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 5sigma depth of g > 22.8 (AB mag) at 1.7 days and i > 23.1 and i > 23.9 at 3.7 and 8.7 days, respectively. These observations cover a mean total integrated probability of 67.0% 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 5sigma 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 Mej < 0.015Msun for a 'blue' (kappa = 0.5 cm^2 g^-1) kilonova, and Mej < 0.04Msun for a 'red' (kappa = 5-10 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.

中文翻译：

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对可能的中子星-黑洞合并 GW190814 对应物的深度 CFHT 光学搜索

我们对可能的中子星 - 黑洞 (NS-BH) 合并 GW190814/S190814bv 的电磁对应物进行了宽场光学成像搜索。这种紧凑的双星合并是由 LIGO/Virgo 干涉仪通过引力波探测到的，质量提示 NS-BH 合并。我们使用加拿大-法国-夏威夷望远镜上的 MegaCam 仪器对 LIGO/Virgo 定位区域进行了成像。我们描述了我们的平铺和星系目标观测的混合观测策略，以及我们的图像差异和瞬态检测管道。我们的观测活动在合并后 1.7 到 8.7 天之间产生了该地区的一些最深的多波段图像，在 1.7 天达到 g > 22.8（AB mag）的 5sigma 深度，在 3.7 和 i > 23.1 和 i > 23.9 和分别为 8.7 天。这些观察覆盖了 67.0% 的定位区域的平均总积分概率。我们在我们的图像中没有发现这次合并的引人注目的候选瞬态对应物，这表明较轻的物体在 BH 最内部的稳定圆形轨道内被潮汐干扰，瞬变位于观察到的天空足迹之外，或者较轻的物体是一个低- 质量 BH。我们在这次合并的 NS-BH 解释中使用来自我们图像的 5sigma 源检测上限来将千新星喷射物的质量限制为 Mej < 0.015Msun 对于“蓝色”（kappa = 0.5 cm^2 g^-1） Kilonova 和 Mej < 0.04Msun 对于“红色”（kappa = 5-10 cm^2 g^-1）kilonova。