Astronomy and Astrophysics – Astronomy
Scientific paper
Dec 1993
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993aas...183.1804p&link_type=abstract
American Astronomical Society, 183rd AAS Meeting, #18.04; Bulletin of the American Astronomical Society, Vol. 25, p.1320
Astronomy and Astrophysics
Astronomy
2
Scientific paper
The 5() 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 7000Angstroms. 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 Angstroms region and have a resolution of ~ 18Angstroms. These data display FUV emission in the 1000--1150 Angstroms region and EUV emission near 800Angstroms 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 ~ 4*E(-11) erg cm(-2) s(-1) . This suggests that the individual FUV components have characteristic line strengths that are 1/2 to 1/4 of the strengths of the Lyalpha and MgII 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 ~ 8*E(-12) erg cm(-2) 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: <= 5*E(17) 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 ( ~ 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.
Polidan Ronald S.
Shore Steve N.
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