Gamma-ray Burst 061025

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:          GCN/INTEGRAL NOTICE
NOTICE_DATE:    Wed 25 Oct 06 18:36:42 UT
NOTICE_TYPE:    INTEGRAL Wakeup
TRIGGER_NUM:    3525,   Sub_Num: 0
GRB_RA:         300.9108d {+20h 03m 39s} (J2000),
                301.0345d {+20h 04m 08s} (current),
                300.0007d {+20h 00m 00s} (1950)
GRB_DEC:        -48.2433d {-48d 14' 35"} (J2000),
                -48.2238d {-48d 13' 25"} (current),
                -48.3844d {-48d 23' 03"} (1950)
GRB_ERROR:      2.68 [arcmin, radius, statistical only]
GRB_INTEN:      17.48 [sigma]
GRB_TIME:       66961.94 SOD {18:36:01.94} UT
GRB_DATE:       14033 TJD;   298 DOY;   06/10/25
SC_RA:          292.19 [deg] (J2000)
SC_DEC:         -42.52 [deg] (J2000)
SUN_POSTN:      210.02d {+14h 00m 06s}  -12.24d {-12d 14' 20"}
SUN_DIST:        81.57 [deg]   Sun_angle= -6.1 [hr] (East of Sun)
MOON_POSTN:     250.34d {+16h 41m 21s}  -27.32d {-27d 19' 29"}
MOON_DIST:       44.17 [deg]
GAL_COORDS:     350.95,-31.59 [deg] galactic lon,lat of the burst
ECL_COORDS:     292.62,-27.20 [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:    Wed 25 Oct 06 18:39:43 UT
NOTICE_TYPE:    INTEGRAL Refined
TRIGGER_NUM:    3525,   Sub_Num: 1
GRB_RA:         300.9168d {+20h 03m 40s} (J2000),
                301.0405d {+20h 04m 10s} (current),
                300.0068d {+20h 00m 02s} (1950)
GRB_DEC:        -48.2443d {-48d 14' 39"} (J2000),
                -48.2248d {-48d 13' 28"} (current),
                -48.3855d {-48d 23' 07"} (1950)
GRB_ERROR:      2.65 [arcmin, radius, statistical only]
GRB_INTEN:      19.02 [sigma]
GRB_TIME:       66971.03 SOD {18:36:11.03} UT
GRB_DATE:       14033 TJD;   298 DOY;   06/10/25
SC_RA:          292.19 [deg] (J2000)
SC_DEC:         -42.52 [deg] (J2000)
SUN_POSTN:      210.03d {+14h 00m 06s}  -12.24d {-12d 14' 22"}
SUN_DIST:        81.57 [deg]   Sun_angle= -6.1 [hr] (East of Sun)
MOON_POSTN:     250.37d {+16h 41m 28s}  -27.33d {-27d 19' 43"}
MOON_DIST:       44.15 [deg]
GAL_COORDS:     350.95,-31.59 [deg] galactic lon,lat of the burst
ECL_COORDS:     292.63,-27.20 [deg] ecliptic lon,lat of the burst
COMMENTS:       INTEGRAL GRB Coordinates.  
COMMENTS:       Possibly real GRB event

GCN NOTICE

TITLE:          GCN/INTEGRAL NOTICE
NOTICE_DATE:    Wed 25 Oct 06 19:36:27 UT
NOTICE_TYPE:    INTEGRAL Offline
TRIGGER_NUM:    3525,   Sub_Num: 2
GRB_RA:         300.9121d {+20h 03m 39s} (J2000),
                301.0358d {+20h 04m 09s} (current),
                300.0020d {+20h 00m 00s} (1950)
GRB_DEC:        -48.2440d {-48d 14' 38"} (J2000),
                -48.2245d {-48d 13' 27"} (current),
                -48.3852d {-48d 23' 06"} (1950)
GRB_ERROR:      2.00 [arcmin, radius, statistical only]
GRB_INTEN:      19.02 [sigma]
GRB_TIME:       66971.03 SOD {18:36:11.03} UT
GRB_DATE:       14033 TJD;   298 DOY;   06/10/25
SC_RA:          292.19 [deg] (J2000)
SC_DEC:         -42.52 [deg] (J2000)
SUN_POSTN:      210.06d {+14h 00m 15s}  -12.25d {-12d 15' 11"}
SUN_DIST:        81.53 [deg]   Sun_angle= -6.1 [hr] (East of Sun)
MOON_POSTN:     250.92d {+16h 43m 40s}  -27.40d {-27d 24' 15"}
MOON_DIST:       43.74 [deg]
GAL_COORDS:     350.95,-31.59 [deg] galactic lon,lat of the burst
ECL_COORDS:     292.62,-27.20 [deg] ecliptic lon,lat of the burst
COMMENTS:       INTEGRAL GRB Coordinates.  
COMMENTS:       UPDATED_POSITION_AFTER_OFFLINE_ANALYSIS

GCN Circular #5751
S.Mereghetti, A.Paizis (IASF-Milano), D.Gotz (CEA, Saclay), S.Shaw, M.Beck, I.Kreykenbohm (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 18:35:50 UT on October 25, 2006.
```
The coordinates (J2000)  are:
RA: 300.9121 [degrees], 
DEC: -48.2442 [degrees]
```
with an uncertainty of 2 arcmin (90% c.l.).
The peak flux in the 20-200 keV is 1.3 ph/cmq/s (1.5x10e-7 erg/cmq/s) over 1 s integration time and the fluence in the same energy range is 8x10e-7 erg/cmq
A plot of the light curve will be posted at
http://ibas.mi.iasf.cnr.it/IBAS_Results.html
This message can be cited.
GCN Circular #5752
E.S. Rykoff (U Mich), B. E. Schaefer (Louisiana State), R. Quimby (U Texas), H. Swan (U Mich), S.A. Yost (U Mich), report on behalf of the ROTSE collaboration:
ROTSE-IIIc, located at the H.E.S.S. site at Mt. Gamsberg, Namibia, responded to GRB 061025 (Integral trigger 3525, Mereghetti, et al, GCN 5751), producing images beginning 4.6 s after the GCN notice time. An automated response took the first image at 18:36:46.6 UT, 44.7 s after the burst, under excellent conditions. We took 10 5-sec, 10 20-sec and 31 60-sec eposures. These unfiltered images are calibrated relative to USNO A2.0 (R).
Comparison to the DSS (second epoch) reveals no new sources within the 90% INTEGRAL error circle, for both single images and coadding into sets of 10; however, we are limited as the field is somewhat crowded. We note that the bright elliptical galaxy NGC 6851 is in the error box. Individual images have limiting magnitudes ranging from 13.3-16.9; we set the following specific limits.
```
start UT       end UT      t_exp(s)   mlim   t_start-tGRB(s)  Coadd?
--------------------------------------------------------------------
18:36:46.6   18:36:51.6         5     15.2           44.7       N
18:36:46.6   18:39:01.9       135     16.9           44.7       Y
18:39:11.4   18:43:57.0       285     17.5          189.5       Y
```
GCN Circular #5753
T.Mineo (IASF-Pa), V.Mangano (IASF-Pa), G.Cusumano (IASF-Pa), and B.Sbarufatti (IASF-Pa) report on behalf of the Swift XRT team:
Swift/XRT began a target of opportunity observation of the INTEGRAL detected GRB 061025 (Mereghetti et al., GCN Circ. 5751) at 20:08 UT October 25 2006 (~2 hours after the burst). We have analyzed the first 3 orbits of XRT data (2000 s exposure) and we find a previously uncatalogued source at the following coordinates:
```
RA(J2000):    20h03m36.97
Dec(J2000):   -48:14:37.39
```
with an estimated uncertainty of 5.35 arcseconds radius (90% containment). Data have been processed with the new TELDEF files that include the new boresight information (Burrows et al. 2006 GCN. 5750). This position is 19.3 arcseconds from the INTEGRAL position given in GCN Circ. 5751. Further observations and analysis are in progress.
GCN Circular #5754
E. Berger (Carnegie) reports:
"We observed the error circle of the INTEGRAL burst GRB 061025 (GCN 5751) with GMOS on the Gemini-south telescope starting on 2006 Oct. 26.004 UT (5.5 hr after the burst). A total of 1470 s were obtained in i-band in good seeing conditions (0.6"). Within the XRT error circle (GCN 5753) we find a single point source with i=22.0 mag, located at (J2000):
```
 	RA = 20:03:37.1
 	DEC= -48:14:37.0
```
with an uncertainty of about 0.5" in each coordinate. At the present we do not have evidence for variability, but we consider this source to be an afterglow candidate."
GCN Circular #5755
P. D'Avanzo, S. Covino, E. Molinari, G. Chincarini, F.M. Zerbi, V. Testa, G. Tosti, F. Vitali, P. Conconi, L.A. Antonelli, G. Cutispoto, G. Malaspina, L. Nicastro, E. Palazzi, E. Meurs, and P. Goldoni report on behalf of the REM/ROSS team:
We imaged the field of GRB 061025 (Mereghetti et al. GCN 5751) with the robotic 60-cm REM telescope located at La Silla (Chile). A first set of observations was performed automatically in the optical and near infrared (V,R,I and z', J, H, K bands) starting on October 25 23:56 UT.
No obvious candidate is visible in our set of images in the XRT error box (Mineo et al. GCN 5753). In the NIR we report the following limiting magnitudes (3sigma level):
```
J > 16.0
H > 15.6
K > 14.6
```
In particular, no candidate is seen at the position reported by Berger (GCN 5754).
This message may be cited.
GCN Circular #5757
S. B. Pandey (UCL-MSSL) & M. Stamatikos (NASA-GSFC), on behalf of the Swift UVOT team.
The Swift/UVOT began observing the field of long duration GRB 061025 around ~1.5 hours after the INTEGRAL trigger at 18:35:50 UT on October 25 (Mereghetti et al., GCN 5751). We do not find any source in the co-added UVOT observations within the XRT position reported by Minoe et al. (GCN 5753).
Following are the 3-sigma magnitude upper limits from the observations.
```
Filter   T_start    T_stop   Exposure (s)    mag, 3 sigma UL
V         11282      39711      875           20.5
B         11112      38644      1082          21.4
U         9302       38427      1267          21.2
UVW1      8875       38210      2581          21.4
UVM2      11318      40316      2468          22.0
UVW2      11150      39494      3524          22.4
```
T_start and T_stop are calculated from the time of the burst. The upper limits are not corrected for Galactic extinction E(B-V) = 0.047 mag along the line of sight to the burst.
GCN Circular #5758
T. Mineo (IASF-Pa), V. Mangano (IASF-Pa), G. Cusumano (IASF-Pa), and B. Sbarufatti (IASF-Pa) report on behalf of the Swift XRT team:
We analysed the first 9 ks of Swift-XRT data obtained in PC mode for GRB061025 detected by INTEGRAL (Mereghetti et al. 2006, GCN 5751).
The light-curve shows a first shallow decay (alpha1=3D0.7+/-0.8) up to a break at t_break=3D20+/-4 ks, followed by a steeper decay (alpha2=3D3.4+/-1.2). If decaying at the present rate the source will reach a level of 1E-4 c/s at 24 hr since the trigger.
The average spectrum can be modelled with a power-law of photon index Gamma =3D 1.7 =B1 0.4, with an absorbing column consistent with the Galactic value of 5E20 cm-2. The average unabsorbed flux is (4.3 =B10.8)E-13 ergs cm-2 s-1, corresponding to a count rate of 5.3E-3 c/s. All errors are quoted at 90% confidence level.
This circular is an official product of the Swift-XRT team.
GCN Circular #5759
F. Yuan (U Mich), E.S. Rykoff (U Mich) report on behalf of the ROTSE collaboration:
Further analysis of the early ROTSE-IIIc images (Rykoff, et al, GCN 5752) reveals a faint, fading afterglow at the XRT position (Mineo, et al, GCN 5753) consistent with the position of the i-band candidate reported by Berger (GCN 5754). This source was not detected in the original analysis because of source confusion with a nearby star, and because the afterglow is near our detection threshold.
In our initial 5 s image beginning at 18:36:46.6 UT, 44.7 s after the burst, the afterglow is at 15.6+/-0.2 mag calibrated relative to USNO B1.0 (R). It decays with a power law index ~ -0.9 up to ~155 s after the burst when it is no longer detected.
```
start UT       end UT      t_exp(s)   mag      t_start-tGRB(s)  Coadd?
--------------------------------------------------------------------
18:36:46.6   18:36:51.6      5      15.6+/-0.2     44.7          N
```
GCN Report 10.1
GCN_Report 10.1 has been posted: http://gcn.gsfc.nasa.gov/reports/report_10_1.pdf by M.Stamatikos et al. titled: "Swift Observations of INTEGRAL GRB 061025"

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Jochen Greiner, last update: 27-Oct-2006 [Disclaimer]