Gamma-ray Burst 081204

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:          GCN/INTEGRAL NOTICE
NOTICE_DATE:    Thu 04 Dec 08 16:45:27 UT
NOTICE_TYPE:    INTEGRAL Wakeup
TRIGGER_NUM:    5385,   Sub_Num: 0
GRB_RA:         349.7157d {+23h 18m 52s} (J2000),
                349.8454d {+23h 19m 23s} (current),
                348.9850d {+23h 15m 56s} (1950)
GRB_DEC:        -60.1668d {-60d 10' 00"} (J2000),
                -60.1179d {-60d 07' 03"} (current),
                -60.4404d {-60d 26' 25"} (1950)
GRB_ERROR:      3.07 [arcmin, radius, statistical only]
GRB_INTEN:      9.68 [sigma]
GRB_TIME:       60309.01 SOD {16:45:09.01} UT
GRB_DATE:       14804 TJD;   339 DOY;   08/12/04
SC_RA:            3.81 [deg] (J2000)
SC_DEC:         -68.99 [deg] (J2000)
SUN_POSTN:      251.48d {+16h 45m 55s}  -22.35d {-22d 20' 44"}
SUN_DIST:        74.77 [deg]   Sun_angle= -6.6 [hr] (East of Sun)
MOON_POSTN:     330.69d {+22h 02m 46s}  -10.19d {-10d 11' 21"}
MOON_DIST:       51.93 [deg]
GAL_COORDS:     322.07,-53.39 [deg] galactic lon,lat of the burst
ECL_COORDS:     318.93,-49.51 [deg] ecliptic lon,lat of the burst
COMMENTS:       INTEGRAL GRB Coordinates.  
COMMENTS:       Possibly real GRB event

red DSS finding chart ps-file

GCN NOTICE

TITLE:          GCN/INTEGRAL NOTICE
NOTICE_DATE:    Thu 04 Dec 08 16:48:25 UT
NOTICE_TYPE:    INTEGRAL Refined
TRIGGER_NUM:    5385,   Sub_Num: 1
GRB_RA:         349.7378d {+23h 18m 57s} (J2000),
                349.8675d {+23h 19m 28s} (current),
                349.0072d {+23h 16m 02s} (1950)
GRB_DEC:        -60.1781d {-60d 10' 40"} (J2000),
                -60.1292d {-60d 07' 44"} (current),
                -60.4517d {-60d 27' 05"} (1950)
GRB_ERROR:      3.00 [arcmin, radius, statistical only]
GRB_INTEN:      10.41 [sigma]
GRB_TIME:       60315.01 SOD {16:45:15.01} UT
GRB_DATE:       14804 TJD;   339 DOY;   08/12/04
SC_RA:            3.81 [deg] (J2000)
SC_DEC:         -68.99 [deg] (J2000)
SUN_POSTN:      251.48d {+16h 45m 56s}  -22.35d {-22d 20' 45"}
SUN_DIST:        74.78 [deg]   Sun_angle= -6.6 [hr] (East of Sun)
MOON_POSTN:     330.72d {+22h 02m 52s}  -10.18d {-10d 10' 42"}
MOON_DIST:       51.95 [deg]
GAL_COORDS:     322.04,-53.38 [deg] galactic lon,lat of the burst
ECL_COORDS:     318.93,-49.53 [deg] ecliptic lon,lat of the burst
COMMENTS:       INTEGRAL GRB Coordinates.  
COMMENTS:       Possibly real GRB event

GCN NOTICE

TITLE:          GCN/INTEGRAL NOTICE
NOTICE_DATE:    Thu 04 Dec 08 18:07:39 UT
NOTICE_TYPE:    INTEGRAL Offline
TRIGGER_NUM:    5385,   Sub_Num: 2
GRB_RA:         349.7734d {+23h 19m 06s} (J2000),
                349.9031d {+23h 19m 37s} (current),
                349.0430d {+23h 16m 10s} (1950)
GRB_DEC:        -60.2212d {-60d 13' 15"} (J2000),
                -60.1723d {-60d 10' 19"} (current),
                -60.4949d {-60d 29' 41"} (1950)
GRB_ERROR:      2.28 [arcmin, radius, statistical only]
GRB_INTEN:      10.41 [sigma]
GRB_TIME:       60315.01 SOD {16:45:15.01} UT
GRB_DATE:       14804 TJD;   339 DOY;   08/12/04
SC_RA:            3.81 [deg] (J2000)
SC_DEC:         -68.99 [deg] (J2000)
SUN_POSTN:      251.54d {+16h 46m 10s}  -22.35d {-22d 21' 11"}
SUN_DIST:        74.75 [deg]   Sun_angle= -6.6 [hr] (East of Sun)
MOON_POSTN:     331.34d {+22h 05m 22s}   -9.89d {-09d 53' 15"}
MOON_DIST:       52.16 [deg]
GAL_COORDS:     321.98,-53.36 [deg] galactic lon,lat of the burst
ECL_COORDS:     318.91,-49.57 [deg] ecliptic lon,lat of the burst
COMMENTS:       INTEGRAL GRB Coordinates.  
COMMENTS:       refined_coordinates_after_offline_analysis

GCN Circular #8614
D. Gotz (CEA-Saclay), S.Mereghetti, A.Paizis (IASF-Milano), R. Galis, V.Beckmann, M. Beck (ISDC, Versoix), and J. Borkowski (CAMK, Torun) on behalf of the IBAS Localization Team report:
A GRB lasting about 20 s has been detected by IBAS in IBIS/ISGRI data at 16:44:55 UT on December 4th. The refined coordinates (J2000) are:
```
RA = 349.7735 [degrees]
DEC= -60.2213 [degrees]
```
with an uncertainty of 2.3 arcmin (90% c.l.).
A preliminary analysis gives a peak flux in the 20-200 keV range of about 0.7 ph/cmq/s (1-s integration time) and a fluence over the same energy range of about 7x10e-7 erg/cmq.
A plot of the light curve will be posted at
http://ibas.iasf-milano.inaf.it/IBAS_Results.html
This message can be cited.
GCN Circular #8616
V. Mangano, B. Sbarufatti, V. La Parola (INAF-IASF PA) report on behalf the Swift XRT team:
We have analyzed the first orbit data (632 s exposure) of the Swift ToO observation of the INTEGRAL detected burst GRB 081204 (Gotz, GCN Circ. #8614). The Swift observation started on 2008 Dec 04 at 19:29 UT, about 2h 45m after the INTEGRAL trigger. We detected a single X-ray source within the INTEGRAL error box at RA, Dec =349.7873, -60.2253 which is equivalent to:
```
RA (J2000):  23 19 08.96
Dec (J2000): -60 13 31.3
```
with an uncertainty of 7 arcsec (radius, 90% confidence). The source lies 29 arcsec from the INTEGRAL position and has a count rate of ~2.0E-02 counts/s with a 2.6 sigma significance. At the moment it is not possible to determine whether it is fading, but the Swift observation is still on going and we are waiting for more data.
This is an official product of the Swift XRT team.
GCN Circular #8620
V. Mangano, B. Sbarufatti, V. La Parola (INAF IASF PA), and W. H. Baumgartner (GSFC/UMBC) report on behalf the Swift XRT team:
The Swift ToO observation of GRB 081204 started on 2008 Dec 4th at 19:32 UT consists of 3.6 ks XRT exposure in PC mode. We confirm the detection of the previously reported afterglow candidate (Mangano et al., GRC Circ. #8616) at the refined position RA, Dec =3D 349.7880, -60.2255 which is equivalent to:
```
RA (J2000):   23 19 09.13=20
Dec (J2000): -60 13 31.7
```
with an uncertainty of 5.3 arcsec (radius, 90% confidence). This is 30 arcsec from the INTEGRAL position (Gotz, GCN Circ. #8614). The source is fading with a power law decay index of about -2, and will reach a level of about 5.0e-4 counts/s in 24 hours from the trigger.
The average spectrum accumulated in the time interval from 10 ks to 37 ks after the event was fitted, using Cash statistics, with an absorbed power law. The best fit photon index is 2.7 =B1 1.5. The spectrum shows evidence of absorption at the level of (4.4 =B1 4.0)e21 cm-2, in excess of the estimated Galactic value (1.89e+20 cm-2, Kalberla et al. 2005).=20 The average observed[unabsorbed] 0.3-10 keV average flux is about 2.7[8.5]e-13 ergs cm-2 s-1. The count-rate-to-flux conversion factor is 1.5e-10.
All quoted errors are at 90% confidence level.
This circular is an official product of the Swift-XRT team.
GCN Circular #8621
P.A. Curran (UCL-MSSL) and W. Baumgartner (GSFC) report on behalf of the Swift/UVOT team:
The Swift Ultra-Violet/Optical Telescope (UVOT) began settled ToO observations of the INTEGRAL-IBAS localised GRB 081204 (Gotz et al., GCN 8614) ~ 3 hours after the event. The field was observed with the white filter only. No afterglow is detected within the 7" XRT position (Mangano et al., GCN 8616) in the co-added image, down to the following 3-sigma limiting magnitude:
```
Filter      T_start(s)    Exp(s)     Mag UL (3sig)
-----------------------------------
white      1.01e5        3.4e3      >  22.04
-----------------------------------
```
There is a DSS detected object approximately 11" south-west of the center of the XRT position with an observed white magnitide of ~20.5.
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 along the line of sight which corresponds to a reddening of E(B-V)=0.027 mag (Schlegel et al. 1998).
GCN Circular #8624
E. Berger and A. Rest (Harvard) report:
"We observed the position of GRB 081204 (GCN 8614) with the LDSS3 instrument on the Magellan/Clay telescope. A total of 30 sec were obtained in r- and i-band on 2008 Dec 5.067 UT (8.86 hour after the burst). Within the XRT error circle (GCN 8620) we detect a single faint source with r=23.5+/-0.3 mag and i=23.0+/-0.2 mag located at:
```
	RA  = 23:19:09.41
	DEC = -60:13:31.4  (J2000)
```
with an uncertainty of about 0.3" in each coordinate (astrometry relative to USNO-B). At the moment we have no information on whether the source is variable."
GCN Circular #8627
A. Updike (Clemson University), C. Clemens, and J. Greiner (both MPE Garching) report on behalf of the GROND team:
We observed the field of GRB 081204 (INTEGRAL trigger #5385; D. Gotz et al., GCN #8614) for two epochs simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2 m ESO/MPI telescope at La Silla Observatory (Chile).
Observations began at 00:30 UT on Dec 5, 2008, 7.75 hr after the GRB trigger, and consisted of 2.4 hours of exposures. The second epoch began at 00:31 UT on Dec 6, 31.75 hr after the trigger, and consisted of 1.3 hours of exposures. Observations were performed under favorable sky conditions.
We detect two sources within the refined 5.3'' Swift-XRT error circle reported by V. Mangano et al. (GCN #8620), at the astrometrically corrected positions:
```
RA (J2000.0) 23h 19m 09.10s
Dec (J2000.0) -60d 13' 29.7"
```
and
```
RA (J2000.0) 23h 19m 09.37s
Dec (J2000.0) -60d 13' 31.2"
```
The second candidate agrees with the position reported by Berger & Rest (GCN #8624).
We detect no evidence of fading in either source between the two epochs. Therefore, we suggest that neither of the sources are the afterglow of GRB 081204.
Our upper limits from the first epoch in g'r'i'z'JHK are as follows:
```
g' > 24.2
r' > 24.3
i' > 23.6
z' > 22.9
J  > 20.7
H  > 19.4
K  > 18.3
```
The given magnitudes are calibrated against GROND zeropoints as well as 2MASS field stars.

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Jochen Greiner, last update: 06-Dec-2008 [Disclaimer]