The abundance of interstellar oxygen toward Orion: Evidence for recent infall?

We present high S/N (>800) Goddard High-Resolution Spectrograph observations of the weak interstellar O I] λ1356 absorption in the low-density sight lines toward ι Ori and κ Ori. By comparing these data with observations toward more reddened stars, we find no evidence of density-dependent depletion from the gas phase for oxygen. The derived total oxygen abundance (gas plus grains) toward ι Ori and κ Ori is consistent with stellar and nebular determinations in Orion at a level that is one-half the solar value. We speculate that the O/H abundance ratio is lower in Orion compared to the Sun because the local Milky Way has suffered a recent infall of metal-poor material, perhaps from the Magellanic Stream.