Article

Astrophysics and Space Science

, Volume 283, Issue 4, pp 577-582

First online:

Does the fine structure constant vary? A detailed investigation into systematic effects

  • M.T. MurphyAffiliated withSchool of Physics, University of New South Wales
  • , J.K. WebbAffiliated withSchool of Physics, University of New South Wales
  • , V.V. FlambaumAffiliated withSchool of Physics, University of New South Wales
  • , S.J. CurranAffiliated withSchool of Physics, University of New South Wales

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Abstract

We have previously presented 5.7 σ evidence for a smaller αat redshifts 0.2 < zabs < 3.7 from a sample of 128 Keck/HIRES quasar absorption systems: Δα/α = (-0.57 ± 0.10) x10-5. A non-zero <Δα/α manifests itself as a distinct pattern of shifts in the measured absorption line wavelengths. The statistical error is now small: we do detect small line shifts in the HIRES data. Whether these shifts are due to systematic errors or due to real variation in α is now the central question. Here we summarize the two potentially most important systematic effects: atmospheric dispersion and isotopic abundance evolution. Previously, these have been difficult to quantify/model but here we find that neither of them can explain our results. Furthermore, the HIRES spectra themselves contain no evidence for these effects. Independent measurements of Δα/α with a different telescope and spectrograph are now crucial if we are to rule out or confirm the present evidence for a variable α.