GRB 081025
GCN Circular 8514
Subject
GRB 081025: Swift-XRT further analysis
Date
2008-11-10T17:05:33Z (18 years ago)
From
Jirong Mao at INAF-OAB <jirong.mao@brera.inaf.it>
J. Mao (INAF-OAB) on behalf of the Swift-XRT team reports:
Swift-XRT re-observed the Swift-BATSS GRB 081025 (Copete et al., GCN
8409) from 12.9 days after the burst with an exposure time of 6.9 ks.
We did not detect any source in the field. The 3-sigma upper limit is
1.7e-3 count/s. We compared this result with the previous observation
(Mao et al., GCN 8411). Thus we confirm that XRT observed the fading
afterglow of GRB 081025.
This circular is an official product of the Swift-XRT team.
GCN Circular 8483
Subject
GRB 081025: Fermi GBM observation
Date
2008-11-05T17:11:18Z (18 years ago)
From
Andreas von Kienlin at MPE <azk@mpe.mpg.de>
A. von Kienlin (MPE) and E. Bissaldi (MPE)
report on behalf of the Fermi GBM Team:
"At 08:23:05.29 UT on 25 October 2008, the Fermi GBM triggered and located
GRB 081025 (trigger 246615786 / 081025349) which was also detected by the
SWIFT-BAT Slew Survey (A. Copete et al. 2008, GCN 8409) and followed up by
SWIFT-XRT (J. Mao et al. 2008, GCN 8411). The GBM on-ground location is
consistent with the Swift position.
The GBM light curve shows a multipeaked structure with a duration (T90) of
about 45 s (8-1000 keV). The time-averaged spectrum from T0-1.536 s to
T0+24.064 s is best fit by an exponentially cutoff power law model with
Epeak = 251 +/- 25 keV, and index -0.35 +/- 0.13 (chi squared 736 for 700
d.o.f.). The event fluence (8-1000 keV) in this time interval is
(7.1 +/- 0.5)E-06 erg/cm^2. The 1-sec photon flux measured from T+2.56 sec
in the 8-1000 keV band is 4.50 +/- 0.22 ph/cm2/sec. A Band function fit
the spectrum equally well (chi squared 732 for 699 d.o.f.) with
Epeak= 200 +/- 33 keV, alpha = 0.15 +/- 0.22 and beta = -2.05 +/- 0.25.
The spectral analysis results presented above are preliminary; final results
will be published in the GBM GRB Catalog."
GCN Circular 8445
Subject
GRB 081025: Suzaku WAM observation of the prompt emission
Date
2008-10-29T09:53:27Z (18 years ago)
From
Yoshitaka Hanabata at Hiroshima U <hanabata@hep01.hepl.hiroshima-u.ac.jp>
C. Kira, Y. Hanabata, T. Uehara, T. Takahashi, Y. Fukazawa(Hiroshima U.),
T. Enoto, K. Nakazawa, K. Makishima (Univ. of Tokyo), S. Sugita,
K. Yamaoka (Aoyama Gakuin U.), M. Ohno, M. Kokubun, M. Suzuki,
T. Takahashi (ISAS/JAXA), Y.E. Nakagawa, T. Tamagawa (RIKEN),
M. Tashiro, Y. Terada, Y. Urata, A. Endo, K. Onda,
N. Kodaka, K. Morigami, T. Sugasahara, W. Iwakiri (Saitama U.),
E. Sonoda, M. Yamauchi, H. Tanaka, R. Hara, N. Ohmori, K. Kono, H.Hayashi,
(Univ. of Miyazaki),S. Hong (Nihon U.), on behalf of the Suzaku WAM team, report:
The long GRB 081025 (Copete et al., GCN 8409)
triggered the Suzaku Wide-band All-sky Monitor (WAM)
which covers an energy range of 50 keV - 5 MeV at 2008-10-25 08:23:07 UT (=T0).
The observed light curve shows a multi-peaked structure
starting at T0-0.5s, ending at T0+21.5s,
with a duration (T90) of about 22 seconds.
The fluence in 100 - 1000 keV was 3.8(-0.7, +0.5)*10^-06 erg/cm^2.
The 1-s peak flux measured from T0 was 1.5 +/- 0.2 photons/cm^2/s
in the same energy range.
Preliminary result shows that the time-averaged spectrum from T0-0.5s to
T0+21.5s is well fitted by a single power-law with a photon index
of 1.93 (-0.25, +0.29) (chi^2/d.o.f = 10/9).
All the quoted errors are at statistical 90% confidence level,
in which the systematic uncertainties are not included.
The light curves for this burst are available at:
http://www.astro.isas.jaxa.jp/suzaku/HXD-WAM/WAM-GRB/grb/trig/grb_table.html
GCN Circular 8420
Subject
GRB 081025: TLS upper limits
Date
2008-10-28T00:28:59Z (18 years ago)
From
Alexander Kann at TLS Tautenburg <kann@tls-tautenburg.de>
D. A. Kann, S. Schulze, C. Hoegner, S. Klose (TLS Tautenburg) and J.
Greiner (MPE Garching) report:
We observed the BAT Slew GRB 081025 (A. Copete et al., GCN 8409) with the
TLS Tautenburg 1.34m Schmidt telescope. Observations were initialized in
RRM mode (S. Klose et al., GCN 3609) as the BAT_SLEW_POSITION had been
received at dusk. After obtaining 2 x 120 sec Ic-band images, we realized
the large time delay and switched to deeper imaging. We further obtained 2
x 600 sec Ic-band images and one 600 sec Rc-band image.
At the position of the X-ray afterglow candidate (J. Mao et al., GCN
8411), we do not detect any source. We find the following upper limits in
comparison with the USNOB1.0 star at (catalog position, J2000) R.A. =
16:21:28.125, Dec. = +60:28:42.35, which has R2 = 18.61, I = 17.84:
dt exp Filter upper limit (2 sigma)
0.38672 2x120+2x600 Ic 21.5
0.40047 1x600 Rc 22.5
These limits are in agreement with the g-band limit of Khamitov et al.
(GCN 8418).
We point out the existence of the galaxy cluster NSC 2162144+602602 at
z=0.3903 (accoriding to SIMBAD) to the southeast of the afterglow
position. The nearest galaxy (about 100" distant) seems to be a massive
elliptical, possible a cD galaxy.
No further observations are planned.
This message may be cited.
GCN Circular 8418
Subject
GRB081025: RTT150 optical observations
Date
2008-10-27T09:09:48Z (18 years ago)
From
Rodion Burenin at IKI, Moscow <rodion@hea.iki.rssi.ru>
I. Khamitov (TUG), N. Aleksandrovich,
R. Burenin, M. Pavlinsky, R. Sunyaev (IKI),
I. Bikmaev, N. Sakhibullin (KSU/AST),
Z. Eker (TUG), U. Kiziloglu (METU), E. Gogus (Sabanci Uni.)
report:
We observed the field of the Swift-BATSS GRB 081025 (Copete et al., GCN8409)
with Russian-Turkish 1.5-m telescope (RTT150, Bakirlitepe, TUBITAK National
Observatory, Turkey), starting at 25 Oct, 19:51 UT, i.e. approximately 11.5 hours
after the burst, using Andor CCD.
We made 3x300s exposures in sdss-g filter, at high zenith distance (~70 degree)
and with bad seeing ~ 3". We do not detect any new source inside the XRT error circle
(Mao et al., GCN8411) as compared to DSS plates. Using photometric solution from
previous nights we estimated the limiting magnitude of combined image as m_g ~ 22.
GCN Circular 8415
Subject
GRB 081025 BAT refined analysis
Date
2008-10-26T19:12:08Z (18 years ago)
From
Jay R. Cummings at NASA/GSFC/Swift <jayc@milkyway.gsfc.nasa.gov>
J. R. Cummings (GSFC/UMBC), A. Copete (Harvard), J. Grindlay (Harvard),
S. D. Barthelmy (GSFC), N. Gehrels (GSFC), C. Guidorzi (INAF-OAB)
Using the data set from T+9 to T+129 sec (T0 is here defined as the
beginning of the Swift slew manuever), we report further analysis of
BATSS GRB 081025 (Copete, et al., GCN Circ. 8409).
Using the the previously reported position, the partial coding averaged
over the event was 70%. This is 2.1 arcmin from the XRT afterglow
candidate (Mao et al. GCN Circ. 8411).
The mask-weighted lightcurve features a main peak starting at T+63 sec
lasting 12 sec, followed in succession by 3 peaks, a 1.4 sec long peak
at T+77 sec, a 4.2 sec long peak at T+83sec, and a 2.2 sec long peak at
T+88sec. T90 (15-350 keV) is 23 +- 2 sec (estimated error including
systematics).
The time-averaged spectrum from T+63 to T+89 sec is best fit by a
simple power-law model. The power law index of the time-averaged
spectrum is 1.12 +- 0.05. The fluence in the 15-150 keV band is
(1.9 +- 0.2) x 10-06 erg/cm2. The 1-sec peak photon flux measured from
T+68 sec in the 15-150 keV band is 1.3 +- 0.2 ph/cm2/sec. All the
quoted errors are at the 90% confidence level.
The results of the analysis will be available (in a few days) at
http://gcn.gsfc.nasa.gov/notices_s/BATS0021/BA/
GCN Circular 8414
Subject
Swift UVOT observations of GRB081025
Date
2008-10-26T17:50:10Z (18 years ago)
From
Patricia Schady at MSSL/Swift <msslba@yahoo.co.uk>
P. Schady (MSSL/UCL) and J. Mao (INAF-OAB) report on behalf of the Swift UVOT team.
The Swift UltraViolet/Optical Telescope (UVOT) began ToO observations
of the Swift-BATSS GRB 081025 (Copete et al., GCN Circ. 8409), 20.7 hours
after the trigger. We do not detect any new source at the XRT position
reported in GCN Circ. 8411 (Mao et al.) in any of the individual or
co-added images down to the following 3-sigma upper limits:
Filter Tstart(hrs) Exp(s) 3-sigma UL
b 21.2 130 > 19.44
u 20.9 885 > 20.18
uvw1 20.7 1015 > 20.60
uvm2 22.2 886 > 20.63
The values quoted above are on 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)=0.02 mag
in the direction of the burst (Schlegel et al. 1998).
GCN Circular 8412
Subject
Konus-Wind observation of GRB 081025
Date
2008-10-26T15:33:49Z (18 years ago)
From
Valentin Pal'shin at Ioffe Inst <val@mail.ioffe.ru>
S. Golenetskii, R. Aptekar, E. Mazets, V. Pal'shin,
D. Frederiks, P. Oleynik, D. Svinkin, M. Ulanov
and T. Cline, on behalf of the Konus-Wind team report:
The long Swift-BATSS GRB 081025 (Copete et al., GCN 8409) triggered
Konus-Wind at T0=30186.316 s UT (08:23:06.316).
The burst light curve shows a multipeaked structure with a total
duration of ~25 s.
As observed by Konus-Wind the burst
had a fluence of 5.37(-0.82, +0.96)x10^-6 erg/cm2,
and a 256-ms peak flux measured from T0-0.224 s
of 8.90(-2.62, +2.75)x10^-7 erg/cm2/s
(both in the 20 keV - 1 MeV energy range).
The time-integrated spectrum of the burst
(from T0 to T0+24.832 s) is well fitted (in the 20 keV-1 MeV range)
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with alpha = -0.67(-0.33, +0.43) ,
and Ep = 222(-46, +81) keV (chi2 = 55.5/60 dof).
Fitting by GRBM (Band) model yields only an upper limit on
the high energy photon index: beta < -2.07.
All the quoted errors are at the 90% confidence level.
The Konus-Wind light curve of this GRB is available
at http://www.ioffe.ru/LEA/GRBs/GRB081025_T30186/
GCN Circular 8411
Subject
GRB 081025: Swift-XRT position
Date
2008-10-26T11:08:44Z (18 years ago)
From
Cristiano Guidorzi at INAF-OAB <cristiano.guidorzi@brera.inaf.it>
J. Mao, C. Guidorzi, R. Margutti (INAF-OAB) report on behalf of
the Swift-XRT team:
Swift began observing the field of the Swift-BATSS GRB 081025 (Copete et
al., GCN Circ. 8409) 74.5 ks after the trigger. In 2.9 ks of Photon
Counting mode data, we detect a single uncatalogued source within the
BAT error circle at a position of RA, Dec = 245.36626, 60.47428,
which is equivalent to
RA(J2000): 16 21 27.90
Dec(J2000): +60 28 27.4
with an uncertainty of 6.7 arcsec (radius, 90% containment). The source
lies 125 arcsec from the BAT centroid and has a count rate of
~3e-3 counts/s during this observation.
It is not possible to determine whether this source is fading given the
current statistics.
This circular is an official product of the Swift-XRT team.
GCN Circular 8409
Subject
GRB 081025: Burst detection from Swift-BAT slew data
Date
2008-10-26T01:18:16Z (18 years ago)
From
Antonio Copete at Harvard U <acopete@head.cfa.harvard.edu>
A. Copete, J. Grindlay (Harvard)
J. Cummings, S. Barthelmy, C. Markwardt, N. Gehrels (NASA/GSFC)
We report the detection of a GRB candidate by the BAT Slew Survey
(BATSS) in the slew that started at 08:22:02 UT. The ground-calculated
position is
RA, Dec = 245.298 +60.466 deg, which is
RA (J2000) = 16h 21m 11s
Dec(J2000) = +60d 27' 58"
with an uncertainty of 2.87 arcmin (90% confidence, including
systematic error). The detection was triggered by simultaneous
independent detections of 12.9 sigma and 13.7 sigma from imaging in
the 15-50 keV and 50-150 keV energy bands, respectively. The burst
profile shows a series of 4 main peaks starting at T+63sec, which a
measured T90 = 23sec and T50 = 17sec, and the burst leaves the BAT
field-of-view at T+120.
A follow-up Swift ToO observation has been scheduled to begin on
10/26/08 at 04:58 UT, 20.6 hours after the burst.