GRB 081128
GCN Circular 8571
Subject
GRB 081128: Swift detection of a burst
Date
2008-11-28T17:31:30Z (17 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
R. Margutti (Univ Bicocca&OAB), S. D. Barthelmy (GSFC),
W. H. Baumgartner (GSFC/UMBC), P. J. Brown (PSU),
D. N. Burrows (PSU), S. Campana (INAF-OAB), M. Capalbi (ASDC),
P.A. Curran (MSSL-UCL), P. A. Evans (U Leicester),
C. Guidorzi (INAF-OAB), S. T. Holland (CRESST/USRA/GSFC),
J. A. Kennea (PSU), W.B Landsman (GSFC), V. Mangano (INAF-IASFPA),
J. Mao (INAF-OAB), C. B. Markwardt (CRESST/GSFC/UMD),
F. E. Marshall (NASA/GSFC), K. L. Page (U Leicester),
T. Sakamoto (NASA/UMBC), M. Stamatikos (NASA/ORAU),
R. L. C. Starling (U Leicester) and T. N. Ukwatta (GSFC/GWU) report
on behalf of the Swift Team:
At 17:18:44 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 081128 (trigger=335895). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 20.798, +38.115, which is
RA(J2000) = 01h 23m 12s
Dec(J2000) = +38d 06' 54"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The TDRSS lightcurve for this image trigger
does shows a possible peak (or possibly background variation
during the slew).
The XRT began observing the field at 17:22:02.2 UT, 197.5 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
uncatalogued X-ray source located at RA, Dec 20.80537, 38.12728 which
is equivalent to:
RA(J2000) = 01h 23m 13.29s
Dec(J2000) = +38d 07' 38.2"
with an uncertainty of 4.0 arcseconds (radius, 90% containment). This
location is 48 arcseconds from the BAT onboard position, within the BAT
error circle. This position may be improved as more data are received;
the latest position is available at http://www.swift.ac.uk/sper.
A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density consistent with the Galactic value of
6.09e+20 cm^-2 (Kalberla et al. 2005).
The initial flux in the 2.5 s image was 8.04e-10 erg cm^-2 s^-1 (0.2-10
keV).
UVOT took a finding chart exposure of 150 seconds with the White filter
starting 206 seconds after the BAT trigger. No credible afterglow candidate has
been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of
the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag.
No correction has been made for the expected extinction corresponding to
E(B-V) of 0.05.
Burst Advocate for this burst is R. Margutti (raffaella.margutti AT brera.inaf.it).
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 Circular 8572
Subject
GRB 081128: Optical observation of xinglong TNT
Date
2008-11-28T19:34:24Z (17 years ago)
From
L.P. Xin at NAOC <xlp@bao.ac.cn>
J.Wang, L.P. Xin, Y.L. Qiu, J.Y. Wei, J.Y. Hu, J.S. Deng,
W.K. Zheng on behalf of EAFON report:
We began to observe GRB081128 (Margutti et al., GCN 8571)
with Xinglong TNT telescope at 17:25:16(UT),6min32s
after the burst.A series of white, R band have been obtained.
After combined 10*20s white band data (without bias,flat-field
correction) and made a preliminary analysis,
a marginal object within the
errorbar of XRT was detected with an estimated
brightness of R ~ 20.9+/- 0.44 calibrated to USNO-B1.0,
at the mean time of 500s after the burst.
We are not sure whether it is the OT or not, because of
lack of flat images at the moment.
We will reduce it tomorrow and give a more precise
result and analysis.
This message may be cited.
For more information about Xinglong GRBs Follow-up
observations, please visit the website:
http://www.xinglong-naoc.org/grb/
GCN Circular 8573
Subject
GRB 081128: Enhanced Swift-XRT position
Date
2008-11-28T20:31:18Z (17 years ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester)
report on behalf of the Swift-XRT team.
Using 2095 s of XRT Photon Counting mode data and 2 UVOT
images for GRB 081128, 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 = 20.8041, +38.1271 which is equivalent
to:
RA (J2000): 01h 23m 12.98s
Dec (J2000): +38d 07' 37.5"
with an uncertainty of 1.8 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 8574
Subject
GRB 081128: Swift-BAT refined analysis
Date
2008-11-28T20:59:47Z (17 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
J. Tueller (GSFC), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),
J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC),
H. A. Krimm (GSFC/USRA), R. Margutti (U Bicocca&OAB), C. B. Markwardt (GSFC/UMD),
D. M. Palmer (LANL), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS),
M. Stamatikos (GSFC/ORAU), T. N. Ukwatta (GWU)
(i.e. the Swift-BAT team):
Using the data set from T-239 to T+303 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 081128 (trigger #335895)
(Margutti, et al., GCN Circ. 8571). The BAT ground-calculated position is
RA, Dec = 20.800, 38.123 deg, which is
RA(J2000) = 01h 23m 12.0s
Dec(J2000) = +38d 07' 23.8"
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 74%.
The mask-weighted light curve shows two overlapping peaks. The first start
probably before the object comes into the BAT FOV at T-95 sec and peaks at
~T=18 sec. The second peak peaks around T=35 sec and ends at ~T+90 sec.
T90 (15-350 keV) is 100 +- 11 sec (estimated error including systematics).
The time-averaged spectrum from T-69.0 to T+62.7 sec is best fit by a power law
with an exponential cutoff. This fit gives a photon index 1.08 +- 0.45,
and Epeak of 45.1 +- 4.7 keV (chi squared 34.6 for 56 d.o.f.). For this
model the total fluence in the 15-150 keV band is 2.3 +- 0.2 x 10^-6 erg/cm2
and the 1-sec peak flux measured from T+17.60 sec in the 15-150 keV band is
1.3 +- 0.2 ph/cm2/sec. A fit to a simple power law gives a photon index
of 1.98 +- 0.09 (chi squared 48.9 for 57 d.o.f.). 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/335895/BA/
GCN Circular 8575
Subject
GRB081128 : Lulin optical follow-ups
Date
2008-11-29T02:33:48Z (17 years ago)
From
Yuji Urata at Saitama U <urata@asiaa.sinica.edu.tw>
C.S Lin (NCU), Y. Urata (Saitama U/ASIAA) and K.Y Huang (ASIAA)
on behalf of EAFON report:
"We observed the error region of GRB081128 (Margutti et al. GCN8571)
using the Lulin 1m telescope from 10.9 min after the burst. The R-band
images show possible optical afterglow as reported by Wang et al (GCN
8572) at RA=01:23:13.070 Dec=+38:07:38.77 with R=20.4 magnitude.
However, the source shows no variability during our observations (10.9
-- 33.3 min after the burst).
Time (min) Rmag, error
10.9 20.4 0.1
33.3 20.4 0.1
There is no other optical sources in the XRT error region
down to the R~21.4."
GCN Circular 8576
Subject
GRB081128: optical observations
Date
2008-11-29T05:28:34Z (17 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
M. Andreev, A. Sergeev, (Terskol Branch of Institute of Astronomy), A.
Pozanenko (IKI) on behalf of larger GRB follow up collaboration report:
We observed the field of GRB 081128 detected by SWIFT (Margutti et al,
GCN 8571) with the Z-600 telescope of Mt. Terskol observatory. A set of
90 s unfiltered exposures was taken starting (UT) Nov. 28 17:37. In a
combined image of first exposures (3x90 s) we do not detect any new
object in the enhanced XRT (Evans, et al, GCN 8573) up to 18.5m. In a
combined image 18x90 s at mid time (UT) Nov. 28 18:08 we detect a faint
object at coordinates (J2000) RA, Dec = 01 23 13.02 +38 07 38.1 with
brightness of ~20.3m. A photometry and astrometry is preliminary and based
on USNO-A2.0 and R mag of USNO-A2.0. Our photometry at ~ 50 min after
burst is consistent with the photometry reported early (Wang et al, GCN
8572, Lin et al, GCN 8575) suggesting non fading source within XRT error
box.
GCN Circular 8577
Subject
GRB 081128: Liverpool Telescope afterglow confirmation
Date
2008-11-29T11:21:44Z (17 years ago)
From
Cristiano Guidorzi at INAF-OAB <cristiano.guidorzi@brera.inaf.it>
C. Guidorzi (INAF-OAB), N. Tanvir (U. Leicester), I.A. Steele, R.J. Smith,
C.G. Mundell, D. Bersier (Liverpool JMU), A. Gomboc (U. Ljubljana)
report on behalf of a larger collaboration:
On 2008 November 28 (22:16:14 UT) we began observing the field of GRB 081128
(Margutti et al. GCN Circ. 8571) with the Liverpool Telescope.
Observations consisted of two sequences of 6x300s exposures acquired
using the SDSS-i and SDSS-r filters, respectively.
In our coadded frame we detect a single source inside the refined XRT
error box (Evans et al. GCN Circ. 8573) at the position
RA(J2000)=01:23:13.05, Dec(J2000)=+38:07:38.7 (0.6" error radius)
consistent with the optical candidate reported by Lin et al. (GCN Circ.
8575) and Andreev et al. (GCN Circ. 8576).
We found the following magnitude for this object:
Telescope Filter T_mid[hr] Exposure[s] M_lim
-----------------------------------------------------------
LT SDSS-r 6.66 6x300 21.9 +/- 0.2
-----------------------------------------------------------
The calibration was performed using the R2 magnitudes of several USNOB-1
catalogue field objects. Compared with the value reported by Lin et al.
(GCN Circ. 8575), our measurement shows that the candidate has faded
between the two epochs.
There also appears to be a neighbouring source just outside the XRT
error circle, which might be a host galaxy.
GCN Circular 8578
Subject
GRB 081128: Swift-XRT refined analysis
Date
2008-11-29T12:13:25Z (17 years ago)
From
Raffaella Margutti at U. di Milano Bicocca <raffaella.margutti@brera.inaf.it>
R. Margutti (Univ. Bicocca & INAF-OAB), J.Mao (INAF-OAB) and C. Guidorzi
(INAF-OAB)
report on behalf of the Swift XRT team:
We have analysed the first 4 orbits of Swift-XRT data obtained for
GRB 081128 (Margutti et al., GCN Circ.8571), covering 100 s of
Windowed Timing (WT) and 6 ks of Photon Counting (PC) mode data,
respectively, between 195 s and 35 ks after the trigger.
The UVOT-enhanced XRT position was given by Evans et al. in GCN Circ.8573.
The light-curve can be modelled by a broken power-law, with a steep
decay of alpha_1=4.1 � 0.2 and a break time of about 1000 s.
The decay then flattens to alpha_2=0.4 � 0.1
The spectrum extracted from WT data can be poorly modelled with an
absorbed simple power-law, with Gamma =3.7 � 0.4 and
NH = (2.7 � 0.1)x1021 cm-2 (P-value=5x10-5).
The fit is statistically improved adding a black body component of
temperature T=0.15 � 0.03 keV. In this case we obtain Gamma= 1.8 � 0.6 and
NH = (1.2 � 0.1)x1021 cm-2 (P-value=0.4).
This result makes GRB 081128 similar to the sample considered by
Moretti et al.,2008 A&A 478,409.
The spectrum extracted from PC data in the time interval 0.3-35 ks
can be modelled with an absorbed power-law, with Gamma = 1.7 � 0.2
and a column density of NH = (0.5 � 0.4)x1021 cm-2,which is
compatible with the Galactic value in this direction (0.6x1021 cm-2).
The observed (unabsorbed) 0.3 -10 keV flux over this time
interval is 3.0x10-12 (3.3x10-12) erg cm-2 s-1.
Uncertainties are given at 90% confidence.
If the light-curve continues to decay with alpha ~0.4, the count rate 24
hours after the burst is estimated to be 9.2x10-3 count s-1, which
corresponds to an observed flux of 4x10-13 erg cm-2 s-1.
The results of the xrt automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00335895.
This is an official product of the Swift-XRT team.
GCN Circular 8581
Subject
GRB081128: Swift/UVOT Upper Limits
Date
2008-11-29T21:22:41Z (17 years ago)
From
Peter Brown at PSU <pbrown@astro.psu.edu>
P. J. Brown (PSU) and R. Margutti (Univ. Biococca & OAB)
report on behalf of the Swift UVOT team:
The Swift/UVOT observed the field of GRB 081128 starting 206 s
after the BAT trigger (Margutti et al., GCN Circ. 8571).
We do not detect any source inside the UVOT-enhanced XRT
error circle (Evans, et al., GCN Circ. 8573)
down to the following 3-sigma upper limits in the
finding chart and co-added images:
Filter T_start T_stop Exp(s) Mag
------------------------------------------
white 207 356 150 >20.9
white 207 959 308 >21.3
v 363 5643 247 >19.4
b 462 826 58 >19.6
u 437 801 58 >19.3
uvw1 413 777 58 >19.0
uvm2 388 752 58 >18.6
uvw2 512 4429 236 >19.9
white 10015 34512 625 >21.4
v 27370 75499 3535 >21.0
-----------------------------------------
The quoted upper limits have not been corrected for the expected
Galactic extinction along the line of sight corresponding to a
reddening of E(B-V) = 0.05 mag (Schlegel, et al., 1998, ApJS, 500,
525). All photometry is on the UVOT photometry system described in
Poole et al. (2008, MNRAS, 383, 627).
GCN Circular 8594
Subject
GRB 081128: optical observation
Date
2008-12-03T12:34:20Z (17 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
S. Sergeev (CrAO), V. Rumyantsev (CrAO), A. Pozanenko (IKI) on behalf of
larger GRB follow up collaboration report:
We observed the error box of Swift GRB 081128 (Margutti et al, GCN 8571)
in I band on Nov. 28 between (UT) 20:20:28 - 20:31:16 with AZT-8 telescope
of CrAO. Inside the refined XRT error box (Evans et al. GCN 8573) we do
not detect the source reported as possible afterglow (Wang et al, GCN
8572; Lin et al, GCN 8575; Andreev et al, GCN 8576; Guidorzi et al, GCN
8577). The photometry of the combined image is following:
T0+ Filter, Exposure, mag.
(h) (s)
3.23 I 5x120 >20.0 (3 sigma)
GCN Circular 8628
Subject
GRB 081128: Optical afterglow observations
Date
2008-12-06T12:11:55Z (17 years ago)
From
Shashi Bhushan Pandey at ARIES, INDIA <shashi@aries.ernet.in>
Brajesh Kumar, S. B. Pandey and Rupak Roy (ARIES, NainiTal, India, on
behalf of larger Indian GRB collaboration)
GRB 081128, localized by Swift (Margutti et al. GCN 8571), was observed
with 1.04m telescope at NainiTal starting ~ 2.5 hours after the burst
in R_c filter.
Photometry of the co-added R_c frames (300 sec x 5) does not detect the
optical afterglow candidate (Wang et al. GCN 8572) down to a limiting
magnitude of ~ 20 mag in comparison to nearby USNO stars.
This message may be cited.
GCN Circular 8630
Subject
GRB 081128: optical observation in CrAO
Date
2008-12-06T15:33:01Z (17 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
V. Rumyantsev, D. Shakhovkoy, S. Sergeev (CrAO), M.Andreev (Terskol Branch
of Institute of Astronomy), A. Pozanenko (IKI) on behalf of larger GRB
follow up collaboration report:
We observed the error box of Swift GRB 081128 (Margutti et al, GCN 8571) in
R band on Nov. 28 between (UT) 17:53:23 - 19:05:55 with AZT-11 telescope of
CrAO. Inside the refined XRT error box (Evans et al. GCN 8573) we detect the
source reported as possible afterglow (Wang et al, GCN 8572; Lin et al, GCN
8575; Andreev et al, GCN 8576; Guidorzi et al, GCN 8577). The coordinates
of the source are RA(J2000): 01 23 13.03 Dec(J2000): +38 07 37.7 with
uncertainty of 0.5". A photometry based on USNO-B1.0 star 1281-0027628
(01:23:11.75 +38:07:43.6) R2=17.91 is following:
T0+ Filter, Exp., mag. UL
(h) (s) (3 sigma)
1.207 R 23x180 21.5 +/-0.2 22.4
Taking above photometry and photometry reported earlier (Lin et al, GCN
8575; Andreev et al, GCN 8576; Guidorzi et al, GCN 8577) we confirm the
fading nature of the source. We also detected the source (Guidorzi et al,
GCN 8577) which is ~4" South of OT.
A combined image can be found at
http://grb.rssi.ru/GRB081128/GRB081128_AZT11_R_18_31_09.gif
GCN Circular 8639
Subject
GRB 081128: afterglow observations
Date
2008-12-08T08:35:39Z (16 years ago)
From
Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst <malesani@astro.ku.dk>
D. Malesani, J.P.U. Fynbo, G. Leloudas (DARK/NBI), H. Pedersen (NBI), P.
Jakobsson (Univ. Iceland), S.-M. Niemi, H. Uthas, and C. Villforth
(NOT), report on behalf of a larger collaboration:
We observed the field of GRB 081128 (Margutti et al., GCN 8571) with the
Nordic Optical Telescope equipped with ALFOSC. Observations were carried
out on two epochs, first on 2008 Nov 28.962 (0.24 days after the GRB) in
the V, R and i bands and then on Dec 7.827 (9.10 days after the GRB) in
the R band. In the first epoch we detect the afterglow candidate
reported by Wang et al. (GCN 8572) in all filters. We estimate R=22.3 +-
0.1 assuming R=17.91 for the USNO star at RA = 01:23:11.73, Dec =
+38:07:43.58 (consistent with the calibration of Guidorzi et al., GCN
8577; C. Guidorzi, priv. comm.). In the second epoch, the afterglow
candidate remains undetected to a limit R > 23.5, and we hence confirm
that this source is the GRB afterglow. We note that the V-band detection
sets a limit on the GRB redshift, z <~ 5.
We also detect in both epochs a second object at the border of the XRT
error circle (RA = 01:23:12.98, Dec = +38:07:38.4), which is likely the
one reported by Guidorzi et al. (GCN 8577), with a magnitude R = 22.7.
The angular separation from the afterglow is 1.2".