GRB 061025
GCN Circular 5759
Subject
GRB061025: ROTSE-III Confirmation of Optical Counterpart
Date
2006-10-26T19:56:13Z (20 years ago)
From
Fang Yuan at ROTSE <yuanfang@umich.edu>
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 Circular 5758
Subject
GRB061025: Swift XRT refined analysis
Date
2006-10-26T15:07:08Z (20 years ago)
From
Vanessa Mangano at INAF-IASFPA <vanessa@ifc.inaf.it>
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=0.7+/-0.8) up
to a break at t_break=20+/-4 ks, followed by a steeper decay
(alpha2=3.4+/-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 = 1.7 � 0.4, with an absorbing column consistent with
the Galactic value of 5E20 cm-2. The average unabsorbed flux is
(4.3 �0.8)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 5757
Subject
GRB061025: Swift/UVOT observations
Date
2006-10-26T14:09:09Z (20 years ago)
From
Shashi Pandey at MSSL <sbp2@mssl.ucl.ac.uk>
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 Mineo 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 OPS NOTE(26oct06): Per author's request, the typo 'Minoe' was changed
to 'Mineo'.]
GCN Circular 5755
Subject
GRB 061025: REM observations
Date
2006-10-26T08:44:24Z (20 years ago)
From
Paolo D'Avanzo at INAF-OAB <davanzo@merate.mi.astro.it>
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 5754
Subject
GRB 061025: Gemini-S observations
Date
2006-10-26T06:14:48Z (20 years ago)
From
Edo Berger at Carnegie Obs <eberger@ociw.edu>
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 5753
Subject
GRB061025: Swift XRT position
Date
2006-10-26T05:31:40Z (20 years ago)
From
Vanessa Mangano at INAF-IASFPA <vanessa@ifc.inaf.it>
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 5752
Subject
GRB 061025: ROTSE-III Optical Limits
Date
2006-10-25T19:55:31Z (20 years ago)
From
Eli Rykoff at U of Michigan/ROTSE <erykoff@umich.edu>
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 5751
Subject
GRB 061025: a long GRB detected by INTEGRAL
Date
2006-10-25T19:48:15Z (20 years ago)
From
Sandro Mereghetti at IASF/CNR <sandro@iasf-milano.inaf.it>
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.