TITLE: GCN CIRCULAR NUMBER: 24206 SUBJECT: LIGO/Virgo S190425z: ZTF19aarykkb Imaging from Las Cumbres Observatory DATE: 19/04/26 03:24:29 GMT FROM: Jamison Burke at Las Cumbres Observatory/UCSB Jamison Burke (LCO/UCSB), Daichi Hiramatsu (LCO/UCSB), Iair Arcavi (Tel Aviv University), D. Andrew Howell (LCO/UCSB), Curtis McCully (LCO), Craig Pellegrino (LCO/UCSB) on behalf of the Las Cumbres GW Follow-up Collaboration Beginning 2019-04-25 21:34:17 we obtained 14 g-, r-, and i-band images of the GW optical counterpart candidate ZTF19aarykkb (Kasliwal et al. 2019, GCN 24191) with the Las Cumbres Observatory 1m telescope at the South African Astronomical Observatory. We present the following PSF photometry of the target: Datetime (UT) JD Filter Mag Magerr 2019-04-25 21:34:17 2458599.3987 g 18.79 0.03 2019-04-25 21:38:04 2458599.4013 g 18.79 0.02 2019-04-25 21:42:05 2458599.4041 r 18.18 0.03 2019-04-25 21:44:31 2458599.4058 r 18.18 0.03 2019-04-25 21:47:12 2458599.4076 i 17.95 0.04 2019-04-25 21:49:39 2458599.4093 i 17.96 0.04 2019-04-25 22:15:11 2458599.4271 g 18.80 0.03 2019-04-25 22:20:38 2458599.4309 g 18.82 0.02 2019-04-25 22:26:19 2458599.4348 i 17.93 0.05 2019-04-25 22:31:46 2458599.4386 i 17.97 0.05 2019-04-25 23:25:31 2458599.4759 g 18.97 0.03 2019-04-25 23:29:18 2458599.4785 g 18.95 0.03 2019-04-25 23:33:18 2458599.4813 r 18.12 0.04 2019-04-25 23:35:45 2458599.4830 r 18.14 0.03 These values disagree with the photometry presented in Bhalerao et al. 2019 (GCN 24201) despite the observations being contemporaneous. The g- and r-band photometry presented here is roughly 0.3 magnitudes fainter, and the i-band photometry is almost a full magnitude fainter.