Si III 4552 Å absorption line in m₁ observed on 2013 June 23 over a 47 min timespan (phases 0.818–0.826), and the profile of 2013 June 19 (phase 0.822), stacked in order of increasing time from bottom to top. The prominent blue “bump” that migrates from the left absorption wing toward line center is illustrated with the dash line and the quasi-stationary “red spike” with the dotted line. Note the stronger “red spike” on the June 19 profile.