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We present multi-epoch spectroscopic follow-up of a sample of ellipsoidalvariables selected from Gaia DR3 as candidates for hosting quiescent blackholes (BHs) and neutron stars (NSs). Our targets were identified as BH/NScandidates because their optical light curves -- when interpreted with modelsthat attribute variability to tidal distortion of a star by a companion thatcontributes negligible light -- suggest that the companions are compactobjects. From the likely BH/NS candidates identified in recent workaccompanying Gaia DR3, we select 14 of the most promising targets forfollow-up. We obtained spectra for each object at 2-10 epochs, strategicallyobserving near conjunction to best-constrain the radial velocitysemi-amplitude. From the measured semi-amplitudes of the radial velocitycurves, we derive minimum companion masses of $M_{2,\min} \leq 0.5 ~ M_{\odot}$in all cases. Assuming random inclinations, the typical inferred companion massis $M_2 \sim 0.15 ~ M_{\odot}$. This makes it unlikely that any of thesesystems contain a BH or NS, and we consider alternative explanations for theobserved variability. We can best reproduce the observed light curves andradial velocities with models for unequal-mass contact binaries with starspots.Some of the objects in our sample may also be detached main-sequence binaries,or even single stars with pulsations or starspot variability masquerading asellipsoidal variation. We provide recommendations for future spectroscopicefforts to further characterize this sample and more generally to search forcompact object companions in close binaries.

Spectroscopic follow-up of black hole and neutron star candidates in ellipsoidal variables from Gaia DR3