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Astrometry from the Gaia mission was recently used to discover the twonearest known stellar-mass black holes (BHs), Gaia BH1 and Gaia BH2. Bothsystems contain $\sim 1\,M_{\odot}$ stars in wide orbits ($a\approx$1.4 AU,4.96 AU) around $\sim9\,M_{\odot}$ BHs. These objects are among the firststellar-mass BHs not discovered via X-rays or gravitational waves. Thecompanion stars -- a solar-type main sequence star in Gaia BH1 and alow-luminosity red giant in Gaia BH2 -- are well within their Roche lobes.However, the BHs are still expected to accrete stellar winds, leading topotentially detectable X-ray or radio emission. Here, we report observations ofboth systems with the Chandra X-ray Observatory and radio observations with theVery Large Array (for Gaia BH1) and MeerKAT (for Gaia BH2). We did not detecteither system, leading to X-ray upper limits of $L_X < 10^{29.4}$ and $L_X <10^{30.1}\,\rm erg\,s^{-1}$ and radio upper limits of $L_r < 10^{25.2}$ and$L_r < 10^{25.9}\,\rm erg\,s^{-1}$. For Gaia BH2, the non-detection impliesthat the the accretion rate near the horizon is much lower than the Bondi rate,consistent with recent models for hot accretion flows. We discuss implicationsof these non-detections for broader BH searches, concluding that it is unlikelythat isolated BHs will be detected via ISM accretion in the near future. Wealso calculate evolutionary models for the binaries' future evolution usingModules for Experiments in Stellar Astrophysics (MESA). We find that Gaia BH1will be X-ray bright for 5--50 Myr when the star is a red giant, including 5Myr of stable Roche lobe overflow. Since no symbiotic BH X-ray binaries areknown, this implies either that fewer than $\sim 10^4$ Gaia BH1-like binariesexist in the Milky Way, or that they are common but have evaded detection,perhaps due to very long outburst recurrence timescales.

No X-Rays or Radio from the Nearest Black Holes and Implications for Future Searches