Tracing the Pulse of the Universe: X-ray Binaries in the Time-Domain Era

X-ray binaries, powered by accretion onto neutron stars or black holes, are among the most variable objects in the Universe. From coherent pulsations and thermonuclear bursts to quasi-periodic oscillations and torque reversals, these systems reveal a rich tapestry of time-dependent behavior driven by extreme gravity and magnetic fields. In this talk, I will present recent results from AstroSat, NICER, and NuSTAR that reveal how fast timing and broadband spectral studies probe inner disk physics and magnetospheric coupling across a variety of compact binaries—including X-ray pulsars, accreting millisecond pulsars, and bursting low-mass X-ray binaries. I will also highlight the powerful synergy with optical surveys like TESS and Gaia, which inform on orbital modulation, companion properties, and long-term variability. These multi-wavelength approaches are vital for decoding the full variability fingerprint of these systems. Looking ahead, the LSST and upcoming UV missions will open new windows on compact binaries across timescales and wavelengths.