Rocket spectroscopy of ζ Puppis below 1100 Å

Abstract

A spectrum of ζ Pup extending from 920 Å to 1360 Å with approximately 0.8 Å resolution has been recorded at rocket altitudes. Tentative identification of 38 multiplets below 1100 Å has been made from which it is concluded that all the lines appearing in a model atmosphere (Hickok and Morton, 1968) with Te = 37450K have been detected with the exception of those masked by telluric N2 or strong P Cygni-like profiles. Additional absorption lines indicate a wide range of ionization and excitation entirely consistent with observations in the visible spectral region of similar type stars; they also appear to affect sensibly the energy distribution within the spectrum. From newly detected blue-shifted absorption features produced by the ions Svi (933.4 Å, 944.5 Å), Niv (955.3 Å), Niii (991.0 Å), and Ovi (1033.8 Å) mean radial velocities of 1200, 530, 1800 and 1900 km sec−1 respectively have been derived. It is pointed out that the transition in Niv (955.3 Å) does not originate in the ground state configuration as do the other P Cygni profile transitions, but from an excited level which can decay radiatively to the ground state. It seems likely, therefore, that the profile is generated close to the photosphere, and this, together with previously reported results, constitutes evidence for a positive velocity gradient in the detected portion of the circumstellar envelope. On the basis of available data, ions in the ground state of Nv, Niv (by inference) and Niii are all present in the circumstellar envelope, the abundance of the latter remaining large enough to produce a strong P Cygni profile.