GRB 061006
GCN Circular 5699
Subject
GRB 061006: Swift detection of a burst
Date
2006-10-06T17:13:38Z (19 years ago)
From
David Palmer at LANL <palmer@lanl.gov>
P. Schady (MSSL-UCL), D. N. Burrows (PSU), J. R. Cummings (NASA/UMBC),
N. Gehrels (NASA/GSFC), C. Guidorzi (Univ Bicocca&INAF-OAB),
S. T. Holland (GSFC/USRA), S. D. Hunsberger (PSU),
V. Mangano (INAF-IASFPA), D. C. Morris (PSU),
P. T. O'Brien (U Leicester), C. Pagani (PSU),
K. L. Page (U Leicester), D. M. Palmer (LANL),
S. B. Pandey (UCL-MSSL), J. L. Racusin (PSU),
P. Romano (Univ. Bicocca & INAF-OAB), G. Sato (GSFC/ISAS),
M. Stamatikos (NASA/ORAU), R. L. C. Starling (U Leicester),
D. E. Vanden Berk (PSU) and H. Ziaeepour (UCL-MSSL) report on behalf
of the Swift Team:
At 16:45:50 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 061006 (trigger=232585). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA,Dec 111.090, -79.202 {07h 24m 22s, -79d 12' 05"} (J2000)
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve showed a large peak about
5 seconds long during the pre-planned slew immediately preceding the start
of the 64-second image in which the burst was found. The peak count rate
was ~5500 counts/sec (15-350 keV), at ~24 sec before the trigger.
The XRT began taking data at 16:48:13 UT, 143 seconds after the BAT
trigger. The XRT on-board centroid algorithm did not find a source in
the image, but ground analysis of the data found a faint source at a
position of RA, Dec = 07h 24m 06.47s, -79d 11' 54.5" (J2000), with
an estimated error radius of 8 arcsec (90% containment, including
boresight uncertainties). This is 44 arcsec from the BAT position.
UVOT took a finding chart exposure of 400 seconds with the V filter
starting 140 seconds after the BAT trigger. The 2.7'x2.7' sub-image
covers 25% of the BAT error circle. The typical 3-sigma upper limit
has been about 18.5 mag. The 8'x8' region for the list of sources
generated on-board covers 100% of the BAT error circle. The list of
sources is typically complete to about 18.0 mag. No correction has
been made for the expected extinction of about 1.1 magnitudes.
GCN Circular 5700
Subject
GRB061006: Faulkes Telescope South Observations
Date
2006-10-06T18:01:17Z (19 years ago)
From
Carole Mundell at ARI, JMU,Liverpool <cgm@astro.livjm.ac.uk>
C.G. Mundell (Liverpool JMU), A. Gomboc (University of Ljubljana)
C. Guidorzi (Univ Bicocca & INAF-OAB), C.J. Mottram,
A. Melandri, I.A. Steele, R.J. Smith, A. Monfardini, D. Carter,
S. Kobayashi, D. Bersier, (Liverpool JMU), P. O'Brien,
N. Bannister (Leicester) report:
"The 2m Faulkes Telescope South (Siding Spring, Australia) automatically
reacted to Swift burst GRB 061006 (Schady et al. GCN Circ. 5699).
We find no new sources in the XRT error circle to
R~18.7 +/-0.3 mag at t~20.45 minutes
or
i'~18.0+/-0.3 mag at 26.3 minutes after the burst
(Magnitudes are calibrated with respect to the USNO-B1)
Observations and analysis are on-going."
GCN Circular 5702
Subject
GRB061006 (Swift 232585) might be a short-hard GRB
Date
2006-10-07T01:22:46Z (19 years ago)
From
Kevin Hurley at UCBerkeley/SSL <khurley@ssl.berkeley.edu>
K. Hurley and T. Cline, on behalf of the Ulysses, Mars Odyssey,
and Konus GRB teams,
D. M. Smith, R. P. Lin, J. McTiernan, R. Schwartz, C. Wigger, W.
Hajdas, and A. Zehnder, on behalf of the RHESSI GRB team,
S. Golenetskii, E. Mazets, V. Pal'shin, and D. Frederiks on behalf of
the Konus-Wind team, and
K.Yamaoka, M.Ohno, Y.Fukazawa, T.Takahashi, M.Tashiro, Y. Terada,
T.Murakami, and K.Makishima on behalf of the Suzaku WAM team, report:
RHESSI, Konus, and Suzaku observed a short duration (<~ 1 s) gamma-ray
burst at 60328 s. We have triangulated it to an annulus centered at
RA, Dec=193.534, 11.116 degrees, with radius 77.720 +/- 2.080 degrees
(3 sigma). The BAT position for Swift 232585 lies 0.051 degrees from the center line of this annulus, and occurs at 60350 s. Thus, this Swift burst
might be the same as the earlier IPN event. The spectrum of the IPN
burst will be given in a forthcoming GCN Circular. If it turns out
to be a hard spectrum burst, then the Swift event could be the soft
spectrum portion or afterglow of it.
This IPN annulus can be improved with data from Ulysses and Odyssey,
which are expected within 24 hours.
GCN Circular 5703
Subject
GRB 061006: Swift-XRT Team Refined Analysis
Date
2006-10-07T02:24:20Z (19 years ago)
From
Eleonora Troja at INAF-IASFPA <nora@ifc.inaf.it>
E. Troja (U. Leicester/INAF-IASFPa), K. L. Page(U. Leicester),
D. N. Burrows (PSU) & P. Schady (MSSL-UCL) report on behalf of the Swift-XRT
Team:
We have analysed the first 4 orbits of Swift-XRT data obtained for GRB 061006
(GCN Circ. 5699; Schady et al.). Our data set consists of 7.8 ks in Photon
Counting (PC) mode.
We derived a XRT refined position of:
RA(J2000) = 07h 24m 06.36s
Dec(J2000) = -79d 11' 56.80''
with an estimated error radius of 6 arcsec (90% containment, including
boresight uncertainties). This lies 2.3 arcsec from the preliminary XRT
position and 45'' arcsec from the on-board calculated BAT position, reported
in GCN 5699.
The X-ray lightcurve shows an initial slope of 2.26 +/- 0.10, breaking around
290 s after the burst to a flatter decay slope of 0.77 +/- 0.07.
The time-averaged spectrum (from T+155 s to T+18.6 ks) can be fit with an
absorbed power-law with a photon index of 1.7 +/- 0.4 and an absorption
column of 1.8e21 cm^-2, consistent at the 90% confidence level with the
Galactic value in the direction of the burst (1.33e21 cm^-2).
The mean observed (unabsorbed) flux in the 0.2-10 keV energy band is 1.4e-12
(1.9e-12) erg cm^-2 s^-1.
If the afterglow continues decaying at the same rate, the count rate at T+24 h
is predicted to be 1.8e-3 cts s^-1, corresponding to an unabsorbed 0.2-10 keV
flux of 1.5e-13 erg cm^-2 s^-1.
This circular is an official product of the Swift-XRT team.
GCN Circular 5704
Subject
GRB 061006: Swift-BAT refined analysis of the short-hard burst
Date
2006-10-07T05:56:21Z (19 years ago)
From
David Palmer at LANL <dmpalmer@mac.com>
H. Krimm (GSFC/USRA), L. Barbier (GSFC), S. Barthelmy (GSFC),
J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC),
D. Hullinger (BYU-Idaho), M. Koss (GSFC/UMD), C. Markwardt (GSFC/UMD),
D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/ORAU),
G. Sato (GSFC/ISAS), P. Schady (MSSL-UCL), M. Stamatikos (GSFC/ORAU),
J. Tueller (GSFC), on behalf of the Swift-BAT team:
Using the data set from T-240 to T+300 sec from the recent telemetry
downlink, we report further analysis of BAT GRB 061006 (trigger #232585)
(Schady, et al., GCN Circ. 5699). The BAT ground-calculated
position is (RA,Dec) = 110.998,-79.195 {07h 23m 59.6s , -79d 11' 42"}
[deg; J2000] +-1.8 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 73 %.
This burst began with an intense double-spike from T-22.8 to T-22.3
seconds.
This spike was also seen as a short GRB by RHESSI, Konus, and Suzaku
(Hurley et al., GCN 5702). This was followed by lower-level persistent
emission at least until ~T+110 seconds. T90 (15-350 keV) is 130 +/-
10 s
(estimated error including systematics).
The power law index of the time-averaged spectrum of the entire burst
is 1.74 +/- 0.17 . The fluence in the 15-150 keV band is
(1.43 +/- 0.14) x 10^-6 erg/cm2.
The peak 1-sec interval measured from T-23.2 sec, including the initial
spikes, has a power law index of 0.93 +/- 0.07 with a photon flux in the
15-150 keV band of 5.36 +/- 0.22 ph/cm2/sec.
All the quoted errors are at the 90% confidence level.
Because the initial spikes occurred during a preplanned slew, BAT
did not trigger until it had analyzed the first 64 second image
following
the slew, which contained only this persistent emission.
This light curve of a hard spike followed by a softer persistent
emission
is characteristic of BAT observations of the 'Short-Hard' class of GRBs.
GCN Circular 5705
Subject
GRB 061006: VLT observation
Date
2006-10-07T09:56:53Z (19 years ago)
From
Daniele Malesani at SISSA-ISAS,Trieste,Italy <malesani@sissa.it>
Daniele Malesani (SISSA/ISAS), Luigi Stella (INAF/OAR), Stefano Covino
(INAF/OABr), Chris Lidman, and Dominique Naef (ESO), report on behalf of
the MISTICI collaboration:
We observed the field of the short GRB 061006 (Schady et al., GCN 5699;
Krimm et al., GCN 5704), with the ESO-VLT UT2 equipped with FORS1.
Observations, carried out in the I band, started on 2006 Oct 7.30728 UT
(14.6 hr after the GRB).
Inside the XRT error box (Troja et al., GCN 5703), we find a single,
faint source at the coordinates (J2000, 0.5" accuracy):
alpha = 07:24:07.66
delta = -79:11:55.1
There is a further, brighter, pointlike source outside the error circle
(9.9" away of the XRT position) at
alpha = 07:24:03.3
delta = -79:11:52.46
At the present stage, it is not clear whether any of these objects is
related to the GRB. Further observations are planned to look for
variability. There are also no apparent bright galaxies in the proximity
of the XRT position.
We acknowledge excellent support from the VLT staff. This message can be
cited.
GCN Circular 5710
Subject
Konus-Wind observation of the short hard GRB 061006
Date
2006-10-07T16:22:04Z (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 061006 (Hurley et al., GCN 5702; Krimm et al.,
GCN5704; Swift trigger #232585 - Schady et al., GCN 5699)
triggered Konus-Wind at T0=60326.896 s UT (16:45:26.896).
As observed by Konus-Wind the burst shows
two main multipeaked pulses with a total duration of ~0.5 s.
The weak extended tail detected by BAT
(Krimm et al., GCN 5704) is marginally seen
in the Konus-Wind soft energy range G1 (23-80 keV).
The burst fluence is 3.57(-1.92, +0.31)x10^-6 erg/cm2,
and the 16-ms peak flux measured from T0+0.028 s
2.13(-1.20, +0.41)x10^-5 erg/cm2/s
(both in the 20 keV - 2 MeV energy range).
The spectrum of the most intense part integrated from T0 to T0+0.256 s
(this interval comprises ~2/3 of the burst total counts)
is well fitted (in the 20 keV - 2 MeV range)
by a power law with exponential cutoff model:
dN/dE ~ E^(-alpha) * exp(-(2-alpha)*E/Ep)
with alpha = 0.62(-0.21, +0.18)
and Ep = 664(-144, +227) keV (chi2 = 36/30 dof).
All the quoted errors are at the 90% confidence level.
GCN Circular 5711
Subject
GRB 061006: Swift/UVOT optical observations
Date
2006-10-07T20:33:52Z (19 years ago)
From
Shashi Pandey at MSSL <sbp2@mssl.ucl.ac.uk>
S. B. Pandey and P. Schady (MSSL-UCL) report on behalf of
the Swift-UVOT team:
The Swift UVOT began observing the GRB 061006 field (trigger 232585), 129
seconds after the BAT trigger (GCN 5699). No new source was detected
in the co-added UVOT observations down to the following 3-sigma magnitude
upper limits within the refined XRT error circle (GCN 5703):
Filter T_range (s) Exposure (s) 3sigma UL
V 129-18315 2131 20.85
B 617-30237 789 21.23
U 593-45827 2534 21.86
W1 569-41793 2902 21.50
M2 545-35908 3462 21.69
W2 633-17402 1318 21.12
T_range is calculated from the time of the burst. The upper limits
are not corrected for Galactic extinction E(B-V) = 0.32 mag along
the line of sight to the burst.
GCN Circular 5717
Subject
GRB 061006 : Suzaku/WAM observation of the prompt emission
Date
2006-10-08T10:31:51Z (19 years ago)
From
Yuji Urata at Saitama U <urata@crystal.heal.phy.saitama-u.ac.jp>
Y. Urata, M. Tashiro, K. Abe, K. Onda, Y. Sato, M. Suzuki (Saitama U)
M. Ohno, T. Takahashi, T. Asano, T. Uehara, Y. Fukazawa (Hiroshima U),
K. Yamaoka, S. Sugita (Aoyama Gakuin U), Y. Terada, T. Tamagawa,
M. Suzauki (RIKEN), T. Enoto, R. Miyawaki, K. Kokubun,
K. Makishima (Univ. of Tokyo), K. Nakazawa, T. Takahashi (ISAS/JAXA),
S. Hong (Nihon U.), on behalf of the Suzaku WAM team report:
"The short duration GRB 061006 (Schady et al. #5699, Hurley #5702 ),
triggered the Suzaku Wideband All-sky Monitor (WAM), which covers the
energy range of 50 keV - 5 MeV, at 16:45:27 UT October 6, 2006. The
duration T90 was about 0.42 second. The fluence in 100 - 1000 keV of
the burst was about 2.55 x 10-6 erg/cm2. Preliminary result shows that
the time-averaged spectrum is well described by a power law with an
exponential cutoff as follows.
dN/dE ~ E^{-alpha} * exp(-(2-alpha)*E/Epeak)
alpha 0.75 (-0.34, +0.28), and
Epeak 966 (-208, +386) keV.
All the quoted errors are at statistical 90% confidence level, while
systematic errors are not included.
The WAM light curve of this event is available at
http://www.astro.isas.jaxa.jp/suzaku/HXD-WAM/WAM-GRB/grb/grb_table.html "
GCN Circular 5718
Subject
GRB 061006: optical afterglow
Date
2006-10-08T12:09:35Z (19 years ago)
From
Daniele Malesani at SISSA-ISAS,Trieste,Italy <malesani@sissa.it>
Daniele Malesani (SISSA/ISAS), Luigi Stella (INAF/OAR), Paolo D'Avanzo,
Stefano Covino (INAF/OABr), Emmanuele Jehin, Chris Lidman, and Dominique
Naef (ESO) report on behalf of the MISTICI collaboration
We observed again the field of the short GRB 061006 (Schady et al., GCN
5699; Krimm et al., GCN 5704), with the ESO-VLT UT2 equipped with FORS1.
Observations were carried out in the I band (30 minutes on source), and
started on 2006 Oct 8.2936 UT (1.60 days after the GRB). The seeing
(0.85") was comparable to that of our previous observation.
We still detect the two sources reported by Malesani et al. (GCN 5705).
The object inside the XRT error circle (alpha = 07:24:07.66, delta =
-79:11:55.1) has faded by 0.53 +- 0.09 mag with respect to our previous
observation. We thus suggest that this source is the optical afterglow
of GRB 061006, possibly contaminated by the host galaxy. In fact, the
inferred power-law decay slope is quite shallow (alpha = 0.50+-0.08).
However, the object in the last epoch is not clearly extended.
The lack of a bright galaxy suggests that this short burst is not very
nearby.
Further observations are planned.
GCN Circular 5723
Subject
GRB 061006: astrometry-corrected XRT position
Date
2006-10-09T14:57:28Z (19 years ago)
From
Eleonora Troja at INAF-IASFPA <nora@ifc.inaf.it>
E. Troja (U.Leicester,INAF/IASFPa), K. L. Page (U.Leicester), N. Gehrels
(NASA/GSFC) and D. N. Burrows (PSU) report on behalf of the Swift XRT team:
Using the first 22 ks of XRT PC observations we detected 6 serendipitous X-ray
sources with S/N>3 in the field of view of GRB 061006.
Comparing the X-ray centroids to positions of nearby infrared sources, listed
in the 2MASS catalogue, we noted that a systematic offset is present. We then
improved the XRT position considering three infrared/X-ray associations and
we obtained the new X-ray afterglow position:
RA(J2000)= 07h 24m 07.33s
Dec(J2000)= -79d 11' 55.77''
with a shift of Delta RA=2.73 arcsec and Delta Dec=-1.03 arcsec with respect
to the previous one, reported in GCN Circ. 5703. The corresponding error
radius is 2.2 arcsec (90% containment).
This new position lies 1.1 arcsec from the optical afterglow candidate
proposed by Malesani et al. (GCN Circ. 5718).
This circular is an official product of the Swift-XRT team.