Two-epoch spectra of quasar SDSS J1452+0932. The y-axis of the upper panel is in units of 10⁻¹⁷ erg s⁻¹ cm⁻². The top x-axis depicts the blueshift velocity, derived from the Si IV or C IV emission lines (in 10³ km s⁻¹), while the bottom x-axis indicates the rest-frame wavelength (in Å). Two vertical dashed blue lines, spanning both panels, signify the rest wavelengths of the Si IV and C IV emission lines. In the upper panel, the solid black and red lines represent pristine spectra obtained at two distinct epochs, with their MJDs indicated in the upper-right corner and coloured to match the corresponding spectra. The dashed black and red lines depict the respective pseudo-continuum fits. The solid black and red lines at the bottom of the upper panel are the formal 1σ errors. The bottom panel displays the pseudo-continuum-normalised spectra corresponding to the pristine spectra presented in the upper panel. Horizontal solid black bars delineate the BAL troughs imprinted on the spectra. The velocity range of a BAL is delineated by the most extreme limits observed across the two epochs. The vertical dotted black and red lines highlight the line centres of the C IV BAL of system A, which exhibit velocity shifts between observations at different epochs.