Assigned ID: 549 ----- Attempting Submission 1 (Fri Feb 26 19:55:24 GMT 2010) ----- Molecular hydrogen is the most abundant species in the interstellar medium and is observed in emission and absorption towards a wide range of astronomical objects. The presence of H2 is fundamental for the formation of complex molecules and dust. The H2 Lyman bands long-ward of 1200 A are usually not detected in a cold gaseous environment but, surprisingly, appears strongly in the spectrum of Eta Car's cold Homunculus. More than 800 H2 transitions have been identified in the mid-UV. The H2 absorption spectrum changes with Eta Car's 5.54 year spectroscopic period. These changes in H2 absorption strengths can provide information regarding the radiative flux variability caused by the companion star. We propose to use HST/STIS data recorded with the E140M grating between 1990.0 to 2004.3 to model the H2 spectrum and derive H2 column densities in the Eta Car Homunculus and how the column densities vary with phase. This will provide necessary input for accurate modeling of the Homunculus, which is an important step in the analysis of this unusual ejecta, and can be used for future studies of other massive stars.

ISM AND CIRCUMSTELLAR MATTER 12 55000 false 0.0 0.0 false false false false false false SUPPORTED