[AAVSO-HEN] GRB090518 : Optical upper limit by MOA-II telescope

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TITLE:   GCN CIRCULAR
NUMBER:  9389
SUBJECT: GRB090518 : Optical upper limit by MOA-II telescope
DATE:    09/05/18 12:03:46 GMT
FROM:    Takashi Sako at Nagoya U./MOA  <sako at stelab.nagoya-u.ac.jp>

T. Sako, A. Fukui, K. Nishimoto (STE Lab, Nagoya Univ.)
on behalf of the MOA Collabration  report:

We searched for an optical afterglow of GRB090518 (GCN 9386, Evans et al.;
GCN 9387, Evans et al.) starting from 7:02:10 UT (5 hours after the burst)
with the MOA-II 1.8m telescope at Mt.John observatory in New Zealand.
In a single image of a 300sec exposure with a wideband Red filter (center 
wavelength ~ 750nm and FWHM ~ 250nm), we did not find any object
within the error circle of the Swift XRT source position (GCN 9387).
A 5 sigma upper limit is set in the I magnitude at 18.9 mag.   
This photometry was done by using the DoPhoto and calibrated against the 
USNO-B1.0 catalog stars, and not corrected for the Galactic extinction.