Gamma-ray Burst 081104

(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 04 Nov 08 09:35:35 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     333666,   Seg_Num: 0
GRB_RA:          100.485d {+06h 41m 56s} (J2000),
                 100.530d {+06h 42m 07s} (current),
                 100.232d {+06h 40m 56s} (1950)
GRB_DEC:         -54.732d {-54d 43' 55"} (J2000),
                 -54.741d {-54d 44' 27"} (current),
                 -54.682d {-54d 40' 54"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       34841 [cnts]    Image_Peak=514 [image_cnts]
TRIGGER_DUR:     8.192 [sec] 
TRIGGER_INDEX:   477     E_range: 25-100 keV
BKG_INTEN:       253700 [cnts]
BKG_TIME:        34388.77 SOD {09:33:08.77} UT
BKG_DUR:         64 [sec]
GRB_DATE:        14774 TJD;   309 DOY;   08/11/04
GRB_TIME:        34482.46 SOD {09:34:42.46} UT
GRB_PHI:         -177.40 [deg]
GRB_THETA:        47.83 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     6.70 [sigma]
IMAGE_SIGNIF:    9.32 [sigma]
MERIT_PARAMS:     +1  +0  +0  +4  +2  +1  +0  +0  +5  +0 
SUN_POSTN:       219.90d {+14h 39m 35s}  -15.54d {-15d 32' 22"}
SUN_DIST:         93.09 [deg]   Sun_angle= 8.0 [hr] (West of Sun)
MOON_POSTN:      295.04d {+19h 40m 10s}  -23.24d {-23d 14' 08"}
MOON_DIST:       101.03 [deg]
MOON_ILLUM:      33 [%]
GAL_COORDS:      264.06,-23.18 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      118.18,-77.14 [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 = 71.45,-14.95 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 04 Nov 08 09:38:16 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     333666,   Seg_Num: 0
GRB_RA:          100.485d {+06h 41m 56s} (J2000),
                 100.530d {+06h 42m 07s} (current),
                 100.232d {+06h 40m 56s} (1950)
GRB_DEC:         -54.732d {-54d 43' 55"} (J2000),
                 -54.741d {-54d 44' 27"} (current),
                 -54.682d {-54d 40' 54"} (1950)
GRB_DATE:        14774 TJD;   309 DOY;   08/11/04
GRB_TIME:        34482.46 SOD {09:34:42.46} UT
TRIGGER_INDEX:   477
GRB_PHI:         -177.40 [deg]
GRB_THETA:        47.83 [deg]
DELTA_TIME:      71.00 [sec]
TRIGGER_DUR:     8.192 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     6.70 [sigma]
IMAGE_SIGNIF:    9.32 [sigma]
LC_URL:          sw00333666000msb.lc
SUN_POSTN:       219.90d {+14h 39m 36s}  -15.54d {-15d 32' 24"}
SUN_DIST:         93.10 [deg]   Sun_angle= 8.0 [hr] (West of Sun)
MOON_POSTN:      295.07d {+19h 40m 16s}  -23.23d {-23d 13' 48"}
MOON_DIST:       101.04 [deg]
MOON_ILLUM:      33 [%]
GAL_COORDS:      264.06,-23.18 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      118.18,-77.14 [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 = 71.45,-14.95 [deg].

GCN Circular #8473
A. M. Parsons (GSFC), A. P. Beardmore (U Leicester), P. J. Brown (PSU), P. A. Evans (U Leicester), C. Gronwall (PSU), C. Guidorzi (INAF-OAB), S. T. Holland (CRESST/USRA/GSFC), N. P. M. Kuin (MSSL), V. La Parola (INAF-IASFPA), V. Mangano (INAF-IASFPA), J. Mao (INAF-OAB), P. T. O'Brien (U Leicester), J. P. Osborne (U Leicester), K. L. Page (U Leicester), P. Romano (INAF-IASFPA), T. N. Ukwatta (GSFC/GWU) and H. Ziaeepour (UCL-MSSL) report on behalf of the Swift Team:
At 09:34:42 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 081104 (trigger=333666). The BAT on-board calculated location is RA, Dec 100.485, -54.732 which is
```
   RA(J2000) = 06h 41m 56s
   Dec(J2000) = -54d 43' 55"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a multiple peaked structure with a duration of about 30 sec. The peak count rate was ~1000 counts/sec (15-350 keV), at ~10 sec after the trigger.
Due to an observing constraint, Swift will not slew until T0+40.5 minutes. There will be no XRT or UVOT data until this time.
Burst Advocate for this burst is A. M. Parsons (parsons AT milkyway.gsfc.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:     Tue 04 Nov 08 10:18:48 UT
NOTICE_TYPE:     Swift-XRT Nack-Position
TRIGGER_NUM:     333666,   Seg_Num: 0
POINT_RA:        100.489d {+06h 41m 57s} (J2000)
POINT_DEC:       -54.750d {-54d 45' 00"} (J2000)
IMG_START_DATE:  14774 TJD;   309 DOY;   08/11/04
IMG_START_TIME:  37115.69 SOD {10:18:35.69} UT,   2633.2 [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 04 Nov 08 10:21:44 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     333666,   Seg_Num: 0
POINT_RA:        100.489d {+06h 41m 57s} (J2000)
POINT_DEC:       -54.750d {-54d 45' 00"} (J2000)
POINT_ROLL:      122.868d
IMG_START_DATE:  14774 TJD;   309 DOY;   08/11/04
IMG_START_TIME:  37119.85 SOD {10:18:39.85} UT,   2637.4 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.782
N_STARS:         109
X_OFFSET:        363 [pixels]
Y_OFFSET:        524 [pixels]
X_MAX:           1322 [pixels]
Y_MAX:           1483 [pixels]
DET_THRESH:      11
PHOTO_THRESH:    5
SL_URL:          sw00333666000msufc2637.fits
SUN_POSTN:       219.93d {+14h 39m 43s}  -15.55d {-15d 32' 57"}
SUN_DIST:         93.09 [deg]   Sun_angle= 8.0 [hr] (West of Sun)
MOON_POSTN:      295.44d {+19h 41m 46s}  -23.14d {-23d 08' 25"}
MOON_DIST:       101.06 [deg]
MOON_ILLUM:      34 [%]
GAL_COORDS:      264.08,-23.18 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      118.22,-77.16 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 04 Nov 08 10:22:15 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     333666,   Seg_Num: 0
POINT_RA:        100.489d {+06h 41m 57s} (J2000)
POINT_DEC:       -54.750d {-54d 45' 00"} (J2000)
POINT_ROLL:      122.868d
IMG_START_DATE:  14774 TJD;   309 DOY;   08/11/04
IMG_START_TIME:  37119.85 SOD {10:18:39.85} UT,   2637.4 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.782
N_STARS:         109
X_OFFSET:        363 [pixels]
Y_OFFSET:        524 [pixels]
X_MAX:           1322 [pixels]
Y_MAX:           1483 [pixels]
DET_THRESH:      11
PHOTO_THRESH:    5
SL_URL:          sw00333666000msufc2637.fits
SUN_POSTN:       219.93d {+14h 39m 43s}  -15.55d {-15d 32' 58"}
SUN_DIST:         93.09 [deg]   Sun_angle= 8.0 [hr] (West of Sun)
MOON_POSTN:      295.45d {+19h 41m 47s}  -23.14d {-23d 08' 21"}
MOON_DIST:       101.06 [deg]
MOON_ILLUM:      34 [%]
GAL_COORDS:      264.08,-23.18 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      118.22,-77.16 [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 04 Nov 08 10:23:02 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     333666,   Seg_Num: 0
POINT_RA:        100.489d {+06h 41m 57s} (J2000)
POINT_DEC:       -54.750d {-54d 45' 00"} (J2000)
ROLL:            122.868d
IMG_START_DATE:  14774 TJD;   309 DOY;   08/11/04
IMG_START_TIME:  37119.85 SOD {10:18:39.85} UT,   2637.4 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     247486723
X_OFFSET:        682 [pixels]
Y_OFFSET:        843 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       842
Y_GRB_POS:       1003
BINNING_INDEX:   1
IM_URL:          sw00333666000msuni2637.fits
SUN_POSTN:       219.93d {+14h 39m 43s}  -15.55d {-15d 32' 58"}
SUN_DIST:         93.09 [deg]   Sun_angle= 8.0 [hr] (West of Sun)
MOON_POSTN:      295.45d {+19h 41m 49s}  -23.14d {-23d 08' 15"}
MOON_DIST:       101.06 [deg]
MOON_ILLUM:      34 [%]
GAL_COORDS:      264.08,-23.18 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      118.22,-77.16 [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 04 Nov 08 10:23:30 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     333666,   Seg_Num: 0
POINT_RA:        100.489d {+06h 41m 57s} (J2000)
POINT_DEC:       -54.750d {-54d 45' 00"} (J2000)
ROLL:            122.868d
IMG_START_DATE:  14774 TJD;   309 DOY;   08/11/04
IMG_START_TIME:  37119.85 SOD {10:18:39.85} UT,   2637.4 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     247486723
X_OFFSET:        682 [pixels]
Y_OFFSET:        843 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       842
Y_GRB_POS:       1003
BINNING_INDEX:   1
IM_URL:          sw00333666000msuni2637.fits
SUN_POSTN:       219.93d {+14h 39m 43s}  -15.55d {-15d 32' 59"}
SUN_DIST:         93.09 [deg]   Sun_angle= 8.0 [hr] (West of Sun)
MOON_POSTN:      295.46d {+19h 41m 50s}  -23.14d {-23d 08' 12"}
MOON_DIST:       101.06 [deg]
MOON_ILLUM:      34 [%]
GAL_COORDS:      264.08,-23.18 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      118.22,-77.16 [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 04 Nov 08 10:26:17 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     333666,   Seg_Num: 0
GRB_RA:          100.4835d {+06h 41m 56.04s} (J2000),
                 100.5284d {+06h 42m 06.80s} (current),
                 100.2297d {+06h 40m 55.13s} (1950)
GRB_DEC:         -54.7210d {-54d 43' 15.5"} (J2000),
                 -54.7300d {-54d 43' 47.9"} (current),
                 -54.6709d {-54d 40' 15.4"} (1950)
GRB_ERROR:       4.0 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  14774 TJD;   309 DOY;   08/11/04
IMG_START_TIME:  37130.00 SOD {10:18:50.00} UT,   2647.5 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       219.93d {+14h 39m 44s}  -15.55d {-15d 33' 01"}
SUN_DIST:         93.11 [deg]   Sun_angle= 8.0 [hr] (West of Sun)
MOON_POSTN:      295.48d {+19h 41m 56s}  -23.13d {-23d 07' 51"}
MOON_DIST:       101.09 [deg]
MOON_ILLUM:      34 [%]
GAL_COORDS:      264.05,-23.18 [deg] galactic lon,lat of the burst
ECL_COORDS:      118.16,-77.13 [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 NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 04 Nov 08 10:30:43 UT
NOTICE_TYPE:     Swift-XRT Position UPDATE
TRIGGER_NUM:     333666,   Seg_Num: 0
GRB_RA:          100.4831d {+06h 41m 55.94s} (J2000),
                 100.5280d {+06h 42m 06.71s} (current),
                 100.2293d {+06h 40m 55.03s} (1950)
GRB_DEC:         -54.7203d {-54d 43' 13.0"} (J2000),
                 -54.7293d {-54d 43' 45.3"} (current),
                 -54.6703d {-54d 40' 12.9"} (1950)
GRB_ERROR:       4.9 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  14774 TJD;   309 DOY;   08/11/04
IMG_START_TIME:  37130.00 SOD {10:18:50.00} UT,   2647.5 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       219.93d {+14h 39m 44s}  -15.55d {-15d 33' 04"}
SUN_DIST:         93.11 [deg]   Sun_angle= 8.0 [hr] (West of Sun)
MOON_POSTN:      295.52d {+19h 42m 05s}  -23.12d {-23d 07' 18"}
MOON_DIST:       101.09 [deg]
MOON_ILLUM:      34 [%]
GAL_COORDS:      264.05,-23.18 [deg] galactic lon,lat of the burst
ECL_COORDS:      118.16,-77.13 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        This is an Update Notice -- the RA,Dec values herein supersede the previous XRT_POS Notice.  
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 #8474
V. Mangano, V. La Parola (INAF-IASF PA), P. Evans (U. Leicester) report on behalf the Swift XRT Team:
Swift slewed to the target (trigger=333666, Parsons et al., GCN Circ. 8473) at about 10:14:00 UT. Using promptly downlinked XRT data we find an uncatalogued source located at RA,Dec = 100.4835, -54.7211 which is equivalent to:
```
RA  (J2000.0) =  06 41 56.04
DEC (J2000.0) =  -54 43 15.9
```
with an uncertainty of 4.04 arcsec (radius, 90% containment). This location is 39.4 arcsec from the BAT position, inside the BAT error circle.
This is an official product of the Swift XRT Team.
GCN Circular #8475
A. Melandri, D.F. Bersier, M. Burgdorf, C.G. Mundell, R.J. Smith, I.A. Steele (Liverpool JMU) on behalf of a larger collaboration report:
On 2008 November 04 on 12:13 UT we observed the field of GRB 081104 (trigger = 333666, Parsons et al., GCN 8473) with the robotic 2m Faulkes Telescope South located in Australia.
We do not detect any fadind optical source within the XRT error circle (Mangano et al., GCN 8474) down to the following limit:
```
   Dt_mid    T_exp     Filter      Mag_lim
    [hr]     [min]
===========================================
    2.89     30.0        R         > 21.9
===========================================
```
Limiting magnitude has been estimated using the R2 magnitude of the USNO-B1 catalogue. The reported value is not corrected for the Galactic extinction.
GCN Circular #8478
P. J. Brown, C. A. Swenson (PSU), S. T. Holland, and A. M. Parsons (GSFC), on behalf of the Swift/UVOT team.
The Swift Ultra-Violet/Optical Telescope (UVOT) began settled observations of GRB 081104 (trigger 333666) 2638 seconds after the BAT trigger (Parsons et al., GCN Circ. 8473). No afterglow is detected at the XRT position (Mangano et al., GCN Circ. 8474) in any filter. The limiting magnitudes (3-sigma in 5" radius apertures) in each of the UVOT filters are as follows:
```
Filter  T_start(s)  T_stop(s)  Exp(s)  Mag UL (3sig)

white     2638      3882       209     >21.1
v         2794      9582       1082    >20.5
b         3614      3814       197     >20.4
u         3409      3609       197     >20.1
uvw1      3204      3404       197     >19.8
uvm2      2999      9874       479     >20.1
uvw2      2788      5368       197     >19.9
```
The values quoted above are in the UVOT photometric system (Poole et al. 2008, MNRAS, 383, 627). They are not corrected for the expected Galactic extinction corresponding to a reddening of E(B-V)=0.11 mag in the direction of the burst (Schlegel et al. 1998).
GCN Circular #8479
H. A. Krimm (GSFC/USRA), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC),C. B. Markwardt (GSFC/UMD), K. McLean (GSFC/UMD), D. M. Palmer (LANL), A. M. Parsons (GSFC), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC), T. N. Ukwatta (GWU) (i.e. the Swift-BAT team):
Using the data set from T-240 to T+962 sec from the recent telemetry downlink, we report further analysis of BAT GRB 081104 (trigger #333666) (Parsons, et al., GCN Circ. 8473). The BAT ground-calculated position is RA, Dec = 100.500, -54.722 deg which is
```
   RA(J2000)  =  06h 42m 00.0s
   Dec(J2000) = -54d 43' 17.4"
```
with an uncertainty of 1.3 arcmin, (radius, sys+stat, 90% containment). The partial coding was 32%.
The BAT mask-weighted light curve shows a single FRED peak. T90 (15-350 keV) is 59.1 +- 13.9 sec (estimated error including systematics).
The time-averaged spectrum from T-23.5 to T+51.2 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.00 +- 0.14. The fluence in the 15-150 keV band is 2.0 +- 0.2 x 10^-06 erg/cm2. The 1-sec peak photon flux measured from T+13.54 sec in the 15-150 keV band is 1.0 +- 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/333666/BA/
GCN Circular #8480
A.P. Beardmore, P.A. Evans, M.R. Goad and J.P. Osborne (U. Leicester) report on behalf of the Swift-XRT team.
Using 4796 s of XRT Photon Counting mode data and 6 UVOT images for GRB 081104, 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 = 100.4886, -54.7199 which is equivalent to:
```
RA (J2000): 06h 41m 57.26s
Dec (J2000): -54d 43' 11.5"
```
with an uncertainty of 1.6 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 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 #8481
V. Mangano, V. La Parola, B. Sbarufatti (INAF-IASF PA) report on behalf the Swift-XRT Team:
Swift XRT follow-up observation of the field of GRB 081104 (trigger=333666, Parsons et al., GCN Circ. 8473) started on 2008 11 04 at 10:18:45 UT (about 40 min after the trigger).
We have analysed the first four orbits of PC mode XRT data accumulated from T+2640 s to T+22153 s (6.5 ks exposure). The light curve of the X-ray source given in Mangano e. at, GCN Circ. 8474 shows a power-law decay with slope -1.0 +/- 0.2, with an initial count rate at the level of 0.1 counts/s. If decaying at this rate the source will reach a count rate level of 3.e-3 counts/s at T+24 hours.
The average spectrum of the source have been fitted with Cash statistics. It can be modeled with a highly absorbed power law, with NH=(1.5 +/ -0.4)e22 cm^-2 (significantly in excess with respect to the Galactic absorption along the line of sight, of 7.0e20 cm^-2; Kalberla et al. 2005) and a photon index of 5.2 +/- 1.0 (C-statistic=84.4 with 93 bins).
With the power law fit, the average observed (unabsorbed) flux in the 0.3-10 keV energy range is of 8.0e-13 (1.9e-10) erg cm^-2 s^-1.
This is an official product of the Swift-XRT Team.
GCN Circular #8482
C. Clemens, T. Kruehler, J. Greiner, R. Filgas, A. Yoldas (all MPE Garching), A. Kupcu Yoldas (ESO) and G. Szokoly (Eoetvoes Univ., Budapest) report on behalf of the GROND team:
We observed the field of GRB 081104 (Swift trigger 333666; Parsons et al., GCN #8473) 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 started at 07:43 UT on November 5th, 2008, 22.1 hr after the GRB trigger. They were performed at an average seeing of 1.0" and at an average airmass of 1.1.
We found a single point source at the edge of the astrometrically corrected 1.6'' Swift-XRT error circle reported by Beardmore et al. (GCN #8480) at
```
RA (J2000.0) = 06h 41m 57.13s  
DEC (J2000.0) = -54d 43' 09.9''
```
with an uncertainty of 0.5".
Based on the first 25 min of total exposures in g'r'i'z' and 20 min in JHK, we estimate preliminary magnitudes (all in AB system) of
```
g' ~ 22.7 mag, 
r' ~ 22.6 mag, 
i' ~ 21.8 mag, 
z' ~ 21.7 mag, 
J ~ 21.2 mag,
H > 21.1 mag and
K > 20.0 mag
```
with errors of +/- 0.2. These magnitudes are calibrated against GROND zeropoints as well as 2MASS field stars, and are not corrected for the galactic foreground extinction of E(B-V)= 0.1
The extinction-corrected spectral energy distribution is only marginally consistent with a power law, so at present (without proper calibration) we cannot distinguish between a foreground star, an afterglow, or a host. No statement about variability can be made at this point either.
We note that a very faint object is also visible on the POSS-IIN plate at this location.
GCN Circular #8493
C. Clemens, T. Kruehler, J. Greiner (all MPE Garching) and G. Szokoly (Eoetvoes Univ., Budapest) report on behalf of the GROND team:
We observed the field of GRB 081104 for a second time at 04:29 UT on November 6th, 2008, 42.9 hr after the GRB trigger with 73.0 min of total exposures in g'r'i'z' and 64.0 min in JHK. Observations were performed at an average seeing of 1.7".
We still detect the previously reported source (Clemens et al., GCN #8482) with magnitudes identical within the errors to our first epoch observations.
Therefore, this object is most likely not the afterglow of GRB 081104.
GCN Circular #8635
Aquib Moin (Curtin Institute of Radio Astronomy / Australia Telescope National Facility), Steven Tingay (Curtin Institute of Radio Astronomy), Chris Phillips (Australia Telescope National Facility), Gregory Taylor (University of New Mexico), Mark Wieringa (Australia Telescope National Facility) and Ralph Martin (Perth Observatory) report:
We observed the GROND position of the GRB 081104 optical afterglow (GCN 8482) at 4.800 and 4.928 GHz with the Australia Telescope Compact Array (ATCA) between 01:15:05 UT, November 24, 2008 and 20:35:30 UT November 25, 2008.
We did not detect a radio source at the optical afterglow position of the GRB 081104 (GCN 8482). The data at 4.800 and 4.928 GHz were merged and the radio flux density at the afterglow position found out to be -0.142 +/- 0.152 mJy/beam (1-sigma).
The Australia Telescope Compact Array (/ Parkes telescope / Mopra telescope / Long Baseline Array) is part of the Australia Telescope which is funded by the Commonwealth of Australia for operation as a National Facility managed by CSIRO.
See the 4.800 & 4.928 GHz combined image at:
http://cira.ivec.org/dokuwiki/doku.php/grb/grb081104_field_image

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Jochen Greiner, last update: 08-Dec-2008 [Disclaimer]