- GCN/BACODINE POSITION NOTICE
TITLE: GCN/INTEGRAL NOTICE
NOTICE_DATE: Thu 12 Aug 04 06:03:34 UT
NOTICE_TYPE: INTEGRAL Wakeup
TRIGGER_NUM: 1901, Sub_Num: 0
GRB_RA: 246.4898d {+16h 25m 58s} (J2000),
246.5722d {+16h 26m 17s} (current),
245.5979d {+16h 22m 23s} (1950)
GRB_DEC: -44.7131d {-44d 42' 46"} (J2000),
-44.7233d {-44d 43' 23"} (current),
-44.6000d {-44d 36' 00"} (1950)
GRB_ERROR: 2.87 [arcmin, radius, statistical only]
GRB_INTEN: 12.28 [sigma]
GRB_TIME: 21724.61 SOD {06:02:04.61} UT
GRB_DATE: 13229 TJD; 225 DOY; 04/08/12
SC_RA: 250.81 [deg] (J2000)
SC_DEC: -46.25 [deg] (J2000)
SUN_POSTN: 142.28d {+09h 29m 08s} +14.85d {+14d 51' 16"}
SUN_DIST: 110.48 [deg]
MOON_POSTN: 98.19d {+06h 32m 46s} +27.62d {+27d 37' 28"}
MOON_DIST: 149.58 [deg]
GAL_COORDS: 337.90, 3.11 [deg] galactic lon,lat of the burst
ECL_COORDS: 252.10,-22.72 [deg] ecliptic lon,lat of the burst
COMMENTS: INTEGRAL GRB Coordinates.
- GCN/BACODINE POSITION NOTICE
TITLE: GCN/INTEGRAL NOTICE
NOTICE_DATE: Thu 12 Aug 04 06:42:02 UT
NOTICE_TYPE: INTEGRAL Offline
TRIGGER_NUM: 1901, Sub_Num: 1
GRB_RA: 246.5228d {+16h 26m 05s} (J2000),
246.6052d {+16h 26m 25s} (current),
245.6308d {+16h 22m 31s} (1950)
GRB_DEC: -44.7087d {-44d 42' 30"} (J2000),
-44.7189d {-44d 43' 07"} (current),
-44.5958d {-44d 35' 44"} (1950)
GRB_ERROR: 2.00 [arcmin, radius, statistical only]
GRB_INTEN: 12.28 [sigma]
GRB_TIME: 21724.61 SOD {06:02:04.61} UT
GRB_DATE: 13229 TJD; 225 DOY; 04/08/12
SC_RA: 250.81 [deg] (J2000)
SC_DEC: -46.25 [deg] (J2000)
SUN_POSTN: 142.28d {+09h 29m 08s} +14.85d {+14d 51' 16"}
SUN_DIST: 110.51 [deg]
MOON_POSTN: 98.19d {+06h 32m 46s} +27.62d {+27d 37' 28"}
MOON_DIST: 149.60 [deg]
GAL_COORDS: 337.92, 3.10 [deg] galactic lon,lat of the burst
ECL_COORDS: 252.13,-22.72 [deg] ecliptic lon,lat of the burst
COMMENTS: INTEGRAL GRB Coordinates.
- red DSS finding chart
ps-file
- GCN notice #2640
D. Gotz, S. Mereghetti (IASF, Milano), N. Mowlavi, M. Beck, J.Borkowsk
(ISDC) on behalf of the IBAS Localization Team report:
A 20 s long GRB has been detected with the INTEGRAL Burst Alert System
(IBAS) on August 12 at 06:01:50 UT. The GRB has been detected with
IBIS/ISGRI in the 15-200 keV band (IBAS Alert # 1901)
Its coordinates (J2000) are:
R.A. 16h 26m 05s
Dec. -44deg 42' 32''
with an uncertainty of 2 arcmin (90% c.l. radius)
The preliminary peak flux in the 20-200 keV range is about 0.6
photons/cmsq/s (5E-8 erg/cmsq/s) (1 s integration time).
A preliminary spectral analysis inidcates that this event is X-ray rich.
This message can be cited.
- GCN notice #2642
B. E. Cobb and C. D. Bailyn (Yale), part of the larger SMARTS
consortium, report:
Using the ANDICAM instrument on the 1.3m telescope at CTIO, we
obtained optical/IR imaging of the error region of GRB 040812
(Gotz et al. GCN 2640) beginning ~18.4 hours post-burst
(2004-08-13 00:25 UT). Optical imaging in B,V,R and I has a
field of view of 6'x6' and, therefore, covers the entire GRB
error circle. IR imaging in J, H, K and Y has a smaller field
of view and covers a region totalling 3 square arcminutes in
the middle of the quoted error region. Several dithered images
were obtained in each filter, with total summed exposure times
of 180s in each of BRIYJK and 120s in each of H and V.
Preliminary visual comparison of the optical images to the SDSS
and the IR images to 2MASS frames does not reveal any new sources
to the limit of the comparison frames.
- GCN notice #2643
A. M. Soderberg (Caltech) reports on behalf of a larger
Caltech/NRAO/Carnegie collaboration:
"We have observed the error box of GRB 040812 (GCN 2640) with the Very
Large Array on 2004 August 14.15 UT (t ~ 2 days since burst). At 8.5
GHz we detect a 0.45 mJy source at location:
RA: 16:26:08.5 Dec: -44:41:04.0 (J2000)
with a positional uncertainty of 8 arcsec (radius). The source is
also detected at 4.9 GHz with a flux density of 0.79 mJy giving
a spectral index of beta ~ -1 between the two observing bands.
This spectral index is inconsistent with those measured for
early radio afterglows.
No other sources are detected within the error box with
a 2 sigma detection limit of 0.14 and 0.16 mJy at 4.9 and 8.5
GHz, respectively.
Further observations are planned."
- GCN notice #2644
E. Berger (Carnegie Observatories), D.B. Fox, S.R. Kulkarni (Caltech),
Wojtek Krzeminski and Mario Hamuy (Las Campanas Observatory, Carnegie)
report on behalf of a larger collaboration:
"We imaged the 2-arcmin error circle of GRB 040812 (GCN #2640) with the
Low-Resolution Imaging Spectrometer on the Keck-I telescope 47 and 104
minutes after the burst, and with the Du Pont 2.5-m telescope at Las
Campanas Observatory (LCO) 1.75 days after the burst. All observations
were taken in the I-band (Galactic extinction, A_I~2.3 mag). Within the
8-arcsec radius error cirle of the VLA source detected by Soderberg (GCN
#2643) we find several sources, but none exhibit significant variability
either between the two Keck epochs or between the Keck and LCO
observations. Visual comparison of the two Keck epochs do not reveal the
presence of a strongly fading source within the entire 2-arcmin INTEGRAL
error circle."
This message may be cited
- GCN notice #2645
E. Berger (Carnegie Observatories), D.B. Fox, S.R. Kulkarni (Caltech),
Wojtek Krzeminski and Mario Hamuy (Las Campanas Observatory, Carnegie)
report on behalf of a larger collaboration:
"We imaged the 2-arcmin error circle of GRB 040812 (GCN #2640) with the
Low-Resolution Imaging Spectrometer on the Keck-I telescope 47 and 104
minutes after the burst, and with the Du Pont 2.5-m telescope at Las
Campanas Observatory (LCO) 1.75 days after the burst. All observations
were taken in the I-band (Galactic extinction, A_I~2.3 mag). Within the
8-arcsec radius error cirle of the VLA source detected by Soderberg (GCN
#2643) we find several sources, but none exhibit significant variability
either between the two Keck epochs or between the Keck and LCO
observations. Visual comparison of the two Keck epochs do not reveal the
presence of a strongly fading source within the entire 2-arcmin INTEGRAL
error circle."
This message may be cited
- GCN notice #2648
S. Patel (USRA/NSSTC), C. Kouveliotou (NASA/MSFC,NSSTC), S. Mereghetti,
D. Gotz (IASF-Milano), N. Lund, J. Chenevez (Danish Space Research
Institute), P. Ubertini (IASF-Rome), E. van den Heuvel (University of
Amsterdam), K. Hurley (UCB), report on behalf of a larger Integral team:
We observed with Chandra/ACIS-S the error box of the Integral GRB 040812
(Gotz et al. 2004, GCN 2640). The observation started at 2004-08-17
7:08:22 UT, approximately 5 days after the trigger, and lasted for 10
ks. We find 4 sources above SNR=2.6 within a 2' radius (90% c.l.)
centered at the refined Integral/IBIS location (RA=246.50, DEC=-44.70).
No. RA Dec Counts* SNR
1 16 26 0.47 -44 41 22.6 9 2.8
2 16 26 2.25 -44 43 49.4 57 6.9
3 16 26 6.48 -44 43 20.8 10 2.9
4 16 26 8.44 -44 41 25.2 33 5.0
*0.5-8.0 keV band
Within the Jem-X error region centered at RA=16:25:55.0, Dec=-44:42:40
(1.7' preliminary error radius) which is consistent with the IBIS
location, we detect no source above SNR=2.6. Our source detection
method found 3 sources above SNR=1.7 in this region as given below.
These sources become more significant when we increase the search
energy band to 0.1-10 keV.
No. RA Dec Counts* SNR
5 16 25 54.65 -44 42 49.4 6 1.9
6 16 25 58.73 -44 41 47.0 4 1.9
7 16 26 1.21 -44 42 46.6 4 1.9
*0.5-8.0 keV band
All coordinates are given in J2000.
None of these sources exhibits significant variability within the 10ks
observation. No X-ray source was found at the position of the radio
source reported by Soderberg et al (2004, GCN 2643). At this point we
cannot identify any of these sources as the counterpart of GRB040812,
and we strongly encourage searches for optical variability. Another
planned 10 ks Chandra DDT observation may reveal the GRB counterpart.
We are grateful to the Chandra Science Data Center for processing the
data rapidly and in particular to Harvey Tananbaum and Andrea Prestwich
for approving this DDT observation.
- GCN notice #2649
S. Campana and A. Moretti (INAF-Osservatorio di Brera) report:
"We analyzed the Chandra ACIS-S data of the XRF040812 (Gotz et al. 2004,
GCN 2640) region. We carried out spectral analysis of the second source
(CXOJ162602.3-444349) in the Patel et al. (2004, GCN 2648), the only one
with a sizable number of counts. The source is extremely hard with a
photon index of 0.1+\-0.6 (90% confidence level), fixing the column
density to the Galactic value of 5.3x10^21 cm-2. Leaving free the column
density the error on the photon index increases to 0.1_(-1.0)^(+1.5).
This hard photon index is typical of GRB X-ray afterglows. The
unabsorbed 0.5-10 keV source flux is 2.53E-13 erg cm-2 s-1. The
following Chandra observation (August 22, 2004) will allow to assess
the afterglow nature of CXOJ162608.4-444125."
We acknowledge the extraordinary effort by the CXC in providing rapid
processing of this challenging data-set, thereby enabling this report.
This message can be cited.
- GCN notice #2650
E. Berger (Carnegie Observatories) reports on behalf of a larger
collaboration:
"We inspected the positions of Chandra sources CXO 1-7 (GCN #2648),
detected in the error circle of GRB 040812 (GCN #2640), in our Keck LRIS
and Las Campanas Du Pont 2.5-m I-band images (GCN #2645):
CXO# RA Dec Counterpart?
---------------------------------------------------
1 16 26 00.47 -44 41 22.6 star
2 16 26 02.25 -44 43 49.4 ---- *
3 16 26 06.48 -44 43 20.8 star
4 16 26 08.44 -44 41 25.2 none **
5 16 25 54.65 -44 42 49.4 star/galaxy
6 16 25 58.73 -44 41 47.0 star/galaxy
7 16 26 1.21 -44 42 46.6 star
* CXO-2 is located about 20" away from a very bright star, and this
position is saturated in all of our images
** CXO-4 is located about 2" away from a galaxy/star
In addition, none of the optical counterparts (excluding CXO-2) exhibit
any significant variability either between the two Keck epochs (taken 47
and 104 minutes after the burst) or between the Keck and LCO observations
(taken 1.75 days after the burst)."
- GCN notice #2651
P. D'Avanzo, A. Cucchiara, G. Tagliaferri, D. Malesani, D. Fugazza, S.
Covino, S. Campana, on behalf of a larger collaboration, report
We observed the field of XRF 040812 (Gotz et al. GCN 2640) with the
ESO-VLT on Aug 12.9795 UT (~17.5 hours after the GRB) and Aug 13.9844 UT
(~41.5 hours after the GRB). Observations were performed in the I-band,
under good observing conditions.
Ten 1-minute exposures were taken in both nights. The seeing was 1.1" on
Aug 12 and 0.8" on Aug 13. We estimate the limiting magnitude to be I ~ 24.
To avoid saturation from the bright star close to the center of the field,
we had to place on occulting bar, which hides 9% of the error box.
We briefly report about the Chandra X-ray sources (Patel et al. GCN 1648).
Source #1, #3 and #7 are visible in the DSS, as well as in our images.
Source #2 (see also Campana & Moretti, GCN 1649) is not detected in the
DSS and, moreover, in our images it is falling just behind the occulting
bar.
Source #4 is close (~1.5"), but not coincident, with a faint source in the
VLT images, not visible in the DSS.
Source #5, #6 are visible in our images but not in the DSS.
None of the counterparts of the Chandra sources shows any significant
variability. Moreover we don't have evidence of candidates in the whole
Integral error-box (Gotz et al. GCN 2640), in particular at the radio
position (Soderberg GCN 2643).
PSF-matched photometry was performed with DAOPHOT and image subtraction
with ISIS.
We thank the ESO staff at Paranal for carefully performing the
observations.
This message may be cited.
- GCN notice #2653
C.H. Ishwara Chandra and A.P. Rao (National Centre for Radio Astrophysics,
Pune, India), L. Resmi and D. Bhattacharya (Raman Research Institute,
Bangalore, India) report:
We imaged the XRF040812 field at 1280 MHz on Aug 16, 2004 using the
Giant Metrewave Radio Telescope. The following previously uncatalogued
sources were detected within a 15' field of view centered at the
position of the VLA source reported by Soderberg et al (2004, GCN 2643).
No. RA (J2000) Dec (J2000) flux (mJy)
1. 16 26 08.404 -44 41 27.2 0.8
2. 16 26 15.674 -44 43 56.2 2.5
3. 16 26 13.025 -44 47 08.8 1.9
4. 16 26 08.795 -44 47 46.0 1.0
5. 16 26 09.448 -44 47 51.0 1.9
Typical astrometric uncertainties in the above coordinates are
expected to be better than an arcsec, but ionospheric refraction due to
low elevation could introduce a systematic shift up to 2 arc sec.
All sources except no. 5 are point sources. Source no. 5 shows extended
emission.
We note that source no. 1 in the above list is within 2 arc sec
of source no. 4 in the list of Chandra sources reported by Patel
et al (2004, GCN 2648), and could be coincident with it.
No detectable emission was found at the location of the VLA source
(GCN 2643).
At present we are unable to determine the extent of variability,
if any, of the above sources.
This message may be cited.
- GCN notice #2655
S. Patel (USRA/NSSTC), C. Kouveliotou (NASA/MSFC,NSSTC), S. Mereghetti,
D. Gotz (IASF-Milano), N. Lund, J. Chenevez (Danish Space Research
Institute), P. Ubertini (IASF-Rome), A. Levan (U. Leicester),
E. van den Heuvel (University of Amsterdam), K. Hurley (UCB), report on
behalf of a larger Integral team:
We observed with Chandra/ACIS-S the error box of the Integral GRB 040812
(Gotz et al. 2004, GCN 2640) for a second time starting on 2004-08-22 9:55
UT,
approximately 10 days after the trigger for 10 ks. We have compared the
sources reported in our earlier GCN on the first CXO observation (Patel et
al., 2004, GCN 2648) with the second CXO image, applying a SNR>2 selection
threshold. The results are shown in the Table below.
No. RA Dec Counts(1)* SNR Counts(2) SNR
1 16 26 0.47 -44 41 22.6 9 2.8 -- --
2 16 26 2.25 -44 43 49.4 57 6.9 38 5.4
3 16 26 6.48 -44 43 20.8 10 2.9 10 2.7
4 16 26 8.44 -44 41 25.2 33 5.0 33 5.2
5 16 26 1.71 -44 43 27.9 -- --- 16 3.7
*0.5-8.0 keV band
All coordinates are given in J2000.
We do not detect source #1 above SNR=2.0; a search in the corresponding
error
region in the second epoch CXO image reveals 5 net counts at this location.
We
conclude that there is no significant variation in that source within
statistics. Source #2 decayed with an index of approximately 0.6 between the
two CXO observations; this source, thus, seems to be most likely the
candidate
of the GRB 040812 afterglow, as also pointed out by Campana et al. 2004
(GCN 2649). Finally, a new source (#5) appeared within the IBIS error box;
inspection of the first image reveals 3 net counts at this location,
indicating a variable source.
We detect two of the radio sources (#2 and #4) reported by Ishwara Chandra
et al. 2004 (GCN # 2653) at the same flux level in both CXO observations.
We are grateful to the Chandra Science Data Center for processing the
data rapidly and in particular to Harvey Tananbaum and Andrea Prestwich
for approving this DDT observation.
- GCN notice #2656
S. Campana and A. Moretti (INAF-Osservatorio astronomico di Brera) report on
behalf of a larger team:
"We analyzed the second Chandra ACIS-S observation of the XRF040812
(Gotz et
al. 2004, GCN 2640). We carried out spectral analysis of our previous
afterglow candidate (CXOJ162602.3-444349, Campana & Moretti GCN 2649,
see also
Patel et al. GCN 2648, 2655). The source is still very hard with a power law
photon index of 0.9+/-0.6 (fixing the column density to the Galactic
value of
5.3x10^21 cm-2 and using Cash statistics in the XSPEC fit). The spectrum is
slightly softer than in the first observation (Campana & Moretti GCN
2649). The unabsorbed 0.5-10 keV source flux is 9.30x10^-14 erg cm-2 s-1 a
factor of ~3 lower than in the previous Chandra observation. A constant
temporal evolution is not consistent with the data at a ~4.5 sigma level. A
power law decay describes better the temporal evolution with a time decay as
t^-1.4(+/-0.6) (90% confidence level, note that this is different from the
Patel et al. GCN 2655, since we fitted the flux evolution and not the counts
evolution)."
This message can be cited.
- GCN notice #2824
S. Kulkarni, A. Soderberg and D. Fox report on behalf of the
Caltech/Carnegie/NRAO collaboration:
"As part of our large HST program on GRBs and XRFs, we have used ACS to
observe the fields of XRF 040701 and XRF 040812. Observations were
taken in the F625W (r) and F775W (i) filters 39 and 60 days after the
burst (XRF040701) and 32 and 54 days after the burst (XRF040812).
Comparison of the two epochs for each XRF does not reveal a variable
source within the 1-arcsec position of the putative Chandra X-ray
afterglow candidates (GCNs 2630 and 2655 for XRFs 040701 and 040812,
respectively). Our 3-sigma limits are the following:
XRF Filter Limit:
==============================================
040701 F625W 27.5
F775W 27.0
040812 F625W 27.5
F775W 27.0
- astro-ph/0612644 from 21 Dec 2006
DAvanzo: Discovery of the optical afterglow of XRF 040812: VLT and Chandra observations
We present Chandra and VLT observations of the X-Ray Flash XRF 040812. The
X-ray analysis reveals with high precision the position of a hard, fading
source. A careful analysis of our I-band VLT images taken starting 17 hours
after the burst led to the discovery of the optical afterglow superimposed to a
bright (I=21.5) host galaxy. The optical afterglow is seen decaying with an
index of 1.1. We do not detect any jet break and supernova rebrightening in the
optical light curve. The bright apparent luminosity of the host galaxy allows
us to get a rough estimate of the redshift, comparing with a set of GRB/XRF
host galaxies with known luminosity and redshift. Such comparison suggests a
redshift of XRF 040812 in the range 0.3<z<0.7. This is also consistent with the
lack of emission features in our spectrum. The low inferred redshift is in
agreement with the idea that XRFs are low-luminosity, closer events.
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