Gamma-ray Burst 080916B

(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 16 Sep 08 14:45:34 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     324907,   Seg_Num: 0
GRB_RA:          163.624d {+10h 54m 30s} (J2000),
                 163.771d {+10h 55m 05s} (current),
                 162.772d {+10h 51m 05s} (1950)
GRB_DEC:         +69.044d {+69d 02' 39"} (J2000),
                 +68.998d {+68d 59' 52"} (current),
                 +69.311d {+69d 18' 39"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       19877 [cnts]    Image_Peak=338 [image_cnts]
TRIGGER_DUR:     4.096 [sec] 
TRIGGER_INDEX:   300     E_range: 25-100 keV
BKG_INTEN:       182171 [cnts]
BKG_TIME:        53028.89 SOD {14:43:48.89} UT
BKG_DUR:         40 [sec]
GRB_DATE:        14725 TJD;   260 DOY;   08/09/16
GRB_TIME:        53087.32 SOD {14:44:47.32} UT
GRB_PHI:         -58.95 [deg]
GRB_THETA:        30.05 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     8.48 [sigma]
IMAGE_SIGNIF:    7.33 [sigma]
MERIT_PARAMS:     +1  +0  +0  +4  +2  +2  +0  +0 -38  +1 
SUN_POSTN:       174.58d {+11h 38m 20s}   +2.34d {+02d 20' 37"}
SUN_DIST:         67.05 [deg]   Sun_angle= 0.7 [hr] (West of Sun)
MOON_POSTN:        7.48d {+00h 29m 56s}   +7.57d {+07d 34' 19"}
MOON_DIST:       101.67 [deg]
MOON_ILLUM:      98 [%]
GAL_COORDS:      137.16, 44.72 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      126.48, 54.75 [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 = 97.13,11.95 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 16 Sep 08 14:48:16 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     324907,   Seg_Num: 0
GRB_RA:          163.624d {+10h 54m 30s} (J2000),
                 163.771d {+10h 55m 05s} (current),
                 162.772d {+10h 51m 05s} (1950)
GRB_DEC:         +69.044d {+69d 02' 39"} (J2000),
                 +68.998d {+68d 59' 52"} (current),
                 +69.311d {+69d 18' 39"} (1950)
GRB_DATE:        14725 TJD;   260 DOY;   08/09/16
GRB_TIME:        53087.32 SOD {14:44:47.32} UT
TRIGGER_INDEX:   300
GRB_PHI:         -58.95 [deg]
GRB_THETA:        30.05 [deg]
DELTA_TIME:      77.00 [sec]
TRIGGER_DUR:     4.096 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     8.48 [sigma]
IMAGE_SIGNIF:    7.33 [sigma]
LC_URL:          sw00324907000msb.lc
SUN_POSTN:       174.58d {+11h 38m 20s}   +2.34d {+02d 20' 34"}
SUN_DIST:         67.05 [deg]   Sun_angle= 0.7 [hr] (West of Sun)
MOON_POSTN:        7.51d {+00h 30m 01s}   +7.58d {+07d 35' 01"}
MOON_DIST:       101.66 [deg]
MOON_ILLUM:      98 [%]
GAL_COORDS:      137.16, 44.72 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      126.48, 54.75 [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 = 97.13,11.95 [deg].

GCN Circular #8240
G. Stratta (ASDC), S. D. Barthelmy (GSFC), A. P. Beardmore (U Leicester), P. A. Evans (U Leicester), N. Gehrels (NASA/GSFC), C. Guidorzi (INAF-OAB), S. T. Holland (CRESST/USRA/GSFC), E. A. Hoversten (PSU), S. D. Hunsberger (PSU), J. A. Kennea (PSU), H. A. Krimm (CRESST/GSFC/USRA), J. Mao (INAF-OAB), C. B. Markwardt (CRESST/GSFC/UMD), F. E. Marshall (NASA/GSFC), P. T. O'Brien (U Leicester), S. R. Oates (UCL-MSSL), J. P. Osborne (U Leicester), K. L. Page (U Leicester), M. Perri (ASDC), B. Preger (ASDC), R. L. C. Starling (U Leicester), M. C. Stroh (PSU) and T. N. Ukwatta (GSFC/GWU) report on behalf of the Swift Team:
At 14:44:47 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 080916B (trigger=324907). The BAT on-board calculated location is RA, Dec 163.624, +69.044 which is
```
   RA(J2000) = 10h 54m 30s
   Dec(J2000) = +69d 02' 39"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a multi-peaked structure with a duration of about 50 sec. The peak count rate was ~750 counts/sec (15-350 keV), at ~0 sec after the trigger.
Due to an observing constraint, Swift will not slew until T0+18.9 minutes. There will be no XRT or UVOT data until this time.
Burst Advocate for this burst is G. Stratta (giulia.stratta 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 NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 16 Sep 08 15:07:48 UT
NOTICE_TYPE:     Swift-XRT Nack-Position
TRIGGER_NUM:     324907,   Seg_Num: 0
POINT_RA:        163.687d {+10h 54m 45s} (J2000)
POINT_DEC:       +69.061d {+69d 03' 38"} (J2000)
IMG_START_DATE:  14725 TJD;   260 DOY;   08/09/16
IMG_START_TIME:  54442.20 SOD {15:07:22.20} UT,   1354.9 [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 16 Sep 08 15:09:24 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     324907,   Seg_Num: 0
POINT_RA:        163.686d {+10h 54m 45s} (J2000)
POINT_DEC:       +69.061d {+69d 03' 38"} (J2000)
POINT_ROLL:      168.126d
IMG_START_DATE:  14725 TJD;   260 DOY;   08/09/16
IMG_START_TIME:  54445.94 SOD {15:07:25.94} UT,   1358.6 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.194
N_STARS:         26
X_OFFSET:        653 [pixels]
Y_OFFSET:        671 [pixels]
X_MAX:           1612 [pixels]
Y_MAX:           1630 [pixels]
DET_THRESH:      9
PHOTO_THRESH:    4
SL_URL:          sw00324907000msufc1358.fits
SUN_POSTN:       174.60d {+11h 38m 23s}   +2.34d {+02d 20' 14"}
SUN_DIST:         67.07 [deg]   Sun_angle= 0.7 [hr] (West of Sun)
MOON_POSTN:        7.69d {+00h 30m 46s}   +7.67d {+07d 40' 30"}
MOON_DIST:       101.53 [deg]
MOON_ILLUM:      98 [%]
GAL_COORDS:      137.12, 44.72 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      126.50, 54.78 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 16 Sep 08 15:09:53 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     324907,   Seg_Num: 0
POINT_RA:        163.686d {+10h 54m 45s} (J2000)
POINT_DEC:       +69.061d {+69d 03' 38"} (J2000)
POINT_ROLL:      168.126d
IMG_START_DATE:  14725 TJD;   260 DOY;   08/09/16
IMG_START_TIME:  54445.94 SOD {15:07:25.94} UT,   1358.6 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.194
N_STARS:         26
X_OFFSET:        653 [pixels]
Y_OFFSET:        671 [pixels]
X_MAX:           1612 [pixels]
Y_MAX:           1630 [pixels]
DET_THRESH:      9
PHOTO_THRESH:    4
SL_URL:          sw00324907000msufc1358.fits
SUN_POSTN:       174.60d {+11h 38m 23s}   +2.34d {+02d 20' 13"}
SUN_DIST:         67.07 [deg]   Sun_angle= 0.7 [hr] (West of Sun)
MOON_POSTN:        7.69d {+00h 30m 47s}   +7.68d {+07d 40' 38"}
MOON_DIST:       101.53 [deg]
MOON_ILLUM:      98 [%]
GAL_COORDS:      137.12, 44.72 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      126.50, 54.78 [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 16 Sep 08 15:10:34 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     324907,   Seg_Num: 0
POINT_RA:        163.686d {+10h 54m 45s} (J2000)
POINT_DEC:       +69.061d {+69d 03' 38"} (J2000)
ROLL:            168.126d
IMG_START_DATE:  14725 TJD;   260 DOY;   08/09/16
IMG_START_TIME:  54445.94 SOD {15:07:25.94} UT,   1358.6 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     243270449
X_OFFSET:        972 [pixels]
Y_OFFSET:        990 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1132
Y_GRB_POS:       1150
BINNING_INDEX:   1
IM_URL:          sw00324907000msuni1358.fits
SUN_POSTN:       174.60d {+11h 38m 23s}   +2.34d {+02d 20' 13"}
SUN_DIST:         67.07 [deg]   Sun_angle= 0.7 [hr] (West of Sun)
MOON_POSTN:        7.70d {+00h 30m 48s}   +7.68d {+07d 40' 48"}
MOON_DIST:       101.53 [deg]
MOON_ILLUM:      98 [%]
GAL_COORDS:      137.12, 44.72 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      126.50, 54.78 [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 16 Sep 08 15:11:02 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     324907,   Seg_Num: 0
POINT_RA:        163.686d {+10h 54m 45s} (J2000)
POINT_DEC:       +69.061d {+69d 03' 38"} (J2000)
ROLL:            168.126d
IMG_START_DATE:  14725 TJD;   260 DOY;   08/09/16
IMG_START_TIME:  54445.94 SOD {15:07:25.94} UT,   1358.6 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     243270449
X_OFFSET:        972 [pixels]
Y_OFFSET:        990 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1132
Y_GRB_POS:       1150
BINNING_INDEX:   1
IM_URL:          sw00324907000msuni1358.fits
SUN_POSTN:       174.60d {+11h 38m 24s}   +2.34d {+02d 20' 12"}
SUN_DIST:         67.07 [deg]   Sun_angle= 0.7 [hr] (West of Sun)
MOON_POSTN:        7.70d {+00h 30m 49s}   +7.68d {+07d 40' 55"}
MOON_DIST:       101.52 [deg]
MOON_ILLUM:      98 [%]
GAL_COORDS:      137.12, 44.72 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      126.50, 54.78 [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:        If you have elected to receive attachments:  
COMMENTS:        The uvot_sources_image.fits.gz file does not exist; skipping the attachment.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 16 Sep 08 15:22:58 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     324907,   Seg_Num: 0
GRB_RA:          163.6657d {+10h 54m 39.7s} (J2000),
                 163.8127d {+10h 55m 15.0s} (current),
                 162.8139d {+10h 51m 15.3s} (1950)
GRB_DEC:         +69.0659d {+69d 03' 57.2"} (J2000),
                 +69.0194d {+69d 01' 09.6"} (current),
                 +69.3325d {+69d 19' 56.9"} (1950)
GRB_ERROR:       3.6 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  14725 TJD;   260 DOY;   08/09/16
IMG_START_TIME:  54456.00 SOD {15:07:36.00} UT,   1368.7 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       174.61d {+11h 38m 25s}   +2.33d {+02d 20' 01"}
SUN_DIST:         67.08 [deg]   Sun_angle= 0.7 [hr] (West of Sun)
MOON_POSTN:        7.81d {+00h 31m 14s}   +7.73d {+07d 44' 01"}
MOON_DIST:       101.45 [deg]
MOON_ILLUM:      98 [%]
GAL_COORDS:      137.13, 44.71 [deg] galactic lon,lat of the burst
ECL_COORDS:      126.48, 54.78 [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.

GCN Circular #8242
G. Stratta, M. Perri, P. Evans report on behalf of the Swift-XRT Team:
The XRT began observing the field at 15:07:22.2 UT, 1354.9 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 163.66560, 69.06574 which is equivalent to:
```
   RA(J2000)  = 10h 54m 39.74s
   Dec(J2000) = +69d 03' 56.7"
```
with an uncertainty of 3.7 arcseconds (radius, 90% containment). This location is 94 arcseconds from the BAT onboard position, within the BAT error circle.
A power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the Galactic value of 1.8e+20 cm^-2 (Kalberla et al. 2005).
GCN Circular #8247
M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team.
Using 1049 s of XRT Photon Counting mode data and 1 UVOT images for GRB 080916B, 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 = 163.66512, +69.06545 which is equivalent to:
```
RA (J2000): 10h 54m 39.63s
Dec (J2000): +69d 03' 55.6"
```
with an uncertainty of 5.1 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 http://www.swift.ac.uk/xrt_positions/Goad.pdf), the current algorithm is an extension of this method.
This circular was automatically generated, and is an official product of the Swift-XRT team.
GCN Circular #8250
S. D. Barthelmy (GSFC), W. Baumgartner (GSFC/UMBC), J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), D. Palmer (LANL), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), M. Stamatikos (GSFC/ORAU), G. Stratta (ASDC), J. Tueller (GSFC), T. Ukwatta (GWU) (i.e. the Swift-BAT team) report:
Using the data set from T-239 to T+617 sec from the recent telemetry downlink, we report further analysis of BAT GRB 080916B (trigger #324907) (Strata, et al., GCN Circ. 8240). The BAT ground-calculated position is RA, Dec = 163.632, 69.061 deg, which is
```
   RA(J2000)  =  10h 54m 31.6s 
   Dec(J2000) = +69d 03' 38.2" 
```
with an uncertainty of 2.1 arcmin, (radius, sys+stat, 90% containment). The partial coding was 53%.
The mask-weighted light curve shows a weak FRED-like peak starting at ~T-4 sec, peaking at ~T+3 sec, and ending at ~T+50 sec. There is a possibility of very weak emission lasting out to at least T+350 sec, at which time the spacecraft slewed away fro the burst location. T90 (15-350 keV) is 32 +- 8 sec (estimated error including systematics).
The time-averaged spectrum from T-3.3 to T+35.7 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.49 +- 0.23. The fluence in the 15-150 keV band is 6.3 +- 0.9 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T+3.30 sec in the 15-150 keV band is 0.6 +- 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/324907/BA/
GCN Circular #8252
E. A. Hoversten (PSU) and G. Stratta (ASDC) report on behalf of the Swift UVOT team:
The Swift/UVOT began settled observations of the field of GRB 080916B, 1359s after the BAT trigger (Stratta et al., GCN 8240). There is a possible detection of an afterglow in the UVOT white filter at:
```
     RA (J2000)  10:54:39.78
    Dec (J2000)  69: 3:57.9
```
with an estimated uncertainty of 0.8 arcsec (radius, 90% confidence). This position is consistent with the UVOT enhanced XRT position (Evans et al., GCN 8247). The afterglow candidate does not appear in the DSS images, and photometry from the second orbit of Swift observations suggests that it has faded.
UVOT magnitudes and 3-sigma upper limits are reported in the following table:
```
Filter   T_start   T_stop   Exp(s)  Mag (3-sigma upper limit)
-----------------------------------------------------
white    1359.0    1458.8    98.2   20.50 +/- 0.21
white    7826.0    8025.7   196.6     > 21.27
v        1340.9    2920.7   342.1     > 19.62
b        1516.3    2676.5   155.6     > 20.32
u        1491.6    2651.7   155.6     > 19.91
uvw1     1467.3    2627.3   155.5     > 19.91
uvm2     1604.9    3076.8   285.0     > 20.06
uvw2     1556.0    2716.0   155.5     > 19.91
```
The quoted upper limits have not been corrected for the expected Galactic extinction along the line of sight of E_{B-V} = 0.02 mag. All photometry is on the UVOT flight system described in Poole et al. (2008, MNRAS, 383, 627).
GCN Circular #8260
G. Stratta, M. Perri, B. Preger (ASDC) report on behalf of the Swift-XRT team:
We have analyzed the first two orbits of Swift XRT data of GRB 080916B (Stratta et al., GCN Circ. 8242), consisting of 2.8 ks of Photon Counting data collected starting from 22.8 min after the burst.
During the XRT observation, from T0+1.4 ks to T0+8.5 ks, the source shows a fading behaviour from 0.08 cts/s to 0.02 cts/s. Assuming a power law model, the best fit decay index is alpha =3D 1.0 =B1 0.2. At this rate we predict a count rate level of 1.7 x 10-3 cts/s one day after the trigger.
The 0.3-10 keV extracted spectrum (2.8 ks of integration time) is consistent with an absorbed power law model. Fixing the column density to the Galactic value (NH =3D 1.8 x 1020 cm-2 from Kalberla et al. 2007) the best fit photon index is 2.0 =B1 0.5.
The observed 0.3-10.0 keV flux is (1.0+/-0.6) x 10-12 erg cm-2 s-1 which corresponds to an unabsorbed flux of 1.1 x 10-12 erg cm-2 s-1. The count to observed flux conversion factor is 6.6 x 10-11 erg cm-2 count-1.
This Circular is an official product of the Swift-XRT team.
GCN Report 164.1
GCN_Report 164.1 has been posted: http://gcn.gsfc.nasa.gov/reports/report_164_1.pdf by G. Stratta at ASDC titled: "Final observations of Swift GRB 080916B"
GCN Report 164.2
GCN_Report 164.2 has been posted: http://gcn.gsfc.nasa.gov/reports/report_164_2.pdf by G. Stratta at ASDC titled: "Revised Final observations of Swift GRB 080916B"
1009.5178 from 28 Sep 10
Katsuaki Asano et al.: Prompt X-ray and Optical Excess Emission due to Hadronic Cascades in Gamma-Ray Bursts
A fraction of gamma-ray bursts exhibit distinct spectral features in their prompt emission below few 10s of keV that exceed simple extrapolations of the low-energy power-law portion of the Band spectral model. This is also true for the prompt optical emission observed in several bursts. Through Monte Carlo simulations, we model such low-energy spectral excess components as hadronic cascade emission initiated by photomeson interactions of ultra-high-energy protons accelerated within GRB outflows. Synchrotron radiation from the cascading, secondary electron-positron pairs can naturally reproduce the observed soft spectra in the X-ray band, and in some cases the optical spectra as well. These components can be directly related to the higher energy radiation at GeV energies due to the hadronic cascades. Depending on the spectral shape, the total energy in protons is required to be comparable to or appreciably larger than the observed total photon energy. In particular, we apply our model to the excess X-ray and GeV emission of GRB 090902B, and the bright optical emission of the "naked-eye" GRB 080916B. Besides the hard GeV components detected by {\it Fermi}, such X-ray or optical spectral excesses are further potential signatures of ultra-high-energy cosmic ray production in gamma-ray bursts.

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Jochen Greiner, last update: 28-Sep-2010 [Disclaimer]