Profiles of the SiO rotational transitions (2–1), (3–2), (5–4), (6–5), (9–8), and (10–9), for V_s = 30 km s^-1 and b = 1.5. The line temperatures have been divided by the peak temperature of the (5–4) transition, except for the (5–4) transition itself, for which the absolute line profiles are given (for models M1 and M2; for model M3, the line temperature has been divided by a factor of 7 for the purposes of presentation). Full lines: M1; dotted lines: M2; broken lines: M3.