[en] Recent surface chemistry experiments have shown that the hydrogenation of molecular oxygen on interstellar dust grains is a plausible formation mechanism, via hydrogen peroxide (H₂O₂), for the production of water (H₂O) ice mantles in the dense interstellar medium. Theoretical chemistry models also predict the formation of a significant abundance of H₂O₂ ice in grain mantles by this route. At their upper limits, the predicted and experimental abundances are sufficiently high that H₂O₂ should be detectable in molecular cloud ice spectra. To investigate this further, laboratory spectra have been obtained for H₂O₂/H₂O ice films between 2.5 and 200 μm, from 10 to 180 K, containing 3%, 30%, and 97% H₂O₂ ice. Integrated absorbances for all the absorption features in low-temperature H₂O₂ ice have been derived from these spectra. For identifying H₂O₂ ice, the key results are the presence of unique features near 3.5, 7.0, and 11.3 μm. Comparing the laboratory spectra with the spectra of a group of 24 protostars and field stars, all of which have strong H₂O ice absorption bands, no absorption features are found that can definitely be identified with H₂O₂ ice. In the absence of definite H₂O₂ features, the H₂O₂ abundance is constrained by its possible contribution to the weak absorption feature near 3.47 μm found on the long-wavelength wing of the 3 μm H₂O ice band. This gives an average upper limit for H₂O₂, as a percentage of H₂O, of 9% ± 4%. This is a strong constraint on parameters for surface chemistry experiments and dense cloud chemistry models.

[en] IRAS 19312+1950 is a peculiar object that has eluded firm characterization since its discovery, with combined maser properties similar to an evolved star and a young stellar object (YSO). To help determine its true nature, we obtained infrared spectra of IRAS 19312+1950 in the range 5–550 μ m using the Herschel and Spitzer space observatories. The Herschel PACS maps exhibit a compact, slightly asymmetric continuum source at 170 μ m, indicative of a large, dusty circumstellar envelope. The far-IR CO emission line spectrum reveals two gas temperature components: ≈0.22 M _⊙ of material at 280 ± 18 K, and ≈1.6 M _⊙ of material at 157 ± 3 K. The O i 63 μ m line is detected on-source but no significant emission from atomic ions was found. The HIFI observations display shocked, high-velocity gas with outflow speeds up to 90 km s⁻¹ along the line of sight. From Spitzer spectroscopy, we identify ice absorption bands due to H₂O at 5.8 μ m and CO₂ at 15 μ m. The spectral energy distribution is consistent with a massive, luminous (∼2 × 10⁴ L _⊙) central source surrounded by a dense, warm circumstellar disk and envelope of total mass ∼500–700 M _⊙, with large bipolar outflow cavities. The combination of distinctive far-IR spectral features suggest that IRAS 19312+1950 should be classified as an accreting, high-mass YSO rather than an evolved star. In light of this reclassification, IRAS 19312+1950 becomes only the fifth high-mass protostar known to exhibit SiO maser activity, and demonstrates that 18 cm OH maser line ratios may not be reliable observational discriminators between evolved stars and YSOs.