The Possible Electromagnetic Counterparts of the First High-Probability NSBH Merger LIGO/Virgo S190814bv

LIGO/Virgo S190814bv is the first high-probability neutron star - black hole (NSBH) merger candidate, whose gravitational waves (GWs) triggered LIGO/Virgo detectors at 21:10:39.012957 UT, 14 August 2019. It has a probability $>99\%$ of being an NSBH merger, with a low false alarm rate (FAR) of 1 per 1.559e+25 years. For an NSBH merger, electromagnetic counterparts (especially short gamma-ray bursts (GRBs)) are generally expected. However, no electromagnetic counterpart has been found in the extensive follow-up observing campaign. In the present work, we propose a novel explanation to this null result. In our scenario, LIGO/Virgo S190814bv is just a GW mirror image of the real NSBH merger which should be detected before 14 September 2015, but at that time we had no ability to detect its GW signals. The electromagnetic counterparts associated with the real NSBH merger should be found in the archive data before 14 September 2015. In this work, we indeed find 9 short GRBs as the possible electromagnetic counterparts.