GRB 061201
GCN Circular 5880
Subject
GRB 061201: Coincidence with a Galaxy Cluster
Date
2006-12-01T16:23:13Z (19 years ago)
From
Josh Bloom at UC Berkeley <jbloom@astron.berkeley.edu>
J. S. Bloom (UC Berkeley) notes:
"We note that this apparent short burst GRB (Swift trigger 241840)
was localized to within 10 arcmin of a known cluster of galaxies
(J2000 center = 22h09m34s, -74d27.3m, Abell 995; Abell et al. ApJS,
1989). Though no redshift is known for this galaxy cluster and the
GRB has not (as of yet) been associated with a member of this
cluster, we suggest, tentatively, that GRB 061201 has arisen from
what is likely a relatively low redshift (z < 0.3). The XRT position
appears consistent with the outskirts of a faint galaxy detected in
the DSS."
This message may be cited.
GCN Circular 5881
Subject
GRB 061201: Swift detection of a short hard burst
Date
2006-12-01T16:24:30Z (19 years ago)
From
David Palmer at LANL <palmer@lanl.gov>
F. E. Marshall (NASA/GSFC), S. D. Barthelmy (GSFC),
A. P. Beardmore (U Leicester), O. Godet (U Leicester),
S. T. Holland (GSFC/USRA), J. A. Kennea (PSU),
H. A. Krimm (GSFC/USRA), W. B. Landsman (NASA/GSFC),
V. Mangano (INAF-IASFPA), C. B. Markwardt (GSFC/UMD),
K. M. McLean (LANL/UTD), A. Moretti (INAF-OAB), D. M. Palmer (LANL),
S. B. Pandey (UCL-MSSL), A. M. Parsons (GSFC),
T. Sakamoto (NASA/ORAU), R. L. C. Starling (U Leicester) and
D. E. Vanden Berk (PSU) report on behalf of the Swift Team:
At 15:58:36 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 061201 (trigger=241840). Swift slewed immediately to the
burst. The BAT on-board calculated location is RA, Dec 331.972,
-74.600 which is
RA(J2000) = 22h 07m 53s
Dec(J2000) = -74d 36' 01"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve showed a single peak
with some sub-structure and total duration of about 2 sec. The peak
count rate was ~20000 counts/sec (15-350 keV), at ~1 sec after the
trigger. This is also a very hard burst with ~8000 counts/sec in the
highest energy bin (100-350 keV) and ~1000 counts/sec in the lowest
energy bin (15-25 keV).
The XRT began taking data at 15:59:58 UT, 81 seconds after the BAT
trigger. The XRT on-board centroid algorithm did not find a source in the
image and no prompt position is available. Down-linked
data show a variable source at position:
RA(J2000) = 22h 08m 32.07s
DEC(J2000) = -74d 34' 47.0"
with 3.8" of uncertainty (90% confidence).
This position lies 170 arcseconds from the BAT position.
UVOT took a finding chart exposure of 100 seconds with the White (160-650 nm)
filter starting 86 seconds after the BAT trigger. No afterglow candidate has
been found in the initial data products. The 2.7'x2.7' sub-image covers none of
the XRT error circle. The 8'x8' region for the list of sources generated
on-board covers 100% of the XRT error circle. The list of sources is typically
complete to about 18 mag. No correction has been made for the expected
extinction corresponding to E(B-V) of 0.08.
GCN Circular 5882
Subject
GRB 061201, Swift-BAT refined analysis of the SHB
Date
2006-12-01T21:30:20Z (19 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
C. Markwardt (GSFC/UMD), L. Barbier (GSFC), S.D. Barthelmy (GSFC),
J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC),
H. Krimm (GSFC/USRA), F.E. Marshall (NASA/GSFC), 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-239 to T+366 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 061201 (trigger #241840)
(Marshall, et al., GCN Circ. 5881). The BAT ground-calculated position
is RA, Dec = 332.079, -74.569 deg which is
RA(J2000) = 22h 08m 19.0s
Dec(J2000) = -74d 34' 6.6"
with an uncertainty of 1.2 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 48%.
The mask-weighted lightcurve shows two main peaks separated by ~0.7 sec,
the first starting at T+0 sec, and the second ending at T+1.1 sec.
A visual scan of the lightcurve (from T+2 to T+300 sec) places an
upper limit of 0.01 ph/cm2/sec for any extended emission.
T90 (15-350 keV) is 0.8 +- 0.1 sec (estimated error including systematics).
The time-averaged spectrum from T+0.0 to T+0.9 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum
is 0.81 +- 0.15. The fluence in the 15-150 keV band is 3.3 +- 0.3 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T-0.05 sec in the 15-150 keV
band is 3.9 +- 0.3 ph/cm2/sec. All the quoted errors are at the 90%
confidence level.
The burst shows significant hard to soft spectral evolution. A fit to the
first peak (T+0.0 to T+0.7) gives a simple power law index of 0.57 +/- 0.15,
while a fit to the second peak (T+0.7 to T+0.9) has a power law index of
2.10 +/- 0.35. Similarly, the light curve shows that the emission in the
15-25 keV channel extends to T+1.5 sec, while emission in the
100-350 keV channel lasts only until ~T+0.6 sec.
GCN Circular 5883
Subject
GRB 061201: Initial UVOT Observations
Date
2006-12-01T23:43:24Z (19 years ago)
From
Stephen Holland at USRA/NASA/GSFC/SSC <sholland@milkyway.gsfc.nasa.gov>
S. T. Holland (CRESST/GSFC/USRA) and F. Marshall (GSFC) report on
behalf of the Swift team:
UVOT took a finding chart exposure of 98 seconds with the White
filter (160-650 nm) filter starting 86 seconds after the BAT trigger.
There is a possible faint source in the XRT error circle (Marshall et
al. GCN Circ. 5881) at
RA(J2000) = 22:08:32.21
DEC(J2000) = -74:34:47.3
with a 1-sigma error radius of about 1.0 arc sec. The possible source
has a preliminary White magnitude of 20.9 +/- 0.6 and is detected at
the 2.5-sigma significance level. No correction has been made for the
expected Milky Way extinction corresponding to E(B-V) of 0.08 mag.
This possible source is also detected in a 197 s White exposure
starting 6202 s after the BAT trigger with a significant of 3.1-sigma
and a preliminary White magnitude of 20.9 +/- 0.4. Since the source
is not fading, it is unlikely to be the optical afterglow of GRB
061201, but it may be the host galaxy.
GCN Circular 5884
Subject
GRB 061201: VLT optical observations
Date
2006-12-02T02:19:07Z (19 years ago)
From
Paolo D'Avanzo at INAF-OAB <paolo.davanzo@brera.inaf.it>
P. D'Avanzo (INAF-OAB & Univ. Insubria), S. Piranomonte (INAF-OAR), G.
Chincarini (INAF.OABr & Univ. Milano-Bicocca), & L. Stella (INAF-OAR),
on behalf of the MISTICI collaboration, report:
We observed the field of the short GRB061201 (Marshall et al., GCN 5881,
Markwardt et al. GCN 5882) with the VLT equipped with the FORS2 camera.
Our observations started on Dec 02.014 UT (8.38 hr after the GRB). We
took 10 I-band images, for a total exposure of 900 s.
An object is clearly visible in the resulting average of our set of
images at the following coordinates (J2000):
R.A.=22:08:32.090
Dec.=-74:34:47.08
with an uncertainty of 0.2 arcsecs. This position is consistent with the
one reported by Holland and Marshall (GCN 5883). We measure I ~ 22.3
based on the
zeropoints reported on the ESO web pages. Given the different adopted
filter and the large error in the UVOT measurement, it is difficult to
assess
variability between the two epochs. We note that the object does not
seem to be extended.
We also clearly resolve a galaxy 17" NW of the XRT position.
Further analysis is in progress.
We thank the excellent support of the ESO staff, in particular Paola
Amico and Chris Lidman.
This message can be cited.
GCN Circular 5885
Subject
GRB 061201: Swift XRT Team refined analysis
Date
2006-12-02T03:20:58Z (19 years ago)
From
Matteo Perri at ISAC/ASDC <perri@asdc.asi.it>
M. Perri, G. Stratta, M.L. Conciatore (ASDC), D. N. Burrows (PSU) and
F. E. Marshall (NASA/GSFC) report on behalf of the Swift XRT team:
We have analysed the first 4 orbits of Swift XRT data on the GRB 061201
(Marshall et al., GCN Circ. 5881). A 2.7 ks photon counting mode image
provides a refined XRT position:
RA(J2000) = 22h 08m 32.21s
Dec(J2000) = -74d 34m 47.6"
with an uncertainty of 3.6 arcsec (90% containment). This position is 0.8
arcsec away from the first XRT position quoted in Marshall et al.
(GCN Circ. 5881), 0.3 arcseconds from the UVOT optical source
(Holland et al., GCN Circ. 5883) and 0.7 arcseconds from the
object reported by D'Avanzo et al. (GCN Circ. 5884).
The 0.3-10 keV X-ray light curve between 86s and 18.1ks after the trigger
can be fit with a broken power-law with an initial decay slope of
-0.56+/-0.15, a break at 1835+1178-1139s, and a post-break slope
of -1.6+/-0.4.
The X-ray spectrum covering the time period from T+99s to T+729s is
well fit by an absorbed power-law with a photon index of 1.5+/-0.2
and column density of (1.2+/-0.6)e21 cm**-2. We note the Galactic column
density in the direction of the source is 5.0e20 cm**-2.
Assuming the X-ray emission continues to decline at the same rate, we
predict a 0.3-10 keV XRT count rate of 0.002 count/s at T+24hr, which
corresponds to an observed 0.3-10 keV flux of 1.1e-13 erg/cm**2/s.
This circular is an official product of the Swift XRT Team.
GCN Circular 5890
Subject
Konus-Wind observation of GRB 061201
Date
2006-12-02T17:42:07Z (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 team report:
The short hard GRB 061201 (Swift-BAT trigger #241840;
Marshall et al., GCN 5881; Markwardt et al., GCN 5882)
triggered Konus-Wind at T0=57514.558 s UT (15:58:34.558).
As observed by Konus-Wind it had a duration of ~0.6 s,
fluence 5.33(-4.44, +0.70)x10^-6 erg/cm2,
the 16-ms peak flux measured from T0+0.528
3.19(-2.72, +0.72)x10^-5 erg/cm2/s
(both in the 20 keV - 3 MeV energy range).
The time-integrated spectrum of the GRB
(from T0 to T0+8.448 s) is well fitted (in the 20 keV - 3 MeV range)
by a power law with exponential cutoff model:
dN/dE ~ E^(-alpha) * exp(-(2-alpha)*E/Ep)
with alpha = 0.36(-0.65, +0.40)
and Ep = 873(-284, +458) keV (chi2 = 79/67 dof).
All the quoted errors are at the 90% confidence level.
The Konus-Wind light curve of this GRB is available
at http://www.ioffe.rssi.ru/LEA/GRBs/GRB061201_T57514/
GCN Circular 5895
Subject
GRB 061201: SOAR Confirmation of Candidate Afterglow
Date
2006-12-03T20:55:46Z (19 years ago)
From
Josh Haislip at U.North Carolina <haislip@physics.unc.edu>
J. Haislip, A. LaCluyze, D. Reichart, S. Heathcote, P. Ugarte, A. Alvares,
R. Baptista, & M. Nysewander report on behalf of the UNC team of the FUN
GRB Collaboration:
We observed the localization of the short/hard GRB 061201 (Marshal et al.,
GCN 5881) with SOAR/OSIRIS in JKs beginning 10.2 hours after the burst.
We detect the source identified by Holland et al. (GCN 5883) and D'Avanzo
et al. (GCN 5884).
We reobserved the field in J beginning 33.6 hours after the burst. The
source appears to have faded by at least 1.3 mag (3 sigma) and is no longer
detected.
Consequently, this source appears to be the afterglow.
GCN Circular 5896
Subject
GRB 061201: VLT optical decay
Date
2006-12-03T22:58:20Z (19 years ago)
From
Paolo D'Avanzo at INAF-OAB <paolo.davanzo@brera.inaf.it>
P. D'Avanzo (INAF-OABr & Univ. Insubria) and S. Piranomonte (INAF-OAR)
report on behalf of the MISTICI collaboration:
We continued monitoring the afterglow of the short GRB061201 (Marshall
et al., GCN 5881) with the VLT equipped with the FORS2 camera.
Observations were carried out in the I filter. From a comparison with a
set of nearby field stars we conclude that the object detected in our
previous images (D'Avanzo et al. GCN 5884; see also Holland et al. GCN
5883) faded in the I-band by about 1.8 mag between Dec 2.025 UT and Dec
3.045 UT (0.359 and 1.379 days after the burst, respectively). The
inferred decay index is thus ~ 1.2.
We note a discrepancy of about 0.7 mag in the absolute calibration
during the two nights, based on observations of Landolt standard fields.
We thus warn that the absolute calibration is still preliminary. The
decay slope is however independent of this and thus robust.
We thus fully confirm that the object proposed by Holland et al. (GCN
5883) and D'Avanzo et al. (GCN 5884) is the optical afterglow of GRB 061201,
as already found by Haislip et al. (GCN 5895).
We thank the support of the ESO staff.
This message can be cited.
[GCN OPS NOTE(03dec06): Per author's request, the missing phrase
"is the optical afterglow of GRB 061201" was added to the 3rd paragraph.]
GCN Circular 5898
Subject
GRB 061201: UVOT Observations of a Fading Optical Afterglow
Date
2006-12-05T14:14:05Z (19 years ago)
From
Stephen Holland at USRA/NASA/GSFC/SSC <sholland@milkyway.gsfc.nasa.gov>
S. T. Holland (CRESST/GSFC/USRA) and F. E. Marshall (NASA/GSFC) report
on behalf of the Swift team:
UVOT observed the field of GRB 061201 during the first 19972 s
after the BAT trigger (Marshall et al., GCN Circ. 5881). We detect
the source seen by D'Avanzo (2006, GCN Circ. 5884) at the 4.2-sigma
level in the White filter (160-650 nm) and at the 4.5-sigma level in
a coadded image of all the UV filters. The coordinates of the source
in the White image are:
RA(J2000) = 22:08:32.06
DEC(J2000) = -74:34:47.9
with a 1-sigma error radius of about 0.5 arcsec, consistent with the
VLT source.
Our magnitudes and 3-sigma upper limits for all the UVOT filters
are:
Filter Start Stop Exposure Mag Err Significance
V 191 12,136 1118 20.8 3-sigma upper limit
B 669 6197 206 20.9 3-sigma upper limit
U 645 5992 216 20.7 0.4 2.6
UVW1 621 17,926 519 20.7 0.5 2.9
21,392 58,442 11,555 22.9 0.5 2.5
86,427 160,471 19,972 23.0 3-sigma upper limit
UVM2 5384 15,948 676 20.5 0.5 2.7
UVW2 697 6512 122 19.8 0.5 2.5
White 86 6402 304 20.8 0.3 4.2
Comb. UV 621 17,926 1337 20.8 0.4 4.5
The magnitude in the combined UV exposure (coadded UVW1, UVM2, and
UVW2) between 621 sand 17,926 s is 20.8 +/- 0.4, assuming that the
source has equal magnitude in each of these filters.
Since the source is detected in the UVW2 filter, we estimate an
upper limit to the redshift of about 1.7.
GCN Circular 5909
Subject
GRB061201, VLT optical decay: correction
Date
2006-12-12T15:00:46Z (19 years ago)
From
Paolo D'Avanzo at INAF-OAB <paolo.davanzo@brera.inaf.it>
P. D'Avanzo (INAF-OABr & Univ. Insubria) and S. Piranomonte (INAF-OAR)
report on behalf of the MISTICI collaboration:
A careful inspection and re-analysis of our VLT I-band images of the
short GRB061201 (D'Avanzo & Piranomonte, GCN 5896) reveals that in our
second epoch of observations (carried out 1.379 days after the burst) no
object is clearly visible at the position of the optical counterpart
(Holland et al. GCN 5883, Haislip et al. GCN 5895, D'Avanzo et al. GCN
5884) down to I > 23.6 mag (3sigma confidence level).
So, with respect to our first epoch of observation (D'Avanzo et al. GCN
5884) the afterglow clearly faded, but we can only constrain the decay
index to be > 0.8.
This message can be cited.
GCN Circular 5944
Subject
GRB 061201: Magellan Redshift of nearby Abell cluster
Date
2006-12-20T07:42:22Z (19 years ago)
From
Josh Bloom at UC Berkeley <jbloom@astron.berkeley.edu>
S. Blondin, G. Narayan (Harvard/CfA), J. S. Bloom (UC Berkeley), H-
W. Chen (U Chicago), R. P. Kirshner, P. Challis, M. Hicken, M.
Modjaz, A. Friedman, M. Wood-Vasey (Harvard/CfA), and J. X. Prochaska
(UC Santa Cruz) report on behalf of a larger collaboration:
"The final X-ray afterglow position (Perri et al. 2006; GCN 5885) of
the short-hard GRB 061201 (Marshall et al. 2006; GCN 5881) lies 8.5
arcmin from the center of the rich Abell cluster 995 (Bloom 2006; GCN
5880). On 13 December 2006 UT, we obtained several spectra of bright
apparent cluster members with the LDSS-3 instrument mounted on the
Magellan Clay 6.5m Telescope in Chile. We find the following
redshifts based upon a preliminary inspection of the spectra:
RA (J2000) DEC(J2000)
===========================
object A: z=0.239 22:08:32.1 -74:34:47
object B: z=0.235 22:09:37.1 -74:26:39
object D: z=0.238 22:09:05.3 -74:29:29
Based on this, we claim a redshift of z=~0.237 for Abell 995 and note
that while the GRB is not yet definitively associated with a cluster
member galaxy, this redshift (and hence the implied energetics of the
event) are very similar to the putative redshifts of short-hard GRBs
050509b (z=0.225), 050724 (z=0.258), and 060502b (z=0.287)."
This message may be cited.
GCN Circular 5945
Subject
GRB 061201: Correction to GCN 5944
Date
2006-12-20T18:19:35Z (19 years ago)
From
Josh Bloom at UC Berkeley <jbloom@astron.berkeley.edu>
J. S. Bloom (UC Berkeley) notes:
"The coordinates for one of the galaxies observed in the Abell
cluster 995 was given incorrectly in GCN 5944. The correct
coordinates are:
object A: z=0.239 22:09:51.9 -74:31:11
We thank Paolo D'Avanzo for pointing out the error."
This message may be cited.
GCN Circular 5952
Subject
GRB 061201: Magellan redshift of nearby galaxy
Date
2006-12-21T21:13:16Z (19 years ago)
From
Edo Berger at Carnegie Obs <eberger@ociw.edu>
E. Berger (Carnegie) reports:
"Starting on 2006 Dec. 21.07 UT we used LDSS3 on Magellan to obtain an
1800 sec spectrum of the galaxy located 17 arcsec NW of the optical
afterglow of the short GRB 061201 (see also GCN #5884). This is the
nearest bright galaxy (R~19 mag) to the GRB position. We detect several
emission lines, which we identify as H-beta, [OIII], H-alpha, [NII], and
[SII] at a redshift of z=0.111. At this redshift the projected offset of
the burst is about 34 kpc, significantly smaller than about 1.9 Mpc
relative to the center of Abell 995 (GCN #5944)."
GCN Circular 5995
Subject
GRB 061201: Nearby Galaxy Cluster Abell 995 is at z=0.0865
Date
2007-01-04T23:39:54Z (19 years ago)
From
Edo Berger at Carnegie Obs <eberger@ociw.edu>
E. Berger (Carnegie Observatories) reports:
"On December 21.06 UT we used LDSS3 on the Magellan/Clay 6.5-m telescope
to obtain spectra of nine apparent members of the galaxy cluster Abell 995
located 8.5 arcmin away from the position of the short GRB 061201 (GCN
5880). Three of these galaxies have been previously observed by Blondin
et al. leading to a proposed redshift of z~0.237 for the cluster (GCN
5944). Based on our spectra, which cover the range of about 4000-9500A,
we find instead the following redshifts for the nine cluster members:
Redshift RA Dec
--------------------------------------------
z=0.0866 22:09:43.735 -74:26:28.92
z=0.0877 22:09:37.067 -74:26:39.84 *(object B)
z=0.0873 22:09:05.248 -74:29:29.55 *(object D)
z=0.0849 22:09:51.790 -74:31:11.06 *(object A)
z=0.0843 22:08:34.675 -74:26:20.81
z=0.0864 22:09:40.015 -74:26:53.18
z=0.0866 22:09:48.052 -74:28:26.22
z=0.0876 22:09:25.530 -74:29:50.85
z=0.0872 22:09:32.120 -74:27:35.99
These redshifts are based on absorption features corresponding to CaII
H&K, G-band, Mg b, E-band, and Na D, as well as H-alpha emission in four
of the nine objects. We therefore conclude that the redshift of Abell 995
is z=0.0835. The previously claimed redshift of z~0.237 is likely based
on a mis-identification of the Na D feature at lambda_rest ~ 5893A as Mg b
at lambda_rest ~ 5174A.
At the correct redshift of the cluster, the projected offset of GRB 061201
is about 0.8 Mpc from the center of the cluster. To cover this distance
over a period of about 10 Gyr, the kick velocity would have to be >80
km/sec.
Finally, we re-iterate the presence of a z=0.111 galaxy about 17 arcsec
from the optical position of GRB 061201, corresponding to a significantly
smaller offset of about 34 kpc (GCN 5952)."
*Objects A,B,D refer to the designation in GCN 5944