X-ray binaries (XRBs), hosting either a neutron star or black hole accreting from a stellar companion, emit across the electromagnetic spectrum, making them key laboratories for studying accretion and disk–jet coupling. This talk presents an overview of their multi-wavelength behavior during accretion outbursts, thermonuclear (Type-I) X-ray bursts, and general spectral variations in high-mass and low-mass X-ray binaries (HMXBs and LMXBs). During outbursts, XRBs undergo hard-to-soft spectral state transitions accompanied by correlated variability from radio to X-rays, linking compact jets, accretion disks, and reprocessing in optical/infrared bands. Thermonuclear bursts in neutron-star LMXBs produce rapid X-ray flashes followed by optical/UV counterparts that probe disk structure and the binary system geometry. HMXBs, dominated by stellar-wind accretion, show strong photoionized lines and their orbital modulation, while all transient disk-fed XRBs exhibit disk emission and outbursting activity. Coordinated multi-wavelength observations provide a unified picture of accretion flow, outflows, and the physical environments surrounding compact objects.
Dr. Sayantan Bhattacharya is a postdoctoral fellow at the Tata Institute of Fundamental Research (TIFR), Mumbai. He earned his PhD in 2024 from the University of Massachusetts Lowell, USA, and joined TIFR soon after. Sayantan completed his B.Sc. from Banaras Hindu University (BHU), Varanasi, and his M.Sc. from the University of Hyderabad. His research focuses on X-ray astronomy, compact object binaries, and accretion physics, etc.