TITLE: GCN CIRCULAR NUMBER: 25907 SUBJECT: LIGO/Virgo S190930t: Upper limits on the two of the ZTF/GROWTH candidates DATE: 19/10/01 19:16:47 GMT FROM: Tomoki Morokuma at U of Tokyo Morokuma, T. (U. Tokyo); Utsumi, Y. (Stanford/SLAC) on behalf of J-GEM collaboration We report optical follow-up imaging observations for the electromagnetic counterpart candidates of the gravitational wave event S190930t (The LIGO Scientific Collaboration and the Virgo Collaboration, GCN Circ. 25876) reported by Stein et al. (GCN Circ. 25899). We took 12 contiguous frames of 0.5-second exposures 19-22 hours from the possible neutron star and black hole merger for the regions around ZTF19acbpqlh (AT2019rpn) and ATLAS19wyn (AT2019rpj) with Tomo-e Gozen (Sako et al. 2018, SPIE, 10702, 107020J) on the 1.05-m Kiso Schmidt telescope. No filters are used and the data are calibrated relative to r-band data from Pan-STARRS DR2. We find no transients at the reported locations down to depths in the AB system shown below. | MJD | AT | depth (5 sigmas) | | 58757.40871 | ZTF19acbpqlh (AT2019rpn) | 18.69 | | 58757.51431 | ZTF19acbpqlh (AT2019rpn) | 17.66 | | 58757.43221 | ATLAS19wyn (AT2019rpj) | 18.53 | | 58757.52506 | ATLAS19wyn (AT2019rpj) | 18.04 | We note that the ZTF/GROWTH reported magnitudes are 1.0-2.4 magnitudes fainter than our detection limits above.