GRB 021004

Andrew Levan (U. Leicester/STScI), Andrew Fruchter (STScI), Johan Fynbo
(U. Aarhus), Paul Vreeswijk (ESO) and Javier Gorosabel (IAA-CSIC/STScI)
report for the GOSH collaboration.

The field of GRB 021004 has been observed using the ACS/WFC on HST
in four epochs: the 7th, 11th and 22nd Oct and 26th Nov 2002.

A difference image of the last two epochs, which were dithered, reveals a
declining point source whose position is consistent within the astrometric
errors (~0."01) with the peak of the light in the later image.  The source
is marginally resolved in that image (with a FWHM of 0".11, compared to a
point source FWHM of ~0."09) indicating a host galaxy directly underlying
the OT. This differs from the astrometry of Mirabal et al
(astro-ph/0303616) who find the OT position well offset from the host. As
the source lies on the peak of the light, and the object is only
marginally resolved, it is possible that the OT continues to contribute
significantly to the observed brightness even at the later epoch. Hence
the magnitude found for the source in November, F606W(AB)=24.3 +/- 0.1,
is an upper limit on the true brightness of the host galaxy.

We have scheduled late time observations of GRB 021004 which will enable
an accurate determination of both the host galaxy magnitude and the late
time decay of the afterglow.

Images of the field can be found at

http://www.stsci.edu/~fruchter/GRB/021004

T.A. Fatkhullin, V.N. Komarova, A.V. Moiseev (SAO RAS) report for the
larger GOSH collaboration:


The field of the GRB 021004 optical transient was observed with the SCORPIO
instrument at the 6-m telescope of SAO RAS. The images were taken
starting from 15:30 to 17:45 UT on Nov 29 and from 18.55 to 20.00 UT on Nov 30
under conditions of thin cirrus with seeing of about 1.2 arcsec in the first
night and 1.5 arcsec in the second one. The V, Rc and Ic filters were used.
The absolute astrometry was done relatively to USNO-B1.0 stars with internal
error of 0.3 arcsec. We detect an object which coincides with the position
of the optical transient (Henden et al. GCN #1592
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 )  within the astrometric
error. Photometric calibration was performed using 6 standards
(Henden et al. GCN #1630
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 ) in our FOV.
The results of the photometry are given below:

 Data    Filter  Exp.       OT mag.     Aperture
------------------------------------------
 29 Nov   Rc   15x180s   24.36+/-0.18   3.5 arcsec
 29 Nov    V    5x450s   24.53+/-0.18   3.5 arcsec
 30 Nov   Ic   14x120s   >23.9
------------------------------------------

At this stage it is not clearly whether the object is the pure host
galaxy. Further observations are planned.
Images can be seen at URL:
http://www.sao.ru/~sokolov/GRB/FOLLOWUP/GRB021004/GRB021004.html

This message may be cited.

M. Sako & F. A. Harrison report on behalf of the Caltech-NRAO 
collaboration:

We report a second TOO observation of GRB021004 taken with the Advanced CCD
Imaging Spectrometer (ACIS-S) onboard the Chandra X-ray Observatory.  The
observation started at 17:35 on November 25 (52.229 days after the GRB) for a
total exposure time of 30.0 ksec.  Ten counts were detected in a circular
region with a radius of 1 arcsec centered on the source position of GRB021004,
of which 1 - 2 photons are estimated to be background events.  Assuming the
same power-law spectral index as that observed during an earlier Chandra observation
(GCN 1624
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 ), this corresponds to a 2 - 10 keV flux of (7.2 +/- 2.5) x 10^-16
erg/cm2/s.  The source, therefore, has decayed with a characteristic power
law decay time slope of approximately -1.7 since the previous observation.

The data can be accessed through the Chandra Data Archive.  We thank Harvey
Tananbaum for allocating Director's Discretionary Time and the Chandra X-ray
Center for implementing the obervation.

T. Giannini, B. Nisini, L.A. Antonelli, F. Fiore, and L. Stella 
(INAF-Oss. Astronomico Roma) report:

"K band spectra of GRB021004 were obtained on October 05 2002 05:27 UT
using ISAAC at VLT/UT1.  The observations cover the spectral range
1.8-2.5 micron at a resolution of R=450. The total exposure time was
of 3000 seconds. At the time of the observations the afterglow
magnitude was K~16.5 (Di Paola et al. GCN #1616
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 ).


A preliminary analysis of the spectra reveals no strong emission or
absorption features in the range 2.1-2.4 micron, where the signal to
noise is highest. In particular, no significant absorption or emission
line is detected at 2.18-2.19 micron where the Halpha transition
associated to the host galaxy (z=2.335 Moller et al.  astro-ph
0210654) or to the strongest absorption system (z=2.328, Savaglio et
al. GCN #1633
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 ) should lie. The 3 sigma limit to the redshifted Halpha
absorption is of about 8 Angstrom."


This message may be quoted.

Lifan Wang (Lawrence Berkeley National Laboratory), 
Dietrich Baade(European Southern Observatory), 
Peter Hoeflich, and J. Craig Wheeler (University of Texas, Austin) report: 
"Spectropolarimetry of GRB021004 was obtained on Oct. 05 using the ESO-VLT
with FORS1. The spectral coverage is from 350 to 860 nm. Preliminary
reduction shows that the synthesized V-band polarimetry is consistent 
with that reported by Covino et al. (GCN 1595
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 ) and Rol et al. (GCN1596
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 ). 
The data are suggestive of polarization changes across 
the Lyman-alpha absorption features at 401 and 404 nm, and increasing 
degree of polarization blueward of 400 nm. "

P. Garnavich and J. Quinn (Notre Dame)

We observed the optical afterglow of GRB 021004
(Fox et al. GCN 1564
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 ) with the 1.8m Vatican Advanced
Technology Telescope beginning 2002 Oct 26.25 (UT).
Seven, 10 minute exposures in the R band were combined
and an unresolved source was detected within 0.2"
of the afterglow position. Assuming the star at
00:26:51.44 18:54:36.3 (2000) has a magnitude of
R=17.142 (Henden GCN 1630
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 ) we find the afterglow
brightness to be R=23.39+/-0.12. Combining the
Williams, Lindsay, & Milne (GCN 1652
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 ) observation with
the VATT image provides a power-law decay index of -1.7
between one and three weeks after the burst. This is
significantly steeper than the "average" decay index
between 0.4 and 3 days after the burst (Holland et al.
GCN 1597
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 ) and may indicate a final break in the light
curve. Although, the odd variability of GRB 021004 makes 
this conclusion uncertain. 

This note can be cited

E.A.Barsukova (SAO), V.P.Goranskij (Sternberg Institute),
G.M.Beskin (SAO), V.L.Plokhotnichenko (SAO), A.S.Pozanenko  (IKI).

We have observed GRB 021004 on October 8, 2002 four days after the burst,
using 1-m Zeiss telescope and CCD with Rc filter under good seeing
conditions. Five 20-min exposures were taken in the time interval between
20:49:56 and 22:35:14 UT. Object is seen near the frame limit in each of
these frames. The photometry and astrometry of images were performed. The
sum of all frames (total exposure is 100 minutes) gives the magnitude of OT

Rc = 20.9 +/- 0.3

relative to comparison star by Fox (GCN 1564
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 ) with Henden's (GCN 1630
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 )
calibration magnitude of 15.538 Rc.

The astrometry of all the frames taken both on October, 4 (GCN 1606
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 ) and
October, 8 shows that the image of the object is displaced by 0".5 West on
October, 8 relative to that on October, 4. The accuracy of the astrometry is
0".2. One may suggest that the displacement results from influence of a host
galaxy.

This message may be cited.

G. Williams (MMTO/SAO), K. Lindsay (Clemson University), P.  Milne (LANL)

We observed the optical afterglow of GRB021004 (Fox et al., GCN 1564
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 ) with
the Steward Observatory 90-inch Bok Telescope.  We obtained 8 x 300s
exposures in each of the B, V, R, and I bands.  Observations began at
04:19:49 UT, and ended at 07:39:15 UT, on 12 October 2002 (T + 7.67 - 7.82
days).  Aperture photometry was performed on the coadded images and the
results were calibrated utilizing standards reported by Henden et al., GCN
1583
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 .  The following preliminary results were obtained:

B = 22.60 +- 0.11  (12 Oct 07:18 UT)

V = 21.95 +- 0.07  (12 Oct 06:23 UT)
 
R = 21.47 +- 0.09  (12 Oct 04:41 UT)

I = 21.23 +- 0.18  (12 Oct 05:31 UT)

This report may be cited.

Malesani D., Stefanon M., Covino S., Ghisellini G. (INAF-OAB), Lazzati D., 
Rossi E. (IOA, Cambridge, UK), Fugazza D., Guerra J.C., Pedani M. (INAF-TNG), 
Masetti N. (IASF-CNR), Pian E. (INAF-OATs), on behalf of a larger Italian 
collaboration, report:


On Oct ~16.9 UT, we observed the optical counterpart of GRB 021004 (Shirasaki 
et al., GCN 1565
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 ; Fox, GCN 1564
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 ) using the 3.6m TNG telescope in the Canary 
Islands; observations were performed with V (20 min), R (9 min) and I (15 
min) filters under mediocre conditions (seeing 1.5-1.8 arcsec, thin clouds). 
With respect to the comparison star used by Fox and calibrated by Henden (GCN 
1583
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 ), the source has the following magnitudes:


UT      Band  Mag    Error
--------------------------
16.979  I     21.65  0.12
16.942  R     22.38  0.20
16.962  V     22.49  0.07


The object is quite faint in our images. Actually, it lies about ~0.7 mag 
below the powerlaw extrapolation of the previously published data (R band), 
if we include the three early-time data points of Fox (t < 20 min). If 
instead we let the powerlaw fit to begin ~2 hours after the trigger, there is 
no disagreement. A light curve with the relevant fits is reported at 
http://www.merate.mi.astro.it/~malesani/GRB/021004 .


If indeed a break has occured between Oct 10 and Oct 17 (6 to 13 days after 
GRB), this is in agreement with the prediction of GCN 1607
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 .


Further observation are encouraged to assess the nature of this break.


This message may be cited.

Kevin Lindsay, Dieter H. Hartmann, Keith Davis,
Mark Leising (Clemson University)

We have observed the optical afterglow of GRB021004,
originally reported by Fox et al., GCN 1564
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 , with the
SARA 0.9m telescope at KPNO.  We obtained 16 300s 
exposures in the Johnson R band filter.  Observations
began at 06:46:17UT, and ended at 08:09:02UT, on October 
9th.  The observations were carried out under good seeing
conditions.  Aperature photometry was performed, and 
calibrated utilizing standards reported by Henden et al.,
GCN 1583
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 .

We find a mean R magnitude of 21.2 +- 0.2

More information on the SARA Observatory can be found
at http://www.saraobservatory.org/.

This report may be cited.

A. J. Castro-Tirado, E. Pérez, J. Gorosabel (IAA-CSIC,
Granada), J. M. Castro Cerón (ROA, San Fernando),
M. Andersen (AIP, Potsdam), J. Hjorth (Univ. of Copenhagen),
E. Rol, R. Wijers (Univ. of Amsterdam), A. Fruchter
(STScI, Baltimore), S. Klose (TLS, Tautenburg),
J. Greiner (MPE, Garching) and E. Pian (OAT-INAF, Trieste)
on behalf of the GRACE Collaboration

report:

"We have obtained a 7200-s spectrum with the FORS1
spectrograph at the ESO's 8.2-m VLT3 telescope at
Paranal on Oct 11.125-11.231 UT. The range is 3500-
5700 A with a resolution of about 1 A/pix.

We confirm the detection of the Ly-alpha (1215.7 A)
emission line plus the C IV (1548,2 A, 1550.8 A)
absorption line system at a redshift z = 2.327 (GCN
1605
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 ). The Al II (1670 A) absorption line (GCN 1618
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 )
is detected as well at the same redshift.

We also detect another two absorption line systems at
z = 2.297 and z = 2.321 on the basis of C IV (1548,2 A,
1550.8 A) lines.  The latter system is also detected in
Si IV (1393.8, 1402.8).  These two systems are consistent
with those reported by Salamanca et al. (GCN 1611
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 ) and
Savaglio et al. (GCN 1633
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 ).

The flux of the Ly-alpha line (1.9e-16 erg/cm2/s/A) is
comparable with the one measured by Keck (GCN 1620
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 ),
i.e. the Lyman-alpha flux is constant and we conclude that
arises from the GRB 021004 host galaxy, at z = 2.327."


This message may be cited.

S. Savaglio (INAF-OAR and JHU), F. Fiore, G. Israel, G. Marconi,
L.A. Antonelli, A. Fontana, L. Stella, A. Di Paola, G. Stratta (INAF-OAR),
S. Covino, G. Chincarini, G. Ghisellini, P. Saracco, F. Zerbi (INAF-OABrera),
D. Lazzati (Cambridge, UK), R. Perna (CfA), M. Vietri (Univ. Roma Tre),
F. Frontera (Univ. di Ferrara), S. Mereghetti (CNR-IASF),
E.J.A. Meurs (Dunsink Obs.) and N. Kawai (Titech, RIKEN) report:

"Starting on October 05 2002 01:37 UT we have obtained high resolution
spectra (R=50,000, 6 km/s in the observer frame) of the optical
afterglow of GRB021004 (Fox et al., GCN #1564
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 ) using UVES at VLT.  The
observations cover the full spectral range 3200-9800 Angstrom, in good
seeing conditions. At the time of the observations the afterglow
magnitude was R~18.6 and B~19.0.

A preliminary analysis of the first hour of observation reveals
several absorption lines associated with at least 4 metal systems
(also see Salamanca et al., GCN #1611
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 ).

The z=2.321,2.327 system is probably very close to the GRB itself or
the circumburst medium. C IV absorption lines associated with this
system are in fact extremely strong and complex, spanning a velocity
range of about 1000 km/s. This system may show the so called "line
locking", possibly relativistic, effect, where the second component of
the z=2.321 C IV doublet is "locked" to the first component of the
z=2.327 C IV doublet. This effect has been observed in the past in
narrow absorption systems associated with high redshift quasars (e.g.
Wampler 1991, ApJ, 368, 40) and O stars (Lucy & Solomon, 1970, ApJ,
159, 879).

Low ionization lines of AlII1670 and possibly SiII1526 are also
detected in the red wing of the z=2.327 component. Low ionization
lines are not detected in the lower redshift system at z=2.321.

The z=2.2958,2.2985 system is shifted by ~2500 km/s blueward of the
strong z=2.321,2.327 system and shows much weaker, but still very
strong, C IV lines and no low ionization lines. The velocity range of
this absorption is of about 300 km/s.

The z=1.6019 intervening system shows a narrow Al III absorption with
column density of log N(AlIII)=13.2 +\- 0.1 and Doppler parameter b=12
+\- 1 km/s.

The other system at z=1.38 shows a complex structure with at least 4
components spanning a velocity range of about 200 km/s.  The FeII
column densities suggest that this system may be associated with a
Damped Lyman Alpha system in the interstellar medium of an intervening
galaxy."

This message may be cited.

A. Henden (USRA/USNO) reports on the behalf of the USNO GRB team:

Two additional photometric nights of UBVRcIc all-sky photometry
for the 11x11 arcmin field centered at the afterglow coordinates
for GRB021004 (Shirasaki et al. GCN 1565
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 ; Fox et al. GCN 1564
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 )
have been aquired with the USNOFS 1.0-m telescope.  Stars brighter
than V=14.0 are saturated and should be used with care.
The photometric data on the NOFS anonymous ftp site has
been updated:
ftp://ftp.nofs.navy.mil/pub/outgoing/aah/grb/grb021004.dat
The astrometry in this file is based on linear plate solutions
with respect to UCAC2.  The external errors are less than 100mas.

The comparison star given by Fox et al. has the following
updated coordinates, magnitudes and colors:

6.744892  18.948922 00:26:58.77  +18:56:56.1  J2000

    V     B-V    U-B    V-R   R-I     errors
  16.258  1.172  1.115  0.720 0.642   0.006 0.028 0.034 0.015 0.023

These colors suggest an approximate K5 spectral classification.

One possibility for the various bumps in the afterglow lightcurve
(suggested privately by B. Schaefer, D. Reichart and P. Price),
is that the Fox et al. comparison star is variable.
This has been investigated by performing differential
photometry with respect to an ensemble of other comparison
stars on the three photometric nights.  The BV results are
given below.

     HJD       V     B-V    verr   bverr
  52552.9804 16.256  1.172  0.003  0.006
  52556.7223 16.256  1.174  0.003  0.005
  52556.7751 16.258  1.176  0.002  0.004
  52556.8276 16.255  1.172  0.002  0.004
  52556.8802 16.259  1.166  0.002  0.004
  52556.9312 16.262  1.122  0.002  0.005
  52557.7823 16.258  1.168  0.002  0.004
  52557.8196 16.252  1.168  0.003  0.005
  52557.8569 16.248  1.181  0.003  0.005
  52557.8942 16.248  1.180  0.002  0.004
  52557.9315 16.255  1.173  0.002  0.004

The datapoint at HJD 2452556.9312 was contaminated by
a cosmic ray hit and so should be given lower weight.
All other measures indicate that the comparison star
is constant over the three nights of observation.  Unless
this star was doing something different between UTD 021005
and UTD 021009, there is no evidence that the afterglow
lightcurve changes are due to comparison star variation.
Using more than one comparison star (or at least including
a check star) when performing differential photometry, and also
selecting comp stars that are close to the program object in
magnitude and color space, is always recommended
to guard against possible variability of any comparison star.

Kevin Lindsay, Dieter H. Hartmann, John Tassinari
(Clemson University)

We have observed the optical afterglow of GRB021004,
originally reported by Fox et al., GCN 1564
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 , with the
SARA 0.9m telescope at KPNO. We obtained 30, 300s
exposures in the Johnson R band filter.  Observations
began at 07:03:05UT, and ended at 09:42:20UT, on October
5th.  The obsevations were carried out under good seeing
conditions.  Aperture photometry was performed, and
calibrated utilizing standards reported by Henden et al.,
GCN 1583
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 .

We find a mean R magnitude of 19.1 +- 0.2.

Observations were also performed on the night of October
9th. Data analysis is currently in progress.

We thank SARA Observatory director Dr. J. Webb for making
part of his observing time available to us.

More information on the SARA Observatory
can be found at http://www.saraobservatory.org/.

This report may be cited.

SUB-MM SEARCH FOR GRB 021004

Jan Wouterloot (1), Gary Davis (1), David Naylor (2), Remo Tilanus (1), 
Gerald Moriarty-Schieven (1,3)

(1) Joint Astronomy Centre
(2) University of Lethbridge
(3) National Research Council of Canada

Observations were made of GRB021004 (position from GCN 1564
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 ) using the 
SCUBA bolometer array on the James Clerk Maxwell Telescope located on 
Mauna Kea, Hawaii, on October 11.43 - 11.55 UT, under excellent sky 
conditions.  After 5400 seconds of integration, the object was not 
detected at 850microns (347GHz), with a 3sigma upper limit of 3.3mJy.

M. Sako, F. A. Harrison report on behalf of the Caltech-NRAO collaboration:

We report TOO observations of GRB021004 taken with the High-Energy
Transmission Grating (HETG) on the Chandra X-ray observatory.  Chandra
observed the afterglow for a total exposure of 87 ksec, beginning at
8:55 UT on October 5, 20.5 hours after the burst.  A preliminary
reduction of the data shows a fading X-ray source at the position of
the optical transient.  The count rate decreased with time throughout
the observation with a power law decay time slope of -1.0 +/- 0.2.
The total HEG + MEG countrate is 0.018 counts sec^-1.  The source is
well-characterized by a power-law spectrum with photon index Gamma =
2.1 +/- 0.1, and flux normalization of 1.9 +/- 0.1 x 10^-4 photons
cm^-2 s^-1 keV^-1 at 1 keV.  There are no signs of excess absorption
above the Galactic value.  The corresponding mean 2 - 10 keV X-ray
flux in the observed frame is 4.3 x 10^-13 erg cm^-2 s^-1.  The
0th-order ACIS-S spectrum is consistent with that of the HETG, with an
average count rate of 0.014 counts sec^-1.

No obvious discrete features are detected in the spectrum.  We note
that the signal-to-noise ratio in this spectrum is a factor of two
better than that of the GRB991216 spectrum obtained with the Chandra
HETG, so that a line feature of similar strength to that reported for
GRB991216 should have been detected.

We thank Harvey Tananbaum for approving director's discretionary time
for this observation, and the staff at the Chandra Science Center
for skillfully implementing this rapid TOO observation.

Stefanon M., Covino S., Malesani D., Ghisellini G., (INAF-Brera),
Fugazza D., Tessicini G. (INAF-TNG), Masetti N. (IASF-CNR), Pian E.
(INAF-OATs), on behalf of a larger Italian collaboration, report:

On Oct 10.1 UT, we observed the optical counterpart of GRB 021004
(Shirasaki et al., GCN 1565
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 ; Fox, GCN 1564
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 ) using the 3.6m TNG telescope
in the Canary Islands, with DOLORES (B and R filters) and NICS (H
filter).  Calibration was performed with respect to the comparison star
used by Fox and calibrated by Henden (GCN 1583
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 ) and the 2MASS
calibration of the field. The source has the following magnitudes:

UT      Band    Mag     Error
10.072  H       18.80   0.05
10.105  R       21.05   0.05
10.115  B       22.12   0.05


This message is citable.

S. Covino, G. Ghisellini, D. Malesani, G. Tagliaferri, F. Zerbi (INAF Brera, 
Italy); A. Cimatti, M. Della Valle, S. Di Serego (INAF Arcetri, Italy); F. 
Fiore, G.L. Israel, L. Stella (INAF Roma, Italy); E. Costa, P. Soffitta (IASF 
Roma, Italy), S. Mereghetti (IASF Milano, Italy), N. Kawai (Tokyo Tech, 
Japan); D. Lazzati, E.M. Rossi (IoA, Cambridge, UK); S. Ortolani (Univ. of 
Padova, Italy); L. Pasquini (ESO, Germany); G. Ricker (MIT, USA); E. Le 
Floch, P. Goldoni, F. Mirabel (CEA, France), C. Lidman, G. Marconi, C. Melo, 
P. Vaisanen (ESO Paranal), B. Aracil (IAP, France) report:



We observed the optical counterpart to GRB 021004 (Shirasaki et al. GCN 1565
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 ; 
Fox, GCN 1564
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 ) on October 8.225 (89.3 hours after the GRB trigger). The 
observations were performed with the ESO VLT-UT3 (Melipal) telescope equipped 
with FORS1 and a Bessel V filter in the imaging polarimetry mode. The 
transient source is clearly detected with a magnitude V = 20.89 +/- 0.03 with 
respect to the USNO star at 00:26:58.713 +18:56:56.61 (Fox, GCN 1564
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 ) as 
calibrated by Henden (GCN 1583
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 ).

The polarimetric observations allowed us to single out linear polarization at 
the level of P = (0.67 +/- 0.23)% with position angle (89.0 +/- 10.0) degrees 
(uncertainties are 1-sigma errors) for the optical transient. The field star 
polarization was of course constant within the errors between our two 
polarimetric observations (Covino et al. GCN 1595
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 ). 
Once we remove the estimated polarization induced by the interstellar matter 
(ISM) in our Galaxy, as discussed in our GCN 1595
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 , the intrinsic polarization 
of the optical transient turns out to be consistent with zero. 

Independently of any ISM induced polarization, the present result compared to 
the polarimetric observations performed on October 5.115 [Covino et al. GCN 
1595
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 , P = (1.26 +/- 0.1)%, angle = (114.2 +/- 2.2) degrees] and 5.175 [Rol et 
al. GCN 1596
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 , P = (1.32 +/- 0.28)%, angle = (125 +/- 1) degrees] could show  
a marginal hint for a change of the polarization degree and of the position 
angle.   



This message is citeable.

G. Masi (Ceccano, Italy) reports:

Following the afterglow detection of this GRB (D.W. Fox et al.: GCN 1564
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 ; M.
Uemura et al.: GCN 1566
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 ), A. Tasselli (Mahlow, Germany) imaged, on Masi's
request, the field around the position given in GCN 1564
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 . 36 CCD frames, each
with 45 seconds of integration, have been grabbed unfiltered with a 0.15m
telescope + CCD on Oct. 5.04375 UT, 2002,  and then coadded. The final image
clearly shows an object in very good agreement with the cited astrometry.

G. Masi performed the photometry of the source, using for calibration data from
A. Henden (GCN 1583
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 ). The resulting magnitude is 18.5 CR. This value fits well
with the data plotted by N. Mirabal et al. (GCN 1602
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 ).

This message may be cited.

S. G. Djorgovski, A. Barth, P. Price, D. Fox, W.L.W. Sargent, R. Simcoe,
A. Soderberg, S. Yost, E. Berger, S.R. Kulkarni, F.A. Harrison (Caltech) and
D. Frail (NRAO) report on behalf of the Caltech-NRAO-CARA GRB collaboration:

Analysis of spectra of the OT + host galaxy associated with GRB 021004,
obtained by W. Sargent and R. Simcoe using the LRIS spectrograph at the
WMKO Keck-1 telescope, confirms the exitence of the multi-component z ~ 2.3
redshift systems reported by Chornock & Filippenko (GCN 1605
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 ), Salamanca
et al. (GCN 1611
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 ) and Mirabal et al. (GCN 1618
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 ).

For the emission component of the Ly-alpha line we measure the flux of
1.7e-16 cgs, which after the correction for the Galactic extinction becomes
2.2e-16 cgs.

This places the host galaxy of GRB 021004 in the top 0.5 to 1 percent of the
field galaxy population at comparable redshifts, in terms of the Ly-alpha
line flux (on the basis of data by A. Shapley, C. Steidel, et al., priv.
comm.)

In the currently popular cosmology with h = 0.65, Omega_0 = 0.3, and
Lambda_0 = 0.7, the luminosity distance is 6.2e28 cm, and the inferred
Ly-alpha luminosity is 1.1e+43 erg/s.  Using the standard conversion, this
corresponds to an unobscured star formation rate of 15 M_sun/yr.  However,
this is certainly a lower limit, since the blue half of the Ly-alpha line is
absorbed, there is an unknown atennuation factor due to the resonant
scattering and absorption, and an unknown, fully obscured star formation
component.  Thus, the true SFR in the host is at least twice as high, and
could be an order of magnitude higher (or more).

This note can be cited.

SUB-MM SEARCH FOR GRB 021004

Jonathan Kemp (1), Jason Fiege (2), Kristen Coppin (3), Michael Zemcov (3),
Remo Tilanus (1), Gerald Moriarty-Schieven (1,2)

(1) Joint Astronomy Centre
(2) National Research Council of Canada
(3) University of British Columbia

Observations were made of GRB021004 (position from GCN 1564
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 ) using the 
SCUBA bolometer array on the James Clerk Maxwell Telescope located on 
Mauna Kea, Hawaii, on October 6.35-6.48 UT, under good sky 
conditions.  After 4662 seconds of integration, the object was not 
detected at 850microns (347GHz), with a 3sigma upper limit of 4.5mJy.

N. Mirabal, J. P. Halpern (Columbia), R. Chornock, and A. V. Filippenko
(UC Berkeley) report:

"Continued monitoring of the optical afterglow of GRB 021004 with the
MDM 1.3m by E. K. Armstrong yields the following measurements:

	----------------------------
	      UT   	  R     +/-
	----------------------------
	Oct. 8	07:05	20.48	0.03
	Oct. 9	04:21	20.72	0.04
	----------------------------

Here we use the calibration of Henden (GCN #1583
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 ) in which the reference star
has R=15.52.  An updated decay curve accounting for revised calibrations of
GCN reported data is at:

http://www.astro.columbia.edu/~jules/021004.ps

Further examination of the optical spectrum reported by Chornock and Filippenko
(GCN #1605
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 ) yields the following features in the highest redshift system 
("em" refers to emission, "bl" denotes a broad blend of z=2.323 and 2.318):

	-------------------------------------------
	Line		Rest wavelength      z
	-------------------------------------------
	Ly beta		1025.7		   2.323 bl
					   2.291


	Ly alpha 	1215.7		   2.328 em
					   2.319 bl
					   2.295

	Si IV		1393.8,1402.8	   2.323
					   2.318
					   2.293

	C IV		1548.2,1550.8	   2.323
					   2.317
					   2.293

	Al II		1670.8		   2.328
	-------------------------------------------

This spectrum was taken in five 1200 s exposures from Oct 8 10:14-14:05 UT.
In view of the 6 Angstrom resolution of this spectrum, we consider that the
lowest redshift absorber of the three is a blend of two of the four systems that
were seen by Salamanca et al. (GCN #1611
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 ) in higher resolution data.  Also, we
detect one absorption line (Al II 1670) at the same redshift as the Ly alpha
emission, z=2.328, which we therefore designate the redshift of the host galaxy.
The detection of this lone low-ionization absorber is plausible because of its large 
oscillator strength, f=1.83.  Thus, all of the high-ionization absorbers are 
blueshifted from the host redshift, by up to 3,200 km/s.
   
The decay curve shows significant deviations from a power law, which might be
understood in terms of inhomogeneities in the ambient medium in which the afterglow 
expands.  In view of the revised redshift of 2.328 and the multiple blueshifted
H, C IV, and Si IV absorption lines, we hypothesize that the velocity span of
3,200 km/s in these components is indicative of a clumpy wind from a massive hot star
progenitor, such as a Wolf-Rayet star.  This would avoid the difficulties of scenarios 
involving supernova ejecta or cosmic clustering, as explained in GCN #1611
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 .  The absence
of nitrogen lines and the presence of Ly alpha and Si IV weaker than C IV is consistent
with a WC star, in which the bulk of the wind is approximately equal parts He and C.

We assume a typical mass-loss rate of 10(-5) Msun/yr and a wind terminal velocity 
of 3,000 km/s.  Following Chevalier & Li (2000, ApJ, 536, 195), the predicted radius 
r_s of a spherical adiabatic blast wave in such a stellar wind at an observed time of
1 day is 3.5x10(17) cm for an isotropic energy of 5.6x10(52) erg (Malesani et al.,
GCN #1607
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 ), or 3.5x10(16) cm if there is a beaming correction of 1/100 to the energy.  
Chosing the larger value of r_s, the column density of C in the wind is at least
3.6x10(15) cm(-2) between the shock and the deceleration radius of the wind, which
is of order 5x10(17) cm or greater (Ramirez-Ruiz et al. 2000, MNRAS, 327, 829).  This
would be enough to account for the observed absorption at high velocities.  We note that 
for a typical nu(-1) broad-band spectrum, C IV ions in the wind would absorb in the line 
before being photoionized.  Detailed photoionization models are needed to predict the 
evolution of the column densities.  A consequence of this model is that the high-velocity 
components of C IV should decline after being photoionized, or as the shock overruns the 
wind in several days.  Continued spectroscopic monitoring of this bright afterglow is
urged in order to search for this definitive signature of the massive star progenitor of 
GRBs.  Changes in the decay curve could also result when the afterglow reaches the 
termination of the stellar wind with the ISM."

A. Di Paola (1), A. Boattini (2), M. Del Principe (3),
T. Konstantinova (4), V. Larionov (4), L. A. Antonelli (1)

1) Rome Astronomical Observatory (IT)
2) IASF - CNR (IT)
3) Teramo Astronomical Observatory (IT)
4) St.Petersburg University (RU)

on the behalf of the GROAR Team, report:

We have imaged the GRB021004 OT (GCN 1565
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 ) from the
Campo Imperatore Observatory both with the 1.1 meters
AZT-24 telescope at NIR wavelengths and with the
60cm Schmidt telescope at optical wavelengths .
The last I band point has been obtained using the
AZT-8 telescope from the Crimea Observatory.

Observations on both Campo Imperatore and Crimea
Observatory have been triggered by the FAMe
facility at http://grb.mporzio.astro.it/.

The Campo Imperatore observations started on
2002-10-05 19:50:00 UT and ended on
2002-10-06 04:20:00 UT, respectively 32.1 and 39.7
hours after the burst.

We obtained two run using V, R, I, J and K filters.

Run #1:
2002-10-05.840498 V-band: OT ~ 20.06 +- 0.06
2002-10-05.865937 R-band: OT ~ 19.52 +- 0.05
2002-10-05.884722 I-band: OT ~ 19.1  +- 0.1
2002-10-05.863102 J-band: OT ~ 18.4  +- 0.1
2002-10-05.909583 K-band: OT ~ 16.4  +- 0.1

Run #2:
2002-10-06.062256 V-band: OT ~ 20.78 +- 0.10
2002-10-06.083842 R-band: OT ~ 19.89 +- 0.07
2002-10-06.116319 J-band: OT ~ 18.5  +- 0.1
2002-10-06.159548 K-band: OT ~ 17.1  +- 0.3

The Crimea I point has been obtained on:
2002-10-06.965972 I-band: OT ~ 19.3  +- 0.1

The color indexes at Run#1 are:
  V-J ~ 1.7 +- 0.2
  V-K ~ 3.7 +- 0.2

The magnitudes calibration is obtained from
A. Henden GCN 1583
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  for the optical points and from
2MASS catalog for the infrared points.

The refined analysis is underway.

A. Klotz and M. Boer CESR/CNRS (Toulouse, France), and W. Thuillot
IMCCE/BDL Paris, France report the following data on GRB 021004 obtained
with the 1.20 meter telescope at the OHP/CNRS (Observatoire de Haute
Provence - France).

Images were R-cousin filtered. Each measurement image results of
co-addition of 4 frames of 40s (dark and flat corrected). Magnitudes are
computed compared to the USNO star at 00:26:58.713 +18:56:56.61 (Fox et
al. GCN 1564
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 ) assuming R=15.64.

Magnitudes of GRB021004 : (R band) 

2002 oct. 04 22:04:44.5 UT (JD=2452552.41996) : 18.29
2002 oct. 04 22:12:01.7 UT (JD=2452552.42502) : 18.37
2002 oct. 04 22:20:32.3 UT (JD=2452552.43093) : 18.40
2002 oct. 04 23:51:04.3 UT (JD=2452552.49380) : 18.67
2002 oct. 04 23:57:13.2 UT (JD=2452552.49807) : 18.65

Dates are middle of exposures. This data fill nicely a gap around T0 +
0.4 when the decay index of the light curve increases.

A. Klotz and M. Boer, CESR/CNRS (Centre d'Etude Spatiale des
Rayonnements, Toulouse, France) report measurements obtained by members
of the AUDE network (Association des Utilisateurs de Detecteurs
Electroniques). As images were not filtered, the authors computed the
magnitudes in reference to the R band system which is expected to be the
most reliable for unfiltered CCD images. 

Magnitudes of GRB 021004 : 

2002 oct. 5, 01h04 UT : R=18.8 by R. Poncy (1) 
2002 oct. 5, 22h30 UT : R=19.70 +/- 0.1 (referenced to USNO) by P.
Martinez & P.M. Berger (2) 

(1) Diam. 254 mm 
    Integ. 30 x 60 sec. 
    Location : Le Cres, France (IAU station 177)

(2) Diam. 820 mm 
    Integ. 23 x 60 sec. 
    Location : ADAGIO observatory, Belesta, France (IAU station A05) 

Note also a detection of the optical counterpart at 2002 oct. 5, 21h30
UT, by A. Klotz using a telescope of only 200 mm diameter. Low signal to
noise did not allow to measure the magnitude, but the limiting magnitude
of the image is about 20.5 (addition of 60 frames of 60 sec). This
demonstrates that small telescopes can detect the afterglow of a GRB
even 1.4 days after the GRB event.

Images are available at the following URL:
http://www.cesr.fr/~klotz/grb021004/aude.html

These data are coherent with already reported magnitude in other
circulars, and fill some gaps in the light curve.

E. Berger, D. A. Frail, and S. R. Kulkarni report on behalf of a larger
collaboration:

"We observed the radio afterglow of GRB 021004 (Frail & Berger GCN 1574
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 ;
Berger, Kulkarni, & Frail GCN 1612
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 ) with the VLA at 1.43, 4.86, and 8.46
GHz on October 10.17 UT.  We measure the following flux densities:
F(1.43)=48+/-53 microJy, F(4.86)=359+/-38 microJy, and F(8.46)=598+/-33
microJy.  The resulting spectral slope is beta~1 (F_nu~nu^beta), in
excellent agreement with the unusual value of beta=0.9 between 8.5 and 86
GHz measured by Berger, Kulkarni, & Frail (GCN 1612
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 ).  This again
indicates that the spectrum is not due to a transition from
optically-thick (nu^2) to optically-thin (nu^1/3) emission, and it further
highlights the unusual nature of this radio afterglow."

This message may be cited.

E. Berger, S. R. Kulkarni D. A. Frail report on behalf of the larger
Caltech-NRAO-CARA GRB collaboration:

"We have continued to monitor the radio afterglow of GRB 021004 (GCN 1574
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 )
with the VLA at 8.5 and 22.5 GHz.  Combining our observations with the
Ryle Telescope 15 GHz measurements (GCN 1588
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 ) and the IRAM Plateau de Bure
Interferometer 86 GHz measurement (GCN 1590
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 ) we find a spectral slope
nu^0.9 between 8.5 and 86 GHz.  There is no sign of curvature in the range
of 8.5 to 86 GHz as would be expected for a transition from
optically-thick (nu^2) to optically-thin (nu^1/3) emission.

Millimetric emission from an underlying host galaxy could steepen the
spectrum (from the reasonably expected nu^1/3).  However, the upper limit
at 232 GHz from IRAM PdBI (GCN 1590
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 ) indicates that there is no
significant millimeteric emission from a host galaxy.

It therefore appears that the radio spectrum is unusual compared to the
radio afterglows of most other well-studied afterglows.  However, we note
that the early spectrum of the radio afterglow of SN 1998bw/GRB 980425
(Kulkarni et al. Nature 395, 663, 1998) also did not conform to the
synchrotron spectrum expected from a single power law electron energy
spectrum with uniform magnetic fields.  Multiple components or some other
emission mechanism may be needed to explain this unusual spectrum."

This message may be cited.

Isabel Salamanca(1), Evert Rol(1), Ralph Wijers (1), Sara Ellison(2),
Lex Kaper(1), and Nial Tanvir (3) (1) University of Amsterdam (2)
Universidad Catolica de Chile (3) University of Hertfordshire, report:

We obtained a spectrum with the double arm spectrograph ISIS at the
4.2-m WHT telescope at La Palma (Spain) on October 4. A partial
calibration of the blue arm spectrum (2 Angstrom spectral resolution)
reveals the presence of four absorption components at detected in CIV
at redshifts 2.295, 2.298, 2.320, and 2.327, i.e. spanning a total
velocity range of approximately 3000 km/s.  The latter three
components are also clearly detected in SiIV, with a marginal
detection of SiIV at z=2.295.  The lines around 4000-4050 Angstrom can
be then identified as Ly-alpha (for which we also detect the emission
component reported earlier); there is a close match for the components
at z=2.320 and 2.327, whilst the two lowest redshift Lya components
are blended.

The interpretation of this 4-component absorption system could be of
absorption local to the burst source, or of cosmological components.

If all arise local to the burst, we must be viewing through ejecta in
a supernova-like explosion. After a day, supernova ejecta are so
opaque that we cannot see through them, and so we must be viewing the
results of an explosion that occurred weeks or more before the burst,
as in the supranova model. The narrowness of the components then must
mean that the ejecta have already cooled and partly condensed into
filaments. It is a challenge to have this happen within weeks, and
given the small filling factor inherent to filamentation, to have our
line of sight intersect four filaments.

If cosmological, we see our line of sight pass through 4 mass
concentrations of a magnitude well in excess of lyman limit systems in
quasar absorption line terms. These would all be local to the host
galaxy in cosmological terms, but with velocity separations large for
even a present-day massive cluster. Given that only 10-20% of quasars
at redshift 1 - 2 have even one such system, one concludes nonetheless
that seeing four systems implies a physical relation between them.
Thus we would be seeing a very large cosmic structure at z=2.3 with an
extent of 3000 km/s in velocity space. This is very difficult to get
in any cosmology, and would push cosmological models to very low
values of Omega_matter.

Further high-resolution spectroscopy is required to resolve the
velocity structure, and to determine the abundances and thermodynamic
state of these absorption systems, in order that we may understand the
nature of this remarkable system. In local models, one might find
variability in the Lyman-alpha emission.  Since the source is now
fading past R=21, these observations are most urgent.

This message may be cited.

K. Sahu, A. Fruchter, I. Burud, and K. Sembach (STScI) report for the
larger GOSH collaboration:

GRB 020411 was observed from 14:00 to 23:00 UT on Oct 6 using the STIS
CCD spectrograph and G430L grism, and the NUV MAMA and prism.   The 
CCD spectrum shows two prominent absorption features, at 404.1 nm and
401.1 nm.    The first of these agrees well with a previously reported
feature that has been identified as Lyman alpha at z=2.323.  The second
absorption feature would then appear to be Si III at z=2.324, which
would
imply an offset of order 100 km/s in the restframe between the ionized
and neutral components.  

The NUV MAMA prism observation shows a break shortward of approximately 
303.0 nm, which would correspond to the Lyman limit of the z=2.323
system.  
Calibration of both the CCD and NUV MAMA observations may be improved
when all files from the observation are available to us.

Malesani D., Covino S., Ghisellini G., (INAF-OAB), D. Lazzati (IOA,
Cambridge, UK), Cecconi M., Fugazza D., Guerra J.C. (INAF-TNG), Masetti
N. (IASF-CNR), Pian E. (INAF-OATs), on behalf of a larger Italian
collaboration, report:

On Oct 6.05 UT, we observed the optical counterpart of GRB 021004
(Shirasaki et al., GCN 1565
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 ; Fox, GCN 1564
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 ) using the 3.6m TNG telescope
in the Canary Islands, with an R and an I filter. With respect to the
comparison star used by Fox and calibrated by Henden (GCN 1583
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 ), the
source has the following magnitudes:

UT     Band  Mag    Error
6.062  R     19.72  0.04
6.058  I     19.22  0.04

Our values are in good agreement with the nearly simultaneous
measurements of Holland et al. (GCN 1585
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 ), Bersier et al. (GCN 1586
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 ),
and Halpern et al. (GCN 1593
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 ).


To estimate the break time t_break of the light curve, we can use the
correlation discovered by Frail et al. (2001, ApJ, 562:L55), upon which
the standard energy reservoir result is based; this can be expressed
through

t_break = t_0 * (1+z) / E_iso

where t_0 = 22(+34)(-16) days and E_iso is the isotropic energy in units
of 10^52 ergs. The large error for t_0 originates from the intrinsic
dispersion (a factor of 2) in the distribution of beaming-corrected
energies (Frail et al. 2001). This result, however, holds independently
of the unknown jet opening angle, external density and radiative
efficiency.

Using the HETE-2 fluence (Lamb et al., GCN 1600
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 ), and assuming a
bolometric correction k = 1.3+-0.2 (calculated following Bloom, Frail &
Sari 2001, AJ, 121:2879), we can predict the break time for this
afterglow; we quote the results for the two reported values of the
redshift z:

1) z = 1.60 (Fox et al., GCN 1569
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 ):
   E_iso = 3.1*10^52 ergs;
   7.5 days < t_break < 47 days;
   t_break_best = 18.8 days.

2) z = 2.32 (Chornock & Filippenko, GCN 1605
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 ):
   E_iso = 5.6*10^52 ergs;
   5.3 days < t_break < 34 days;
   t_break_best = 13.4 days.

Given the slow average decline shown by this burst, this event should
remain bright longer than usual. Further observations are hence
encouraged.


This message is citeable.

E.A.Barsukova (SAO), V.P.Goranskij (Sternberg Institute),
G.M.Beskin (SAO), V.L.Plokhotnichenko (SAO), A.S.Pozanenko  (IKI).

We have observed the GRB021004 afterglow (GCN 1564
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 ) with SAO RAN
1-m Zeiss telescope and UBVRcIc photometer with Electron K-585
CCD.  Observations cover time interval from 7 to 12 hours after
the burst. Exposure time of each frame is 10 minutes, the field
is 3'x4'. Results of the photometry are in the table below. Standards
are taken relative to A.Henden and U.Munari, AsApSuppl. v.143,
343 (1999) standard near V407 Cyg.

        R.A., Decl, 2000          Rc        V        B
       position from A1.0
    C 0 26 57.9 +18 56 07   16.35    16.71    17.15
    F 0 26 58.7 +18 56 56   15.53    16.30    17.13
 +/-0.01  +/-0.02  +/-0.02
    a 0 26 52.0 +18 55 13   13.85    14.55    15.29
 +/-0.01  +/-0.02  +/-0.02

  Date             UT           mag
               (Mean epoch)

  filter=Rc, Typical errors=0.05

  021004   18  58  12    17.89
  021004   19  31  49    17.88
  021004   20  05  28    18.06
  021004   20  41  33    18.09
  021004   21  25  37    18.17
  021004   21  58  50    18.35
  021004   23  08  06    18.39
  021004   23  41  19    18.54
  021005   00  03  05    18.57

  filter=V, Typical errors=0.07

  021004   19  09  24    18.33
  021004   19  42  55    18.34
  021004   20  19  36    18.43
  021004   20  52  43    18.45
  021004   21  02  35    18.60
  021004   21  36  45    18.66
  021004   22  09  46    18.82
  021004   23  27  40    18.89
  021004   23  52  09    18.87

  filter=B, Typical errors=0.10

  021004   19  20  49    18.67
  021004   19  54  03    18.78
  021004   20  30  35    18.77
  021004   21  14  29    18.98
  021004   21  47  49    19.10
  021004   22  20  46    19.05
  021004   23  30  11    19.26

The data obtained is compatible with achromatic decay.
Analysis of the data set is underway and result will be improved.
The figures of BVRc observations may be found in
http://grb.rssi.ru/GRB021004/

This message can be cited.

R. Chornock and A. V. Filippenko, University of California, Berkeley,
report that optical spectra (range 300-940 nm) of the GRB 021004
afterglow (GCN 1564
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 , 1565
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 ) were obtained with the Low Resolution
Imaging Spectrometer on the Keck-I 10-m telescope on Oct. 8 UT.  We
detect the absorption lines due to Mg I, Mg II, and Fe II associated
with systems at z=1.381 and 1.603 previously noted (GCN 1569
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 ).  We
also detect the unidentified absorption lines at 463, 466, 510, and
514.5 nm reported in GCN 1579
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 , as well as the narrow emission line at
405 nm and the absorption lines between 400 and 404 nm (GCN 1599
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 ).

We identify the emission line as Lyman-alpha at z=2.323, in
contradiction to the identification as C IV in GCN 1599
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 .  We note that
P-Cygni absorption line profiles from a hypothetical starburst host
galaxy should not be prominent above the bright continuum of the
transient.  In addition, we feel that a lone UV emission line is
significantly more likely to be Lyman-alpha than C IV.  The
previously unidentified absorption lines can now be identified as the
Si IV 1393.8, 1402.8 Angstrom doublet and C IV 1548.2, 1550.8
Angstrom doublet.  These absorption lines have multiple velocity
components, as does the Lyman-alpha absorption.  We note the
wavelength coincidence of one of the components of Lyman-alpha with
the expected C IV absorption from the Mg II system at z=1.603, but
believe it only to be a coincidence.

An additional point in favor of the z=2.323 interpretation is the
appearance of the continuum to the blue of the Lyman-alpha line.
While there is no substantial Lyman break, there are many more
absorption lines blueward of Lyman-alpha than redward.  A previously
unnoted absorption feature with multiple components is present at
341 nm, consistent with Lyman-beta at this redshift.

This message may be cited.

A third observation of the field of GRB021004 has been made at 15 GHz
with the Ryle Telescope from 2002 Oct 07 23:03 to 2002 Oct 8 02:52 UT.
The flux density measured at the position of the OT was
1.14 +- 0.30 (rms) mJy.


Guy Pooley
MRAO, Cavendish Laboratory, Cambridge UK.

N. Masetti, G. Pizzichini (IASF/CNR, Bologna), C. Bartolini, A. Guarnieri,
A. Piccioni, E. Maiorano, A. Simoncelli (Dip. Astronomia, Univ. of
Bologna) and A. De Blasi (INAF - Astron. Obs. of Bologna) report:

"On 2002 October 7 we have imaged the optical counterpart (Fox et al., 
GCN #1564
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 ) of GRB021004 (=H2380; GCN #1565
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 ) in the R band with the
1.52-m Loiano telescope (plus BFOSC) of the Astronomical Observatory of
Bologna. Our 30-minutes observation, which started at 18:45 UT, was 
carried out under poor seeing conditions (the seeing was ~3 arcsec).

Using the R-magnitude calibration of Henden et al. (GCN #1583
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 ), we find 
the optical afterglow of GRB021004 at R = 20.4 +- 0.1.
Therefore, the decline seems to have started again after the halt remarked
by Stanek et al. (GCN #1598
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 ); this is suggestive of a step-like decay
behaviour similar to that displayed by GRB000301c (Masetti et al., 2000,
A&A, 359, L23).

This message is quotable.".

[GCN OPS NOTE (07oct02):  This Circular was received at 21:46 UT,
but was delayed due to a change in the submittor's vetted address.]

N. Mirabal, E. K. Armstrong, J. P. Halpern (Columbia), and
J. Kemp (Joint Astronomy Centre and Columbia) report for the
MDM GRB follow-up team:

"Continued monitoring of the optical afterglow of GRB 021004 with
the MDM 1.3m yields the following measurements on 2002 Oct 7 UT:

                --------------------
                  UT      R     +/-
                --------------------
                02:38   20.19   0.03
                06:37   20.14   0.02
                11:21   20.21   0.04
                --------------------

Here we used the revised calibration of Henden (GCN #1583
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 ) in which
the reference star has R=15.52.  Although the decay appears to have
slowed over the past day, it is difficult to know at this time whether
it has stopped fading, or for how long."

An updated decay curve accounting for revised calibrations of
GCN published data is at:

http://www.astro.columbia.edu/~jules/021004.ps

James Rhoads, Ingunn Burud, and Andrew Fruchter report
on behalf of a larger collaboration:

H band images of GRB 021004 were obtained at the NASA Infrared
Telescope Facility (IRTF) on October 5, 6, and 7 UT.
Quick look photometry of the October 6 and 7 data show
continued fading of the OT, in contrast to the optical
behavior reported by Stanek et al (GCNC 1598)
over a very similar period.

Date	Time		H	err_H
--------------------------------------
Oct 6	12:26 UT	17.74 	0.05
Oct 7	11:31 UT	18.21	0.05

The errors are the error in 2MASS photometry of our
local photometric calibrator; hence the fading is known
more precisely than the absolute photometry,
and is about 0.47 +- 0.04 mags.

This implies that the transient became bluer from Oct.
6 to Oct 7, with a change in logarithmic spectral slope of
about 0.4.  This could correspond to the arrival of
fresh energy at the blast wave external shock,
carried by slow ejecta.
Interestingly, the color shift corresponds roughly to the
change between a frequency below and above the cooling break.

We thank David Griep, Bill Golisch, and John Rayner for
their invaluable assistance in obtaining these observations.

[GCN_OPS NOTE (11 Nov 02):  Added the last paragraph of acknowledgements.]

D. Lamb, G. Ricker, J-L Atteia, N. Kawai, and S. Woosley on behalf of
the HETE Science Team;

J-F Olive, M. Boer, J-P Dezalay, and K. Hurley on behalf of the HETE
FREGATE Team;

Y. Shirasaki, M. Matsuoka, T. Tamagawa, K. Torii, T. Sakamoto,
A. Yoshida, E. Fenimore, M. Galassi, T. Tavenner, C. Graziani, and
T. Donaghy, on behalf of the HETE WXM Team;

J. Villasenor, R. Vanderspek, J. Doty, 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;

write:

Analysis of the FREGATE data for GRB021004 (=H2380) shows that
the fluence-averaged photon number spectrum of the burst is well-fit
by a single power-law spectrum with slope alpha = 1.64 +/- 0.09, and
gives the following values for the fluences of the burst:

S = 1.8 x 10-6 erg cm-2 (50-300 keV), and

S = 3.2 x 10-6 erg cm-2 (7-400 keV).

Using the latter value and assuming Omega_Lambda = 0.7, Omega_m = 0.3,
and H_0 = 70 km s-1 Mpc-1, the isotropic-equivalent energy of the
burst is

E_iso = 2.06 x 10^(52) ergs.

Using this value of E_iso and equation (1) of Frail et al. (ApJ 562,
L55, 2001) [see also Sari et al. (ApJ 519, L17, 1999)] to estimate the
jet break time, we find

t_j = 1.3 [(1+z)/2.60] (theta_j/0.070)^(8/3) [E_iso/2 x 10^(52) ergs]
           x (eta/0.2)^(-1/8) (n/0.1 cm-3)^(-1/8)  days.


Analysis of the WXM data for GRB021004 gives the following value for the
fluence of the burst in the WXM energy band:

S = 7.5 x 10-7 erg cm-2 (2-25 keV).

The fluence ratio S(2-25)/S(50-300)= (7.5 x 10-7)/(1.8 x 10-6) = 0.42
implies that GRB021004 is an X-ray rich GRB [log (S_x/S_gamma) > -0.5].

This message is citable.

F. Javier Castander (IEEC-Barcelona/U. de Chile), E. Gawiser (Yale/U. de Chile),
C. Foltz, S. West (MMTO), G. Williams (MMTO/SAO), E. Falco (FLWO), 
T. Matheson, K.Z. Stanek (CfA), P. Garnavich (Notre Dame) and L. Macri (NOAO)
report:

Spectra of the GRB 021004 afterglow were obtained with the
Magellan 6.5m Baade Telescope on Oct. 5.0 UT and with the
MMT on Oct. 5.1, 5.3 and 6.3 UT. The spectra confirm two major MgII
absorption systems at z=1.38 and z=1.60 (GCN 1569
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 , 1579
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 , 1582
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 ). The moderate
resolution Magellan spectra show that the strong, unidentified line
at 515 nm is made of 3 components separated by 0.9 nm. The MMT spectra
extended to 330 nm and show no Lyman forest break implying a
limit to the redshift of z<1.7. 

The CIV absorption in the z=1.60 system is very strong with an
equivalent width of 0.5 nm (rest frame). There is another strong
line 2000 km/s to the blue of the CIV which may be  a second CIV
component. In addition, an emission line is detected at 405.2 nm forming
a P-Cygni profile with the CIV absorption. We conclude that the host
is a starburst galaxy.

This message may be cited.

GRB021004: not fading anymore?

K. Z. Stanek, D. Bersier, J. Winn (Harvard-Smithsonian Center
for Astrophysics), P. Garnavich (Notre Dame) report:

R-band images of the afterglow associated with GRB 021004 (GCN 1564
Loading...
 
 )
were obtained with the Fred L. Whipple Observatory 1.2m telescope on
Oct. 7 between 02:43 and 11:09 UT. The afterglow seems to have stopped
fading.  We give below our last measurement from the night of Oct. 6
and our last measurement on Oct. 7

Date   Time      R      err_R
-----------------------------
Oct 6  11:25 UT  20.08   0.05
Oct 7  11:09 UT  20.09   0.06

This could be due to the presence of a bright host galaxy, but PSF
fitting shows no residual as would be expected from an extended
source.  Furthermore, such a bright host galaxy would be in conflict
with the upper limits of Wood-Vasey et al. (GCN 1572
Loading...
 
 ).

This message may be cited.

GRB 021004: Optical Photometry at 2.5 Days

S. T. Holland (Notre Dame), J. P. U. Fynbo, M. Weidinger (Aarhus)
M. P. Egholm (NOT), A. Levan (Leicester),
J. Hjorth and H. Pedersen (Copenhagen)
on behalf of a larger collaboration report:

     We have obtained deep Rc-band images of the field containing
GRB 021004 using the 2.56-meter Nordic Optical Telescope on La Palma
on the evening of Oct. 6 UT.  The optical afterglow of GRB 021004
is visible in our images.  Using the comparison star from
Fox et al. (2002, GCN 1564
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 ) and the calibration of
Henden (2002, GNC 1583) we find the following preliminary magnitudes:

          Date       UT     t(days)   Rc   Err
          -------------------------------------
          Oct. 6  19:57:07   2.327   20.12 0.10
          Oct. 6  20:37:26   2.355   20.08 0.01
          Oct. 6  21:56:38   2.410   20.16 0.03
          Oct. 6  22:08:09   2.418   20.15 0.03      

     These magnitudes, and those of Holland et al. (2002, GCN 2002
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 ),
imply that the optical afterglow faded at a rate a rate of alpha =
-0.9 between 32 and 58 hours after the burst.  We note that that the
optical afterglow appears to be fading less slowly than it did between
12 and 17 hours after the burst.  A deep Rc image constructed from all
of our data shows no evidence for a host galaxy.  A plot of our
preliminary Rc-band light curve is available at
<http://www.nd.edu/~sholland/grb/grb021004/lightcurve2.eps>.

This message may be cited.

GRB 021004: polarimetric observations
---------------------------------------

E. Rol (University of Amsterdam), J.M. Castro Cerón (ROA, San Fernando),
J. Gorosabel, A.J. Castro-Tirado (IAA-CSIC, Granada), A. Fruchter (STScI,
Baltimore), J. Greiner (MPE, Garching), J. Hjorth (Univ. of Copenhagen),
E. Pian (OAT-INAF, Trieste) R.A.M. Wijers and E. van den Heuvel (Univ.
of Amsterdam), on behalf of GRACE, report:


"We have performed polarimetric observations of the afterglow of
GRB 021004 (Fox, GCN 1564
Loading...
 
 ; Shirasaki et al. GCN 1565
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 ) with the FORS1
instrument at the VLT. The observations were done between October 5.15
and October 5.20 UT in the V-band.
   Independently of Covino et al. (GCN 1595
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 ), we find a polarization value
for the OT of P = (1.32 +/- 0.28) %, with a position angle of theta =
(125 +/- 1) degrees.
   Correcting for possible polarization due to the interstellar medium is
rather difficult, since there are few bright stars close to the OT position.
Using 12 bright stars within 4.5 arcmin from this position, we find a mean
ISM polarization of P = (0.7 +/- 0.3) % and theta = (116 +/- 4) degrees.
The error in the degree of polarization is obtained from the spread in the
values found for the field stars.
   The resultant degree of polarization for the OT is P = (0.57 +/- 0.40) %.
Since this result could be entirely due to polarization induced by ISM,
we derive a 3-sigma upper limit of P = 1.2 % for the degree of
polarization.
   The QU Stokes' parameter plane can be seen at:
 http://zon.wins.uva.nl/~evert/grb021004/

This note can be cited."

S. Covino, G. Ghisellini, D. Malesani, G. Tagliaferri, F. Zerbi (INAF Brera, 
Italy); A. Cimatti, M. Della Valle, S. Di Serego (INAF Arcetri, Italy); F. 
Fiore, G.L. Israel, L. Stella (INAF Roma, Italy); E. Costa, P. Soffitta (IASF 
Roma, Italy), S. Mereghetti (IASF Milano, Italy), N. Kawai (Tokyo Tech, 
Japan); D. Lazzati, E.M. Rossi (IoA, Cambridge, UK); S. Ortolani (Univ. of 
Padova, Italy); L. Pasquini (ESO, Germany); G. Ricker (MIT, USA); E. Le 
Floch, P. Goldoni, F. Mirabel (CEA, France),  M. Dahlem, P. Vaisanen, C. 
Melo, C.  Lidman (ESO Paranal) report:


We observed the optical counterpart to GRB 021004 (Shirasaki et al. GCN 1565
Loading...
 
 ; 
Fox, GCN 1564
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 ) on October 5.077 (13.75 hours after the GRB trigger). The 
observations were performed with the ESO VLT-UT3 (Melipal) telescope equipped 
with FORS1 and a Bessel V filter in the imaging polarimetry mode. The 
transient source is clearly detected in the acquisition image with a 
magnitude V = 19.34 +/- 0.02 with respect to the USNO star at 00:26:58.713 
+18:56:56.61(Fox, GCN 1564
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 ) as calibrated by Henden (GCN 1583
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 ).

The polarimetric observations were obtained from October 5.080 to 5.149 UT 
(from 13.82 to 15.48 hours after the burst). We found linear polarization at 
the level of P = (1.26 +/- 0.10)% with position angle (114.2 +/- 2.2) degrees 
(uncertanties are 1-sigma errors).

The polarization induced by the interstellar matter in our Galaxy was 
estimated by field stars and accounts to P = (0.61 +/- 0.04)% with position 
angle (114.4 +/- 1.7) degrees. Once we remove the effect of ISM the intrinsic 
polarization of the optical transient turns out to be P = (0.65 +/- 0.11)% 
and position angle (114.4 +/-  4.6) degrees. Given that the field stars show 
a rather wide distribution in polarization degree and that the position angle 
for the stars and the optical transient are essentially the same, we can not 
rule out the possibility that the measured polarization is entirely due to 
the ISM in the Galaxy. This, in addition, leaves little room for host galaxy 
ISM induced polarization, that could account for at most a small fraction of 
the observed polarization. 


At the web page http://www.merate.mi.astro.it/~malesani/GRB021004 we report 
the QU Stokes' parameter plane.



This message is citeable.

K. Matsumoto (Okayama Univ.), T. Kawabata (BAO), K. Ayani (BAO), 
Y.Urata (Titech / RIKEN), H. Yamaoka (Kyushu Univ.), 
N. Kawai (Titech / RIKEN) report:

"We have corrected our photometric data at Oct. 4 14:13 UT of the
GRB021004 afterglow (reported in GCN1567
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 ), which was obtained by using
the R-band photometric reference USNO star RA=00:26:58.77,
DEC=+18:56:56.1 as R=15.52 in the field photometry (Henden, GCN 1583
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 ),
and present the additional preliminary results as follows.

epoch  start time UT  exposure   R-mag.
1      Oct. 4 13:57   60s        16.38
2      Oct. 4 14:13   60s        16.36
3      Oct. 4 14:55   60s        16.63
4      Oct. 4 16:31   60s x 3    17.03

Their typical errors (1 sigma) are 0.12 mag.

We find that our point 1 is fainter than the magnitude extrapolated back
from the observations at later epochs (decay index 1.32, Weidinger et al.
GCN 1573
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 ).  This suggests that the break occurred during our
observations between 0.08 d and 0.2 d after the burst.

Analyses of the full data set of our time-resolved photometry in
VRI-bands are underway."

This message may be cited.

J. P. Halpern, N. Mirabal, E. K. Armstrong, C. C. Espaillat (Columbia),
J. Kemp (Joint Astronomy Centre and Columbia) report for the MDM GRB
follow-up team:

"Continued monitoring of the optical afterglow of GRB 021004 with
the MDM 1.3m yields the following measurements on On 2002 Oct 6 UT:

		--------------------
		  UT      R     +/-
		--------------------
		02:41	19.84	0.03
		07:03	19.91	0.02
		11:39	20.00	0.02
		--------------------

Here we used the revised calibration of Henden (GCN #1583
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 ) in which
the reference has star has R=15.52.  Previous R magnitudes reported
in GCN #1578
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  would have to be decreased by 0.12 to match this reference.
The mean R-band decay between 8 and 48 hours as determined by the NOT and
MDM measurements can be described as a power law of slope -1.05, but with
highly significant deviations from a power law (Winn et al., GCN #1576
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 )
that are robust against cross-calibration issues."

An updated decay curve will be maintained at:

http://www.astro.columbia.edu/~jules/021004.ps

A. Henden (USRA/USNO) and S. Levine (USNO) report on behalf
of the USNO GRB team:

We have measured the two high signal/noise Ic images
acquired on the Strand 1.55m astrometric telescope at NOFS
on 021005 UT.  Using 23 UCAC2 stars on each frame,
we derive the following accurate position for the optical
afterglow of GRB021004:

  00:26:54.674  +18:55:41.59  J2000

with approximately 50mas external error in each coordinate.
This is in good agreement with the coordinates given
by Fox, et al. (GCN 1564
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 ).

Arto Oksanen (Nyrola), Mika Aho (Nyrola), Kevin Rivich (Ft. Bend),
Kim Rivich (Ft. Bend), Doug West (West Skies),
and Doug Durig (Cordell-Lorenz) report on behalf of the AAVSO
International GRB team:

We have observed the optical afterglow candidate
(Fox et al., GCN 1564
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 ) for GRB021004 (Shirasaki et al.,
GCN 1565
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 ; Doty et al., GCN 1568
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 ) from multiple observatories.
The preliminary photometric reductions are given below;
these measures will be improved, but indicate the
datasets that are currently available:

   Date     UT  sec x n  fil  Site           mag
  021004  19:53  60x22   Rc  Nyrola   0.4m  17.90
  021004  21:24  120x10  Rc  Nyrola   0.4m  17.96
  021004  21:48  120x11  Rc  Nyrola   0.4m  18.22
  021004  22:25  240x9   Rc  Nyrola   0.4m  18.37
  021004  23:26  240x10  Rc  Nyrola   0.4m  18.41
  021004  00:13  240x10  V   Nyrola   0.4m  19.25
  021005  01:04  240x10  Rc  Nyrola   0.4m  18.83
  021005  01:28  60x12   CR  West     0.2m  19.0
  021005  02:08  300x3   CR  Cordell  0.3m  19.0
  021005  04:43  20x60   Rc  Ft. Bend 0.9m  19.2

Where CR indicates unfiltered measures, zeropointed
onto the Rc system.  Further observations are in progress.

This report can be cited.

IRAM Millimeter detection of GRB 021004
=================================================

Michael Bremer [1] and Alberto J. Castro-Tirado[2]
  [1] IRAM, Grenoble , [2] IAA-CSIC, Granada

The GRB afterglow has been observed with the IRAM Plateau de 
Bure Interferometer in a six-antenna compact configuration 
under good meteorological conditions from UT October 5th 22:17 to 
October 6th 2002 01:02.

 The source has been detected at 86.233 GHz (8.3 sigma).
 Upper limits have been obtained 231.700 GHz.

We have used the coordinates by Fox et al. (GCN 1564
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 ), detecting the
source at offsets d_RA 0.21"(+-0.42"), d_DEC +0.47" (+-0.30").
Results of UV point source fits fixed to the phase center are given below.

 Frequency       Flux and 1 sigma error            Beam size
-------------------------------------------------------------------------
 86.233 GHz       2.5 (+-0.3) mJy/beam         8.44" x 4.96" at PA=76 deg
231.700 GHz       1.9 (+-1.5) mJy/beam         3.50" x 1.63" at PA=76 deg

We will continue to monitor the source.

   This message may be cited.

K. Torii (RIKEN), T. Kato (Kyoto Univ.), and H. Yamaoka (Kyushu Univ.)
report:

 In response to the GCN/HETE burst position notice, a part of the
error region of GRB 021004 (Shirasaki, et al., GCN 1565
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 ) was observed
by the automated system at RIKEN. Starting at 12:09:27 UT (193-s after
the burst trigger), 30-s exposures were repeated with the 0.20-m
reflector equipped with unfiltered CCD AP7p.

 Frequent passages of clouds significantly degraded the limiting
magnitudes of the data. The optical afterglow reported by Fox (GCN
1564
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 ) is not visible in our early phase images. Comparison with the
USNO-A2.0 red magnitudes gave the following 3-sigma upper limits for
the afterglow. Further analyses for the full data set are in progress.

----------------------------------------
Mean epoch     From GRB   Magnitude  
----------------------------------------
12:09:42 UT    208 s      > 13.6    
12:10:21       247        > 13.6    
12:11:00       286        > 13.6    
12:11:40       326        > 14.2
12:12:19       365        > 13.6
----------------------------------------

A further observation of the field of GRB021004 has been made with the Ryle 
Telescope at 15 GHz. The observation was from 20:12 UT 2002 Oct 5
to 02:00 2002 Oct 06. The formal flux density determined from a quick-look
analysis was 0.82 mJy +- 0.28 mJy (rms).  Cf GCN 1574
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 , 1575
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 .

Guy Pooley
MRAO, Cavendish Lab, Cambridge.

D.K. Sahu, B.C. Bhatt, G.C. Anupama, T.P. Prabhu (Indian Institute of
Astrophysics, Bangalore) report on behalf of a larger collaboration:

GRB 021004 was observed with the HFOSC instrument on the 2-m Himalayan
Chandra Telescope on 4 and 5 October 2002. The magnitudes with respect to
the comparison star of Fox (GCN 1564
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 ) as calibrated by Henden (GCN 1583
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 )
on October 4 are listed below:

October 4 	   R    error
UT(center)	(300 s)

16:34:36 	17.13	0.01
16:44:03	17.20   0.01
16:52:29	17.24   0.01
17:01:16	17.21   0.01
17:09:26	17.28   0.01
17:18:12	17.39   0.01
18:04:37	17.69   0.01
19:48:36	17.90   0.02
20:33:36	18.06   0.02
22:05:58	18.20   0.03
23:36:22	18.46   0.05

		  B
		(600s)

17:34:18	18.42   0.01
20:01:07	18.90   0.02
22:18:14	19.18   0.03
23:03:11	19.31   0.03

		  V
		(400s)

17:42:32	18.01   0.01
20:14:38	18.50   0.02
22:40:30	18.77   0.03
23:14:33	18.78   0.03

These results supersede the ones reported in GCN 1581
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 . Preliminary
magnitudes for October 5 are

UT	R

17:38	19.38
22:10	19.70

The decay appears to have steepened following the bump noticed by Winn et
al (GCN 1576
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 ).

The spectra recorded with the same instrument on October 4 show the
redshift systems with z=1.38 and 1.60 (GCN 1582
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 ). The identification of
z=1.72 in GCN 1582
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  was erroneous and is regretted. On the other hand, we
confirm the presence of unidentified lines reported by Eracleous et al
(GCN 1579
Loading...
 
 ).

The message may be cited.

D. Bersier, J. Winn, K.Z. Stanek (Harvard-Smithsonian Center
for Astrophysics), P. Garnavich (Notre Dame) report:

Images of the afterglow associated with GRB 021004 (GCN 1564
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 )
were obtained with the Fred L. Whipple Observatory 1.2m
telescope on Oct. 6, 2:30 UT. The afterglow has resumed
fading (GCN 1585
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 ), after having shown short time scale
variability (GCN 1576
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 , GCN 1578
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 ).
We give below our last measurement from the night of Oct. 5
and our first measurement on Oct. 6

Date   Time      R      err_R
-----------------------------
Oct 5  12:11 UT  19.29   0.05
Oct 6  02:30 UT  19.92   0.10


This message may be cited.

GRB 021004: Optical Photometry at 1.5 Days

S. Holland (Notre Dame), J. P. U. Fynbo, M. Weidinger (Aarhus)
M. P. Egholm (NOT), and A. Levan (Leicester)
on behalf of a larger collaboration report:

     We have obtained deep R-band images of the field containing
GRB 021004 using the 2.56-meter Nordic Optical Telescope on La Palma
on Oct. 6.0 UT.  The optical afterglow of GRB 011211 is visible in our
images.  Using the comparison star from Fox et al. (2002, GCN 1564
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 )
and the calibration of Henden (2002, GNC 1583) we find the following
preliminary magnitudes:

          Date       UT     t(days)   Rc   Err
          -------------------------------------
          Oct. 5  20:24:58   1.346   19.54 0.04
          Oct. 5  20:36:28   1.354   19.53 0.04
          Oct. 5  22:22:31   1.428   19.62 0.05
          Oct. 6  00:10:41   1.503   19.66 0.04

     These magnitudes imply that the optical afterglow faded at a rate
of alpha = -1.08 during the four hours that these observations were
taken.  Combining these magnitudes with those of Weidinger et al.
(2002, GCN 1573
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 ) suggests that the optical afterglow has decayed with
a constant slope of alpha = -1.01 between 0.09 and 1.50 days after the
burst.  A plot of our preliminary Rc-band light curve is available at
<http://www.nd.edu/~sholland/grb/grb021004/lightcurve1.eps>.

This message may be cite

R. J. Cool, J. J. Schaefer (University of Wyoming) reporting on behalf of 
the University of Wyoming GRB Response Team under the direction of R. 
Canterna:

We observed the optical afterglow of GRB 021004 (GCN #1564
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 ) with the 
Red Buttes Observatory 0.6 meter telescope, operated through the 
University of Wyoming, between 4:37 UT and 6:25 UT on October 5 2002.  
All observations were completed in the R-band under unfavorable
conditions. 

We find R-band magnitudes for two epochs:

     UT          R_mag
     ====================== 
     04:52:36   19.14
     06:20:25   19.23

Typical errors on these values are +/- 0.1 mag.  Calibration was completed 
assuming the USNO star from Weidinger (GCN #1573
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 ) has an R magnitude of 
15.64.  Further analysis and observations are scheduled in the coming 
days.


This message may be cited.

Richard Cool
University of Wyoming
307/766-8918
riccool@uwyo.edu

A. Henden (USRA/USNO) reports on behalf of the USNO GRB team:

We have acquired BVRcIc all-sky photometry for
an 11x11 arcmin field centered at the afterglow coordinates
for GRB021004 (Shirasaki et al. GCN 1565
Loading...
 
 ; Fox et al. GCN 1564
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 )
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/grb021004.dat
The astrometry in this file is based on linear plate solutions
with respect to UCAC2.  The external errors are less than 100mas.

The coordinates of the afterglow, based on UCAC2, are:
  00:26:54.68  +18:55:41.6  J2000
The error in RA is about 0.05arcsec; the error in Dec
is about 0.2arcsec.  These coordinates will be improved,
but are in good agreement with Fox et al.
The object is nor particularly red or blue,
so a typical field star should work for a comparison.

While the night was photometric, the GRB field was observed
at high airmass due to other programs on the 1.0m telescope.
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, and to include
U-band measures.  You should check the dates on
the .dat file prior to final publication to get the latest photometry.

In particular, the comparison star used by Fox et al.
has the following position and magnitudes:

    RA (J2000) DEC           V     B-V    V-R   R-I
00:26:58.77  +18:56:56.1  16.261  1.204  0.737  0.664

These values yield Rc=15.52, somewhat fainter than the
assumed magnitude in Fox.

Calibration of the GRB021004 field will continue around October 9 UT.

G.C. Anupama, D.K. Sahu, B.C. Bhatt and T.P. Prabhu, (Indian Institute of
Astrophysics, Bangalore) report on behalf of a larger collaboration
optical observations of GRB 021004 obtained from the 2-m Himalayan Chandra
Telescope, Indian Astronomical Observatory, Hanle:

We have monitored GRB 021004 in BVRI bands and obtained spectra with a
resolution of 1.8 nm on 2002 October 4. The spectrum in the range of
500-1000 nm at October 4.883 UT shows z=1.38 and 1.60 reported in GCN
#1569
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  and also indicates a higher redshift of z=1.72. The absorption-lines
identified are:

Obs (A)	ident (A)	z

5576	FeII 2343	1.38
6093	FeII 2343	1.60
6166	FeII 2586	1.38
6654	MgII 2796	1.38
6669	MgII 2803	1.38
6757	FeII 2599	1.60
7269	MgII 2796	1.60
7296	MgII 2803	1.60
7601	MgII 2796	1.72
7629	MgII 2803	1.72

Assuming the USNO star has R=15.64, the R magnitudes at the beginning and
end of observing run were:

2002 October 4.70 UT	R=17.44
	     4.95 UT	R=18.59

[GCN OPS NOTE (05oct02):  This submission was received at 13:52 05 Oct 02 UT,
but was delayed in distribution due to the lack of an entry in the vetting
list.  A new entry was added and the submission manually invoked.]

D.K. Sahu, B.C. Bhatt, T.P. Prabhu (Indian Institute of Astrophysics,
Bangalore) report on behalf of a larger collaboration:

We have observed the optical afterglow of GRB021004 with the 2-m Himalayan
Chandra Telescope, Indian Astronomical Observatory, Hanle. Preliminary
magnitude estimates in R band using the USNO star (GCN #1564
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 ) with R=15.3
are:

October 4	R

16:41 UT	17.11
22:47 UT	18.26

[GCN OPS NOTE (05oct02):  This submission was received at 05:30 05 Oct 02 UT,
but was delayed in distribution due to the lack of an entry in the vetting
list.  A new entry was added and the submission manually invoked.]

S. Balman (METU), H.Esenoglu (IU), M.Parmaksizoglu (TUG),
Z. Aslan (TUG), U. Kiziloglu (METU)
report on behalf of a larger collaboration (TUG, IKI, KSU):

We have observed the optical transient (OT) of GRB 021004 (GCN #1564
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 ,
1565
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 , 1568
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 ) with the 1.5m RTT150 telescope of TUG (TUBITAK National
Observatory, Turkey) on Bakirlitepe between 19:30 and 20:30 UT on Oct 4 2002.

We find:

UT start   exp_tim   band  magnitude
 19:48:09   900 s    R     17.82+-0.03
 20:08:25   600 s    I     17.18+-0.04
 20:20:19  1200 s    V     18.19+-0.11

using USNO-A2 magnitude estimates. Analysis of the full data set is underway.

This message may be cited.

Mike Eracleous (Penn State), Bradley E. Schaefer (U. Texas), Jeff Mader
(McDonald Obs.), and Craig Wheeler (U. Texas) report on behalf of the
Hobby-Eberly Telescope GRB followup team:

"We have obtained spectra of the optical counterpart of GRB021004 (GCN
1564
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 ) with the 9.2-m Hobby-Eberly telescope.  The observations
consisted of a series of three 15-minute exposures starting at
2002-Oct-5 3:34UT and a series of three 15-minute exposures starting
at 2002-Oct-5 8:24UT with the Marcario Low-Resolution Spectrograph.
The spectra cover the range 4200 - 9200 Angstrom at a spectral
resolution of approximately 15 Angstrom.  We detect the Mg II
absorption lines reported by Fox et al.  (GCN 1569
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 ) and confirm the
presence of two absorption systems at z=1.38 and z=1.60.  We do not
detect any significant absorption corresponding to the Mg I line at a
rest wavelength of 2853 Angstrom (with z=1.60) as reported by Fox et
al.  (GCN 1569
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 ).  We do not find any lines suggestive of absorption
systems at higher redshifts.  We also detect the Fe II UV1, UV2, and
UV3 absorption multiplets associated with both redshift systems (the
Fe II lines associated with the z=1.60 have already been reported by
Fox et al.).  In addition we also find four prominent absorption lines
at observed wavelengths of 4633, 4664, 5109, and 5152 Angstrom, which
we have not yet been able to identify.  The ratio of wavelengths
between these pair of lines approximately equals (1+1.38)/(1+1.60),
which suggests that these lines are from the same features with rest
wavelengths of 1947 and 1960 Angstroms.  The continuum shape can be
described by a power law of the form f_nu ~ nu^{-p}.  After correcting
for Galactic extinction we tentatively estimate a power-law index of 
p ~ 1.5."

This message may be cited.

J. P. Halpern, E. K. Armstrong, C. C. Espaillat (Columbia),
J. Kemp (Joint Astronomy Centre and Columbia) report for the
MDM GRB follow-up team:

"We observed the optical afterglow (Fox, GCN #1564
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 ) of GRB 021004 with
the MDM 1.3m in BVRI.  On 2002 Oct 5 UT, we measure the following
preliminary magnitudes:

		--------------------
		  UT      R     +/-
		--------------------
		03:02	19.06   0.06
		03:36	19.17   0.05
		04:26	19.24	0.03
		04:51   19.30   0.04
		05:15   19.30   0.03
		05:39   19.25   0.03
		06:10   19.33   0.03
                06:34   19.30   0.04
		06:56   19.32   0.03
                07:19   19.42   0.03
		07:42	19.31	0.03
		08:05   19.31   0.03
		08:28   19.31   0.03
		08:50   19.27   0.03
                09:13   19.29   0.03
		09:41   19.34   0.03
		10:03   19.34   0.03
                10:41   19.41   0.03
		11:04   19.39   0.03
                11:26   19.41   0.04
		11:50   19.39   0.04
		--------------------

We employed the Weidinger et al. (GCN #1573
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 ) revised calibration star.
These measurements are consistent with and extend the steepening light
curve that they saw.  The combined NOT and MDM points indicate a decay
slope alpha = 1.16 +/- 0.07, but there are possible fluctuations of the
type referred to by Winn et al. (GCN #1576
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 ) in our data that are
contemporaneous with theirs.

An updated decay curve is available at:

http://www.astro.columbia.edu/~jules/021004.ps

An equal number of images in each of B, V, and I were obtained, and will
be analyzed subsequently."

S. Zharikov, R. Vazquez, G. Benitez (OAN IA UNAM, Mexico), S. del Rio
(INAOE, Mexico) report: We have observed the optical afterglow of
GRB021004 (HETE Trigger 2380) as reported by Fox et al. (GCN 1564
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 ) with
the 84-cm and 1.5m telescopes of SPM observatory in Mexico between
05:20:00 UT and 09:50 UT on Oct. 5 2002. Using the R-band photometric
zero-point USNO star at RA=00:26:58.713, DEC=+18:56:56.61 (GCN #1564
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 )
R=15.64 from Weidinger et. al. (GCN 1573
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 ), we find preliminary object
magnitudes:
     UT       R
   05:28:19 19.23
   06:47:00 19.29
   07:02:00 19.33
   09:42:24 19.35
   
This message may be cited.

J. Winn, D. Bersier, K.Z. Stanek (Harvard-Smithsonian Center
for Astrophysics), P. Garnavich (Notre Dame) and A. Walker (CTIO)
report:

Images of the afterglow associated with GRB 021004 (GCN 1564
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 )
were obtained with the CTIO 4m + Mosaic Camera and
the Fred Whipple Observatory 1.2m telescope beginning
at Oct. 5.15 (UT). Preliminary analysis of the
R-band images provide the following magnitudes
assuming the USNO star noted in GCN 1573
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  has a
magnitude of R=15.64:

Oct. 5 UT   R
  03:00    19.10
  04:46    19.21
  05:55    19.24
  07:23    19.25
  08:43    19.23
  09:53    19.31

These data indicate that the rapid decay (GCN 1573
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 )
has slowed considerably. The power-law index of
the optical light between 15 and 22 hours after the
burst is only 0.37. This behavior is similar
to the bump seen in GRB 000103c which may have been
due to a microlensing event (Garnavich, Loeb & Stanek
2000, ApJ, 554, 11). Monitoring this object at a
moderate time resolution is urged.

This message may be cited.

The field of GRB 021004 (GCN 1564
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 , 1565
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 ) was observed at 15 GHz
with the Ryle Telescope from 2002 Oct 04 23:31 to 2002 Oct 05 03:35 UT
(about 12 to 15 hours after the detection). The resolution is about 
25 x 80 arcsec.

No radio source was detected at the position of the OT; 
the formal value for the flux density  was 0.59 +- 0.30[rms]  mJy.
Another observation is planned.

Guy Pooley
MRAO, Cavendish Lab, Cambridge UK

D. A. Frail (NRAO) and E. Berger (Caltech) report on behalf of the
Caltech-NRAO-CARA GRB collaboration:

"On 2002, October 05.29 UT we observed the position of the optical
afterglow candidate reported by D. Fox (GCN 1564
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 ) with the VLA at 22.5
GHz (1.3 cm). With a quick-look reduction we detect a 0.6 mJy radio
source coincident with the position of the optical source. Further
observations with the VLA are planned."

This message may be cited.

M. Weidinger (U. of Aarhus), M. P. Egholm (NOT), J. P. U. Fynbo,
B. Thomsen (U. of Aarhus), Palle Moller (ESO), J. Hjorth,
H. Pedersen, P. Jakobsson, B. L. Jensen (U.  of Copenhagen)
report on behalf of a larger collaboration:

"We have observed the optical afterglow of GRB 021004 (GCN #1564
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 ,
1565
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 , 1568
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 ) with the 2.56m Nordical Optical Telescope (NOT) on La
Palma between 20:17:31 UT and 23:55:35 UT on Oct 4 2002.

We find R band magnitudes for five epochs:
      UT       R
   20:17:31  18.14
   20:24:00  18.12
   21:48:20  18.32
   22:37:37  18.40
   23:55:35  18.68

The magnitudes are based on a preliminary photometric calibration.
The USNO star at RA=00:26:58.713, DEC=+18:56:56.61 (GCN #1564
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 ) is
found to have a magnitude of R=15.64.

These five observations indicate that a break in the light curve has
occurred. The current decay slope is alpha=1.32. A light curve is
available at:
http://astro.phys.au.dk/~michaelw/GRB021004/lightcurve.ps
Here we have included the observations from GCN #1564
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 , 1566
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 , 1567
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  and
1570
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  assuming R=15.64 for the USNO star.

We also have obtained polarimetric observations and a spectrum
covering 3800AA-6800AA. From the lack of Ly-alpha absorption we
conclude that z<2.1."

W. M. Wood-Vasey, G. Aldering, and B. C. Lee, Lawrence Berkeley
National Laboratory, using images obtained by E. F. Helin, S. Pravdo,
M. Hicks, and K. Lawrence (Near-Earth Asteroid Tracking project, Jet
Propulsion Laboratory), report upper limits for pre-discovery
observations at the location of the object identified by Fox et
al. (GCN 1564
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 ) as the optical counterpart to GRB 20021004 from
unfiltered observations with the Oschin 48" telescope at Palomar
Observatory (the same instrument as used by Fox et al.).

A co-addition of historical images from 13 October 2001, 26 October
2001, 5 November 2001, 3 September 2002, 3 October 2002 (all dates UT)
from the same instrument show no source visible at this location to a
limiting unfiltered magnitude of 22.3 (calibrated to USNO R-band stars
on the image frame) at a S/N of 3.

A coaddition of images from 3 October 2002 UT shows no source visible
at this location to a limiting unfiltered magnitude of 21.4
(calibrated to USNO R-band stars on the image frame) at a S/N of 3.

The specific UT times for the 3 October 2002 UT observations are:

07:24:18
07:54:50
08:25:19

The historical co-additions of the all 
images mentioned above is available at:

http://supernova.lbl.gov/~wwoodvas/GRB/

A. Oksanen and M. Aho (Jyvaskylan Sirius ry)
report on behalf of AAVSO International GRB Network:

We have observed the optical afterglow of GRB021004 (HETE Trigger 2380)
as reported by Fox et al. (GCN 1564
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 ) with the 16-inch Meade LX200
telescope of Nyrola observatory in Finland.

Using the same R-band photometric zero-point as Fox et. al. (GCN 1564
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 ),
we find object magnitude as Rc=17.7 at epoch of October 4, 2002 19:52 UT.

Further observations and image calibration is in progress.

This message may be cited.

D.W. Fox, A.J. Barth, A.M. Soderberg, and P.A. Price (Caltech), with
H. Buttery (Cambridge) and T. Mauch (U. Sydney), report on behalf of
the Caltech-NRAO GRB Collaboration:

"We have observed the optical afterglow (Fox, GCN 1564
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 ) of GRB021004
(Shirasaki et al., GCN 1565
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 ) with the Siding Springs Observatory 2.3m
telescope and double-beam spectrograph.  Reduction of a single 1200s
spectrum of the source reveals two distinct absorption-line systems,
with redshifts and line identifications as follows:

    Line       Rest Wavelength (Ang)    Redshift
  ================================================
    Mg II      2796.4, 2803.5           1.38
    Mg II      2796.4, 2803.5           1.60
    Mg I       2853.0                   1.60
  ================================================

We have also identified Mn II and Fe II absorption features associated
with the z=1.60 system.  We conclude that the redshift of GRB021004 is
greater than or equal to 1.60."

GRB021004(=H2380): Revised Localization with HETE Soft X-ray Camera (SXC)

J. Doty, G. Crew, J.G. Jernigan, R. Vanderspek, J. Villasenor, G. 
Monnelly, N. Butler, T. Cline, A. Levine, F. Martel, E. Morgan, G. 
Prigozhin, G. Azzibrouck, J. Braga, R. Manchanda, and G. Pizzichini, 
on behalf of the HETE Optical-SXC and HETE Operations Teams;

G. Ricker, J-L Atteia, N. Kawai, D. Lamb, and S. Woosley on behalf of 
the HETE Science Team;

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:

Analysis of the full data set derived from the HETE Soft X-ray Camera 
(SXC) has resulted in a revised location for GRB021004(=H2380; 
Shirasaki et al, GCN Circular #1565
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 ). The revised SXC location can be 
expressed as a 90% confidence circle that is 62 arcsec in radius and 
is centered at:

RA = 00h 26m 55.7s, Dec = +18d 56' 18.6" (J2000)

This revised SXC localization is shifted 38 arcsec with respect to, 
but lies fully within, the original 120 arcsec radius SXC error 
circle reported by Shirasaki et al in GCN1565
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 . The fading optical 
transient reported by Fox in GCN1564
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  is 40 arcsec from the center of, 
and is within, this revised SXC error circle.

Further information regarding GRB021004 is provided at the following URL:

http://space.mit.edu/HETE/Bursts/

This message is citable.

K. Matsumoto (Okayama Univ.), T. Kawabata (BAO), K. Ayani (BAO), Y.
Urata (Titech / RIKEN) and H. Yamaoka (Kyushu Univ.) report:

We are observing the error circle of GRB021004 obtained by HETE-2
(Shirasaki et al. GCN 1565
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 ) with the Bisei Astronomical Observatory (BAO)
1.01-m telescope. We have confirmed the optical transient reported by
Fox (GCN 1564
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 ). The R-magnitude was about 16.0 at Oct. 4 14:13 UT. The
observation and more accurate photometry are in progress.

This message may be cited.

M. Uemura, R. Ishioka, T. Kato (Kyoto U.) and H. Yamaoka (Kyushu U.)
report on behalf of VSNET-GRB collaboration:

  We are observing the WXM error box of GRB 021004 (GCN 1565
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 ) from
Oct. 4 12:41 UT with 0.30-m telescope (+unfiltered CCD) at Kyoto
University.  First 30sec * 52 exposure were obtained until 13:16 UT.
An inspection of a integrated image reveal the optical afterglow
candidate (Fox et al., GCN 1564
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 ) at R mag about 16.3, which confirms 
further rapid decline of this object.  The observation and analysis
are in progress.  

This message can be cited.

Y. Shirasaki, C. Graziani, 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;

G. Ricker, J-L Atteia, N. Kawai, D. Lamb, and S. Woosley on behalf of
the HETE Science Team;

J. Villasenor, R. Vanderspek, J. Doty, 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;

M. Boer, J-F Olive, J-P Dezalay, and K. Hurley on behalf of the HETE
FREGATE Team;

write:


At 12:06:13.57 UTC (43573.57 s UT) on 4 Oct 2002, the HETE FREGATE,
WXM, and SXC instruments detected event H2380, a long GRB.  The WXM
flight localization was correct and was reported in a GCN Position
Notice at 12:07:02 UT, 49 sec after the beginning of the burst.

Ground analysis of the WXM data for the burst produced a refined
location, which was reported in a GCN Position Notice at 13:19:54 UT,
73 minutes after the burst.  The WXM localization SNR was 14.  The WXM
location can be expressed as a 90% confidence circle that is 10
arcminutes in radius and is centered at

RA = 00h 26m 47s, Dec = +18d 59' 13" (J2000).

Ground analysis of the SXC data for the burst produced a further
refinement in the location, which was reported in a GCN Position Notice
at 14:39:51 UT, 154 minutes after the burst.  The SXC localization SNR
was 9.  The SXC location can be expressed as a 90% confidence circle
that is 2 arcminutes in radius and is centered at

RA = 00h 26m 57s, Dec = +18d 55' 44" (J2000).

The SXC localization may be improved.

In the FREGATE 8-40 keV band, the burst had a duration of ~100 seconds.
In the WXM 2-25 keV band, the burst also had a duration of ~100
seconds.

A light curve for GRB021004 is provided at the following URL:

http://space.mit.edu/HETE/Bursts/

This message is citable.

D.W. Fox reports on behalf of the Caltech-NRAO GRB Collaboration:  

"We have observed the error box of GRB021004 (HETE Trigger 2380;
trigger time 12:06:13.57 UT) with the 48-inch Oschin/NEAT robotic
telescope at Palomar Observatory, with three 60-second integrations
beginning at 12:15:11, 12:17:45, and 12:22:52 UT.  We identify a new,
stationary, fading, point-like object by comparison with the Digitized
Sky Survey.  The object coordinates are:

    RA 00:26:54.689, Dec +18:55:41.3   (J2000)

with an uncertainty of less than 0.5" in each coordinate.  Deriving an
R-band photometric zero-point for our unfiltered observations by
reference to the USNO star at 00:26:58.713 +18:56:56.61, which we
assume to have magnitude R=15.3, we find object magnitudes at our
three mean epochs of:

         Mean Epoch  
       UT      From GRB   Magnitude
  ========================================
    12:15:41 UT   567 s   15.34 mag
    12:18:15      721     15.49
    12:23:22     1028     15.78
  ========================================

Given the source brightness and fading behavior we identify the object
as the likely optical afterglow of GRB021004.  A finding chart from
these observations may be found at

    http://www.astro.caltech.edu/~derekfox/grb021004/finder.ps.gz

and a web page presenting the observations will be available soon at
http://www.astro.caltech.edu/~derekfox/grb021004/."