EUV Emission from 17 Leporis
Session 18 -- Stellar Spectra: Individual Objects
Display presentation, Wednesday, January 12, 9:30-6:45, Salons I/II Room (Crystal Gateway)

## [18.04] EUV Emission from 17 Leporis

R. S. Polidan (NASA/GSFC), S. N. Shore (IUSB)

The 5$^{\rm th}$ magnitude star 17 Leporis is a binary system consisting of an early A star plus a low mass M companion star. The two stars are equal in brightness near 7000\thinspace \AA. We have proposed a model for 17 Lep as pre--main sequence binary system consisting of a Herbig A2e star and a low mass M2 star on a fully convective track. Both stars are still contracting toward the main sequence. Voyager\/ UVS observations were made of the 17 Lep system over a 7 day interval in May 1992. The observations cover the 500--1700\AA\ region and have a resolution of $\sim$18\thinspace \AA. These data display FUV emission in the 1000--1150 \thinspace\AA\ region and EUV emission near 800\thinspace \AA\ from 17 Lep. Analysis of the 17 Lep spectra suggest that the FUV and EUV emissions do not arise from continuum processes. They likely represent line emissions from one of the stellar components or the circumstellar environment. The FUV emission is clearly composed of multiple ($>$6) components and has an observed total line flux of $\sim 4\times10^{-11} \thinspace {\rm erg~cm}^{-2}~{\rm s}^{-1}$. This suggests that the individual FUV components have characteristic line strengths that are $1\over2$ to $1\over4$ of the strengths of the Ly\thinspace $\alpha$ and Mg\thinspace II emission lines seen in IUE\/ spectra of 17 Lep. The EUV feature'' is also clearly a complex of multiple ($>$3) emission lines, with a total line flux of $\sim 8\times10^{-12} \thinspace {\rm erg~cm}^{-2}~{\rm s}^{-1}$. In addition, over the 7 days of observation the EUV lines appeared to vary significantly ($>$75\%) with time, whereas the FUV lines were statistically constant. The existence of EUV emission in 17 Lep suggests a very low neutral hydrogen column to the star: $\leq 5\times10^{17}~{\rm cm}^{-2}$. This very low neutral hydrogen column density is not unreasonable since 17 Lep lies in the direction of the Canis Major hole'' and is very nearby ($\sim$75 pc). We discuss the line identifications, observed and intrinsic line strengths, and possible origins for the FUV and EUV emissions along with the implications for the interstellar neutral hydrogen column density along this line of sight.