TITLE: GCN CIRCULAR NUMBER: 24309 SUBJECT: LIGO/Virgo S190425z: ASAS-SN observations DATE: 19/04/27 23:03:16 GMT FROM: Benjamin Shappee at U. of Hawaii B. J. Shappee (IfA-Hawaii), C. S. Kochanek (OSU), K. Z. Stanek (OSU), S. Holmbo (Aarhus), A. Franckowiak (DESY), T. W.-S. Holoien (Carnegie Observatories), J. L. Prieto (Diego Portales; MAS), Subo Dong (KIAA-PKU), T. A. Thompson (OSU), J. F. Beacom (OSU) ASAS-SN covered 10% of the probability region in the 1 hour preceding the LIGO/Virgo Alert GCN #24168 of a BNS merger through normal operations. Following, the LIGO/VIRGO alert optical follow-up was triggered with the All-Sky Automated Survey for SuperNovae (ASAS-SN, Shappee et al. 2014; Kochanek et al. 2017). ASAS-SN covered 67% of the probability region in the 24 hours after the LIGO/VIRGO alert through a combination of normal operations and triggered observations. The majority of the remaining probability region was Sun constrained. We obtained 6 epochs on the highest probability regions during that time. Candidates were scanned in near real time. No obvious candidates were discovered. Given the lunation, our depth was typically between g~18-18.5 mag. Our coverage is shown here: http://www.astronomy.ohio-state.edu/~assassin/LIGO/S190425z_coverage.png We would like to thank Las Cumbres Observatory and its staff for their continued support of ASAS-SN. ASAS-SN is funded in part by the Gordon and Betty Moore Foundation through grant GBMF5490 to the Ohio State University, NSF grant AST-1515927, the Mt. Cuba Astronomical Foundation, the Center for Cosmology and AstroParticle Physics (CCAPP) at OSU, the Chinese Academy of Sciences South America Center for Astronomy (CASSACA), and the Villum Fonden (Denmark). For more information about the ASAS-SN project, see http://www.astronomy.ohio-state.edu/asassn/index.shtml