GRB 061121
GCN Circular 5878
Subject
GRB 061121, SMARTS optical/IR observations
Date
2006-11-29T20:27:41Z (19 years ago)
From
Bethany Cobb at Yale U <cobb@astro.yale.edu>
B. E. Cobb (Yale), part of the larger SMARTS consortium, reports:
Using the ANDICAM instrument on the 1.3m telescope at CTIO, we
obtained optical/IR imaging of the error region of GRB 061121
(GCN 5823, Page et al.) at several epochs. At a mid-exposure
time of 2006-11-22 07:34 UT (16.2 hours post-burst), the afterglow
is detected in a 36 minute I-band image with a magnitude of I=20.1+/-0.1.
No afterglow is detected in a 30 minute J-band image (with the same
mid-exposure time) to a limiting magnitude of J>19.0+/-0.1.
In two subsequent epochs (mid-exposure times: 64.7 and 87.8 hours
post-burst), 15 minute I and V exposures and 12 minute J and K exposures
were obtained. At the position of the optical afterglow, a possibly
extended source is detected in both V-band images. The source does not
appear to vary significantly between epochs and, therefore, may be the
host galaxy of GRB 061121 (also noted by Malesani et al., GCN 5877),
with a magnitude of V=22.4+/-0.2. This source is detected, with low
significance, in each I-band image. In a combined image of the 2
I-band epochs, the source has a magnitude of I=21.9+/-0.2. The source is
also detected just slightly above the background in a combined J-band
image, which has a 3 sigma limiting magnitude of J>19.3+/-0.1.
The source is not detected in the K-band, to a limiting magnitude
of K>17.8+/-0.1. All magnitudes are calibrated using 2MASS stars in IR
and Landolt standard stars in the optical.
GCN Circular 5877
Subject
GRB 061121: flattening of the decay
Date
2006-11-28T22:06:09Z (19 years ago)
From
Daniele Malesani at Niels Bohr Inst,Dark Cosmology Center <malesani@astro.ku.dk>
D. Malesani, J. Hjorth, D. Xu, M.D. Stritzinger, D. Watson, J.P.U.
Fynbo, (NBI-Dark), C. Henriksen, K. Holhjem, T. Pursimo, D. Sharapov, H.
Uthas (NOT), report:
We have observed the afterglow of GRB 061121 (Page et al., GCN 5823) at
several epochs with NOT + ALFOSC. Starting from 2006 Nov. 25 on, the
R-band light curve significantly flattened with respect to earlier
observations (e.g. Halpern et al., GCN 5847; Efimov et al., GCN 5870).
This is likely due to the presence of a relatively bright underlying
host galaxy. Some hints of extension are seen in our images taken during
the night of Nov 27, with a seeing of 0.9".
[GCN OPS NOTE(28nov06): Per author's request, a typo in the author name
Holhjem was corrected.]
GCN Circular 5874
Subject
GRB 061121: Second Epoch ATCA Radio Observations
Date
2006-11-28T00:26:09Z (19 years ago)
From
Alexander van der Horst at U of Amsterdam <avdhorst@science.uva.nl>
A.J. van der Horst, R.A.M.J. Wijers (University of Amsterdam) and E. Rol
(University of Leicester) report on behalf of a larger collaboration:
"We reobserved the position of the GRB 061121 afterglow at 4.8 and
8.6 GHz with the Australia Telescope Compact Array at November 27
14.11 UT to 20.88 UT, i.e. 5.95 - 6.23 days after the burst (GCN 5823).
We do not detect a radio source at the position of the optical afterglow
(GCN 5824). The three-sigma rms noise in het map around that position is
126 microJy per beam at 4.8 GHz, and 129 microJy per beam at 8.6 GHz.
The formal flux measurement for a point source at the location of the
optical afterglow is 7 +/- 42 microJy at 4.8 GHz, and -20 +/- 43 microJy
at 8.6 GHz.
We would like to thank the staff of the Australia Telescope National
Facility, in particular Philip Edwards, for obtaining these
Target of Opportunity observations."
GCN Circular 5871
Subject
GRB 061121: ATCA & WSRT Radio Observations
Date
2006-11-27T15:58:28Z (19 years ago)
From
Alexander van der Horst at U of Amsterdam <avdhorst@science.uva.nl>
A.J. van der Horst, R.A.M.J. Wijers (University of Amsterdam) and E. Rol
(University of Leicester) report on behalf of a larger collaboration:
"We observed the position of the GRB 061121 afterglow (GCN 5823) at
2.3 GHz with the Westerbork Synthesis Radio Telescope, and at 4.8 and
8.6 GHz with the Australia Telescope Compact Array.
We do not detect a radio counterpart of the optical afterglow (GCN 5824).
Our results are given in the table below. We note that the three-sigma
flux limit at 8.6 GHz at ~5.2 days after the burst is significantly
lower than the VLA detection at ~0.8 days after the burst (GCN 5843).
Epoch Delta T Frequency 3-sigma rms noise Formal flux
=============== ======== ========= ================= ==============
Nov 26.76-26.92 5.2 days 8.6 GHz 246 uJy/beam 10 +/- 82 uJy
Nov 26.76-26.92 5.2 days 4.8 GHz 210 uJy/beam 13 +/- 70 uJy
Nov 27.01-27.30 5.5 days 2.3 GHz 144 uJy/beam -50 +/- 48 uJy
We would like to thank the WSRT staff for obtaining these observations
in between VLBI observation runs. Also we would like to thank the staff
of the Australia Telescope National Facility, in particular Philip
Edwards, for obtaining these Target of Opportunity observations."
GCN Circular 5870
Subject
GRB061121: optical observations
Date
2006-11-27T11:33:09Z (19 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
Yu. Efimov, V. Rumyantsev (CrAO), A. Pozanenko (IKI) on behalf of larger GRB
follow up collaboration report:
We observed an afterglow GRB061121 (Page et al., GCN 5823; Yost et al., GCN
5824) with Shajn 2.6m telescope of CrAO on Nov. 24. A photometry of the
afterglow in a combined image is following:
Mid time Exposure, R_mag, Lim_mag (3 sigma)
(UT) s
Nov. 24.0823 41x120 21.96 +/- 0.07 23.6
The photometry is based on the same calibration as in our previous GCN
5850. A power-law decay index between Nov. 23.1040 observation (Efimov et
al., GCN 5850) and Nov. 24.0823 (this circular) is 1.06 and compatible with
the index reported in GCN 5847 (Halpern et al.) for early afterglow decay.
This message may be cited.
GCN Circular 5853
Subject
GRB 061121: MDM Continued Monitoring
Date
2006-11-25T19:45:51Z (19 years ago)
From
Jules Halpern at Columbia U. <jules@astro.columbia.edu>
J. P. Halpern & E. Armstrong (Columbia U.) report on behalf of
the MDM Observatory GRB follow-up team:
"Continuing observations of GRB 061121 for a fourth night
on the MDM 2.4m telescope yield the following results,
using the same calibration as in GCN 5847:
---------------------------------------------------------
Date(UT) Mid-time(UT) t-t0(hr) Exp(s) R(mag) +/-
---------------------------------------------------------
Nov. 25 11:42 92.33 900 22.69 0.06
Nov. 25 12:02 92.66 900 22.64 0.05
Nov. 25 12:20 92.96 900 22.75 0.08
---------------------------------------------------------
A power-law decay index of -0.979+/-0.015 is fitted to the
four nights.
Images and light curve are posted at
http://www.astro.columbia.edu/~jules/grb/061121/
This message may be cited."
GCN Circular 5851
Subject
GRB 061121: MDM Continuing Optical Decay
Date
2006-11-24T20:18:02Z (19 years ago)
From
Jules Halpern at Columbia U. <jules@astro.columbia.edu>
J. P. Halpern & E. Armstrong (Columbia U.) report on behalf of
the MDM Observatory GRB follow-up team:
"Continuing observations of GRB 061121 for a third night
on the MDM 2.4m telescope yield the following results,
using the same calibration as in GCN 5847:
---------------------------------------------------------
Date(UT) Mid-time(UT) t-t0(hr) Exp(s) R(mag) +/-
---------------------------------------------------------
Nov. 24 11:43 68.34 900 22.32 0.04
Nov. 24 12:04 68.69 1200 22.33 0.03
Nov. 24 12:35 69.21 1500 22.41 0.03
Nov. 24 12:55 69.54 600 22.36 0.08
---------------------------------------------------------
This indicates a slight flattening or deviation from the
previously fitted power-law decay.
Images and light curve are posted at
http://www.astro.columbia.edu/~jules/grb/061121/
This message may be cited."
GCN Circular 5850
Subject
GRB061121: optical observations
Date
2006-11-24T17:54:56Z (19 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
Yu. Efimov, V. Rumyantsev (CrAO), A. Pozanenko (IKI) on behalf of larger GRB
follow up collaboration report:
We observed error box of GRB061121 (Page et al., GCN 5823) with Shajn 2.6m
telescope of CrAO. A set of exposures was taken on Nov. 22 in B,R under
poor weather conditions and a set of 22x180 s R-exposures on Nov.23. The
afterglow (Page et al., GCN 5823; Yost et al., GCN 5824) is not detected in
a single images of 60 s exposure on Nov.22 and clearly visible on a single
images of 180 s on Nov. 23. For the analysis of Nov. 22 observation we take
the best single image while for Nov.23 observation we use two combined
images. Preliminary data reduction of the observations is following:
Mid time Exposure, R_mag, Lim_mag (3 sigma)
(UT) s
Nov. 22.1309 1x60 n/d 20.60
Nov. 23.1040 11x180 21.37 +/- 0.05 23.55
Nov. 23.1329 11x180 21.47 +/- 0.06 23.49
Above estimations are based on USNO A2.0 star RA=09 48 57.46 Dec=-13 13
20.10 R=17.30. The combine image of the last epoch can be found in
http://grb.rssi.ru/GRB061121/GRB061121_20061122_ZTSh_R
This message may be cited.
GCN Circular 5848
Subject
GRB 061121: Ep,i - Eiso correlation
Date
2006-11-24T00:40:19Z (19 years ago)
From
Lorenzo Amati at INAF-IASF/Bologna <amati@iasfbo.inaf.it>
L. Amati (INAF-IASF Bologna), F. Frontera (Univ.Ferrara and INAF-IASF Bologna),
C. Guidorzi (Univ.Bicocca/INAF and Osservatorio Astronomico di Brera), E.
Montanari (Univ.Ferrara) and M. Della Valle (INAF-Osservatorio Astrofisico di
Arcetri) report:
"Based on the redshift of 1.314 (GCN 5826) and the fluence and spectral
properties of the prompt emission as measured by Konus-Wind (GCN 5837) and
RHESSI (GCN 5838), we estimate for GRB 061121 a total isotropic released
energy, Eiso, of ~(3+/-0.3)x10^(53) erg (1-10000 keV cosmological
rest-frame, H0=65 km/s/Mpc, Omega_m=0.3, Omega_lambda=0.7) and an
intrinsic peak energy, Ep,i, of ~1200+/-400 keV. These values are
consistent with the best fit of the Ep,i-Eiso correlation within ~0.9 -
2.3 sigma (see, e.g., Figure 1 of Amati et al. 2006, astro-ph/0607148v4).
Given that the Konus-Wind and RHESSI spectra were measured during the
brighter and harder portion of the event (~20s), the inclusion in the
spectral analysis of the BAT and XRT data covering the whole prompt
emission (i.e. up to ~120 s from the Swift trigger, see GCN Report 15.1)
may provide a lower value of Ep,i and a slightly higher value of
Eiso, improving the match with the Ep,i-Eiso correlation."
This message may be cited.
GCN Circular 5847
Subject
GRB 061121: MDM Optical Decay
Date
2006-11-23T21:27:58Z (19 years ago)
From
Jules Halpern at Columbia U. <jules@astro.columbia.edu>
J. P. Halpern, N. Mirabal, & E. Armstrong (Columbia U.)
report on behalf of the MDM Observatory GRB follow-up team:
"We observed the afterglow GRB 061121 (Page et al., GCN 5823)
in the R band for a second night using the MDM 2.4m telescope.
The following magnitudes from fully reduced images supersede
and extend those reported by us in GCN 5840.
---------------------------------------------------------
Date(UT) Mid-time(UT) t-t0(hr) Exp(s) R(mag) +/-
---------------------------------------------------------
Nov. 22 11:57 20.57 300 21.10 0.03
Nov. 22 12:18 20.93 300 21.09 0.03
Nov. 22 12:26 21.06 300 21.10 0.03
Nov. 22 12:33 21.18 300 21.11 0.03
Nov. 22 12:41 21.32 300 21.15 0.03
Nov. 22 12:49 21.44 300 21.15 0.03
Nov. 23 11:46 44.39 300 22.08 0.08
Nov. 23 12:02 44.66 300 21.90 0.06
Nov. 23 12:08 44.76 300 21.92 0.06
Nov. 22 12:14 44.86 300 22.02 0.07
Nov. 23 12:20 44.96 300 21.98 0.07
Nov. 23 12:28 45.09 300 22.08 0.07
Nov. 23 12:36 45.23 300 21.99 0.07
Nov. 23 12:46 45.40 600 22.01 0.05
Nov. 23 12:57 45.58 600 22.13 0.07
---------------------------------------------------------
Magnitudes are referenced to a single USNO-B1.0 star at
(J2000) R.A.=09h48m54.77s, Decl.= -13d11'17.9" with R=18.02.
Quoted uncertainties are statistical only.
The power-law decay index from 21 to 45 hours is -1.08+/-0.03.
Images are posted at http://www.astro.columbia.edu/~jules/grb/061121/
This message may be cited."
GCN Circular 5845
Subject
GRB 061121: ART detection in Ic
Date
2006-11-23T05:22:27Z (19 years ago)
From
Ken ichi Torii at Osaka U <torii@ess.sci.osaka-u.ac.jp>
K. Torii (Osaka U.) reports on behalf of the ART collaboration:
The error region of the bright GRB 061121 (Page et al. GCN
5823) was observed with the 14 inch ART-3a in Toyonaka. The
imaging started at about 5 minutes after the trigger while
the useful frames were obtained after 17:15 UT (t=113
minutes) when the object rose to 20 degrees above the horizon.
The optical afterglow (GCN 5823) is detected at 3.2 sigma
in a stacked frame. Comparison with the USNO-B1.0 I2 mag
gave the following measurement.
-----------------------------------------
StartUT Filter Mag Exposure
=========================================
17:15:24 Ic 18.1 60s x 100
=========================================
GCN Circular 5844
Subject
GRB061121: P60 Observations
Date
2006-11-23T00:32:36Z (19 years ago)
From
S. Bradley Cenko at Caltech <cenko@srl.caltech.edu>
S. B. Cenko (Caltech) reports on behalf of a larger collaboration:
We have imaged the field of GRB 061121 (Page et al., GCN 5823) with the
automated Palomar 60-inch telescope. Observations consisted of 25 x 180 s
exposures in the Kron R and Sloan i' filters, taken at a mean epoch of
approximately 11:30 22 November UT (~ 20.1 hr after the burst).
The afterglow is clearly detected in our images, and we measure the
following magnitudes (calculated with reference to the USNO-B catalog):
R = 21.0 +/- 0.25
I = 20.3 +/- 0.21
The large errors are dominated by photometric uncertainty. We note the
R-band measurements are consistent with nearly-simultaneous observations
reported by Halpern et al. (GCN 5840).
Further observations are planned.
GCN Circular 5843
Subject
Radio detection of GRB 061121
Date
2006-11-23T00:21:55Z (19 years ago)
From
Poonam Chandra at U Virginia/NRAO <pc8s@virginia.edu>
P. Chandra (UVA/NRAO) and D. A. Frail (NRAO) report on behalf of
the Caltech-NRAO-Carnegie GRB Collaboration:
"We used the Very Large Array to observe the field of view toward
GRB061121 (GCN 5823) at a frequency of 8.46 GHz on 2006 November 22nd
starting at 9.18 UT. We detected the radio afterglow of GRB (flux density
of 304 +/- 48 uJy). Further observations are planned.
The National Radio Astronomy Observatory is a facility of the National
Science Foundation operated under cooperative agreement by Associated
Universities, Inc."
GCN Circular 5840
Subject
GRB 061121: MDM Optical Observations
Date
2006-11-22T20:06:25Z (19 years ago)
From
Jules Halpern at Columbia U. <jules@astro.columbia.edu>
J. P. Halpern, N. Mirabal, & E. Armstrong (Columbia U.)
report on behalf of the MDM Observatory GRB follow-up team:
"We began R-band observations of GRB 061121 (Page et al.,
GCN 5823) 20.57 hr after the burst using the MDM 2.4m.
Preliminary results from raw images are:
-----------------------------------------------------------
Date(UT) Mid-time(UT) t-t0(hr) Exp(s) R(mag)
-----------------------------------------------------------
Nov. 22 11:57 20.57 300 21.06 +/- 0.03
Nov. 22 12:49 21.44 300 21.13 +/- 0.04
-----------------------------------------------------------
These are referenced to the USNO B1.0 magnitude R=18.02 for
the star at (J2000) R.A.=09h48m54.77s, Decl.= -13d11'17.9".
Quoted errors are statistical only. Refined magnitudes and
additional results will be forthcoming.
This message may be cited."
GCN Circular 5839
Subject
GRB 061121 declared "Burst of Interest" by Swift team
Date
2006-11-22T19:41:15Z (19 years ago)
From
David Burrows at PSU/Swift <dxb15@psu.edu>
N. Gehrels (GSFC), K. Page (U. Leicester), S. Barthelmy (GSFC), D. N.
Burrows (PSU), F. Marshall (GSFC), P. Roming (PSU), T. Sakamoto
(GSFC), G. Sato (GSFC) report on behalf of the Swift team:
The Swift team declares GRB 061121 to be a "burst of interest". It
is bright in BAT, XRT and UVOT. It was observed by Konus-Wind,
RHESSI, XRT, UVOT and ground-based optical telescope observations
during the prompt phase, giving broad-band coverage of the
burst. The Epeak and redshift have been determined. The X-ray
afterglow has been observed by XMM. Swift will continue intensive
observations of the afterglow as long as it is detectable. We
encourage multiwavelength observations of the burst throughout its lightcurve.
Swift observations of GRB 061121 are discussed in GCN Report 15.1
(http://gcn.gsfc.nasa.gov/reports/report_15_1.pdf).
GCN Circular 5838
Subject
RHESSI Spectrum of GRB061121
Date
2006-11-22T18:31:57Z (19 years ago)
From
Kevin Hurley at UCBerkeley/SSL <khurley@ssl.berkeley.edu>
E. Bellm, M. Bandstra, S. Boggs, C. Wigger, W. Hajdas,
D. M. Smith, and K. Hurley on behalf of the RHESSI team report:
As observed by RHESSI, GRB061121 (Page et al., GCN 5823)
had a duration of ~19s starting at about T0=15:23:28 UT.
The preliminary fit to the time-integrated RHESSI spectrum
from T0 - T0+19s between 30 keV and 3 MeV is a Band function with
alpha = -0.83 +0.24/-0.19
beta = -2.00 +0.18/-0.32
E0 = 390. +250/-150. keV
Epeak = 455. +/-115. keV
(90% confidence levels).
The 30 keV-3 MeV fluence is 4.88 +/- 0.41 E-5 erg/cm^2.
GCN Circular 5837
Subject
Konus-Wind and Konus-A observations of GRB 061121
Date
2006-11-22T18:00:35Z (19 years ago)
From
Valentin Pal'shin at Ioffe Inst <val@mail.ioffe.ru>
S. Golenetskii, R.Aptekar, E. Mazets, V. Pal'shin, D. Frederiks, and
T. Cline on behalf of the Konus-Wind and Konus-A teams report:
The second, brightest pulse of the long GRB 061121 (Swift-BAT trigger
#239899: Page et al., GCN 5823; Fenimore et al., GCN 5831)
triggered Konus-Wind at T0=55412.445 s UT(15:23:32.445).
The first pulse which triggered Swift-BAT was detected
by Konus-Wind in the waiting mode.
The Konus-Wind spectrum integrated over the main episode of emission
(from T0 to T0+21.504 s) can be fitted (in the 20 keV - 5 MeV range)
by a power law with exponential cutoff model:
dN/dE ~ E^(-alpha) * exp(-(2-alpha)*E/Ep)
with alpha = 1.32(-0.05, +0.04)
and Ep = 606(-72, +90) keV (chi2 = 95/75 dof).
The fluence of this part is 5.67(-0.50, +0.30)x10^-5 erg/cm2
and the 64-ms peak flux measured from T0+12.960 s
1.28(-0.19, +0.16)x10^-5 erg/cm2/s
(both in the 20 keV - 5 MeV range).
The fluence of the precursor is estimated as ~10^-6 erg/cm2,
so the total burst fluence equals to the
fluence of the main episode in the limits of its uncertainty.
Assuming z = 1.314 (Bloom, Perley, and Chen, GCN 5826)
and a standard cosmology model with H_0 = 70 km/s/Mpc,
Omega_M = 0.3, Omega_\Lambda = 0.7,
the isotropic bolometric energy release is E_iso ~2.5x10^53 erg, and
the maximum bolometric luminosity is (L_iso)_max ~1.3x10^53 erg/s.
All the quoted errors are at the 90% confidence level.
The GRB 061121 also triggered Konus-A at T0=55350.15 s UT
(15:22:10.15) (so Konus-A triggered on the precursor).
The Konus-A instrument has been operating onboard Cosmos-2421 spacecraft
since June 25, 2006. The instrument consists of 3 NaI(Tl) detectors
200 mm in diameter and 50 mm in height with beryllium entrance windows.
It is designed to study temporal and spectral characteristics
of gamma-ray bursts in the wide energy range from 10 keV up to 10 MeV.
The Konus-Wind and Konus-A light curves of this GRB are available
at http://www.ioffe.rssi.ru/LEA/GRBs/GRB061121_T55412/
GCN Circular 5833
Subject
GRB 061121: Swift/UVOT Observations
Date
2006-11-22T02:49:53Z (19 years ago)
From
Frank Marshall at GSFC <marshall@milkyway.gsfc.nasa.gov>
GRB 061121: Swift/UVOT Observations
F. E. Marshall (NASA/GSFC), S. T. Holland (NASA/GSFC & USRA),
and K. L. Page (U Leicester) report on behalf of the Swift/UVOT team:
The Swift/UVOT began observing the field of GRB 061121 at
15:23:32 on 2006-11-21, 62 s after the BAT trigger (Page et al.,
GCN Cir. 5823). An optical counterpart was detected in the White
filter (160-650 nm) at a position (RA,Dec) = (09:48:54.55,
-13:11:42.4) (J2000) with a 90% confidence interval of 0.6 arcsec.
The afterglow was detected in each of the UVOT filters,
and was still easily detected in the most recent exposure with the
White filter 7026 seconds after the BAT trigger.
The early photometry results are given for the UVOT filters
below where Midpoint is the average time of the exposure, in seconds,
since the BAT trigger. The quoted errors do not include the 0.1 mag
systematic uncertainty in the photometric zero points.
Filter Midpoint Exposure Mag Err
V 368 393 17.06 0.05
B 650 10 17.7 0.2
U 631 10 17.2 0.2
UVW1 4981 197 19.6 0.2
UVM2 6208 197 19.8 0.3
UVW2 5800 197 20.4 0.3
White 112 98 16.23 0.03
7026 197 18.7 0.1
The values quoted above are not corrected for the expected Galactic
extinction of E_{B-V} = 0.04 mag (Schlegel et al. 1998).
GCN Circular 5832
Subject
GRB 061121: Swift-XRT Team Refined Analysis
Date
2006-11-21T21:38:02Z (19 years ago)
From
Kim Page at U.of Leicester <kpa@star.le.ac.uk>
K.L. Page, R.L.C. Starling, J.P. Osborne (U. Leicester), E. Troja (U.
Leicester/INAF-IASFPa) and D. Morris (PSU) report on behalf of the
Swift-XRT team:
We have analysed the first 2 orbits (up to 8ks after the trigger) of
Swift-XRT data obtained for GRB 061121 (Page et al., GCN Circ. 5823).
Using ~3.2ks of Photon Counting (PC) data, we derive a refined position
of
RA(J2000) = 09 48 54.54
Dec(J2000) = -13 11 42.4
with an estimated error radius of 3.5 arcsec (90% confidence, using the
updated teldef file as described by Burrows et al. in GCN Circ. 5750).
This is 4.0 and 0.7 arcsec from the original XRT and UVOT positions (GCN
Circ. 5823) respectively.
Because the BAT triggered on a pre-cursor, XRT was on target for the main
burst. The detected emission peaked at ~74s after the trigger, at a count
rate of ~2400 count s^-1 (corrected for pile-up). After 200s, the decay
follows a slope of alpha_1 = 0.36 +/- 0.07, until about 3ks after the
trigger, when the decay steepens to alpha_2 = 1.4 +/- 0.4.
The Windowed Timing mode data between 200 and 600s after the trigger
(i.e., when the data are clearly no longer piled-up) can be fitted with a
photon index of 2.25 +/- 0.12, with a total absorbing column of 2.3e21
cm^-2; comparison with the PC data from orbit 2 shows no further spectral
evolution. This absorption is significantly in excess of the Galactic
value of 5.1e20 cm^-2. Taking the redshift to be 1.314 from the Keck
measurement (GCN Circ. 5826; Bloom, Perley & Chen), the excess NH is
equivalent to a value of 9.6e21 cm^-2 in the rest-frame of the burst. The
observed (unabsorbed) flux for this spectrum is 2.51e-10 (3.81e-10) erg
cm^-2 s^-1.
If the decay continues with a slope of alpha = 1.4, the estimated count
rate at 24 hours is 0.031 count s^-1. This corresponds to an observed
(unabsorbed) flux of 1.19e-12 (1.80e-12) erg cm^-2 s^-1.
This circular is an official product of the Swift-XRT team.
GCN Circular 5831
Subject
GRB 061121, Swift-BAT refined analysis
Date
2006-11-21T21:37:11Z (19 years ago)
From
Takanori Sakamoto at NASA/GSFC <takanori@milkyway.gsfc.nasa.gov>
E. Fenimore (LANL), L. Barbier (GSFC), S. D. Barthelmy (GSFC),
J. Cummings (GSFC/UMBC), N. Gehrels (GSFC), D. Hullinger (BYU-Idaho),
H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), K. L. Page (U Leicester),
D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/ORAU),
G. Sato (GSFC/ISAS), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC)
on behalf of the Swift-BAT team:
Using the data set from T-240 to T+421 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 061121 (trigger #239899)
(Page, et al., GCN Circ. 5823). The BAT ground-calculated position
is RA,Dec = 147.228, -13.188 deg {9h 48m 54.8s, -13d 11' 16.6"} (J2000)
+- 0.9 arcmin, (radius, sys+stat, 90% containment). The partial coding
was 100%.
The mask-weighted lightcurve starts with small smooth pulse at ~T-5 sec
and returning to instrumental background level at T+20 sec. The the second
and much brighter started at ~T+50 sec with a series of overlapping peaks
the last of which was the brightest. Then there was roughly exponential decay
out to ~T+200 sec. T90 (15-350 keV) is 81 +- 5 sec (estimated error
including systematics).
The time-averaged spectrum from T-0.8 to T+121.8 is best fit by a simple
power-law model. The power law index of the time-averaged spectrum
is 1.41 +- 0.03. The fluence in the 15-150 keV band is
1.37 +- 0.02 x 10^-5 erg/cm2. The 1-sec peak photon flux measured
from T+74.48 sec in the 15-150 keV band is 21.1 +- 0.5 ph/cm2/sec.
The isotropic equivalent energy using the reported redshift of 1.314
(GCN Circ. 5826; Bloom, Perley & Chen) is 7e52 erg in
the 35 keV - 347 keV band at the GRB rest frame.
All the quoted errors are at the 90% confidence level.
GCN Circular 5830
Subject
GRB061121, optical observation
Date
2006-11-21T21:25:22Z (19 years ago)
From
Eri Sonoda at U of Miyazaki/Japan <sonoda@astro.miyazaki-u.ac.jp>
E. Sonoda, S. Maeno, T. Hara, T. Matsumura,
K. Tanaka, H. Tanaka, M. Yamauchi
(University of Miyazaki)
We have observed the field covering the error circle of
GRB061121 (GCN 5823) with the unfiltered CCD camera on
the 30-cm telescope at University of Miyazaki.
The observation was started 18:09:09 UT, 2.77 hour
after the Swift trigger time.
We have compared our data of 30 sec exposures
with the USNO-A2.0 catalog, there is no new source
at the position reported by K. L. Page et al.(GCN 5823)
The upper limits are as follows:
--------------------------------------------------------------
Start(UT) End(UT) Num. of frames Limit (mag.)
--------------------------------------------------------------
18:09:09 18:24:29 9 ~17
18:25:11 19:12:44 29 ~17.2
---------------------------------------------------------------
GCN Circular 5829
Subject
GRB 061121 : Planned XMM-Newton observation
Date
2006-11-21T19:50:23Z (19 years ago)
From
Norbert Schartel at XMM-Newton/ESA <too@xmm.vilspa.esa.es>
XMM-Newton will observe GRB 061121 at location
(RA=09h 48m 54.3s, DEC=-13d 11' 45.9", J2000),
starting at 21:25 UT, on Nov 21, 2006,
for an exposure of 39800 seconds.
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GCN Circular 5828
Subject
GRB 061121: Optical observation at the KANATA 1.5m telescope
Date
2006-11-21T17:42:48Z (19 years ago)
From
Makoto Uemura at Hiroshima U <uemuram@hiroshima-u.ac.jp>
M. Uemura, A. Arai, and T. Uehara (Hiroshima Univ.),
report on behalf of the KANATA GRB team:
We started optical imaging of the field of GRB061121 using
the TRISPEC attached to the KANATA 1.5-m telescope at Higashi-Hiroshima
Observatory, Japan. We detected the optical afterglow reported
in GCN 5823 and 5824 in our images taken with the exposure time of
123 s and the Rc filter. Using the comparison star USNOA2.0
0750-0732588 assuming Rc=14.2, our preliminary analysis yielded
the following photometric result:
UT Time after the burst (s) Rc mag
Nov. 21.71928 6797 18.539 +/- 0.074
We keep time-series observations.
GCN Circular 5827
Subject
GRB 061121: Faulkes Telescope North Optical Observation
Date
2006-11-21T16:38:21Z (19 years ago)
From
Andrea Melandri at Liverpool John Moores U <axm@astro.livjm.ac.uk>
A. Melandri (Liverpool JMU), C. Guidorzi (Univ Bicocca & INAF-OAB),
C.G. Mundell, I.A. Steele, R.J. Smith, A. Monfardini, D. Carter,
S. Kobayashi, D. Bersier, M. Bode (Liverpool JMU), A. Gomboc
(University of Ljubljana), P. O'Brien, E. Rol, N. Bannister (Leicester)
report:
The 2-m Faulkes North Telescope (Hawaii) automatically reacted to the
Swift burst GRB061121 (trigger=239899, Page et al. GCN 5823).
Observations started about 4.4 min after the trigger time. We confirm
the detection of the optical counterpart at the position
RA(J2000) = 09:48:54.58
Dec(J2000) = -13:11:42.8
0.6" uncertainty, coincident with the UVOT and ROTSE counterpart
(Yost et al. GCN 5824).
The automatic pipeline LT-TRAP identified a fading afterglow in BVRi'
filters, and we estimate an initial magnitude R = 16.7 +/- 0.3
(wrt USNOB) at t=4.4min.
The temporal decay index between 4 and 20 minutes after the burst
is alpha = 1.0 +/- 0.1.
Further observations and analysis are ongoing.
[GCN OPS NOTE(21nov06): Per author's reuqest, the error value on alpha
was changed from 1.0 +/- 1.0" to "1.0 +/- 0.1".]
GCN Circular 5826
Subject
GRB061121: Spectroscopic Redshift
Date
2006-11-21T16:26:12Z (19 years ago)
From
Daniel Perley at U.C. Berkeley <dperley@astro.berkeley.edu>
J. S. Bloom, D. A. Perley (UC Berkeley) and H.W. Chen (Chicago) report,
"Following the detection of the optical afterglow (GCN 5823, GCN 5824,
GCN 5825), we obtained approximately 8 spectroscopic exposures of
120-180 seconds each, beginning at ~15:36 UT with the Keck I 10m
telescope + LRIS.
The afterglow is strongly detected in all exposures. Based on a
preliminary wavelength solution, we identify in absorption a doublet and
singlet complex which we identify as redshifted Mg I 2853 Ang, Mg II
2796, 2804 Ang at z = 1.314. We suggest this is redshift of GRB 0611121.
Further analysis is ongoing."
This message may be cited.
GCN Circular 5825
Subject
GRB061121: Keck spectroscopic observations
Date
2006-11-21T15:47:09Z (19 years ago)
From
Daniel Perley at U.C. Berkeley <dperley@astro.berkeley.edu>
D. A. Perley and J. S. Bloom report,
On the night of 21 November 2006 (UT), we began spectroscopic
observations of GRB061121 at 15:35 UT using Keck I (+LRIS). The optical
afterglow is visible in the finder camera in early twilight and is
detected in 120-second spectroscopic exposures down to the atmospheric
cutoff. Strong absorption features are observed. Observations are
continuing.
GCN Circular 5824
Subject
GRB 061121: ROTSE-III Confirmation of Optical Counterpart
Date
2006-11-21T15:46:55Z (19 years ago)
From
Sarah Yost at U.Michigan <sayost@umich.edu>
S.A. Yost (U Mich), B. E. Schaefer (Louisiana State), F. Yuan (U Mich),
report on behalf of the ROTSE collaboration:
ROTSE-IIIa, located at Siding Spring Observatory, Australia, responded
to GRB 061121 (Swift trigger 239899). The first image was at 15:22:49.6
UT, 20.6 s after the burst (7.6 s after the GCN notice time). The
unfiltered images are calibrated relative to USNO A2.0. We detect a 14.9
magnitude, fading source with coordinates:
09:48:54.4 -13:11:42.2 (J2000), with positional
uncertainty of 1" or better.
This is coincident with the UVOT source (GCN 5823)
start UT mag mlim(of image)
----------------------------------
15:23:46.2 14.9 14.9
A jpeg image is available at
http://www.rotse.net/images/gsb239899_3a02_img.jpg Note that the object
marked 65 is the candidate in question.
Continuing observations are in progress.
GCN Circular 5823
Subject
GRB 061121: Swift detection of a bright burst with an optical counterpart
Date
2006-11-21T15:39:45Z (19 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
K. L. Page (U Leicester), S. D. Barthelmy (GSFC),
A. P. Beardmore (U Leicester), P. J. Brown (PSU),
D. N. Burrows (PSU), P. A. Evans (U Leicester),
N. Gehrels (NASA/GSFC), C. Guidorzi (Univ Bicocca&INAF-OAB),
J. A. Kennea (PSU), H. A. Krimm (GSFC/USRA),
W. L. Landsman (NASA/GSFC), V. Mangano (INAF-IASFPA),
F. E. Marshall (NASA/GSFC), J. P. Osborne (U Leicester),
C. Pagani (PSU), D. M. Palmer (LANL), M. Perri (ASDC),
P. Romano (Univ. Bicocca & INAF-OAB), T. Sakamoto (NASA/ORAU),
M. Stamatikos (NASA/ORAU), R. L. C. Starling (U Leicester),
E. Troja (INAF-IASFPA), D. E. Vanden Berk (PSU) and
H. Ziaeepour (UCL-MSSL) report on behalf of the Swift Team:
At 15:22:29 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 061121 (trigger=239899). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA,Dec 147.252, -13.183 {09h 49m 00s, -13d 10' 57"} (J2000)
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve shows an initial pulse of
~3000 cnts/sec lasting ~10 sec. Then a second much brighter peak starts
at ~T+50 sec, peaking at T+70 sec (at 32,000 cnts/sec), and ending at ~T+80 sec.
The XRT began observing the field at 15:23:24 UT, 55 seconds after the
BAT trigger. XRT found a very bright, fading, uncatalogued X-ray
source, located at
RA(J2000) = 09h 48m 54.5s,
Dec(J2000) = -13d 11' 46.4"
with an estimated uncertainty of 4.7 arcseconds (90%
confidence radius). This is a ground calculated position based on
prompt downlinked data. This location is 102 arcseconds from the BAT
on-board position, within the BAT error circle. The initial flux in
the 2.5s image was 1.8e-08 erg/cm2/s (0.2-10 keV). There is a large
flare peaking at about 70 s after the BAT trigger.
UVOT took a finding chart exposure of 526 seconds with the V filter starting
167 seconds after the BAT trigger. There is a candidate afterglow in the
rapidly available 2.7'x2.7' sub-image at
RA(J2000) = 09:48:54.58 = 147.2274
DEC(J2000) = -13:11:42.7 = -13.1952
with a 1-sigma error radius of about 0.5 arc sec. This position is 5.0 arc sec.
from the center of the XRT error circle. The estimated magnitude is 17.2 with a
1-sigma error of about 0.5 mag. No correction has been made for the expected
extinction of about 0.1 magnitudes.
We note that the BAT triggered on a precursor allowing the XRT
and UVOT to observe during the main emission of the burst.