Limits on the dependence of the fine-structure constant on gravitational potential from white-dwarf spectra

TL;DR

This paper investigates whether the fine-structure constant varies in strong gravitational fields by analyzing white dwarf spectra, setting new limits on its potential dependence with high-precision astronomical data.

Contribution

It introduces a novel method using white dwarf spectra to constrain variations in the fine-structure constant in strong gravity environments.

Findings

Limits on alpha variation: (4.2 ± 1.6)×10^(-5) and (-6.1 ± 5.8)×10^(-5).

Potential for two orders of magnitude improvement with better laboratory data.

Provides constraints at a gravitational potential of ~5×10^(-5).

Abstract

We propose a new probe of the dependence of the fine structure constant, alpha, on a strong gravitational field using metal lines in the spectra of white dwarf stars. Comparison of laboratory spectra with far-UV astronomical spectra from the white dwarf star G191-B2B recorded by the Hubble Space Telescope Imaging Spectrograph gives limits on the fractional variation of alpha of (Delta alpha/alpha)=(4.2 +- 1.6)x10^(-5) and (-6.1 +- 5.8)x10^(-5) from Fe V and Ni V spectra, respectively, at a dimensionless gravitational potential relative to Earth of (Delta phi) ~ 5x10^(-5). With better determinations of the laboratory wavelengths of the lines employed these results could be improved by up to two orders of magnitude.