TITLE:   GCN CIRCULAR
NUMBER:  24323
SUBJECT: LIGO/Virgo S190426c: ASAS-SN observations
DATE:    19/04/28 06:35:36 GMT
FROM:    Benjamin Shappee at U. of Hawaii  <shappee@hawaii.edu>

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)

Following the LIGO/VIRGO alert of gravitational wave source S190426c (GCN #
24237), 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 77% of the updated probability region (GCN #24277, 24279) in the 24
hours after the LIGO/VIRGO alert through a combination of normal operations
and triggered observations.  We note that we covered 86% of the
preliminary localization
region.  We obtained up to 13 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/S190426c_coverage.png

Our coverage compared to the preliminary localization region is shown here:

http://www.astronomy.ohio-state.edu/~assassin/LIGO/S190426c_prelim_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.