TITLE:   GCN CIRCULAR
NUMBER:  21560
SUBJECT: LIGO/Virgo G298048: SkyMapper uvgri photometry of the candidate in NGC 4933
DATE:    17/08/18 13:54:11 GMT
FROM:    Seo-Won Chang at ANU  <seowon.chang@anu.edu.au>

C. Wolf, S.W. Chang, A. Möller (ANU)

We report photometry of the optical source in NGC 4993 reported by Coulter et al. (LVC GCN 21529), Allam et al. (LVC GCN 21530), Yang et al. (LVC GCN 21531), Melandri et al. (LVC GCN 21532) in response to LIGO/Virgo GW trigger G298048 (LVC, GCN 21513).

The source at  RA = 13:09:48.09 DECL. = -23:22:53.35 was observed with the 1.35-m ANU SkyMapper telescope at Siding Spring Observatory on the night of 2017-08-18 from 10:00:00 to 10:09:40 UTC.

Initial photometry for the candidate’s AB magnitude is: u-band (350/40) = 17.9 +/- 0.15, v-band (384/28) = 17.9 +/- 0.10, g-band (510/156) = 17.76 +/-0.05, r-band (617/156) = 17.20 +/-0.05 and i-band (779/140) = 16.0 +/- 0.30. Note that the u-band is uncertain because the frames were taken at airmass 2.5 to 2.7, and the i-band is highly uncertain due to a rudimentary host subtraction.