2025ApJ...986..135K

Stellar-mass isolated black holes wandering in the interstellar medium are expected to be abundant in our Galaxy. Recently, an isolated free floating black hole (IsoBH), OGLE-2011-BLG-0462, was unambiguously discovered using astrometric microlensing. We examine prospects for detecting electromagnetic signatures from an accretion flow surrounding the IsoBH. The accretion rate onto the IsoBH should be highly sub-Eddington, which leads to formation of a hot accretion flow. In this paper, we evaluate the detectability of electromagnetic signals from the hot accretion flows in two accretion states: magnetically arrested disk (MAD) and classical radiatively inefficient accretion flows (RIAFs). For the MAD scenario, we find that the optical, infrared, and X-ray signals can be detectable by the current best facilities, such as the Hubble Space Telescope, JWST, and Chandra, if the IsoBH is in a warm neutral medium. In contrast, for the classical RIAF scenario, the optical and X-ray emissions are weaker than the MAD scenario, leading to unobservable signals for a typical parameter set. Future follow-up observations of OGLE-2011-BLG-0462 will provide a good test for theories of accretion processes.