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Session 51 - Interstellar Medium II.
Display session, Thursday, January 08
We have acquired spectra of the optical interstellar absorption lines of Ca II and Na I for 68 OB stars in the direction of the Vela supernova remnant. The data, which were obtained using the echelle spectrograph on the Coude Auxiliary Telescope of the European Southern Observatory, have high spectral resolution (R \sim 75,000) and high signal-to-noise ratios (S/N > 100). For a subset of the sight lines, we re-observed the interstellar profiles several times over the course of several years to assess whether time variability in the profiles, as is seen for HD 72127A (Hobbs et al. 1991, ApJ, 378, 586) and HD 72997 (Danks amp; Sembach 1995, AJ, 109,2627), is a prevalent phenomenon.
By observing the interstellar profiles toward stars of various distances in the direction of the remnant, we seek to map out the velocity structure of both the foreground neutral gas and the high velocity gas within the Vela SNR. The data allow us to provide an accurate (and independent) distance estimate for the remnant. Several investigations, including ours, indicate that the canonical distance estimate of 500 pc is too large by roughly a factor of two. In this poster we discuss the distance estimate, time variability of the interstellar profiles, and possible uses for this dataset in follow-up ultraviolet studies of stars in this interesting region of the sky with the Hubble Space Telescope and Far Ultraviolet Spectroscopic Explorer.
Program listing for Thursday