The Swift/UVOT observed the field of GRB 090518 starting 77 s after the BAT trigger (Evans et al., GCN 9386). No optical afterglow is detected in the initial UVOT exposures at the position of the X-ray afterglow (Evans et al., GCN 9387). Three-sigma upper limits using the UVOT photometric system (Poole et al. 2008, MNRAS, 383, 627) for the first finding chart (FC) exposure and subsequent exposures...Full Text

GROND (Greiner et al. 2008, PASP 120, 405), mounted at the 2.2m ESO/MPI telescope at La Silla Observatory (Chile), observed the field of GRB 090518 (P. Evans et al. 2009, GCN 9386) simultaneously in the g'r'i'z'JHK bands. Observations started on May 18, at 23:01 UTC, 21.1 h after the burst. In stacked images of 49 min total integration time in griz and 40 min in JHK, we do not detect any new object...Full Text

We have imaged the field of GRB 090518 (Evans et al., GCN 9386) with the automated Palomar 60-inch telescope beginning at 3:45 UT on 2009 May 18 (~ 1.83 hr after the burst). Observations were taken in the r', i', and z' filters at high airmass. We find no sources inside the enhanced XRT error circle (Evans et al., GCN 9387), to the following limiting magnitudes: Filter Magnitude -------------------------------- r'...Full Text

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We searched for an optical afterglow of GRB 090518 (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...Full Text

We have analysed 6.4 ks of XRT data for GRB 090518 (Evans et al. GCN 9386), from 88 s to 13.0 ks after the BAT trigger. The data are entirely in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Evans et al. (GCN. Circ 9387). The light curve can be modelled with a series of power-law decays. The initial decay index is alpha=1.5 (+0.4, -0.3). At T+332 s the decay...Full Text

Using 3965 s of XRT Photon Counting mode data and 8 UVOT images for GRB 090518, we find an astrometrically corrected X-ray position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 119.95404, +0.75921 which is equivalent to: RA (J2000): 07h 59m 48.97s Dec (J2000): +00d 45' 33.2" with an uncertainty of 1.6 arcsec (radius, 90% confidence). This position...Full Text

At 01:54:44 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 090518 (trigger=352420). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 119.933, +0.768 which is RA(J2000) = 07h 59m 44s Dec(J2000) = +00d 46' 04" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows a...Full Text