GRB 060906
GCN Circular 5557
Subject
GRB060906: Danish/DFOSC optical observations
Date
2006-09-10T23:53:09Z (20 years ago)
From
Klaas Wiersema at GRACE/U of Amsterdam <kwrsema@science.uva.nl>
K. Wiersema (University of Amsterdam) and E. Rol (University of
Leicester) report:
We observed the position of GRB060906 (Racusin et al. GCN5528) with
the Danish 1.5m telescope at La Silla equipped with DFOSC.
Observations were done under high airmass, starting on
September 8 08:06 UT and ending at 08:52 UT. In the sum of 7 x 5 min
exposures in I band we do not detect the optical afterglow (Cenko et al.
GCN5529). Using a sample of 23 USNO-B stars we find a 3 sigma upper limit
of I = 21.95. The standard deviation in the zeropoint as determined
from the USNO stars is 0.24 mag.
GCN Circular 5542
Subject
GRB060906 , optical observation
Date
2006-09-07T13:38:21Z (20 years ago)
From
Adalberto Piccioni at Astronomy, Bologna U. <adb@piccio.org>
F. Terra (Second University of Roma "Tor Vergata"), G. Greco,
C. Bartolini, A. Guarnieri, A. Piccioni (Bologna University),
D. Nanni (INAF/OAR and Second University of Rome "Tor Vergata"),
I. Bruni (Bologna Observatory), F. Strafella(University of Lecce
and INFN, Lecce) and G. Pizzichini (INAF/IASF Bologna) report:
Using the 152 cm Loiano telescope equipped with the BFOSC camera
system, in poor sky conditions (full moon, seeing = 1.8"), we
obtained one Rc-band image (1 x 900 sec) of the field of
GRB060906 (Racusin et al., GCN 5540), starting on September 6.962 .
At a 3-sigma level the OT reported by Cenko et al. (GCN 5529) is not
detected in our frame, which is slightly deeper than Rc=20.3.
We used NOMAD1 as our reference catalog.
GCN Circular 5540
Subject
GRB 060906: optical observation
Date
2006-09-06T23:23:23Z (20 years ago)
From
Ken ichi Torii at Osaka U <torii@ess.sci.osaka-u.ac.jp>
K. Torii (Osaka U.) reports:
The error region of GRB 060906 (Racusin et al. GCN 5528) was observed
with the 0.3m telescope in the New Mexico Skies Observatory. Starting
at 08:39:08 UT (6.4 minutes after the trigger), 120s x 20 frames were
acquired through Ic filter.
At the position of the optical afterglow (Cenko et al. GCN 5529,
5531), we identify a marginal excess (at 3.2 sigma) that corresponds
to I=17.7 (USNO-B1.0 magnitude) in a stacked frame (120s x first 10
frames). The analysis is preliminary.
===
GCN Circular 5539
Subject
GRB 060906: Early RAPTOR optical limits
Date
2006-09-06T22:01:25Z (20 years ago)
From
James Wren at LANL <jwren@nis.lanl.gov>
J. Wren, W.T. Vestrand, P.R. Wozniak, R. White, S. Evans, and
J. Pergande of Los Alamos National Laboratory report:
The RAPTOR array of telescopes autonomously responded to Swift
trigger 228316. Conditions were cloudy at our primary telescope
site but our wide-field RAPTOR-B small telescope array, located
at our secondary site, imaged the event under clear conditions.
Imaging began at 08:34:12.53 UTC (86.0 s after the trigger, 5.8 s
after receipt). We do not detect the counterpart seen by the Swift
XRT (Racusin et al. GCN 5528) and P60 (Cenko et al. GCN 5529).
The initial unfiltered 5 s exposure yields a 3-sigma limiting
magnitude at the counterpart location of R=15.2 when calibrated
against the GSC 1.1 R-band. This limit has not been corrected
for foreground galactic extinction.
GCN Circular 5538
Subject
GRB 060906, Swift-BAT refined spectral analysis
Date
2006-09-06T21:14:38Z (20 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
G. Sato (GSFC/ISAS), T. Sakamoto (GSFC/ORAU), C. Markwardt (GSFC/UMD),
D. Palmer (LANL), S. D. Barthelmy (GSFC), L. Barbier (GSFC),
J. Cummings (GSFC/UMD), E. Fenimore (LANL), N. Gehrels (GSFC),
D. Hullinger (BYU-Idaho), H. Krimm (GSFC/USRA), A. Parsons (GSFC),
J.L. Racusin (PSU), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC)
on behalf of the Swift-BAT team:
We report the spectral analysis of Swift-BAT GRB 060906 (trigger #228316)
(Racusin, et al., GCN Circ. 5528; & Sakamoto, et al., GCN Circ. 5534).
Using the response matrix appropriate for the burst position in the
BAT field-of-view during the slew:
The time-averaged spectrum from T-41.8 to T+6.0 is best fit by a simple
power-law model. The power law index of the time-averaged spectrum
is 2.02 +- 0.11. The fluence in the 15-150 keV band is
2.21 +- 0.14 x 10^-6 erg/cm2. The 1-sec peak photon flux measured
from T-24.86 sec in the 15-150 keV band is 2.0 +- 0.3 ph/cm2/sec.
All the quoted errors are at the 90% confidence level.
GCN Circular 5537
Subject
GRB 060906: Swift/XRT Refined Analysis
Date
2006-09-06T21:02:17Z (20 years ago)
From
Judith Racusin at PSU <racusin@astro.psu.edu>
J. L. Racusin, D. N. Burrows (PSU), N. Gehrels (NASA/GSFC), D. Grupe, J. A.
Kennea (PSU) report on behalf of the Swift XRT team:
We have analysed the Swift-XRT data from the first 6 orbits of GRB 060906
(Racusin et al., GCN Circ. 5528), with a total exposure of 12200 seconds.
The refined XRT position is:
RA(J2000): 2h 43m 00.66s
Dec(J2000): +30d 21' 37.82"
with an uncertainty of 4 arcseconds (90% containment). This position is
134 arcseconds from the refined BAT position given in GCN Circ. 5534
(Sakamoto et al.), 3.3 arcseconds from the XRT position given in GCN 5528,
and 5.3 arcseconds from the optical counterpart reported by Cenko et al.
(GCN 5529).
The light-curve starts 153 seconds after the BAT trigger and shows a steep
decline with a decay index of -3.4 +/- 1.3 followed by a flattening at
~400 seconds described by a power-law with index -0.2 +/- 0.1, and
breaking again at ~11000 seconds to a power-law index of -1.7 +/- 0.3.
A preliminary spectral fit to the WT data gives a spectral power law
photon index of 2.5 +/- 0.5 in the [0.3-10] keV band, with absorption
column density consistent with the Galactic value (9.66e20 cm^-2). The
average (in the time range 153-776 seconds from trigger) estimated
unabsorbed 0.3-10 keV flux was 1.37e-11 erg cm^-2 s^-1.
The XRT count rate extrapolated to T+24 hr is estimated to be about 0.002
counts/s, corresponding to an unabsorbed 0.3-10 keV flux of about 1.72e-13
erg cm^-2 s^-1.
This Circular is an official product of the Swift XRT Team.
GCN Circular 5536
Subject
GRB 060906: Swift-UVOT observations
Date
2006-09-06T18:31:26Z (20 years ago)
From
Patricia Schady at MSSL/Swift <ps@mssl.ucl.ac.uk>
P. Schady (MSSL-UCL) and J.L. Racusin (PSU) report on behalf of the
Swift-UVOT team:
The Swift UVOT began observing GRB 060906 152 seconds after the BAT
trigger (GCN 5528). No optical afterglow is detected at the 3-sigma level
in the XRT error circle (GCN 5528) or at the location of the afterglow reported
by Cenko et al. (GCN 5529) in individual or coadded exposures of any of the
UVOT filters.
The 3-sigma limiting magnitudes for the coadded images of the
UVOT filters are listed below:
Filter T_range(s) Exp(s) Upper limit (3sig)
WHITE 201-8121 583 20.6
V 457-7210 1297 20.1
B 739-8029 520 20.3
U 720-7824 529 20.0
W1 697-7619 549 19.6
M2 672-7415 549 19.9
W2 773-7006 320 19.7
where T_range is the start and end times of the coadded exposures. No
correction has been made for Galactic reddening along the line of sight
(E(B-V) = 0.20 mag).
GCN Circular 5535
Subject
VLT redshift of GRB 060906
Date
2006-09-06T18:17:49Z (20 years ago)
From
Paul Vreeswijk at ESO <pvreeswi@eso.org>
Paul Vreeswijk (ESO/Cerro Calan), Pall Jakobsson (Hertfordshire),
Cedric Ledoux (ESO), Christina Thoene, Johan Fynbo (DARK) report on
behalf of a larger collaboration:
We observed the optical afterglow (Cenko et al., GCN 5529) of GRB
060906 detected by Swift (Racusin et al., GCN 5528) with ESO's Very
Large Telescope UT2 (Kueyen) at Paranal, Chile. One single FORS1
spectrum with an exposure time of 10min. was taken in twilight, with
the 300V grism and a 1" slit, providing a wavelength coverage of
3800-8900 at a resolution of 12 A.
We detect a damped Ly alpha line and various other absorption features
such as Si II, Si II*, O I, C II, Si IV at a redshift of z=3.685.
It's a pleasure to thank the excellent support of the Paranal staff,
and in particular that of Claudio Melo, Chris Lidman and Linda
Schmidtobreick.
GCN Circular 5534
Subject
GRB 060906, Swift-BAT refined analysis
Date
2006-09-06T15:40:49Z (20 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
T. Sakamoto (GSFC/ORAU), L. Barbier (GSFC), S. D. Barthelmy (GSFC),
J. Cummings (GSFC/UMD), E. Fenimore (LANL), N. Gehrels (GSFC),
D. Hullinger (BYU-Idaho), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD),
D. Palmer (LANL), A. Parsons (GSFC), J.L. Racusin (PSU),
G. Sato (GSFC/ISAS), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC)
on behalf of the Swift-BAT team:
Using the data set from T-119 to T+183 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 060906 (trigger #228316)
(Racusin, et al., GCN Circ. 5528). The BAT ground-calculated position
is RA,Dec = 40.710, 30.356 deg {2h 42m 50.4s, 30d 21' 21.3"} (J2000)
+- 2.5 arcmin, (radius, sys+stat, 90% containment). The partial coding was 45%.
This burst started at ~T-50 sec while the spacecraft was still slewing
between regularly scheduled follow-up targets. The initial emission is
a broad peak of roughly constant flux. It returns to background level
at ~T-4 sec and then the peak which BAT actually triggerred on starts.
It peaks at T~T+4 sec at a level about half of the initial broad peak.
T90 (15-350 keV) is 43.6 +- 1 sec (estimated error including systematics).
Because most of the burst happened during slewing, our standard processing
for the spectral, flux, and fluence results are not appropriate.
We will issue another circular with those results when they become available.
GCN Circular 5533
Subject
GRB 060906: FRAM observations - flash determination (airplane)
Date
2006-09-06T11:31:54Z (20 years ago)
From
Petr Kubanek at AIO <petr@lascaux.asu.cas.cz>
P.Kubanek (AsU AV CR Ondrejov, ISDC Versoix) reports:
The object mentioned in GCN Circ.5530 is:
- outside XRT and BAT location
- show second object roughly 10 arcmin apart (~27m @ 10km)
so it is most probably airplane. This object is not related to GRB 060906.
I apologize for error in position determination - I forget to switch from BAT arcmin error box to XRT arcsec error box when I plot localizations. I thank to S.B.Cenko for pointing that out.
GCN Circular 5532
Subject
GRB 060906: KAIT observations
Date
2006-09-06T11:04:31Z (20 years ago)
From
Weidong Li at UC Berkeley KAIT/LOSS <weidong@astron.berkeley.edu>
W. Li and J. Bloom (University of California, Berkeley), on behalf
of the KAIT GRB team, report:
The robotic 0.76-m Katzman Automatic Imaging Telescope (KAIT)
at Lick Observatory observed GRB 060906, detected with Swift
(Trigger 228316; Racusin et al. GCN 5528). The automatic sequence
started at 08:34:32, 106 s after the burst. In a 15 s unfiltered
image, no afterglow candidate is detected to a limiting magnitude
of 18.2 (from comparison with the USNO B1.0 catalog). We detected
the optical afterglow reported by Cenko et al. (GCN 5529, 5531)
in a 45 s unfiltered image started at 336 s after the burst, with
the following precise (+/- 0.2") position:
RA = 2:43:00.84 Dec = +39:21:41.9 (J2000.)
A table of photometry (3-sigma limits and detections) is reported
below.
======================================================================
Start UT t(GRB) Filter Exp(s) 3sigma-limit detection
08:34:32 106s clear 15.0 <18.2
08:35:07 141s V 15.0 <16.7
08:35:33 167s I 15.0 <17.5
08:35:59 193s clear 20.0 <18.4
08:36:30 224s V 45.0 <17.3
08:37:27 281s I 45.0 <18.3
08:38:22 336s clear 45.0 18.9 +/- 0.3
========================================================================
GCN Circular 5531
Subject
GRB 060906: Confirmation of P60 Optical Afterglow
Date
2006-09-06T10:46:32Z (20 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 continued to image the field of GRB060906 (Racusin et al; GCN
5528) with the automated Palomar 60-inch telescope. Our observations
indicate the candidate identified by Cenko, Ofek and Fox (GCN 5529) has
faded and is therefore the optical afterglow of GRB060906. In particular,
the object faded by ~ 0.9 mag in R-band images taken 11 min and 53 min
after the burst, corresponding to a shallow power-law decay index (t ^
-0.5).
GCN Circular 5530
Subject
GRB 060906: observations with FRAM
Date
2006-09-06T09:42:24Z (20 years ago)
From
Petr Kubanek at AIO <petr@lascaux.asu.cas.cz>
P. Kubanek (AsU AV CR Ondrejov & ISDC Versoix) and M.Prouza (FZU Praha,
UC NY) reports on behalf of the FRAM collaboration:
We observed location of GRB 060906 (GCN Circ. 5528, J. Racusin et al.)
with FRAM telescope at Pierre Auger Observatory, Argentina. Inside XRT
error circle, in R band single image, we detected bright flash at location:
02:42:49.5 +30:24:21.7 (J2000)
Object is not present in DSS images, nor in USNO catalogue.
WE WARN THAT THIS OBJECT IS MOST PROBABLY ARTIFACT FROM CAMERA SHUTTER
FAILURE. At present time, we are unsure about nature of that event. We
kindly request observers with all-sky cameras to check for that object.
Finding chart is available at:
http://lascaux.asu.cas.cz/~petr/20060906.png
Bigger circle is XRT location, smaller is OT candidate (GCN Circ. 5529,
S. Bradley Cenko et al.) and object mentioned above. First image is 20
sec R band exposure starting at 08:34:53 (125 sec post GRB), second is
20 sec starting at 08:35:20. Object is not visible at second image.
Line going from object down is in image Y axis direction, so it might be
a object bloom.
Futher observations, as well as analysis, are in progress.
[GCN OPS NOTE(06sep06): Per author's request, the citation for Circ 5528
was changed to Racusin.]
GCN Circular 5529
Subject
GRB 060906 (?): P60 Optical Afterglow Candidate
Date
2006-09-06T09:14:55Z (20 years ago)
From
S. Bradley Cenko at Caltech <cenko@srl.caltech.edu>
S. B. Cenko, E. O. Ofek (Caltech) and D. B. Fox (Penn State) report on
behalf of a larger collaboration:
We have imaged the field of Swift trigger 228316 (GRB 060906?) with the
automated Palomar 60-inch telescope. Observations were taken in the
Kron R filter beginning approximately 12 minutes after the burst. Inside
the BAT error circle, we find a stationary object not present in the
Digitized Sky Survey at the location (J2000.0):
RA: 02:43:00.9
Dec: +30:21:42.12
We estimate the magnitude of the object to be R ~ 19.0, based on
comparison with several USNO-B objects in the field. Given the brightness
and stationary nature of the object, we consider it a possible optical
afterglow. Further observations are underway to search for variability.
GCN Circular 5528
Subject
GRB 060906: Swift detection of a probable burst
Date
2006-09-06T09:12:48Z (20 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
J. L. Racusin (PSU), S. D. Barthelmy (GSFC), D. N. Burrows (PSU),
N. Gehrels (NASA/GSFC), C. Guidorzi (Univ Bicocca&INAF-OAB),
S. D. Hunsberger (PSU), V. Mangano (INAF-IASFPA), D. C. Morris (PSU),
K. L. Page (U Leicester), D. M. Palmer (LANL), E. Rol (U Leicester),
P. Romano (INAF-OAB), G. Sato (GSFC/ISAS), M. Stamatikos (NASA/ORAU)
and H. Z. Ziaeepour (UCL-MSSL) report on behalf of the Swift Team:
At 08:32:46 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 060906 (trigger=228316). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA,Dec 40.748, +30.349 {02h 42m 60s, +30d 20' 58"} (J2000)
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve is complicated by the fact
that the spacecraft was slewing just prior to the image trigger. There
appears to be an ~5 sec wide peak starting at T_zero. There are possibly
two smaller peaks at T-15 and T-21 sec, but these are during the slew
and may be caused by the slew. The peak count rate
is ~1000 counts/sec (15-350 keV), at ~5 sec after the trigger.
The XRT began taking data at 08:35:15 UT, 148 seconds after the BAT
trigger. The XRT on-board centroid algorithm did not find a source in
the image but ground analysis of 5 seconds of flight data available
at this time reveals a possible faint source at the following coordinates:
RA(J2000): 2h 43m 00.9s
Dec(J2000): +30 21 38.95
with an error of 8 arcseconds (90% confidence). Further analysis of
ground data is necessary to determine the properties of the possible
source.
UVOT took a finding chart exposure of 100 seconds with the White
(160-650 nm) filter starting 152 seconds after the BAT trigger. No
afterglow candidate has been found in the initial data products. 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 mag. No
correction has been made for the expected extinction corresponding to
E(B-V) of 0.20.
We will have the full data set downlinked and processed by ~11:00 UT.