- GCN/BACODINE POSITION NOTICE
TITLE: GCN/HETE BURST POSITION NOTICE
NOTICE_DATE: Sun 12 Sep 04 14:12:21 UT
NOTICE_TYPE: HETE S/C_Alert
TRIGGER_NUM: 3557, Seq_Num: 1
GRB_DATE: 13260 TJD; 256 DOY; 04/09/12
GRB_TIME: 51136.96 SOD {14:12:16.96} UT
TRIGGER_SOURCE: Trigger on the 6-80 keV band.
GAMMA_RATE: 344 [cnts/s] on a 5.200 [sec] timescale
SC_LONG: 152 [deg East]
SUN_POSTN: 170.95d {+11h 23m 47s} +3.90d {+03d 54' 09"}
MOON_POSTN: 150.22d {+10h 00m 53s} +17.22d {+17d 12' 58"}
MOON_ILLUM: 4 [%]
COMMENTS: No s/c ACS pointing info available yet.
COMMENTS: Probable GRB.
- GCN/BACODINE POSITION NOTICE
TITLE: GCN/HETE BURST POSITION NOTICE
NOTICE_DATE: Sun 12 Sep 04 15:33:09 UT
NOTICE_TYPE: HETE Ground Analysis
TRIGGER_NUM: 3557, Seq_Num: 3
GRB_DATE: 13260 TJD; 256 DOY; 04/09/12
GRB_TIME: 51136.96 SOD {14:12:16.96} UT
TRIGGER_SOURCE: Trigger on the 6-80 keV band.
GAMMA_RATE: 344 [cnts/s] on a 5.200 [sec] timescale
SC_-Z_RA: 351 [deg]
SC_-Z_DEC: -2 [deg]
SC_LONG: 152 [deg East]
WXM_CNTR_RA: 359.277d {+23h 57m 06s} (J2000),
359.337d {+23h 57m 21s} (current),
358.636d {+23h 54m 33s} (1950)
WXM_CNTR_DEC: -1.167d {-01d 10' 00"} (J2000),
-1.141d {-01d 08' 26"} (current),
-1.445d {-01d 26' 42"} (1950)
WXM_MAX_SIZE: 22.00 [arcmin] diameter
WXM_LOC_SN: 9 sig/noise (pt src in image)
WXM_IMAGE_SN: X= 9.8 Y= 7.3 [sig/noise]
WXM_LC_SN: X= 12.8 Y= 10.1 [sig/noise]
SUN_POSTN: 170.95d {+11h 23m 47s} +3.90d {+03d 54' 09"}
SUN_DIST: 171.17 [deg]
MOON_POSTN: 150.22d {+10h 00m 53s} +17.22d {+17d 12' 58"}
MOON_DIST: 147.16 [deg]
MOON_ILLUM: 4 [%]
GAL_COORDS: 94.01,-60.95 [deg] galactic lon,lat of the burst
ECL_COORDS: 358.87,-0.78 [deg] ecliptic lon,lat of the burst
COMMENTS: Definite GRB.
COMMENTS: WXM error box is circular; not rectangular.
COMMENTS: Burst_Validity flag is true.
COMMENTS: WXM data refined since S/C_Last Notice.
- GCN/BACODINE POSITION NOTICE
TITLE: GCN/HETE BURST POSITION NOTICE
NOTICE_DATE: Sun 12 Sep 04 15:56:55 UT
NOTICE_TYPE: HETE Ground Analysis
TRIGGER_NUM: 3557, Seq_Num: 4
GRB_DATE: 13260 TJD; 256 DOY; 04/09/12
GRB_TIME: 51136.96 SOD {14:12:16.96} UT
TRIGGER_SOURCE: Trigger on the 6-80 keV band.
GAMMA_RATE: 344 [cnts/s] on a 5.200 [sec] timescale
SC_-Z_RA: 350 [deg]
SC_-Z_DEC: -2 [deg]
SC_LONG: 152 [deg East]
WXM_CNTR_RA: 359.223d {+23h 56m 54s} (J2000),
359.283d {+23h 57m 08s} (current),
358.582d {+23h 54m 20s} (1950)
WXM_CNTR_DEC: -1.001d {-01d 00' 02"} (J2000),
-0.975d {-00d 58' 28"} (current),
-1.279d {-01d 16' 44"} (1950)
WXM_MAX_SIZE: 14.00 [arcmin] diameter
WXM_LOC_SN: 9 sig/noise (pt src in image)
WXM_IMAGE_SN: X= 9.8 Y= 7.3 [sig/noise]
WXM_LC_SN: X= 12.8 Y= 10.1 [sig/noise]
SUN_POSTN: 170.95d {+11h 23m 47s} +3.90d {+03d 54' 09"}
SUN_DIST: 171.17 [deg]
MOON_POSTN: 150.22d {+10h 00m 53s} +17.22d {+17d 12' 58"}
MOON_DIST: 147.12 [deg]
MOON_ILLUM: 4 [%]
GAL_COORDS: 94.06,-60.78 [deg] galactic lon,lat of the burst
ECL_COORDS: 358.89,-0.61 [deg] ecliptic lon,lat of the burst
COMMENTS: Definite GRB.
COMMENTS: WXM error box is circular; not rectangular.
COMMENTS: Burst_Validity flag is true.
COMMENTS: WXM data refined since S/C_Last Notice.
- red DSS finding chart
ps-file
- Email by G. Ricker
Dear Recipients,
Because the GCN Server at GSFC is down today (12 September 2004), and
the HETE satellite has localized a potentially interesting GRB, the
HETE Team is taking the liberty of transmitting this GCN Circular
text directly to you by email.
Since the formal GCN Circular is also queued at GSFC, you should
receive the contents of the formal GCN Circular (see below) from the
GCN when it resumes operation, hopefully later tonight.
Best regards and good hunting,
--George Ricker, on behalf of the HETE Team
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.
See the original HETE Web-page for this GRB at:
http://space.mit.edu/HETE/Bursts/GRB040912/
- GCN notice #2701
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 notice #2702
K. Pimbblet (University of Queensland) and P.A. Price (Institute for
Astronomy) report:
We have observed the error circle of HETE trigger #3557 with the 40-inch
telescope + Wide Field Imager in poor seeing conditions (~ 3 arcsec)
with an R filter at 2004 Sep 12.703 UTC. Preliminary reduction involved
coaddition of 3 x 300 sec exposures, which cover most of the 22 arcmin
diameter error circle (missing the South-most 2 arcmin, and reduced
sensitivity in a mosaic gap) to a limiting magnitude of approximately 20
mag. We do not identify any optical afterglow candidate after visually
comparing with the Digitised Sky Survey 2 F plate.
We plan to reduce and inspect further images, with an integration time
of approximately an hour.
This message may be cited.
- GCN notice #2703
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 notice #2705
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 notice #2707
M. I. Andersen (AIP), M. Weidinger (U. Aarhus), J. Hjorth, J. P. U. Fynbo,
B. L. Jensen (U. Copenhagen) report:
"Using the ALFOSC at the 2.56-m Nordic Optical Telescope, La Palma, we have
obtained 2 x 2 mosaic CCD images covering the HETE-2 error circle of
GRB/XRF 040912 (Butler et al., GCNC 2701) on two epochs. Each pointing
consists of 3 x 300 sec in the R band.
Comparison of the two epochs (Sep 12.92-12.97 and Sep 13.19-13.24 2004 UT)
through visual inspection and difference imaging does not reveal any sources
exhibiting significant variability between the two epochs. The 3-sigma
variability limit is R ~ 23.4."
- GCN notice #2708
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 notice #2709
S.maeno,E.Sonoda,Y.Matsuo, M.Yamauchi
(University of Miyazaki)
We have observed the HETE-2 error circle of
GRB/XRF040912(HETE trigger 3557)with the unfiltered CCD camera
on the 30-cm telescope at University of Miyazaki.
Observed field of view is 43 arcmin centerd on (23h 57m 04s -00d 59' 12" ).
After co-adding a set of 8 images of 30 sec exposures, we have compared
our images with the USNO A2.0 catalog.
Preliminary analysis shows there is no new source brighter than
16.0mag. in our observed field at Sep 13, 12:09:30 UT.
- GCN notice #2710
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 notice #2711
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 notice #2716
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 notice #2720
A. Henden (USRA/USNO) reports on behalf of the USNO GRB team:
We have acquired BVRcIc all-sky photometry for
a 11x11 arcmin field centered on the HETE coordinates
for GRB/XRF040912 (trigger 3557; Butler et al. GCN 2701)
with the USNOFS 1.0-m telescope on one photometric
night. Stars brighter than V=13.5 are saturated and
should be used with care. We have placed the photometric data
on our anonymous ftp site:
ftp://ftp.nofs.navy.mil/pub/outgoing/aah/grb/xrf040912.dat
The astrometry in this file is based on linear plate solutions
with respect to UCAC2. The external errors are less than 100mas.
The estimated external photometric error is about 0.03mag
and will be improved with additional calibration nights
if an afterglow is discovered.
As always, you should check the dates on the .dat file prior to
final publication to get the latest photometry. There is
a README file on the ftp directory to give you information
about the procedures used to calibrate these fields.
- GCN notice #2723
XRF 040912 (=H3557): Spectral and Temporal Properties
J-F Olive, 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;
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-P Dezalay, and K. Hurley, on behalf of the HETE
FREGATE Team;
report:
The burst-average photon number spectrum of GRB 040912 is best fit by
a power-law times exponential (PLE) model with a photon index alpha =
1.75 +0.28/-0.30 and a peak energy E_peak = 14.5 +/-14.5 keV.
The fluence of the burst is (8.3 +1.4/-1.3 ) x 10-7 erg cm-2 in the 2-30
keV energy band and (3.3 +2.9/-1.7) x 10-7 erg cm-2 in the 30-400 keV
energy band. The ratio of the fluences in the two energy bands is 2.5,
clearly making this burst an X-Ray Flash.
The T50 and T90 durations of XRF 040912 are 80 +/-5 sec and 127 +/-13
sec in the 6-40 keV energy band, and 81 +/-5 sec and 122 +/-7 sec in the
6-80 keV energy band, respectively.
This message may be cited.
- GCN notice #2724
J. Gorosabel (IAC-CSIC Granada), J. Cepa (IAC=20
Tenerife), A. de Ugarte Postigo (IAA-CSIC),=20
D. Mart=EDnez-Delgado (AIP Potsdam), V. Casanova,=20
S. Guziy, M. Jel=EDnek (IAA-CSIC, Granada), J. M.=20
Castro Cer=F3n (San Fernando), H. Castaneda (IAC=20
Tenerife), D. Zucker, E. F. Bell (AIP Potsdam)=20
and A. J. Castro-Tirado (IAA-CSIC)
report:
"We have acquired optical images covering the=20
entire error box of the XRF 040912 detected by=20
HETE-2 (Ricker et al. GCN Circ. 2701) starting
on 12 Sep 21:27 UT (i.e. 7.25 hr after the event).=20
The observations were performed with the 4.2m=20
WHT (+PFC) at La Palma (16'x 16' FOV).
The observing log follows:
-----------------------------------
Date 2004 UT Exp.Time (s) Filter =20
-----------------------------------
12 Sep 21:27:56 1455 B
12 Sep 21:53:45 900 V
13 Sep 04:26:41 900 V
13 Sep 21:07:58 1200 V=20
16 Sep 01:49:11 300 I
16 Sep 01:58:17 300 I
16 Sep 02:05:06 300 I
16 Sep 02:11:17 300 I
16 Sep 02:18:16 300 I
16 Sep 02:31:05 180 V
16 Sep 02:35:14 1200 V
----------------------------------
Additional images (I-band, 720-s) were also=20
taken at the 1.5m telescope at IAA Sierra=20
Nevada Observatory on 13 Sep (03:00 UT).=20
Internal comparison between the three V-band=20
frames did not reveal any optical variable=20
source in the entire HETE-2 error box. For=20
the 22 X-rays sources detected by the Chandra=20
X-ray Observatory (Butler et al., GCN Circ=20
2716) we detect the following optical=20
counterparts in the co-added V-band image=20
(3 sigma limiting magnitude =3D 25.1):
-------------------------------------
CXO V-band Distance to
source magnitude X-ray position (")
-------------------------------------
#1 21.6 2.0=20
#2 24.0 2.0=20
#3 21.1 2.0=20
#4 24.0 2.0=20
#5 21.9 1.4 =20
#6 21.0 1.7=20
#7 22.9 1.7=20
#8 23.9 1.4=20
#9 23.9 1.8=20
#10 21.1 1.6=20
#11 23.0 1.4=20
#12 24.2 1.9=20
#13 23.6 0.5=20
#14* 23.9 0.9
22.7 1.8=20
#15 23.9 2.1=20
#16** >25.1 -=20
#17 24.5 2.0=20
#18 23.3 0.1=20
#19 >25.1 -=20
#20 >25.1 - =20
#21 >25.1 -=20
#22 >25.1 -=20
--------------------------------------
* Two possible counterparts
* V =3D 22.1 optical source at 3".5=20
--------------------------------------
Optical magnitudes are based on the calibration=20
provided by A. Henden (GCN Circ. 2720)."
This message can be quoted.
- GCN notice #2728
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 notice #2731
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_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, "" 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.
- GCN notice #2733
A. M. Soderberg (Caltech) and D. A. Frail (NRAO) report on behalf of a
larger collaboration:
"On 2004 Sept. 23.24 UT we carried out follow-up observations with the
VLA at 8.46 GHz toward two positions centered on the X-ray afterglow
candidates (GCN 2716; GCN 2731) of XRF 040912 (GCN 2723). Within a
circle of 1-arcsec radius there are no radio sources toward either
X-ray candidate to a 3-sigma limit of 120 microJy.
No further observations are planned."
- GCN notice #2797
G. Stratta (OMP), F. Malacrino (OMP), M. Boer (OHP), A. Klotz (OMP), J-L Atteia (OMP), P. Martin (CFHT), C. Veillet (CFHT), J-C Cuillandre (CFHT) and Lisa Wells (CFHT) communicate:
We observed the HETE WXM error region of XRF 040912 (Butler et al. GCN 2701) with the wide-field imager MegaCam (36 2048 x 4612 pixel CCDs, 1 square degree FOV), mounted on the 3.6-m CFH Telescope.
Two exposures with integration time of 860s each, in the i' band have been performed consecutively starting on October 5.4197 UT (T_grb+22.8 days).
We looked for a possible SN emission for the 22 X-ray sources detected with Chandra
(Butler et al., GCN Circ=2716). The observation results follow:
First exposure (T) Second exposure (T+15min)
------ --------------------------- --------------------------
CXO Distance to i-band Distance to i-band
source X-ray position mag X-ray position mag
(") (")
------ --------------------------- --------------------------
#1 * 1.5 20.60 - -
#2 1.6 22.25 1.5 22.26
#3 1.4 20.17 1.5 20.20
#4 - - - -
#5 1.4 21.21 1.5 21.00
#6 1.5 18.96 1.3 18.99
#7 1.0 21.82 1.1 21.61
#8 1.8 23.02 1.3 23.09
#9 - - - -
#10 3.2 20.74 2.1 20.66
#11 1.0 21.68 0.9 22.44
#12 - - - -
#13 * - - 0.5 22.21
#14 1.2 21.84 1.6 21.39
#15 1.6 22.79 - -
#16 - - - -
#17 - - - -
#18 0.7 21.35 0.6 20.86
#19 - - - -
#20 - - - -
#21 - - - -
#22 - - - -
--------------------------------------------------------------------
* Source was at the CCD line separation and was missed in one image
--------------------------------------------------------------------
We did not consider sources at distances greater than 2.5" from the
X-ray source position.
Our conclusions from these observations are:
1- If source #4 is the afterglow of XRF 040912 (as suggested in GCN 2731),
we do not observed any SN emission down to i=23.2+/0.2 mag at 22.8 days
after the burst event.
2- Source #13, which has been considered as the tentative afterglow of
XRF 040912 (GCN 2728) does not appear to vary from the second Magellan
observation.
We note that source #6 is coincident with an underlying galaxy with i'=19 mag,
it has a decaying behavior in X-rays (Butler et al. GCN=2716) and shows the
highest V-i' color index (V-i'=2.05, V magnitude reported by Gorosabel et al.,
GCN 2724), requiring a very red galaxy, or a rebrightning.
This resemble the case of XRF 040701 (Barraud et al. GCN 2620) for which the
potentially associated Chandra source (Fox et al. GCN 2626) was coincident
with a z=0.2146 emission-line galaxy (Kelson et al. GCN 2631) with lower
limit R~17.9 mag that possibly prevented the observation of a delayed SN
emission, assuming a SN fainter than SN 1998bw and more similar to SN2002ap
or SN1994I (Pian et al. GCN 2638).
Further observations of source #6 are welcome.
A comparison of the two CFHT images that show the nearest objects to the
Chandra sources detected in the i' band, can be found at
http://www.cfht.hawaii.edu/~grb/XRF040912.html
- astro-ph/0610157 from 5 Oct 2006
Stratta: X-ray Flashes or soft Gamma-ray Bursts? The case of the likely distant XRF 040912
In this work, we present a multi-wavelength study of XRF 040912, aimed at
measuring its distance scale and the intrinsic burst properties. We performed a
detailed spectral and temporal analysis of both the prompt and the afterglow
emission and we estimated the distance scale of the likely host galaxy. We then
used the currently available sample of XRFs with known distance to discuss the
connection between XRFs and classical Gamma-ray Bursts (GRBs). We found that
the prompt emission properties unambiguously identify this burst as an XRF,
with an observed peak energy of E_p=17+/-13 keV and a burst fluence ratio
S(2-30keV)/S(30-400keV)>1. A non-fading optical source with R~24 mag and with
an apparently extended morphology is spatially consistent with the X-ray
afterglow, likely the host galaxy. XRF 040912 is a very dark burst since no
afterglow optical counterpart is detected down to R>25 mag (3 sigma limiting
magnitude) at 13.6 hours after the burst. The host galaxy spectrum detected
from 3800A to 10000A, shows a single emission line at 9552A. The lack of any
other strong emission lines blue-ward of the detected one and the absence of
the Ly alpha cut-off down to 3800A are consistent with the hypothesis of the
[OII] line at redshift z=1.563+/-0.001. The intrinsic spectral properties rank
this XRF among the soft GRBs in the E_peak-E_iso diagram. Similar results were
obtained for most XRFs at known redshift. Only XRF 060218 and XRF 020903
represent a good example of instrinsic XRF(i-XRF) and are possibly associated
with a different progenitor population. This scenario may calls for a new
definition of XRFs.
Previous IAU Circulars 