- GCN/BACODINE POSITION NOTICE
TITLE: GCN/HETE BURST POSITION NOTICE
NOTICE_DATE: Tue 03 Sep 02 13:56:24 UT
NOTICE_TYPE: HETE Ground Analysis
TRIGGER_NUM: 2314, Seq_Num: 1
GRB_DATE: 12520 TJD; 246 DOY; 02/09/03
GRB_TIME: 36337.96 SOD {10:05:37.96} UT
TRIGGER_SOURCE: Trigger on the 2-30 keV band.
WXM_SIG/NOISE: 333300 sig/noise on a 5.120 [sec] timescale
SC_-Z_RA: 341 [deg]
SC_-Z_DEC: -8 [deg]
SC_LONG: 180 [deg East]
WXM_CNTR_RA: 342.354d {+22h 49m 25s} (J2000),
342.390d {+22h 49m 34s} (current),
341.680d {+22h 46m 43s} (1950)
WXM_CNTR_DEC: -20.900d {-20d 53' 59"} (J2000),
-20.886d {-20d 53' 08"} (current),
-21.165d {-21d 09' 52"} (1950)
WXM_MAX_SIZE: 33.32 [arcmin] diameter
WXM_LOC_SN: 4 sig/noise (pt src in image)
WXM_IMAGE_SN: X= 2.2 Y= 2.5 [sig/noise]
WXM_LC_SN: X= 6.0 Y= 6.9 [sig/noise]
SUN_POSTN: 162.23d {+10h 48m 54s} +7.54d {+07d 32' 18"}
SUN_DIST: 166.65 [deg]
MOON_POSTN: 112.48d {+07h 29m 56s} +24.93d {+24d 55' 39"}
MOON_DIST: 134.10 [deg]
MOON_ILLUM: 18 [%]
GAL_COORDS: 38.89,-61.52 [deg] galactic lon,lat of the burst
ECL_COORDS: 335.71,-12.40 [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: HETE GRB Coordinates.
COMMENTS: Probable GRB.
COMMENTS: Burst_Validity flag is true.
COMMENTS: WXM data refined since S/C_Last Notice.
COMMENTS: Weak, soft burst, localized in 2-5 keV band
COMMENTS: Likely an XRF
COMMENTS: Ignore the "Definite GRB" comment above.
- GCN/BACODINE POSITION NOTICE
TITLE: GCN/HETE BURST POSITION NOTICE
NOTICE_DATE: Tue 03 Sep 02 17:00:34 UT
NOTICE_TYPE: HETE Ground Analysis
TRIGGER_NUM: 2314, Seq_Num: 2
GRB_DATE: 12520 TJD; 246 DOY; 02/09/03
GRB_TIME: 36337.96 SOD {10:05:37.96} UT
TRIGGER_SOURCE: Trigger on the 2-30 keV band.
SC_-Z_RA: 341 [deg]
SC_-Z_DEC: -8 [deg]
SC_LONG: 180 [deg East]
SXC_CNTR_RA: 342.252d {+22h 49m 01s} (J2000),
342.288d {+22h 49m 09s} (current),
341.579d {+22h 46m 19s} (1950)
SXC_CNTR_DEC: -20.930d {-20d 55' 47"} (J2000),
-20.916d {-20d 54' 56"} (current),
-21.195d {-21d 11' 40"} (1950)
SXC_CORNER1: 342.2000 -20.6600 [deg]
SXC_CORNER2: 342.1400 -20.7100 [deg]
SXC_CORNER3: 342.2950 -21.1700 [deg]
SXC_CORNER4: 342.3750 -21.1800 [deg]
SXC_MAX_SIZE: 32.70 [arcmin] diameter
SXC_LOC_SN: 3 sig/noise (pt src in image)
SUN_POSTN: 162.23d {+10h 48m 54s} +7.54d {+07d 32' 18"}
SUN_DIST: 166.62 [deg]
MOON_POSTN: 112.48d {+07h 29m 56s} +24.93d {+24d 55' 39"}
MOON_DIST: 134.20 [deg]
MOON_ILLUM: 18 [%]
GAL_COORDS: 38.77,-61.44 [deg] galactic lon,lat of the burst
ECL_COORDS: 335.61,-12.39 [deg] ecliptic lon,lat of the burst
COMMENTS: Definite GRB.
COMMENTS: Burst_Validity flag is true.
COMMENTS: HETE GRB Coordinates.
COMMENTS: Possible XRF
COMMENTS: The WXM & SXC positions are consistant; overlapping error boxes.
COMMENTS: Burst_Validity flag is true.
COMMENTS: WXM data refined since S/C_Last Notice.
COMMENTS: SXC data refined since S/C_Last Notice.
COMMENTS: A one-dimensional SXC localization has reduced
COMMENTS: the WXM 16' radius circle to a box measuring 32' x 4'.
COMMENTS: Ignore the "Definite GRB" comment, above.
- GCN notice #1530
G. Ricker, J-L Atteia, N. Kawai, D. Lamb, and S. Woosley on behalf of
the HETE Science Team;
R. Vanderspek, J. Doty, J. Villasenor, G. Crew, G. Monnelly, N. Butler,
T. Cline, J.G. Jernigan, A. Levine, F. Martel, E. Morgan, G. Prigozhin,
G. Azzibrouck, J. Braga, R. Manchanda, and G. Pizzichini, on behalf of
the HETE Operations and HETE Optical-SXC Teams;
C. Graziani, Y. Shirasaki, M. Matsuoka, T. Tamagawa, K. Torii,
T. Sakamoto, A. Yoshida, E. Fenimore, M. Galassi, T. Tavenner, and
T. Donaghy, on behalf of the HETE WXM Team;
M. Boer, J-F Olive, J-P Dezalay, and K. Hurley on behalf of the HETE
FREGATE Team;
write:
At 10:05:37.96 UTC (36337.96 s UT) on 3 Sep 2002, the HETE WXM and SXC
instruments detected event H2314, an X-ray flash. The WXM flight
localization was correct but was not set out as a GCN Notice because
events which trigger only the WXM are currently not sent out, in order
not to overwhelm the community with X-ray burst localizations. Ground
analysis of the WXM data for the burst produced a refined location,
which was reported in a GCN Position Notice at 13:56:24 UT, 231 minutes
after the burst. The WXM location can be expressed as a 90% confidence
circle that is 16.6 arcminutes in radius and is centered at
RA = 22h 49m 25s, Dec = -20o 53' 59" (J2000).
Ground analysis of the SXC data for the burst produced a
one-dimensional localization, which -- when combined with the WXM
localization -- produced a further refinement in the location. This
refined location was reported in a GCN Position Notice at 17:00:34 UT,
7 hrs after the burst. The refined location produced by combining the
SXC and WXM localizations can be expressed as a 90% confidence
quadrilateral that is 4 arcminutes in width and ~31 arcminutes in
length, is centered at
RA = 22h 49m 01s, Dec = -20o 55' 47" (J2000).
and is defined by
RA = 22h 48m 48.00 -20o 39' 36.0"
RA = 22h 48m 33.60 -20o 42' 36.0"
RA = 22h 49m 10.80 -21o 10' 12.0"
RA = 22h 49m 30.00 -21o 10' 48.0"
In the WXM 2-25 keV band, the burst had a duration of ~3.3 seconds.
The WXM localization SNR was ~10. The SXC localization SNR was ~3.
Further information (including a light curve) for GRB020903 is provided
at the following URL:
http://space.mit.edu/HETE/Bursts/
This message is citable.
- GCN notice #1531
XRF 020903, optical observations
P. Tristram (Univ. of Auckland)
A. J. Castro-Tirado (IAA-CSIC, Granada)
J. Gorosabel (IAA-CSIC, Granada)
J. M. Castro Cer=F3n (ROA, San Fernando)
P. Kilmartin (Mt. John Univ. Observatory)
Y. Furuta (Univ. of Nagoya)
Ph. Yock (Univ. of Auckland)
communicate:
"Following the detection of the X-ray flash 020903 by HETE (Ricker
et al. GCN Circ. 1530), we have imaged the entire error box with
the 0.6-m (+MOA camera) at Mt. John Observatory in a wide B-
and wide R-band filters (600-s and 1200-s respectively) starting
on Sep 3.5944 UT (i.e. 4.18 hr after the event). Comparison of the
frames with the DSS-2 (R-band) reveals no optical transient down
to the DSS-2 limiting magnitude."
- GCN notice #1533
P.A. Price, B.P. Schmidt (RSAA, ANU) and T.S. Axelrod (Arizona) report:
We have observed the error-circle of XRF 020903 (Ricker et al. GCN #1530)
with the robotic 50-inch telescope at Mount Stromlo Observatory beginning
at Sep 4.42 UT. Observations consisted of 3x300 sec exposures in R_MACHO
and cover the entire error circle to a limiting magnitude of approximately
R ~ 19.8 mag. We do not identify any source in our images not present on
the DSS2 upon visual inspection. Further observations are planned.
This message may be cited.
- GCN notice #1535
E.Pavlenko (CrAO), V.Rumyantsev (CrAO) and A.Pozanenko (IKI)
report:
We have imaged of the error box of XRF 020903 (Ricker et al. GCN #1530)
with the 0.38-m Cassegrain telescope of Crimean Astrophysical Observatory
(field 7x10 arcminutes).
We obtained several frames which include the center of error box
and partially covered its area on 2002 Sept. 3.9203
(12h after the burst) - 3.9540 UT.
We did not identify any afterglow candidate by visual comparison with the DSS2
to a limit approximately R ~ 17.4 mag.
Images will by posted shortly in
http://grb.rssi.ru/XRF020903.
This message may be cited.
- GCN notice #1537
M. Uemura, R. Ishioka, T. Kato (Kyoto U) and H. Yamaoka (Kyushu U)
report on behalf of VSNET-grb collaboration:
"We have performed a full analysis of unfiltered CCD images
of XRF 020903 (GCN 1530) taken with 25-cm telescope at Kyoto.
The observation starts on Sept. 3.595 UT, i.e., 4.2 hours after
the flash detection. We imaged the central region of initial
XWM error circle, so the coverage of WXM+SXC error box is
as rather small as 10%. Our field of view is described in:
http://www.rc.kyushu-u.ac.jp/~yamaoka/XRF020903/FOV.gif .
It contains the central region of the cluster Abell 2487.
A stacked image (30s x 60 exposures), whose limiting magnitude
is R ~ 17.5 compared with USNO-A2.0 r mag, revealed no definite
new source within our image compared with DSS 2 red image.
(Note: XRF 020903 occurred at a location very close to GRB 990527
(GCN 347). The WXM+SXC error box of XRF 020903, however, does
not overlap the IPN error box of GRB 990527, as shown in
FOV.gif mentioned above.)"
This message may be cited.
- GCN notice #1554
A.M. Soderberg, P.A. Price, D.W. Fox, S.R. Kulkarni, S.G. Djorgovski, E.
Berger and F. Harrison, S. Yost (Caltech); M. Hamuy and S. Shectman
(OCIW); and N. Mirabal and J. Halpern (Columbia) report:
We imaged the entire error-box of XRF 020903 with the Palomar 200-inch
telescope + Large Format Camera (LFC) on Sep 4.3 UT (epoch 1) and Sep 10.3
UT (epoch 2) in Steidel R-band. Visual comparison of these images with
the Digitised Sky Survey and with each other did not reveal any obvious
transient. Recently, we undertook a more detailed analysis, namely
PSF-matched image subtraction of these two epochs, and found
an optical transient (OT) located at coordinates:
RA: 22:48:42.34 Dec: -20:46:09.3 J2000
with a bright elliptical galaxy 4 arcsec SE (hereafter G2).
The source is also present in images from the MSO 50-inch telescope
(GCN #1533) when the second epoch LFC image is subtracted.
Upon discovery of the OT, we immediately pursued further observations,
thereby obtaining a third epoch of imaging with the MDM 1.3-meter
telescope on Sep 28.3 UT in the R-band. Initial photometry demonstrates
that the object has re-brightened by ~ 0.3-0.4 mag between epochs 2 and
3. We propose that this optical rebrightening is from an associated
supernova, peaking between ~7-24 days after the initial XRF trigger.
Spectroscopic observations by M. Hamuy and S. Shectman for the source were
also obtained with the Magellan 6.5m telescopes (Baade+LDSS2, Clay+B&C) on
Sep 28.1 UT. We detect narrow emission lines from an underlying host
galaxy (hereafter G1) are (Halpha, Hbeta, Hgamma, [O III], [Ne III],
[O II]) at a mean redshift of z = 0.25 +/- 0.01. Subtraction of the
emission lines reveals a continuum that is consistent with a SN-like
transient near maximum. In particular, the spectrum reveals
deficit of emission at rest wavelengths < 4000A, as would be expected
from a SN.
Spectra of G2 (R ~ 17 mag) reveal it to be an elliptical galaxy at
z = 0.23 and therefore is not associated with the optical transient.
If the OT is indeed associated with XRF020903, it is the first known
optical afterglow of an XRF, and may be the most nearby cosmological high
energy transient known yet. Parenthetically we note that microlensing
from G2 may result in sharp variations of the light curve (see
Garnavich, Loeb and Stanek, 2000). We encourage further monitoring of
this OT/SN.
A web page summarizing the discovery and subsequent observations can be
found at:
http://www.astro.caltech.edu/~ams/XrF.html
This message may be cited.
- GCN notice #1555
E. Berger, S. R. Kulkarni, D. A. Frail, A. Soderberg, P. A. Price, D. W.
Fox, F. A. Harrison, and S. Yost report on behalf of the larger
Caltech-NRAO-CARA GRB collaboration:
Following the discovery of the optical transient of GRB 020903 (GCN #1530)
by Soderberg et al. (GCN #1554), we observed the position of the OT with
the VLA on Sep. 27.22 UT. We detect a bright radio source at the position
of the OT, with a flux of 1.1 mJy at 8.46 GHz. The source is not detected
in the NRAO VLA Sky Survey (NVSS; Condon et al. 1998, AJ, 115, 1693) above
their flux limit of 1 mJy at 1.4 GHz. Observations undertaken today (Sep.
29.11 UT) show that the source is fading with a flux of 0.7 mJy at 8.46
GHz.
The variable radio counterpart lends supports to the identification of the
optical transient (OT) reported by Soderberg et al. as the afterglow of
XRF 020903. Unlike the optical emission, the radio emission is dominated
by the afterglow.
The isotropic, prompt energy release of XRF 020903 (using the redshift of
z=0.25, GCN #1554, and a rough estimate of the fluence detected by WXM;
see the HETE-2 web page: http://space.mit.edu/HETE/Bursts/GRB020903/) is
well below those of typical cosmological GRBs but higher than that of GRB
980425. Therefore, the energy in relativistic ejecta of XRF 020903 is
intermediate between that of SN1998bw, about 10^49 erg, as inferred from
the radio emission (Kulkarni et al. 1998, Nature, 395, 663), and that of
typical cosmological GRBs. Finally, the ratio of energy in the
relativistic ejecta to the energy in the SN of XRF 020903 is well below
those of cosmological GRBs (typically 1-10), but higher than SN1998bw
(~0.01). These arguments suggest that XRF 020903 is a "transition" object
-- a link between GRB 980425 and comsological GRBs.
Scaling the ratio of radio to X-ray luminosity of SN1998bw to XRF 020903,
we predict detectable X-ray emission on this timescale, which may be an
additional robust indicator of the relativistic energy in the ejecta.
See http://www.astro.caltech.edu/~ams/XrF.html for a full discussion.
- GCN notice #1556
A. Gal-Yam (Tel Aviv University) reports:
"We have extracted from the USNO plate archive
(http://ftp.nofs.navy.mil/data/fchpix/) two blue plates, covering the
location of the variable object possibly connected with XRF 020903,
reported by Soderberg et al (GCN 1554). Inspecting these plates we find
the following:
1) A plate obtained on UT 1977.6 reveals an object, coincident with the
variable source reported by Soderberg et al. The B-band magnitude of this
object appears to be about one magnitude fainter than that of the nearby
galaxy noted as "G2" by these authors.
2) Comparison of the 1977 plate with the (much poorer) POSSI blue plate
obtained on 1954.6 may suggest a variation of the flux ratio between the
source coincident with the Soderberg et al. variable, and the galaxy G2,
with G2 being brighter on the 1977 plate, but possibly fainter than the
source reported by Soderberg et al., in 1954. This may hint that this
source was variable in the past. We stress, however, that the 1954 data
are quite poor, so past variability can not be ascertained at this stage.
GIF Cutouts from both plates, showing the area around the Soderberg et al.
variable, can be obtained from ftp://wise3.tau.ac.il/pub/avishay/xrf.
These can be compared with the Palomar data shown by Soderberg at
http://www.astro.caltech.edu/~ams/XrF.html.
The source detected on the 1977 plate may be hard to interpret as a
possible "host" galaxy for the Soderberg et al. transient, even if we
disregard its possible past variability. Soderberg et al. report that this
source is not detected on POSSII red plates, and estimate a magnitude of
R=22 from their OT+SN+host model. This fact can be reconciled with the
1977 B-band data, showing this object only about 1 magnitude fainter than
G2 (which has R=17 mag), if this object has a very blue B-R color.
However, this appears to be in contradiction with the Magellan spectrum
presented by Soderberg et al., which is flat, or possibly even red, in
B-R.
An alternative explanation fitting both the archival analysis and the
entire data set presented by Soderberg et al. and Berger et al (GCN 1555)
is that this source is a variable radio-loud AGN. We have recently shown
(Gal-Yam et al. 2002, PASP, 114, 587) that such objects can appear to be
very similar to optical transients associated with GRBs. Further
inspection of archival data, as well as further observations (B-band
especially), can distinguish between an OT+SN model, and an AGN, according
to their variability properties.
If an AGN, the source discovered by Soderberg et al. may still be related
to XRF 020903. However, in that case, a SN component no longer seems to be
required.
Until this issue is clarified, we urge some caution in interpreting the
Soderberg et al. data set as evidence for a connection between XRF 020903
and a SN.
This work has made use of the USNOFS Image and Catalogue Archive operated
by the United States Naval Observatory, Flagstaff Station
(http://www.nofs.navy.mil/data/fchpix/)."
- GCN notice #1557
A. Fruchter, L. Strolger, B. Mobasher, J. Rhoads, A. Levan, I. Burud
(STScI), A. Becker (Lucent) report for a larger collaboration:
We observed the field of XRF 020903 on both September 3.1 and 9.1 (UT) using
the Mosaic imager on the CTIO 4-m telescope. Images were taken in B, R and I
on the first night and in only R on the second. An image subtraction
performed shortly after the second night showed no variability consistent with
that expected of a GRB/XRF.
In light of the report of the possible discovery of a counterpart to this
object (GCN 1554) we have re-examined our data. We find that the object
cited as the possible counterpart declined by approximately 0.2 mags in R
between our two epochs.
Unfortunately, we do not have a reliable absolute calibration of the field at
this moment. We expect that a better calibration and more complete analysis
will be available on a relatively short timescale.
- GCN notice #1558
The date of the first observations of GRB 020903 on the CTIO 4-m reported in
GCN 1557 should have read "September 4.1".
- GCN notice #1560
M. Stefanon, S. Covino, D. Malesani (INAF, Merate Obs., Milan, I), N.
Masetti (IASF/CNR, Bologna, I.), G. Temporin (Inst. fur Astr. Innsbruck,
A), and S. Desidera (Padova Astr. Obs., I), on behalf of a larger
Italian collaboration, communicate:
We observed the variable source in the field of XRF 020903 (Ricker et
al., GCN 1530; Soderberg et al, GCN 1554) on 29.9 UT, with the 182cm
telescope at Cima Ekar-Asiago, near Padova (Italy). The object was at
high airmass.
We find the following magnitudes with respect to the USNO stars (1) and
(2) reported in the finding chart of Soderberg et al. (see
http://www.astro.caltech.edu/~ams/XrF.html ):
Filter UT OT - (1) OT - (2)
--------------------------------------
V 29.923 4.20+-0.09 2.82+-0.09
R 29.931 2.63+-0.01 1.34+-0.01
I 29.937 4.50+-0.13 5.85+-0.13
In the I-band image (300 s exposure), the object is barely visible.
Using the USNO R-magnitudes for the stars 1 (R = 16.0) and 2 (R = 17.1),
we find
R = 18.55 +- 0.2 @29.931 UT (26.5 days after XRF),
where the error is mainly due to calibration. More accurate photometry
will be distributed when available. Our data suggest further brightening
between 28.3 and 29.9 UT, with respect to the value found in Soderberg
et al. web page.
With present data, we cannot say if the varying source is a rising
supernova or a variable radio-loud AGN, as suggested by Gal-Yam (GCN
1556). Further observations are planned this night.
This message is citeable.
- GCN notice #1561
M. Stefanon, S. Covino, D. Malesani (INAF, Merate Obs., Milan, I), N.
Masetti (IASF/CNR, Bologna, I.), G. Temporin (Inst. fur Astr. Innsbruck,
A), and S. Desidera (Padova Astr. Obs., I), on behalf of a larger
Italian collaboration, communicate:
We have found that the star named (2) in our previous circular (GCN
1560) was actually saturated in our images. We hence removed it from our
analysis. Here is the whole correct text.
We observed the variable source in the field of XRF 020903 (Ricker et
al., GCN 1530; Soderberg et al, GCN 1554) on 29.9 UT, with the 182cm
telescope at Cima Ekar-Asiago, near Padova (Italy). The object was at
high airmass.
We find the following magnitudes for the suspect afterglow (AG) with
respect to the USNO star (1) reported in the finding chart of Soderberg
et al. (see http://www.astro.caltech.edu/~ams/XrF.html ):
Filter UT Exposure AG - (1)
------------------------------------
V 29.923 600 sec 4.20+-0.09
R 29.931 600 sec 2.63+-0.01
I 29.937 300 sec 4.50+-0.13
In the I-band image, the object is barely visible. Using the USNO
R-magnitude for the reference star (1), R = 16.0 (star 2 is saturated),
we find
R = 18.63 +- 0.2 @29.931 UT (26.5 days after XRF),
where the error is mainly due to calibration. More accurate photometry
will be distributed when available. Our data suggest further brightening
between 28.3 and 29.9 UT, with respect to the value found in Soderberg
et al. web page.
With present data, we cannot say if the varying source is a rising
supernova or a variable radio-loud AGN, as suggested by Gal-Yam (GCN
1556). Further observations are planned tonight.
This message may be cited.
- GCN notice #1562
K. Torii (RIKEN) and H. Yamaoka (Kyushu Univ.) report:
The entire WXM error circle of XRF 020903 (Ricker, et al. GCN 1530)
was observed at RIKEN with the 0.25-m reflector equipped with
unfiltered cooled CCD AP6E. The observation started at 2002 September
3.6479 UT (5.23 hours after the burst trigger) and 20-s exposures were
repeated.
The first 168 frames, obtained between 3.6479 and 3.6965 UT, have
been stacked and inspected for the variable source (hereafter VS)
found by Soderberg, et al. (GCN 1554). In our image (4".2/pixel) a
spatially unresolvable source is detected at (R.A., Dec.) =
(22:48:42.37, -20:46:13.0) (J2000). The position is derived by using
12 comparison stars from UCAC1 and the fitting error is 0".3 in both
coordinates. This position is closer to the galaxy G2 (as tabulated in
USNO-A2.0) rather than to the VS.
We also find that the flux for the spatially unresolved G2+VS was
2.0+/-0.2 mag fainter than the star 1 in the finding chart of
Soderberg et al. (GCN 1554), which is consistent with the magnitude
difference (G2 - star 1 = +2.17) in GSC-2.2.1 F magnitude. These
results, both astrometrically and photometrically, show that the VS
was much fainter than the galaxy G2 during our observation.
- GCN notice #1563
Covino S., Malesani D., Ghisellini G., Stefanon M., Tavecchio F. (INAF-OAB),
Covone G., Fugazza D. (INAF-TNG), Di Paola A., Israel G.L. (INAF-OAR),
Mannucci F. (IRA-CNR), Masetti N. (IASF-CNR), Pian E. ((INAF-OAT), on behalf
of a larger Italian collaboration, report:
We observed the varying source (VS) in the field of XRF 020903 (Ricker et al.,
GCN 1530; Soderberg et al., GCN 1554) on Oct 1.9 UT, with the Italian 3.5m
TNG telescope, using BVRI filters. Seeing conditions were moderate (about 1.5
arcsec) and airmass about 1.6. Magnitudes were derived by PSF fitting
photometry. One standard star field was also observed under clear (but not
photometric) conditions; therefore a small zeropoint offset is still
possible. The magnitudes for the VS are the following:
Filter UT Magnitude
-----------------------------
B 1.941 21.87 +- 0.06
V 1.932 21.14 +- 0.04
R 1.916 20.60 +- 0.09
I 1.919 20.29 +- 0.07
For comparison, we also report the magnitudes of some nearby USNO stars;
U0675_37142330 is named "star 1" in Soderberg et al. finding chart.
U0675_37143953 U0675_37141960 U0675_37142330
----------------------------------------------
B 18.54 +- 0.02 19.51 +- 0.02 17.14 +- 0.01
V 17.77 +- 0.01 19.02 +- 0.01 16.40 +- 0.01
R 17.21 +- 0.04 18.63 +- 0.04 15.92 +- 0.03
I 16.81 +- 0.03 18.36 +- 0.03 15.58 +- 0.03
Based on the photometry performed at the TNG, we re-analyzed data obtained on
Sep., 29.9 UT with the Asiago telescope (GCN 1561). Seeing conditions were
mediocre (about 2 arcsec) and airmass about 2. Magnitudes were again derived
by PSF fitting photometry. We report the following results for the VS:
Filter UT Magnitude
-----------------------------
V 29.923 20.94 +- 0.12
R 29.931 20.42 +- 0.10
I 29.937 19.98 +- 0.13
The source has simultaneously faded by about 0.2 mag in all V, R and I bands
between Sep 29.9 and Oct 1.9. Comparing with the R-band measurement by
Soderberg et al. on Sep 28.3, the source appears fainter by more than 1
magnitude.
A color-color diagram, together with a BVRI spectrum and a light curve are
shown at the web page:
http://www.merate.mi.astro.it/~malesani/XRF020903.
The values reported here supersede those in our GCN 1561, that were based on a
misidentification of the reference star. We apologize for any inconvenience
this may have caused.
Detailed analsys of these data is still in progress, and more observations
will be performed in the next few days.
This message may be cited.
- GCN notice #1571
A. Henden (USRA/USNO) reports on behalf of the USNO GRB team:
We have acquired BVRcIc all-sky photometry for
a 20x20 arcmin field centered at the variable object coordinates
for XRF020903 (Ricker et al. GCN 1530; Soderberg et al. GCN 1554)
with the USNOFS 1.0-m telescope on one photometric night. Stars
brighter than V=14.0 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/xrf020903.dat
The astrometry in this file is based on linear plate solutions
with respect to UCAC2. The external errors are less than 100mas.
While the night was photometric, the XRF field is towards
our southern horizon and so there is a higher risk of
zeropoint errors. We estimate the present zeropoint errors to
be about 0.03mag. We will be extending this
calibration with additional nights to ensure against
a systematic zeropoint error. You should check the dates on
the .dat file prior to final publication to get the latest photometry.
In particular, the two stars marked on Soderberg et al. finding
chart have the following position and magnitudes:
RA (J2000) DEC V B-V V-R R-I
Star 1 22:48:36.05 -20:44:34.8 16.381 0.789 0.455 0.399
Star 2 22:48:53.48 -20:43:23.1 14.743 0.466 0.304 0.313
These values match closely those given in Covino et al. (GCN 1563).
Calibration of the GRB021004 field will occur around October 9 UT.
- GCN notice #1609
R. Chornock and A. V. Filippenko, University of California, Berkeley, report
that an optical spectrum (range 300-940 nm) of the proposed optical transient
(OT) associated with XRF 020903 (GCN 1554) was obtained with the Low Resolution
Imaging Spectrometer on the Keck-I 10-m telescope on Oct. 8 UT. Our spectrum
is similar to that obtained by Hamuy & Shectman (GCN 1554), revealing a rich
set of narrow emission lines associated with the host galaxy. The host is
clearly a low-metallicity, high-excitation starburst galaxy, with high
[O III]/H-beta and low [N II]/H-alpha intensity ratios; [Ne III] is also
visible. The shape of the underlying continuum suggests the presence of an
older population of stars as well. While we cannot yet rule out a contribution
from an optical supernova (rather than some other type of OT), at this time
there is little if any direct spectroscopic evidence for supernova
features. Specifically, the deficit at rest wavelengths below 4000A (mentioned
in GCN 1554) is consistent with a population of old to intermediate-age stars.
This message may be cited.
- GCN notice #1631
J. Gorosabel (IAA-CSIC), J. Hjorth, H. Pedersen,=20
B.L. Jensen (Univ of Copenhagen), J.P.U. Fynbo (Univ. of Aarhus),
M. Andersen (AIP Potsdam), J.M. Castro Cer=F3n (ROA, San Fernando),=20
A.J. Castro-Tirado (IAA-CSIC) report:
We have imaged the transient source present in the field of XRF 020903
(GCN 1530, GCN 1554) with the 1.54-m Danish Telescope around Oct 10.2
UT, yielding the following preliminary BVR-band magnitudes:
B =3D 21.89 +/- 0.15
V =3D 21.07 +/- 0.12
R =3D 20.54 +/- 0.12
The observations we carried out with a mean seeing of 1". The=20
zeropoint is based on the calibration given in GCN 1571. These
magnitudes agree with the ones measured on Oct 1.9 UT for the
transient source (GCN 1563).=20
The source seems slightly elongated in the North-East direction
at can be seen in at:
http://www.dsri.dk/~jgu/grb020903/FCs/grb020903.R1.gif
http://www.dsri.dk/~jgu/grb020903/FCs/grb020903.R2.gif
Thus, our measurements are consistent with i) a flattening of the=20
light curve due to an underlying host or ii) with a transitory plateau
phase spanning at least 8.3 days (from Oct 1.9 to Oct 10.2 UT).
The elongated appearance of the object supports the first hypothesis (i).
A combination of both effects could be also possible.
Further observations are planned.
- GCN notice #1761
Andrew Levan (U. Leicester/STScI), Andrew Fruchter, Lou Strolger, Ingunn
Burud and James Rhoads (STScI) report for the GOSH collaboration.
The candidate optical transient for XRF 020903 (Soderberg et al, GCN 1554)
was imaged with HST/ACS in F606W on 3rd Dec 2002. 4 dithered exposures
were obtained with a total exposure time of 1840s.
The candidate appears to be within an irregular galaxy, with four
(possibly interacting) components. Astrometry with images obtained
with the CTIO 4-m telescope and Mosaic imager on Sept 4th and 9th 2002
(Fruchter et al, GCN 1558) shows that the transient source is located at
a position coincident with the peak of the most western of these compact
knots (with a positional accuracy of approximately ~0."1). The knot has
an F606W AB magnitude of 22.6 and a FWHM of ~0."14, greater than the PSF
of ACS. Hence the source is resolved at this resolution, indicating that
an AGN does not dominate the optical light from this object.
The galaxy, named G2 by Soderberg et al, (GCN 1554) is clearly an
interacting system. However, as noted by Soderberg et al the redshift
difference (z=0.23 for G2 and z=0.25 for the host of the candidate OT)
indicate that the systems are not associated.
Using a 1" aperture the magnitude of the entire system in F606W is
approximately R=21, roughly consistent with the late time magnitudes
determined by Gorosabel et al (GCN 1631).
Observations taken at a later date will allow a search for further
variability in this source.
Images of the host galaxy, and surrounding field can be found at
http://www.stsci.edu/~fruchter/GRB/020903
The region surrounding the possible optical counterpart of XRF
020903. Showing the position and 1 sigma error for the position of the
optical
transient (when compared to ground based images obtained on the 4th
and 9th Dec). Also showing the nearby interacting galaxy G2. At
a redshift of 0.23 (Soderberg et al GCN 1554). North is up, and east to
the left. The image is approximately 10" across and has been drizzled
onto
an output grid with pixels 0.66 times size of the native ACS pixel.
The host galaxy of XRF 020903. It can be seen to consist of 4,
apparently interacting components. The position of the transient
source is marked and its 1 sigma error box is shown.
- GCN notice #2761
We observed XRF 020903 with the CTIO 0.9-inch 32, 35, and 37 days
after the burst
and with the USNO 1.0-meter 32 and 60 days after the burst. We find no
evidence
for a rebrightening at these times. Zero points for the g' and r'
filters used
for the CTIO 0.9-meter images were taken from Smith, J. A. et al.,
2003, AJ,126, 2037
(Table 3). UBVRI standard star magnitudes were taken from Henden, A.
2002, GCN 1571.
Due to poor seeing at USNO and the close proximity of the galaxy
complexes, a subtraction routine was performed with limited success on
the galaxies labeled G2 + G3 in Soderberg, A. M. et al., 2004, ApJ,
606, 994 (Figure 1) to determine the magnitude of the OT. Within the
errors, the magnitude of the OT does not change between one and two
months post-burst and is thus taken as the magnitude of the G1 complex
(Soderberg et al. 2004).
The CTIO images yield average magnitudes of g' = 21.30 +/- 0.07 mag
and
r' = 20.18 +/- 0.14 mag. The USNO images yield average magnitudes of
R ~ 21 mag
and I ~ 20.4 mag. These results are very consistent with prior
authors regarding the
underlying host galaxy; however, the subtraction routine may be a
source of systematic error.
This message can be cited.
- GCN notice #2762
Authors for GCN 2761:
S. Savage, R. Canterna, A. Smith, A. Henden, D. Reichart, M.
Nyeswander, FUN GRB group
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