# Probing the Gravitational Dependence of the Fine-Structure Constant from Observations of White Dwarf Stars

## TL;DR

This study investigates whether the fine-structure constant varies in strong gravitational fields by analyzing UV spectra of white dwarf stars, employing improved laboratory data and methodologies to detect potential shifts in absorption lines.

## Contribution

It introduces a new analysis of multiple white dwarf stars using enhanced laboratory wavelengths and robust methods, advancing the search for gravitational dependence of fundamental constants.

## Key findings

- Preliminary results from nine white dwarfs show no definitive variation.
- Methodological improvements increase sensitivity to potential variations.
- Analysis sets the stage for more precise future measurements.

## Abstract

Hot white dwarf stars are the ideal probe for a relationship between the fine-structure constant and strong gravitational fields, providing us with an opportunity for a direct observational test. We study a sample of hot white dwarf stars, combining far-UV spectroscopic observations, atomic physics, atmospheric modelling and fundamental physics, in the search for variation in the fine structure constant. This variation manifests as shifts in the observed wavelengths of absorption lines, such as quadruply ionized iron (FeV) and quadruply ionized nickel (NiV), when compared to laboratory wavelengths. Berengut et al. (Phys. Rev. Lett. 2013, 111, 010801) demonstrated the validity of such an analysis using high-resolution Hubble Space Telescope (HST)/Space Telescope Imaging Spectrograph (STIS) spectra of G191-B2B. We have made three important improvements by: (a) using three new independent sets of laboratory wavelengths, (b) analysing a sample of objects, and (c) improving the methodology by incorporating robust techniques from previous studies towards quasars (the Many Multiplet method). A successful detection would be the first direct measurement of a gravitational field effect on a bare constant of nature. Here we describe our approach and present preliminary results from nine objects using both FeV and NiV.