SIMBAD references

We used high-resolution infrared spectra of the heavily embedded T Tauri star HL Tau to search for evidence of absorption due to the R0, R1, and R2 gas-phase CH₄ν₃lines near 3.3 µm. From this, we report a 3 σ upper limit of 1.3x10¹⁵/cm2 for the CH₄gas column density toward HL Tau. Our results are compared to those found for CO gas toward this source and to the recent model for chemistry in the inner (10 AU) disks around T Tauri stars by Markwick et al. We find that the upper limit of methane ice+gas column density toward HL Tau, when compared to CO, is somewhat lower than but consistent with that measured toward other interstellar sources (∼1%) but that it is much lower than that predicted in the Markwick et al. model and much less than the CH₄/CO ratio (10%-80%) found in cometary volatiles. This has important implications for the processing of interstellar material and its incorporation into planetary bodies.