GRB 040912
GCN Circular 2701
Subject
GRB040912 (= H3557): A Long GRB or XRF Localized by HETE
Date
2004-09-12T23:14:09Z (21 years ago)
From
George Ricker at MIT <grr@space.mit.edu>
GRB040912 (= H3557): A Long GRB or XRF Localized by HETE
N. Butler, 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, Y. Yamamoto, and A. Yoshida, on
behalf of the HETE WXM Team;
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 14:12:17 UT (13260 SOD) on 12 September 2004, the Fregate and WXM
instruments on HETE detected GRB040912 (= H3557), an unusual, long
X-ray rich GRB or XRF. The burst has been localized to a circle of
7' radius centered on
RA = 23h 56m 54s, Dec = -1d 00' 02" (J2000)
The burst duration is ~20 seconds in the 7-30 keV band, but the 2-10
keV emission extends for ~150s. Preliminary analyses of the first 40
seconds of burst data show the burst to have Epeak of 58 keV, a 2-30
keV fluence of 7e-7 erg/cms and a 30-400 keV fluence of 4e-7 erg/cm2.
While this analysis shows the burst to be an X-ray rich GRB, we
expect the ratio of 2-30/30-400 keV fluence to increase once the
analysis of the entire burst is complete, at which time H3557 may be
re-classified as an XRF.
We anticipate providing additional spectral information from this
unusual event in a subsequent GCN Circular.
This message may be cited.
GCN Circular 2703
Subject
Optical observations of field of GRB040912
Date
2004-09-13T00:40:23Z (21 years ago)
From
AAVSO GRB Network at AAVSO <aavso@aavso.org>
B. Monard (Bronberg Obs.) reports on behalf of the AAVSO
International GRB network:
Observations of the HETE error circle for GRB040912
(Butler et al., GCN 2701; HETE trigger 3557)
were made with the Bronberg 0.30m telescope + unfiltered CCD.
Fifty-five 28-second exposures with UT midpoint of 040912.813 (5.3hrs
after the burst) were stacked, with a limiting magnitude
of 20.2CR (based on USNO-A red magnitudes). The field was
centered at the revised ground analysis coordinates, with
a field of view of 20arcmin(E/W) x 13arcmin(N/S), covering
all but the extreme north and south limits of the error circle.
No new object is seen down to approximately CR=19.5 when comparing
against a DSS2-red image.
The AAVSO International GRB 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.
GCN Circular 2705
Subject
GRB040912 : Kiso Optical follow-up observation
Date
2004-09-13T07:52:51Z (21 years ago)
From
Yuji Urata at RIKEN <urata@crab.riken.go.jp>
K. Ogura(Kokugakuin Univ.), S. Nishiura (Tokyo Gakugei Univ.)
M. Isogai(Tokyo Univ.) and Y. Urata(RIKEN) report:
" We have imaged the entire HETE-2 error circle (Butler et al.,
GCN 2701) using Kiso 1.05 m Schmidt telescope with 2kx2k CCD camera
starting at 2004 Sep 12.668 UTC. We obtained 3 x 300 sec R-band
images. Each R-band image gives limiting magnitude of R~20 mag. using
R magnitudes of near USNO_A2.0 stars as photometric references. We
found a source around "23:57:10 -00:56:42" (R~19.4 mag.) which is not
in DSS II images. But, comparing our second image with our third one,
it seem to move about 4 arcsec in 5 minute. It may be minor
planet. Because of our network trouble we cannot access "MINOR PLANET
CHECKER" page now."
This message may be cited.
GCN Circular 2708
Subject
GRB 040912, BVRI observations
Date
2004-09-13T14:52:02Z (21 years ago)
From
Sylvio Klose at TLS Tautenburg <klose@tls-tautenburg.de>
S. Klose, U. Laux, Thueringer Landessternwarte Tautenburg,
J. Greiner, MPE Garching,
report:
The error circle of GRB 040912 (HETE trigger 3557; Butler et al., GCN
2701) was imaged in BVRI with the Tautenburg Schmidt telescope equipped
with the prime focus CCD camera (field of view ~40'x 40'). Observations
started Sep 12, 19:34 UT, about 5 hours after the burst, and lasted for
altogether 6 hours. During the observing run the sky conditions were good.
Based on the USNO SA2.0 catalogue (Monet et al. 1996), we estimate a
limiting magnitude of R = 22.5 for the combined R-band image. The combined
I-band image goes about 2 mag deeper than the DSS2 infrared image, while
the combined B-band image is about 1 mag less deep than the DSS1.
In addition to the reported non-detections in the R-band (Pimbblet &
Price, GCN 2702; Monard, GCN 2703; Ogura et al., GCN 2705; Andersen et
al., GCN 2707) we can state that there is no I-band candidate down to
the DSS2 infrared plate limit. There is also no evidence for any point
source in R and I potentially superimposed one of the two brightest
galaxies in the field. There is no potential afterglow candidate in
the B-band.
GCN Circular 2710
Subject
GRB 040912: Optical Observations
Date
2004-09-15T04:36:26Z (21 years ago)
From
James Rhoads at STScI <rhoads@stsci.edu>
Armin Rest (CTIO), James Rhoads (STScI), and Peter Weilbacher (Durham)
report on behalf of a larger collaboration:
We have observed the field of GRB 040912 using the 4m Blanco telescope
and CCD Mosaic-2 camera at CTIO. We obtained two epochs during the
first night following the burst, at UT September 13.033 and 13.205.
Each epoch consisted of four R band exposures of 300 seconds, for a
total of 20 minutes' integration per epoch. Conditions were
photometric but seeing was mediocre, at 1.35" in the first epoch
and 1.01" in the second epoch.
Preliminary image subtraction analysis reveals no compelling afterglow
candidates. Our search is sensitive to a change in flux density of
1.9 microJansky, which corresponds to the complete disappearance
of an object with magnitude R=23.0
GCN Circular 2711
Subject
GRB040912 (= H3557): Chandra Observations Scheduled
Date
2004-09-15T18:35:44Z (21 years ago)
From
George Ricker at MIT <grr@space.mit.edu>
GRB040912 (= H3557): Chandra Observations Scheduled
G. Ricker, P. Ford, N. Butler, R. Vanderspek (MIT), and D. Lamb (U.
Chicago), on behalf of a Chandra GRB ToO Team,
write:
Chandra target-of-opportunity observations of the entire HETE WXM
error circle for GRB040912 (= H3557: Butler et al, GCN 2701) have
been approved and scheduled, subject to possible high background
radiation constraints. The first epoch observation will commence near
22h UT on 15 September, with a second epoch observation ~1 week later.
As noted by Butler et al (GCN 2701), although GRB040912 exhibits the
spectral characteristics of an XRF, its temporal characteristics are
quite unusual. The scheduling of contemporaneous observations at
other wavelengths, especially deep initial and second epoch optical
and IR observations, is strongly encouraged.
We are grateful to Harvey Tananbaum and Andrea Prestwich for
approving this DDT observation.
GCN Circular 2716
Subject
GRB040912(=H3557): Observations with the Chandra X-ray Observatory
Date
2004-09-16T18:21:46Z (21 years ago)
From
Roland Vanderspek at MIT <roland@space.mit.edu>
GRB040912(=H3557): Observations with the Chandra X-ray Observatory
N. Butler, P. Ford, G. Ricker, R. Vanderspek, J. Villasenor,
P. Csatorday (MIT); D. Lamb (U. Chicago); and J.G. Jernigan (UCB), on
behalf of a Chandra GRB ToO Team,
write:
On 15 September 2004, the Chandra Observatory targeted the field of
GRB040912, an X-ray flash localized by the HETE satellite (=H3557;
Butler et al, GCN 2701). The 20 ksec observation spanned the
interval 21:57 UT on 15 September to 3:48 UT on 16 September, 3.32 - 3.57
days after the burst. The WXM error circle from Butler et al. was completely
contained within the field-of-view of the Chandra ACIS-I array.
Within the WXM error region, we detect 22 sources with more than 6
source counts in the 0.5-8 keV band:
# Chandra Name RA DEC Cts HR
1 CXOU J235631.0-005946 23 56 30.96 -0 59 46.1 55 -0.5
2 CXOU J235700.0-010009 23 56 59.96 -1 0 9.7 40 -0.3
3 CXOU J235712.2-005942 23 57 12.17 -0 59 42.1 33 -0.3
4 CXOU J235642.9-005520 23 56 42.91 -0 55 20.4 32 -0.7
5 CXOU J235645.7-005655 23 56 46.71 -0 56 54.9 32 -0.3
6 CXOU J235707.6-005713 23 57 7.57 -0 57 12.6 31 0.8
7 CXOU J235716.4-010109 23 57 16.37 -1 1 8.7 27 -0.2
8 CXOU J235639.1-005556 23 56 39.10 -0 55 55.8 20 0.9
9 CXOU J235651.2-005513 23 56 51.17 -0 55 12.5 17 -0.3
10 CXOU J235636.7-005431 23 56 36.74 -0 54 31.2 15 -0.6
11 CXOU J235711.1-005637 23 57 11.12 -0 56 37.1 12 -0.2
12 CXOU J235637.3-010160 23 56 37.26 -1 1 59.9 12 -0.6
13 CXOU J235656.4-005839 23 56 56.42 -0 58 39.2 11 -0.1
14 CXOU J235700.1-005713 23 57 0.09 -0 57 12.6 11 -1.0
15 CXOU J235659.8-005903 23 56 59.83 -0 59 2.8 10 -0.6
16 CXOU J235649.1-010344 23 56 49.07 -1 3 44.2 9 0.4
17 CXOU J235700.4-010018 23 57 0.36 -1 0 17.6 9 -0.7
18 CXOU J235646.4_005621 23 56 46.45 -0 56 21.4 8 1.1
19 CXOU J235647.0-010045 23 56 46.97 -1 0 45.1 8 0.0
20 CXOU J235648.8-010319 23 56 48.81 -1 3 18.6 8 -1.0
21 CXOU J235704.0-005859 23 57 4.03 -0 58 58.8 8 -0.2
22 CXOU J235707.2-010420 23 57 7.18 -1 4 19.6 7 0.4
We estimate a position uncertainty of 1.0" for the Chandra sources.
Astrometry was performed using five stars from the USNO-A2 catalog.
The column labeled HR in the table above refers to the hardness
ratio ( Cts_2-8keV - Cts_0.5-2keV )/ Cts_0.5-8 keV. This quantity is
typically in the range -0.5 to -0.1 for GRBs at high Galactic latitude
and attenuated by the Galactic absorption only.
An image of the Chandra data, with the detected sources overlaid, can
be found at http://space.mit.edu/HETE/Bursts/GRB040912.
We gratefully acknowledge the timely assistance of the observatory staff
at the Chandra Science Center in arranging for the acquisition and
preliminary processing of these data.
This message may be cited.
GCN Circular 2728
Subject
GRB040912(=H3557): Candidate Optical Afterglow
Date
2004-09-20T17:09:10Z (21 years ago)
From
Nat Butler at MIT/CSR <nrbutler@space.mit.edu>
GRB040912(=H3557): Candidate Optical Afterglow
N. Butler, G. Ricker, R. Vanderspek, J. Villasenor, P. Csatorday,
P. Schechter, S. Burles (MIT); S. Malhotra (STSCI), and D. Osip (LCO),
on behalf of a larger collaboration report:
We observed the HETE WXM error region from Butler et al. (GCN 2701)
in two epochs with the 27'x27' FOV IMACS camera on the Magellan 6.5m
Baade Telescope at Las Campanas Observatory. Epoch1 consisted of
3x180s exposures in R band, with a mean observing time of Sep 13.15716 UT
(t_burst + 13.57 hours). Epoch2 consisted of 2x300s exposures in R
band, with a mean observing time of Sep 14.20236 UT (t_burst + 38.65 hours).
The 3-sigma limiting magnitudes are R=25.3 and R=25.6 for Epoch1 and
Epoch2, respectively.
We calibrate our astrometry and photometry against the USNO stars of
Henden et al. (GCN 2720). We detect sources within 1" of the Chandra
positions for 8 of the 22 Chandra sources reported in Butler et al.
(GCN 2716):
CX0# R-magE1 R-magE2
1 . .
2 23.95+/-0.07 24.10+/-0.07
3 . .
4 24.29+/-0.01 24.02+/-0.08
5 . .
6 . .
7 22.55+/-0.04 22.53+/-0.04
8 . .
9 . 24.4+/-0.1
10 . .
11 . .
12 25.00+/-0.13 24.67+/-0.09
13 22.25+/-0.04 23.27+/-0.05
14 . .
15 . .
16 . .
17 . .
18 22.38+/-0.04 22.31+/-0.03
19 . .
20 . .
21 25.12+/-0.14 24.56+/-0.10
22 . .
Of the optical sources we detect, the source corresponding to
CXO#13 has declined in brightness the most (by 1.02 pm 0.09 mag),
and we tentatively suggest this source to be the optical afterglow
of GRB040912. The flux decay between our 2 epochs corresponds to
a fade with temporal index alpha=-0.9+/-0.1.
This message may be cited.
GCN Circular 2731
Subject
GRB040912(=H3557): Chandra Candidate X-ray Afterglow
Date
2004-09-22T14:23:36Z (21 years ago)
From
Nat Butler at MIT/CSR <nrbutler@space.mit.edu>
GRB040912(=H3557): Chandra Candidate X-ray Afterglow
P. Ford, N. Butler, G. Ricker, R. Vanderspek, J. Villasenor,
P. Csatorday (MIT); D. Lamb (U. Chicago); and J.G. Jernigan (UCB), on
behalf of a Chandra GRB ToO Team,
write:
On 21 September 2004, the Chandra Observatory targeted the field of
GRB040912, an X-ray flash localized by the HETE satellite (=H3557;
Butler et al., GCN 2701; Olive et al., GCN 2723). This was a 20 ksec
followup observation to the observation beginning on 15 September
reported by Butler et al. (GCN 2716). It spanned the interval 10:56 UT
to to 17:01 UT on September 21, 8.86-9.12 days after the burst. The
WXM error circle from Butler et al. (GCN 2701) was completely contained
within the field-of-view of the Chandra ACIS-I array.
At the location of the 22 X-ray sources reported in our Epoch 1 (E1)
observation (GCN 2716), we find:
# Chandra Name <Cts_E1> Cts_E2 Null_Prob
1 CXOU J235631.0-005946 55 53 0.421
2 CXOU J235700.0-010009 35 40 0.703
3 CXOU J235712.2-005942 39 37 0.404
4 CXOU J235642.9-005520 36 15 0.003
5 CXOU J235645.7-005655 30 20 0.068
6 CXOU J235707.6-005713 30 21 0.108
7 CXOU J235716.4-010109 33 41 0.791
8 CXOU J235639.1-005556 19 30 0.921
9 CXOU J235651.2-005513 15 13 0.359
10 CXOU J235636.7-005431 18 27 0.874
11 CXOU J235711.1-005637 15 8 0.090
12 CXOU J235637.3-010160 7 9 0.675
13 CXOU J235656.4-005839 10 8 0.325
14 CXOU J235700.1-005713 13 19 0.848
15 CXOU J235659.8-005903 12 9 0.259
16 CXOU J235649.1-010344 10 3 0.047
17 CXOU J235700.4-010018 16 7 0.042
18 CXOU J235646.4_005621 3 3 0.386
19 CXOU J235647.0-010045 16 7 0.042
20 CXOU J235648.8-010319 10 7 0.297
21 CXOU J235704.0-005859 3 1 0.213
22 CXOU J235707.2-010420 12 3 0.032
In this table, "<Cts_E1>" refers to the number of counts detected in
E1, scaled to the exposure in E2. The number of counts detected in E2 for
each source is reported in the column labeled "Cts_E2," and the probability
that the source remained constant given the E1 and E2 detected count rates
is presented under "Null_Prob."
We note that source #13 has not faded between our two epochs, and this
strongly dis-favors the candidate OT of Butler et al. (GCN 2728).
Several sources appear to have faded at or beyond the 2-sigma significance
level (#'s 4,17,19,and 22). However, given the 22 trials conducted to find
the candidate X-ray afterglow, only source #4 exhibits a statistically
significant decline in brightness (3-sigma single trial, ~2-sigma in 22
trials). The decrease in count rate from source #4 between E1 and E2
implies a temporal decay index of alpha=-0.9+/-0.3. We determine a refined
position for this source of:
RA= 23h 56m 42.96s, Dec= -0d 55' 19.8" (J2000),
with an uncertainty of 1". A faint (R~24) optical source, spatially
coincident with this position, was reported by Butler et al. (GCN 2728).
However, this source did not appear to decrease in flux between t_burst
+ 13.57 hours and t_burst + 38.65 hours.
We gratefully acknowledge the timely assistance of the observatory staff
at the Chandra Science Center in arranging for the acquisition and
preliminary processing of these data.
This message may be cited.