GRB 000307

K. Hurley, T. Cline, C. Kouveliotou, R. M. Kippen, E. Mazets, and S.
Golenetskii, on behalf of the Ulysses, NEAR, BATSE, and Konus GRB
teams, report:

Ulysses, NEAR, BATSE, and Konus observed GRB000307 (BATSE #8022) at
78647 s UT.  As observed by Ulysses, this burst had a 25-100 keV
fluence of ~10^-6 erg/cm^2 and a T90 duration of ~20 s.  We have
triangulated this burst to an ~60 sq. arcmin. error box whose center
and corners (3 sigma) are given by:

    RA(2000)                 DEC(2000)
  5 h 56 m 18.73 s      7 o 56 '  30.94 "  (CENTER)
  5 h 55 m 50.22 s      7 o 54 '   9.95 "  (CORNER)
  5 h 56 m 24.70 s      8 o  1 '  14.01 "  (CORNER)
  5 h 56 m 12.77 s      7 o 51 '  47.82 "  (CORNER)
  5 h 56 m 47.32 s      7 o 58 '  52.45 "  (CORNER)

Some refinement to this position is possible.

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

We have acquired preliminary BVRcIc all-sky photometry for
the field of GRB000307 with the USNOFS 1.0-m telescope on one
photometric night.  This 11x11arcmin field covers the IPN
error box and extends a little fainter than V=20.  All stars
brighter than V=14 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/grb000307.dat
This file will be updated if an optical transient is discovered.
The current photometry has a potential external zero-point
error of about two percent.

The astrometry in this file is based on linear plate
solutions with respect to USNO-A2.0.  The internal errors
are less than 100mas.

J. Kemp & J. P. Halpern (Columbia U.) report on behalf of the MDM
Observatory GRB follow-up team:

"We observed the entire IPN error box of GRB 000307 (Hurley et al. GCN
#601
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 ) in the R band using the MDM 1.3m telescope starting on March 10.12
UT, and again on March 11.12 UT.  One hour of exposure was obtained on
each night in seeing of approximately 1".4.  No new object is apparent
above the limit of the digitized POSS-II plate, and no variable object is
detected brighter than an approximate limiting magnitude of R = 21.7.  
These observations were severely affected by scattered light from the star
Betelgeuse, which is only 0.6 degrees away, making precise photometry
difficult.  We also note that Galactic extinction in this direction is
significant, with E(B-V) = 0.445 according to Schlegel et al. (1998),
corresponding to A_R = 1.19.

This message may be cited."

H. Pedersen, B. L. Jensen (University of Copenhagen),
J. Gorosabel (Danish Space Research Institute, Copenhagen),
J. P. U. Fynbo (Aarhus University) report on behalf of 
a wider, European group: 

We have observed the entire error box of GRB 000307  
(cf. Hurley et al., GCN #601
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 ), using the WFI instrument 
attached to the 2.2-m ESO/MPI telescope at La Silla.

The exposure dates were:

2000 March 10.015 UT, 2 * 600 s R-band, seeing 0.9" - 1.2" 
2000 March 23.019 UT, 3 * 600 s R-band, seeing 1.1" - 1.6"

The two exposure sets were compared, using image blinking.
The closeness of Betelgeuse implies scattered light across 
the error box, and hence a non-uniform limiting magnitude. 
Using the standard stars provided by Henden et al. (GCN #608
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 ) 
we estimate that most of the error box has been searched to 
magnitude R ~22.0.     

No candidate counterpart was found. 

We acknowledge the assistance of the La Silla staff.

Observations were carried out at the European Southern 
Observatory under programme 64.H-0573(A).