Probing Galactic variations in the fine-structure constant using solar twin stars: systematic errors

Abstract

Sun-like stars are a new probe of variations in the fine-structure constant, $\alpha$, via the solar twins approach: velocity separations of close pairs of absorption lines are compared between stars with very similar stellar parameters, i.e. effective temperature, metallicity and surface gravity within 100K, 0.1 dex and 0.2 dex of the Sun's values. Here we assess possible systematic errors in this approach by analysing $\gtrsim$10,000 archival exposures from the High-Accuracy Radial velocity Planetary Searcher (HARPS) of 130 stars covering a much broader range of stellar parameters. We find that each transition pair's separation shows broad, low-order variations with stellar parameters which can be accurately modelled, leaving only a small residual, intrinsic star-to-star scatter of 0-33 m/s (average $\approx$7 m/s, $\approx$10${}^{-4}$Å at 5000Å). This limits the precision available from a single pair in one star. We consider potential systematic errors from a range of instrumental and astrophysical sources (e.g. wavelength calibration, charge transfer inefficiency, stellar magnetic activity, line blending) and conclude that variations in elemental abundances, isotope ratios and stellar rotational velocities may explain this star-to-star scatter. Finally, we find that the solar twins approach can be extended to solar analogues - within 300K, 0.3 dex and 0.4 dex of the Sun's parameters - without significant additional systematic errors, allowing a much larger number of stars to be used as probes of variation in $\alpha$, including at much larger distances.

arXiv comment18 pages, 12 figures. Accepted by MNRAS. The VarConLib (Varying Constants Library) software used in this work is available at https://github.com/DBerke/varconlib. The measurements and results in this work are available at https://github.com/DBerke/Berke_et_alia_2022_supplemental_data

References in corpus (44)

• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• Array Programming with NumPy
• Astropy: A Community Python Package for Astronomy
• The Astropy Project: Building an inclusive, open-science project and status of the v2.0 core package
• The Geneva-Copenhagen survey of the Solar neighbourhood: Ages, metallicities, and kinematic properties of 14,000 F and G dwarfs
• New constraints on the chemical evolution of the solar neighbourhood and Galactic disc(s). Improved astrophysical parameters for the Geneva-Copenhagen Survey
• Further Evidence for Cosmological Evolution of the Fine Structure Constant
• astroquery: An Astronomical Web-Querying Package in Python
• A Search for Time Variation of the Fine Structure Constant
• Varying constants, Gravitation and Cosmology
• Further evidence for a variable fine-structure constant from Keck/HIRES QSO absorption spectra
• Nominal values for selected solar and planetary quantities: IAU 2015 Resolution B3
• CMasher: Scientific colormaps for making accessible, informative and 'cmashing' plots
• Space-Time Variation of Physical Constants and Relativistic Corrections in Atoms
• Chromospheric activity catalogue of 4454 cool stars. Questioning the active branch of stellar activity cycles
• The colours of the Sun
• Measuring precise radial velocities on individual spectral lines. I. Validation of the method and application to mitigate stellar activity
• Evolution of the Fine Structure Constant Driven by Dark Matter and the Cosmological Constant
• TAPAS, a web-based service of atmospheric transmission computation for astronomy
• The status of varying constants: a review of the physics, searches and implications
• Calibrating echelle spectrographs with Fabry-Perot etalons
• Selection of ThAr lines for wavelength calibration of echelle spectra and implications for variations in the fine-structure constant
• Limits on the dependence of the fine-structure constant on gravitational potential from white-dwarf spectra
• Magnesium isotopic abundance ratios in cool stars
• High-precision limit on variation in the fine-structure constant from a single quasar absorption system
• 'Ultimate' Information Content in Solar and Stellar Spectra: Photospheric line asymmetries and wavelength shifts
• A Frequency Comb calibrated Solar Atlas
• Search for a Variation of the Fine Structure around the Supermassive Black Hole in Our Galactic Center
• Subaru Telescope limits on cosmological variations in the fine-structure constant
• Fundamental physics with ESPRESSO: Precise limit on variations in the fine-structure constant towards the bright quasar HE 0515$-$4414
• Five Decades of Chromospheric Activity in 59 Sun-like Stars and New Maunder Minimum Candidate HD 166620
• New solar twins and the metallicity and temperature scales of the Geneva Copenhagen Survey
• unyt: Handle, manipulate, and convert data with units in Python
• Precision and consistency of astrocombs
• New wavelength calibration of the HARPS spectrograph
• Measuring the fine structure constant on a white dwarf surface; a detailed analysis of Fe V absorption in G191-B2B
• Measuring and characterizing the line profile of HARPS with a laser frequency comb
• Variation of $\alpha$ from a Dark Matter Force
• A limit on variations in the fine-structure constant from spectra of nearby Sun-like stars
• SpectroWeb: Oscillator Strength Measurements of Atomic Absorption Lines in the Sun and Procyon
• The Belgian repository of fundamental atomic data and stellar spectra (BRASS). I. Cross-matching atomic databases of astrophysical interest
• Solar Contamination in Extreme Precision Radial Velocity Measurements: Deleterious Effects and Prospects for Mitigation
• Survey for Distant Solar Twins (SDST) -- I. EPIC method for stellar parameter measurement
• Probing Galactic variations in the fine-structure constant using solar twin stars: methodology and results

Cited by in corpus (4)

• A limit on variations in the fine-structure constant from spectra of nearby Sun-like stars
• Solar Photospheric Spectrum Microvariability I. Theoretical searches for proxies of radial-velocity jittering
• Probing Galactic variations in the fine-structure constant using solar twin stars: methodology and results
• Survey for Distant Solar Twins (SDST) -- III. Identification of new solar twin and solar analogue stars