On 2019 August 14 at 21:10:39 UTC, the LIGO/Virgo Collaboration (LVC)
detected a possible neutron star-black hole merger (NSBH), the first ever
identified. An extensive search for an optical counterpart of this event,
designated GW190814, was undertaken using DECam on the CTIO Blanco 4-m
telescope. Target of opportunity interrupts were issued on 8 separate nights to
observe 11 candidates using the SOAR Goodman Spectrograph in order to assess
whether any of these transients was likely to be an optical counterpart of the
possible NSBH merger. Here, we describe the process of observing with the SOAR
Goodman spectrograph, the analysis of our spectra, our spectroscopic typing
methodology, and our resultant conclusion that none of the candidates
corresponded to the black hole-neutron star merger but were all instead other
transient events. Finally, we describe the lessons learned from this effort.
Application of these lessons will be critical for a successful community
spectroscopic follow-up program for LVC season 4 (O4) and beyond.
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