2000ApJ...531..384S

We empirically confirm the theoretical branching ratio and oscillator strength for the weak Mg II 3s-4p doublet at 1240 Å as determined by Theodosiou & Federman. We use the independent methods of apparent optical depth analysis for the sight lines toward µ Col, γ Ara, and ρ Leo and profile component fitting for the sight line toward µ Col in order to determine the branching ratio. We find f₁₂₃₉/f₁₂₄₀=1.74±0.06, in agreement with the theoretical value of 1.78±0.03. Profile fitting for the line of sight toward µ Col gives an f-value for the doublet of 9.71±0.32x10^–4, which agrees with both the theoretical value of Theodosiou & Federman and the empirical value of Fitzpatrick.