TITLE:   GCN CIRCULAR
NUMBER:  796
SUBJECT: GRB000911: Optical Transient
DATE:    00/09/19 23:51:27 GMT
FROM:    Paul Price at RSAA, ANU at CIT  <pap@srl.caltech.edu>

P.A. Price (RSAA,ANU/Caltech), T.J. Galama (Caltech), R.W. Goodrich (W.M.
Keck Observatory) and A. Diercks (Caltech) report on behalf of a larger
collaboration:

"We have observed the optical transient candidate of GRB000911 (Berger
et. al., GCN #795) with the Keck II telescope + ESI, starting at Sep 15.59 UT.
We took 5 x 120 second images in 0.6 arcsec seeing.  We have compared
the combined image with the R_MACHO (~ Cousins R) image from the MSO 50-inch
telescope (Price et. al., GCN #793), using the USNO-A2.0 star U0975_00513791
(RA2000, Dec2000 = 02:18:33.18, +07:45:47.6) with assumed R = 18.6.  Results
are:

Telescope	Epoch		Magnitude

MSO50+MACHO	Sep 12.73	20.257 +/- 0.167
Keck+ESI	Sep 15.59	21.911 +/- 0.053

(Errors are purely statistical.)

In the Keck+ESI image, the candidate is located at
(RA2000, Dec2000) = (02:18:33.21, +07:45:47.86) +/- (0.34", 0.31")
and has a PSF consistent with a point source.  From these figures,
we calculate a decay constant of alpha = 1.4.

In the light of the fading nature of the candidate, it is likely
the optical transient associated with GRB000911."

This message may be cited.