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Rapid temporal variations of interstellar absorption lines in the Carina Nebula

Abstract:

Two observations of the complex interstellar absorption-line profiles in the UV spectrum of CPD -59°2603, obtained 22 months apart in the R ∼ 110,000 mode of the Space Telescope Imaging Spectrograph on the Hubble Space Telescope, reveal substantial variations in the intensities of several high-velocity components, including the virtual disappearance of one of them. These are the first observations of interstellar temporal variations in dominant ions to our knowledge. The most probable interpretation is motion across the line of sight of discrete absorbing features in the near foreground of the O-type star, within the Carina Nebula. Ground-based survey data also indicate that the extreme interstellar profiles throughout this region originate relatively near the most massive stars, suggesting an origin related to their stellar winds. The morphological similarity of these profiles to a low-ionization, narrow-line system in a quasi-stellar object (QSO) spectrum is pointed out. Time variability may provide a critical test among different interpretations of such QSO systems.