SpectroWeb: Oscillator Strength Measurements of Atomic Absorption Lines in the Sun and Procyon

TL;DR

This paper updates the SpectroWeb database with 1178 new oscillator strength measurements for atomic absorption lines in the spectra of the Sun and Procyon, improving atomic data accuracy for stellar spectroscopy.

Contribution

It provides a large set of validated oscillator strengths for key atomic lines, with improvements over existing databases like VALD, based on high-quality spectral synthesis.

Findings

Identified systematic over-estimation of VALD log(gf)-values for weak lines of neutral iron-group elements.

Decreased log(gf)-values for Si I lines to better fit observed spectra.

Enhanced SpectroWeb database with validated atomic line data for stellar analysis.

Abstract

We update the online SpectroWeb database of spectral standard reference stars with 1178 oscillator strength values of atomic absorption lines observed in the optical spectrum of the Sun and Procyon (Alpha CMi A). The updated line oscillator strengths are measured with best fits to the disk-integrated KPNO-FTS spectrum of the Sun observed between 4000 A and 6800 A using state-of-the-art detailed spectral synthesis calculations. A subset of 660 line oscillator strengths is validated with synthetic spectrum calculations of Procyon observed with ESO-UVES between 4700 A and 6800 A. The new log(gf)-values in SpectroWeb are improved over the values offered in the online Vienna Atomic Line Database (VALD). We find for neutral iron-group elements, such as Fe I, Ni I, Cr I, and Ti I, a statistically significant over-estimation of the VALD log(gf)-values for weak absorption lines with normalized central line depths below 15 %. For abundant lighter elements (e.g. Mg I and Ca I) this trend is statistically not significantly detectable, with the exception of Si I for which the log(gf)-values of 60 weak and medium-strong lines are substantially decreased to best fit the observed spectra. The newly measured log(gf)-values are available in the SpectroWeb database at http://spectra.freeshell.org which interactively displays the observed and computed stellar spectra, together with corresponding atomic line data.