Accreting Stellar-Mass Black Holes

Abstract Accreting stellar-mass black holes exhibit dramatic variability across the electromagnetic spectrum, including spectral state transitions, outbursts, and jet production, making them unique laboratories for understanding accretion processes in strong gravitational fields. This review synthesizes recent progress in understanding these systems, focusing on their continuum emission, timing properties, emission lines, and X-ray polarization. A complex interplay between the accretion disk, the so-called corona, and jet underlies the observed spectral and timing behavior, with quasi-periodic oscillations and broadband noise providing windows into the dynamics of the innermost accretion flow. Emission lines across all wavelengths serve as critical diagnostics of the disk structure, outflows, and reprocessing, while iron K lines in the X-ray band probe the properties of the inner disk through relativistic reflection. Polarization studies suggest that the corona is likely extended perpendicular to the jet axis in the hard state, while the soft state remains poorly understood, with observations that do not yet conform to simple theoretical expectations; a puzzle that continues to challenge our interpretation of accretion geometry. Despite significant advances, fundamental questions remain about the physical origins of state transitions, the role of magnetic fields in driving outflows and shaping the accretion flow, and the connection between disk instabilities and jet launching. This review underscores the need for future multi-wavelength, timing, and polarimetric studies to deepen our understanding of accretion physics in strong-gravity environments.