A REVIEW ON THE PHYSICAL NATURE OF ULTRALUMINOUS X-RAY SOURCES (ULXs)

Abstract

In this comprehensive review, we delve into the intricate physical characteristics of Ultraluminous X-ray sources (ULXs). These non-nuclear extraordinary sources exhibit intense X-ray emissions, boasting estimated X-ray luminosities (LX) ≥ 1039 erg s−1 within the 0.3-10.0 keV energy range. The review not only sheds light on the potential spectral states observed in ULXs but also meticulously explores the array of physical models that have been proposed to elucidate their remarkably high luminosity. Furthermore, the review underscores the significance of spectral and variability studies in unraveling the authentic physical nature of ULXs. Emphasis is placed on understanding the dynamics at play, the intricacies of the accretion process, and the identity of the compact object hosted by ULXs. By delving into these details, the review aims to contribute to a more profound comprehension of ULXs and their enigmatic features.