GRB 040916
GCN Circular 2796
Subject
GRB 040916: Afterglow Color at Early Times
Date
2004-10-11T15:18:33Z (21 years ago)
From
Daniel E. Reichart at U.North Carolina <reichart@physics.unc.edu>
Christine Lamanna, Matt Bayliss, Ron Canterna, Dan Reichart, Arne Henden,
Don Lamb, and Melissa Nysewander report on behalf of the U. Wyoming, U.
North Carolina, USNO, and U. Chicago GRB teams of the FUN GRB
Collaboration:
We observed the afterglow location (Kosugi et al., GCN 2726) of XRF 040916
(Yamazaki et al., GCN 2712; Yamamoto et al., GCN 2713) in V with the
2.3-meter WIRO telescope beginning 4.78 hours (mean epoch = 4.86 hours) and
again 1.49 days after the burst. For our first epoch, we find that V =
22.12 +/- 0.06. For our second epoch, we find that V > 21.5 (2 sigma).
Using Subaru, Kosugi et al. (GCN 2726) find the afterglow to be R = 22.3
+/- 0.2 at 5.6 hours. Using USNO's 1.0-meter telescope, Henden (GCN 2727)
finds the afterglow to be Ic = 20.51 +/- 0.23 at 4.6 hours. As Henden
(2727) stated, this implies that the afterglow was very red or rapidly
fading at this time.
The WIRO and USNO observations are nearly simultaneous, and yield a
spectral index -2.8 +/- 0.6, which is very red.
If this is due to extinction, the observer-frame A_V is likely ~3 mag and R
- Ic ~ 0.6 mag and B - R ~ 1.4 mag. Consequently, at the epochs of the
first three Subaru observations (t = 5.6, 8.8, and 60 hours after the
burst) the afterglow would be I ~ 21.7, 22.1, and 24.2 and B ~ 23.7, 24.1,
and 26.2.
If this turns out not to be the case, the color of the afterglow likely
changed, perhaps very rapidly, between the USNO/WIRO observations and the
Subaru observations.
One possible explanation for this would be an early-time dust echo. Moran
& Reichart (astro-ph/0409390, posted two hours before the burst) predict
that light from the optical flash will scatter off of a circum-progenitor
dust shell, similar to the dust shells that are found around late-type WC
stars. This results in excess light on a timescale of minutes to hours
after the burst, and this excess light quickly transitions from blue to red
before fading away. For example, this ~1.6 mag difference between Ic and V
would not be difficult to explain with an optical flash of peak brightness
~12th mag and a dust shell of inner radius ~10^16 cm.
Finally, we note that GRB 980329 had a similar, unexplained two magnitude
difference between the I and R bands, in this case about 18 hours after the
burst (Reichart et al. 1999, ApJ, 517, 692).
Images and light curves will be posted at:
www.physics.unc.edu/~mbayliss/grb040916.html
GCN Circular 2729
Subject
TAROT Observations of GRB 040916 (HETE #3558)
Date
2004-09-21T08:24:52Z (21 years ago)
From
Jean-Luc Atteia at Lab d Astrophys.,OMP,Toulouse <atteia@ast.obs-mip.fr>
TAROT Observations of GRB 040916 (HETE #3558)
Klotz, A., Atteia, J.L., G. Stratta, and Boer M. report:
TAROT observed the HETE Ground alert #3558
from 2004 Sept. 16 02:26:59 UT
to 2004 Sept. 16 02:57:35 UT,
as a series of 30-s unfiltered images
in the field described by Yamazaki et al.
(GCN Circ. 2712, 2713).
We first computed the medians of sub-series
of 3 images to eliminate cosmics, which were
then co added to obtain a single image.
Comparing to the USNO-1B catalog and DSS
image, we are able to detect all stars
brighter than R=19.4, and very few
stars fainter than R=20.0.
The candidate proposed Kosugi et al.
(GCN 2726) is not detected at the 3
sigma level. We conclude that the
afterglow had a magnitude R > 19.4
in a time period extending from 2.39 to 2.89 hours
after the GRB.
We note that a fuzzy patch is seen at
mag R=19.5 in the image at the position of
the afterglow, which we do not
consider as the afterglow, but as a background
fluctuation.
This message may be cited
GCN Circular 2725
Subject
GRB040916 optical limits 17 min after GRB
Date
2004-09-18T08:41:18Z (21 years ago)
From
Grzegorz Wrochna at Soltan Inst.for Nuclear Studies <wrochna@fuw.edu.pl>
M.Cwiok, K.Kwiecinska, L.Mankiewicz, K.Nawrocki,
B.Pilecki, L.W.Piotrowski, G.Pojmanski, R.Salanski,
M.Sokolowski, D.Szczygiel, G.Wrochna,
on behalf of "Pi of the Sky / ASAS" collaboration
http://grb.fuw.edu.pl
The central part of HETE FOV containing GRB040916 error box
was observed by "Pi of the Sky" apparatus at Las Campanas
Observatory for the night of 2004.09.15/16
from 00:20:54 UT (17 min after the GRB) till 09:05:00 UT.
10s exposures were taken continuously with 4s intervals
by two CCD cameras.
No unknown objects wrt Tycho-2 and GSC catalogues
has been observed within the GRB040916 error box.
The limiting magnitude is ~11.5m for single frames
and ~13.0m for 20 coadded frames. More information at
http://grb.fuw.edu.pl/pi/ot/grb040916/
GCN Circular 2718
Subject
GRB040916: Archival optical observations
Date
2004-09-16T19:08:29Z (21 years ago)
From
Michael J.I. Brown at NOAO <mbrown@noao.edu>
Michael J.I. Brown (Princeton) and Nigel C. Hambly (ROE) report:
We have queried the SuperCOSMOS Sky Survey (http://www-wfau.roe.ac.uk/sss/)
for previous optical detections of the GRB040916 optical afterglow
candidate reported by Kilmartin & Gilmore (GCN 2715). This object has been
previously detected in a Bj photographic plate from 1982 taken with the UK
Schmidt Telescope at the Anglo Australian Observatory (UKST plate J8169).
This object is not detected in SuperCOSMOS scans of R or I-band plates
(UKST plates OR14538 and I15787). UK Schmidt photographic survey plates
typically have limiting magnitudes of Bj~22.5, R~21.5 and I~19.5.
The coordinates and magnitude of this object are
RA = 23:01:43.975, Dec = -05:39:12.02 (J2000.0), and Bj = 20.9 +/- 0.2.
These coordinates are 1 arcsecond from the position reported by
Kilmartin & Gilmore (GCN 2715).
We note that this object has a compact morphology and it is therefore
plausible that this is a star or AGN rather than a GRB afterglow or GRB
host galaxy.
This message may be cited.
GCN Circular 2715
Subject
GRB040916: Optical observations
Date
2004-09-16T14:28:07Z (21 years ago)
From
AAVSO GRB Network at AAVSO <aavso@aavso.org>
P. Kilmartin & A. Gilmore (Mt. John Observatory of University of
Canterbury) reports on behalf of the AAVSO International High Energy
network:
Two sets of frames centered on the coordinates for GRB040916 (Yamamoto et
al., GCN 2712; HETE trigger 3558) show a stationary object not visible on
DSS2 R and IR images, at:
RA = 23 01 44.01 Dec = -05 39 11.3 (2000.0)
Unfiltered R magnitudes at mean times
08:29 UT 19.7 S/N = 2.8
09:54 UT 19.9 S/N = 3.3
Observations were made under clear conditions with the 0.6 meter
cassegrain telescope with f/6.4 focal reducer on Mt. John. Seeing was
approximate 3 arcsec and limiting magnitude roughly 20.5 in R. The USNO
A2.0 catalog in Astrometrica was used for photometry and astrometry
reduction. CCD field of view was 9x9 arc minutes.
More information on the exposure and the FITS image itself is available
at: ftp://ftp.aavso.org/grb/
Note, there are many red sources in the field and these observations are
unfiltered so there is a strong possibility that this OT candidate is just
a faint red source.
The AAVSO International High Energy network is greatful for a generous
grant from the Curry Foundation and to NASA for the financial support for
the High Energy Workshops for Amateur Astronomers and to the SWIFT E/PO
program for continued funding.
GCN Circular 2714
Subject
ROTSE-IIIb Observations of GRB 040916 (HETE #3558)
Date
2004-09-16T04:52:14Z (21 years ago)
From
Eli Rykoff at Univ. of Michigan/ROTSE <erykoff@umich.edu>
Rykoff, E. S., Quimby, R. & Schaefer, B. E. Report on behalf of the
ROTSE Collaboration:
ROTSE-IIIb at McDonald Observatory, Texas, responded automatically to
the HETE Ground alert #3558. The first exposure began at 02:29:48.2
(UTC), approximately 2.4 hours after the burst time reported by Yamazaki
et al. (GCN Circ. 2712, 2713). The ROTSE-IIIb system automatically
scheduled a series of 10 20-s images followed by a long series of 60-s
images. As of this writing, we have analyzed 40 images. We have also
co-added sets of 10 images. Our unfiltered limiting magnitudes are
around 18.3 for the single exposures, and 19.2 for the co-added frames.
Visual comparison of the co-added frames to the DSS reveals 3 new
objects in the HETE-2 error circle reported in GCN Circ. 2712. These
three sources are identified as asteroids by their proper motion, and
are in the MpChecker database (Ruanda, 1997 WZ36, and 2004 PN39). At
this time, we have no candidate counterparts to the GRB.
GCN Circular 2713
Subject
GRB040916 (= H3558): Improved Localization from HETE WXM
Date
2004-09-16T04:18:39Z (21 years ago)
From
George Ricker at MIT <grr@space.mit.edu>
GRB040916 (= H3558): Improved Localization from HETE WXM
Y. Yamamoto, G. Ricker, J-L. Atteia, N. Kawai, D. Lamb, and S.
Woosley, on behalf of the HETE Science Team;
T. Donaghy, E. Fenimore, M. Galassi, C. Graziani, M. Matsuoka, Y.
Nakagawa, T. Sakamoto, R. Sato, Y. Shirasaki, M. Suzuki, T. Tamagawa,
Y. Urata, T. Yamazaki, and A. Yoshida, on behalf of the HETE WXM Team;
N. Butler, G. Crew, J. Doty, A. Dullighan, G. Prigozhin, R.
Vanderspek, J. Villasenor, J. G. Jernigan, A. Levine, G. Azzibrouck,
J. Braga, R. Manchanda, and G. Pizzichini, on behalf of the HETE
Operations and HETE Optical-SXC Teams;
C. Barraud, M. Boer, J-F Olive, J-P Dezalay, and K. Hurley, on behalf
of the HETE FREGATE Team;
report:
By utilizing the WXM data from both peaks of GRB040916 (= H3558;
Yamazaki et al, GCN2712), the localization of this unusual XRF has
been refined to an 90% confidence error box with corners at the
following coordinates (J2000):
RA = 23 02 01.68, Dec = -05 50 09.6
RA = 23 00 23.76, Dec = -05 37 51.6
RA = 23 00 58.80, Dec = -05 19 51.6
RA = 23 02 36.72, Dec = -05 32 09.6
The area of the error box is 545 square arc minutes.
This message may be cited.
GCN Circular 2712
Subject
GRB040916 (= H3558): A Long XRF Localized by HETE
Date
2004-09-16T03:01:51Z (21 years ago)
From
Roland Vanderspek at MIT <roland@space.mit.edu>
GRB040916 (= H3558): A Long XRF Localized by HETE
T. Yamazaki, G. Ricker, J-L. Atteia, N. Kawai, D. Lamb, and S. Woosley,
on behalf of the HETE Science Team;
T. Donaghy, E. Fenimore, M. Galassi, C. Graziani, M. Matsuoka,
Y. Nakagawa, T. Sakamoto, R. Sato, Y. Shirasaki, M. Suzuki,
T. Tamagawa, Y. Urata, Y. Yamamoto, and A. Yoshida, on behalf of the
HETE WXM Team;
N. Butler, G. Crew, J. Doty, A. Dullighan, G. Prigozhin, R. Vanderspek,
J. Villasenor, J. G. Jernigan, A. Levine, G. Azzibrouck, J. Braga,
R. Manchanda, and G. Pizzichini, on behalf of the HETE Operations and
HETE Optical-SXC Teams;
C. Barraud, M. Boer, J-F Olive, J-P Dezalay, and K. Hurley, on behalf
of the HETE FREGATE Team;
report:
At 00:03:30 UT (209 SOD) on 16 September 2004, the WXM instrument
on HETE detected GRB040916 (= H3558), a long, two-peaked XRF. The
burst has been localized to a circle of 18' radius centered on
RA = 23h 01m 44s, Dec = -5d 37' 43" (J2000)
The burst consists of two peaks separated by ~250s, each ~100s in
duration. No formal spectral analysis has been performed using WXM
data, but the dearth of counts in bands > 10 keV in either peak is a
strong indication that GRB040916 is an XRF.
We anticipate providing additional spectral information from this
unusual event in a subsequent GCN Circular.
This message may be cited.