2005/10/26 by K. E. Nielsen, G. M. Wahlgren, CR Proffitt +2 · 1 citation
Physics and Astronomy · #Stellar, planetary, and galactic studies #Astrophysics and Star Formation Studies #Astronomy and Astrophysical Research
paper · pdf · doi:10.1086/491703
openalex publication_date 2005/10/26 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/31
The gallium abundance in HgMn stars has been reported to be different for analyses conducted from spectral lines in the optical versus those from the ultraviolet. We pursue this ultraviolet-optical discrepancy from a line-blending perspective by investigating the Hubble Space Telescope ( HST ) Space Telescope Imaging Spectrograph (STIS) spectrum of the sharp-lined HgMn binary star χ Lup. Its gallium abundance is derived to be log N Ga = 4.5 (log N H = 12) based on nonresonance Ga II lines, and we are able to demonstrate the line-blending problems associated with the abundances determined from the resonance lines of Ga II λ1414 and Ga III λ1495. The HST STIS spectrum for χ Lup is also compared with a co-added International Ultraviolet Explorer ( IUE ) spectrum to further illustrate the importance of accounting for the line blending in quantitative abundance analyses. We have compared an IUE co-added spectrum of μ Lep with an LTE-based synthetic spectrum and managed to fit both Ga II λ1414 and Ga III λ1495 with an abundance of log N Ga = 7.3. However, the fitting of these lines requires a dramatic change in the radiative damping constants, which may indicate a breakdown in our LTE modeling or the need to include other atmospheric effects.