Oscillator Strength Measurements of Atomic Absorption Lines from Stellar Spectra

TL;DR

This paper introduces a new method for accurately determining oscillator strengths of atomic absorption lines using detailed spectral synthesis of the Sun and standard stars, updating many log(gf)-values and creating an interactive spectral database.

Contribution

It presents a novel spectral synthesis approach to refine oscillator strength measurements and updates a large set of atomic line data for stellar spectra analysis.

Findings

Systematic over-estimation of literature log(gf)-values for certain lines.

New oscillator strengths validated with curve-of-growth analysis.

Development of an interactive spectral database for stellar reference spectra.

Abstract

We develop a new method to determine oscillator strength values of atomic absorption lines with state-of-the-art detailed spectral synthesis calculations of the optical spectrum of the Sun and of standard spectral reference stars. We update the log(gf)-values of 911 neutral lines observed in the KPNO-FTS flux spectrum of the Sun and high-resolution echelle spectra (R=80,000) of Procyon (F5 IV-V) and {\epsilon} Eri (K2 V) observed with large signal-to-noise (S/N) ratios of ~2,000 using the new Mercator-Hermes spectrograph at La Palma Observatory (Spain). We find for 483 Fe I, 85 Ni I, and 51 Si I absorption lines in the sample a systematic over-estimation of the literature log(gf)-values with central line depths below 15 %. We employ a curve-of-growth analysis technique to test the accuracy of the new oscillator strength values and compare calculated equivalent line widths to the Moore, Minnaert, & Houtgast atlas of the Sun. The online SpectroWeb database at http://spectra.freeshell.org interactively displays the observed and synthetic spectra and provides the new log(gf)-values together with important atomic line data. The graphical database is under development for stellar reference spectra of every spectral sub-class observed with large spectral resolution and S/N ratios.