Circumstellar matter in the binary V Puppis

Results are reported for Copernicus observations of the double-lined binary V Puppis in the wavelength region from 1155 to 1310 A with a resolution of 0.2 A. The sharp-lined UV absorption spectrum is found to provide a line of sight dominated by an apparently 'textbook' H II region in a Stromgren sphere surrounding the stars. Several characteristics of this H II region are deduced by analyzing absorption features arising from excited fine-structure states of N II and Si II. Evidence is given for the presence of a normal interstellar H I region containing H2 and a separate H I region which could be the transition zone of the H II region. A possible blueshifted N V feature is noted in absorption. It is suggested that the H(+) emission measure and a characteristic size and shape for the H II region can probably be determined by optical observations of Balmer recombination lines within about 1 deg of V Puppis.