GCN Circular 24305
Aaron Tohuvavohu (PSU), Phil Evans (U. Leicester), Mike Siegel (PSU), Frank Marshall (NASA GSFC), Brad Cenko (NASA GSFC) and Jamie Kennea (PSU) report on behalf of the Swift Gravitational Wave Galaxy Survey (SGWGS) team The position of the potential Swift/UVOT counterpart (Breeveld et al. GCN. 24296) to the LIGO/Virgo S190425z trigger (LIGO/Virgo Collaboration GCN. 24168) was imaged by the Neil Gehrels Swift Observatory on 2018, October 21/22 UT with the Swift Ultraviolet/Optical Telescope in the u and uvw1 filters for a total 1.2 ks of exposure as part of the Swift Gravitational Wave Galaxy Survey (PI Tohuvavohu). Examining the image we do not detect any source at the position of the counterpart candidate to a 5-sigma limiting magnitude of ~21 mag in U-band, corresponding to ~ -14 mag at the distance of the associated host galaxies (~100 Mpc). These magnitudes are in the AB system and are not corrected for Galactic extinction in the direction of the event. The Swift Gravitational Wave Galaxy Survey is a 5 Million second pre-imaging survey of the ~14,000 most likely host galaxies for BNS mergers within ~100 Mpc. It is performed in the u and uvw1 bands and with XRT in the Photon Counting mode. It is currently ~43% complete. When complete it will cover 41.2% of the integrated B-band luminosity within 100 Mpc down to ~21 mag in u and uvw1 and ~5 �� 10 ���13 erg cm ���2 s ���1 in the X-rays (0.3 - 10 keV).