| Description |
Using HIFI, we will observe three rotational transitions of water vapor, all predicted to be strong submillimeter masers, toward the massive star-forming regions W49N and W51 (Main); and toward the oxygen-rich evolved stars VY CMa and U Her. The target transitions are the 5(23) - 4(41), 5(24) - 3(31), and 6(34) - 5(41) pure rotational lines of water at 621, 970, and 1158 GHz. In combination with maser transitions of lower frequency that can be observed from the ground, the proposed observations will constrain the conditions of gas temperature, gas density, and IR radiation field within the maser-emitting region, providing important constraints upon the maser pumping mechanism. In the case of the star-forming interstellar regions, the proposed observations will also constrain the nature of the shock waves that power the maser emission. |
