GRB 020604

K. Hurley and T. Cline, on behalf of the Ulysses, Mars Odyssey, 
and Konus GRB teams,

I. Mitrofanov, D. Anfimov, A. Kozyrev, M. Litvak and A. Sanin on behalf of the
HEND/Odyssey GRB team,

E. Mazets and S. Golenetskii, on behalf of the Konus-Wind GRB team,

D. M. Smith, R. P. Lin, J. McTiernan, R. Schwartz, C. Wigger, W. Hajdas,
and A. Zehnder, on behalf of the RHESSI GRB team, and

W. Boynton, C. Fellows, K. Harshman, C. Shinohara and R. Starr, on behalf of
the GRS/Odyssey GRB team, report:

Ulysses, Konus, RHESSI, and HEND observed this burst at ~51223 s.
As observed by Ulysses, it had a duration ~10 s, a 25-100 keV
fluence of ~3E-6 erg/cm^2, and a peak flux over 0.5 s of
~5E-7 erg/cm^2 s.  We have triangulated it to a preliminary,
3 sigma error box whose area is ~160 square arcminutes and whose
coordinates are:

    RA(2000)                 DEC(2000)
 16 h 27 m 32.31 s    -29 o 48 '  21.41 "  (CENTER)
 16 h 25 m 56.99 s    -29 o 59 '  26.08 "  (CORNER)
 16 h 27 m 59.70 s    -29 o 41 '  20.90 "  (CORNER)
 16 h 27 m 05.07 s    -29 o 55 '  20.70 "  (CORNER)
 16 h 29 m 08.79 s    -29 o 37 '  05.87 "  (CORNER)

Some improvement in this error box is possible.  A map
will be posted shortly to sunspot.ssl.berkeley.edu/ipn3/020604.
This server will be down from about 7 AM to 5 PM PDT Saturday, June
8.

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 coordinates
for the IPN burst GRB020604 (Hurley et al., GCN 1417
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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/grb020604.dat
The astrometry in this file is based on linear plate solutions
with respect to UCAC2.  The external errors are less than 100mas.
The photometry has potential zeropoint error of about 0.03mag.
This is a fairly crowded field, so the automated reduction pipeline
will have problems on blended objects.

Editorial note: the NOFS 1.0m has a hard declination limit of
-31 degrees.  GRB020604 is as far south as we will normally
observe, and even then, our potential zeropoint error is
quite large due to the high airmass.  GRB020405, at -31 dec,
was just outside our declination limit.  Therefore, any time
a burst is localized south of -30, you will not see
field photometry posted from NOFS.

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

We imaged an 11x11 arcmin field centered at the coordinates
for the IPN burst GRB020604 (Hurley et al., GCN 1417
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with the USNOFS 1.0-m telescope on 020608.295 (3.7d after
the burst), and again on 020611.276.  Coadded images give
a plate limit of V=21.5.  No new object was seen within
the CCD field of view, which does not contain the entire
160 square arcmin error box.  This field is at galactic coordinates
349.07, +13.12 and so is cluttered with stars, with few
extragalactic objects seen.

One object, present on the digitized plates available from
the USNO Pixel Server (http://www.nofs.navy.mil), exhibits
large variability.  Located at
  16:27:38.28  -29:47:38.0  J2000
with astrometric error under 100mas, the object was V=18.9
on 020608 and V=21.4 on 020611.

J. Gorosabel (IAA-CSIC Granada), J. Hjorth, B. L. Jensen, H. Pedersen,
P. Jakobsson (Univ. of Copenhagen), J. Fynbo (IFA Aarhus), 
M. I. Andersen (Univ. of Oulu), report:

 We have carried out optical observations of the GRB 020604 IPN error box
 (GCN 1417
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 ) with the 1.54 Danish Telescope (+DFOSC) on three epochs;
 June 8, 9 and 10. The observations were done following a mosaic as
 detailed below:

 =====================================================================
  Date UT         Filter   R.A.       Dec    Seeing Time since ExpTime 
  June 2002              (J2000)    (J2000)   (")   GRB (days)   (s)   
 ---------------------------------------------------------------------
  8.07874--8.11230   R  16:27:42.0 -29:48:43  1.2     3.50      4x600   
  8.11259--8.14516   R  16:28:39.8 -29:43:44  1.2     3.54      4x600   
  8.14642--8.16250   R  16:29:19.8 -29:39:44  1.1     3.56      2x600   
  8.16629--8.21525   R  16:28:01.7 -29:48:22  1.2     3.60      6x600** 
  8.21554--8.23159   R  16:27:18.4 -29:55:38  1.1     3.63      2x600   
  8.23186--8.23973   R  16:26:45.4 -29:52:52  1.0     3.64        600   
  8.27211--8.31829   I  16:28:01.7 -29:48:22  1.1     3.70      6x500** 
  8.32037--8.34111   I  16:28:39.8 -29:43:44  1.4     3.74      3x500   
  8.34216--8.36298   I  16:27:18.4 -29:55:38  1.8     3.76      3x500   
 ---------------------------------------------------------------------
  9.12684--9.21986   R  16:28:01.7 -29:48:22  1.1     4.58     10x600** 
  9.22098--9.26678   R  16:28:39.8 -29:43:44  1.2     4.65      4x600   
  9.27909--9.30354   R  16:27:18.4 -29:55:38  1.3     4.70      4x600   
  9.30392--9.31180   R  16:26:45.4 -29:52:52  1.3     4.72        600   
  9.31378--9.32165   R  16:27:42.0 -29:48:43  1.2     4.72        600   
  9.32416--9.33202   R  16:29:19.8 -29:39:44  1.5     4.74        600   
 ---------------------------------------------------------------------
 10.16572--10.24745  R  16:28:01.7 -29:48:22  1.0     5.61      6x900** 
 10.26606--10.30406  R  16:28:39.8 -29:43:44  1.3     5.69      3x900   
 10.30569--10.34051  R  16:27:18.4 -29:55:38  1.5     5.73      4x600   
 ---------------------------------------------------------------------
 ** Central part				   	              
 =====================================================================

 The first and the second epoch observations cover the whole error box, 
 whereas the third epoch images contain ~80% of it.

 A gif of the performed mosaic can be seen at:
 http://www.dsri.dk/~jgu/grb020604/FCs/grb020604.R.8-9.06.02.1.54D.gif

 The limiting magnitude depends on the error box position. For the central
 pointing (covering ~50% of the error box), the R-band limiting magnitude 
 (3 sigma) at the three epochs are R=24.5, R=24.7 and R=24.9. For the rest
 of the error box the limiting magnitude are R=23.8, R=23.6 and R=24.0,
 respectively. In the I-band the limiting magnitude ranges from I=22.5 to
 I=23.4.

 Albeit the severe Galactic extinction (AR=1.18, AI=0.86 mag), many
 extragalactic objects are detected in our images. Among the unsaturated
 objects, marginal variability (< 0.2 mag) is detected for 12 of them. 
 None of these objects shows flux variability consistent with a decay, as
 expected for an optical afterglow 3.5-5.7 days after the gamma ray event.