We present a wide-field optical imaging search for electromagnetic counterparts to the likely neutron star – black hole ( NS-BH ) merger GW190814/S190814bv .
This compact binary merger was detected through gravitational waves by the LIGO/Virgo interferometers , with masses suggestive of a NS-BH merger .
We imaged the LIGO/Virgo localization region using the MegaCam instrument on the Canada-France-Hawaii Telescope .
We describe our hybrid observing strategy of both tiling and galaxy-targeted observations , as well as our image differencing and transient detection pipeline .
Our observing campaign produced some of the deepest multi-band images of the region between 1.7 and 8.7 days post-merger , reaching a 5 \sigma depth of g > 22.8 ( AB mag ) at 1.7 days and i > 23.0 and i > 23.9 at 3.7 and 8.7 days , respectively .
These observations cover a mean total integrated probability of 68.8 % of the localization region .
We find no compelling candidate transient counterparts to this merger in our images , which suggests that either the lighter object was tidally disrupted inside of the BH ’ s innermost stable circular orbit , the transient lies outside of the observed sky footprint , or the lighter object is a low-mass BH .
We use 5 \sigma source detection upper limits from our images in the NS-BH interpretation of this merger to constrain the mass of the kilonova ejecta to be M _ { \mathrm { ej } } \lesssim 0.015 M _ { \odot } for a ‘ blue ’ ( \kappa = 0.5 \mathrm { ~ { } cm ^ { 2 } g ^ { -1 } } ) kilonova , and M _ { \mathrm { ej } } \lesssim 0.04 M _ { \odot } for a ‘ red ’ ( \kappa = 5 - 10 \mathrm { ~ { } cm ^ { 2 } g ^ { -1 } } ) kilonova .
Our observations emphasize the key role of large-aperture telescopes and wide-field imagers such as CFHT MegaCam in enabling deep searches for electromagnetic counterparts to gravitational wave events .