Improved V II log($gf$) Values, Hyperfine Structure Constants, and Abundance Determinations in the Photospheres of the Sun and Metal-poor Star HD 84937

TL;DR

This paper reports new experimental atomic data for V II, including transition probabilities and hyperfine structure constants, leading to more accurate vanadium abundance measurements in the Sun and a metal-poor star.

Contribution

It provides improved V II transition probabilities and hyperfine constants, reducing systematic uncertainties in stellar abundance determinations.

Findings

Good agreement with previous V II transition data

More accurate V abundance in the Sun (log ε(V)=3.95)

Determined V abundance in HD 84937 as [V/H]=-2.08 and [V/Fe]=0.24

Abstract

New experimental absolute atomic transition probabilities are reported for 203 lines of V II. Branching fractions are measured from spectra recorded using a Fourier transform spectrometer and an echelle spectrometer. The branching fractions are normalized with radiative lifetime measurements to determine the new transition probabilities. Generally good agreement is found between this work and previously reported V II transition probabilities. Use of two spectrometers, independent radiometric calibration methods, and independent data analysis routines enables a reduction in systematic uncertainties, in particular those due to optical depth errors. In addition, new hyperfine structure constants are measured for selected levels by least squares fitting line profiles in the FTS spectra. The new V II data are applied to high resolution visible and UV spectra of the Sun and metal-poor star HD 84937 to determine new, more accurate V abundances. Lines covering a range of wavelength and excitation potential are used to search for non-LTE effects. Very good agreement is found between our new solar photospheric V abundance, log {\epsilon}(V) = 3.95 from 15 V II lines, and the solar-system meteoritic value. In HD 84937, we derive [V/H] = -2.08 from 68 lines, leading to a value of [V/Fe] = 0.24.