3698          197         >19.1
b                 4319         4518          197         >21.0
u                 4114         4313          197         >20.8
w1                3909         4108          197         >20.3
m2                3704         3903          197         >19.9
w2                4729         4929          197         >21.6
```
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.03 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #12407
J. Wren, W.T. Vestrand, P. Wozniak, and H. Davis, of Los Alamos National Laboratory report:
The RAPTOR network of robotic optical telescopes made observations of Swift trigger 504215 (Hoversten et al., GCN 12394). The burst location was within the field of our wide-field monitors which began a 10 s integration of the location at 01:51:33.0 UT, 1.2 s after the Swift trigger time and during the gamma-ray emitting interval. The next wide-field 10 s integration begins at 01:51:52.1 UT, and is also within the gamma-ray emitting interval. Neither image shows a counterpart at the Swift XRT location (Evans et al., GCN 12398) to an unfiltered 3-sigma limiting magnitude of 10.1 based on comparison to the Tycho-2 V-band. Our narrow-field instruments began imaging at 01:52:40.2 UT, 68.4 s after the Swift trigger. The initial 5 s exposures show no counterpart to a 3-sigma limiting magnitude of 16.1 when compared to the USNO-B1 R-band. The following table gives a sample of our observations. The start time is given as the seconds between the start of the exposure and the initial Swift trigger time.
```
start(s)   exp(s)    mag limit
------------------------------
1.22       10.0      > 10.1
20.32      10.0      > 10.1
68.44       5.0      > 16.1
153.55     10.0      > 16.5
413.45     30.0      > 17.2
```
GCN Circular #12408
J. Haislip, K. Ivarsen, A. LaCluyze, K. McLin, D. Reichart, J. Moore, T. Cromartie, R. Egger, A. Foster, M. Nysewander, A. Oza, E. Speckhard, A. Trotter, and J. A. Crain report:
Skynet observed the field of GRB 110928A (Hoverston et al., GCN 12394) with the GLAST Optical Robotic Telescope (GORT) at the Hume observatory in California beginning roughly 75 minutes after the burst. We do not detect any uncatalogued sources. Stacking only images that increase the limiting magnitude yields:
```
mean            mean
time              
time                                                                3-sigma
since             
since                                                               limiting
trigger        trigger (days)  telescope   exposures     filter      mag

3.186 h         0.13277            GORT     19 x 80 s     Ic         20.0
3.400 h         0.14166            GORT     23 x 80 s     Rc        21.0
```
This message may be cited.
GCN Circular #12409
J. Haislip, K. Ivarsen, A. LaCluyze, M. Maturi, D. Reichart, J. Moore, T. Cromartie, R. Egger, A. Foster, N. Frank, M. Nysewander, A. Oza, E. Speckhard, A.Trotter, and J. A. Crain report:
Skynet observed the field of GRB 110928A (Hoverston et al., GCN 12394) with the 16" Dolomites Astronomical Observatory telescope (DAO) in Italy beginning roughly 16.3 hours after the burst. We do not detect any uncatalogued sources. Stacking only images that increase the limiting magnitude yields:
```
Mean Time                                       3-sigma limiting
Since trigger    Tel      Exposures    Filter    magnitude
17.244 h         DAO      37 x 160 s     g'         21.0
(0.71850 days)
```
This message may be cited.
GCN Report 347.1
GCN_Report 347.1 has been posted: http://gcn.gsfc.nasa.gov/reports/report_347_1.pdf by E.A. Hoversten at PSU titled: "Final Swift Observations of GRB 110928A"

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Jochen Greiner, last update: 30-Sep-2011 [Disclaimer]