# Deep-Learning-Based Identification of Broad-Absorption Line Quasars
## 1 Introduction  
The exploration of the activity of black holes in the universe has become an important topic of contemporary astronomy. Observations have shown that supermassive black holes exist in the centers of the most massive galaxies; however, only a small number of them have shown high activity levels, a phenomenon known as the active galaxy nucleus (AGN) [1]. This activity is characterized by the constant radiation of different wavelengths, including x-rays, ultraviolet rays, and visible light, which are often accompanied by the presence of broad-absorption lines in the spectrum. Among them, broad-line absorption quasars (BAL) have attracted considerable interest because of their unique properties and their potential to provide insights into the physics of active galaxy nuclei and the accumulation of black holes. The discovery of quasars marked a crucial moment in the early 20 th century, significantly shaping the field of extragalactic astronomy. The first quasars were discovered byspectral observations, and unusual features were discovered in their light. In 1917, the American astronomer [PERSON] observed apparent absorption lines in the spectra of some galaxies, likely caused by the absorption of background radiation by stars and surrounding matter [2]. This observation served as a basis for further work. In 1922, the American astronomer [PERSON] discovered that the spectral lines of quasars were very different from those of stars. This made it possible to recognize that quasars must function according to a unique set of physical principles that distinguish them from ordinary stars and galaxies [3]. Improved observation techniques have significantly improved our knowledge of quasars. Originally, such research focused on visible and ultraviolet wavelengths, but the appearance of X-ray and infrared observations allowed astronomers to better understand the properties of quasars. In 1967, the astronomer [PERSON] of Nash University, United Kingdom, detected for the first time the X-rays emitted by quasars, a revolutionary discovery [4]. This revolutionary discovery provided strong evidence of the presence of high-energy, high-temperature particles inside the quasars, likely produced by the accumulation of matter in the supermassive black holes in the centers of quasars. This discovery was essential for improving our understanding of the extreme physical processes that occur in these mysterious objects. Quasars, or quasi-stellar objects (QSOs), represent a fascinating subclass of AGNs, known for their exceptional brightness and intense, high-energy emissions. The discovery of quasars by [PERSON] in 1963 marked a turning point in astronomical research and catalyzed a series of revolutionary advances in the field of astrophysics [5]. [PERSON]'s discovery, which considered quasars to be distant, high-energy objects with unusual spectral characteristics, not only reshaped our understanding of the most powerful phenomena in the universe but also paved the way for later discoveries about the nature of black holes, the evolution of galaxies, and the large-scale structure of the universe. For example, the study of quasars has greatly improved our understanding in areas such as the coevolution of supermassive black holes (SMBHs) and their host galaxies [6; 7; 8; 9], the processes of controlling the structures of large-scale galaxies [10; 11], the interstellar and intergalactic media through various red shifts [12; 13], and cosmic reionization and accumulation mechanisms [14; 15; 16]. BAL quasars represent a distinct subclass within the broader category of quasars, characterized by the blue-shifted absorption troughs in their spectra. These features are indicative of high-velocity gas outflows originating from a quasar's central region, moving along the line of sight. These outflows can exceed velocities of 2000 km s\({}^{-1}\), serving as a potent feedback mechanism within an AGN [17].