H I emission and absorption spectrum of the extragalactic continuum source G43.738-0.620. Top panel: emission spectrum and is measured in an annulus around the source with inner and outer radii of 60′′ and 120′′, respectively (corresponding to 3−6 beams of the H I data). Second panel: absorption spectrum toward the point source. The lower spectrum indicates the inverted absorption spectrum along with the 3σ noise (dashed line). In the first two panels, the gray shaded area and blue curve indicate the 3σ noise and a single-component Gaussian fit, respectively. The third panel shows the optical depth computed using Eq. (2). In the bottom panel we present the spin temperature, which is computed using Eq. (3).