title: Limits on a gravitational field dependence of the proton-electron mass ratio from H2 in white dwarf stars.
abstract: Spectra of molecular hydrogen (H2) are employed to search for a possible proton-to-electron mass ratio (μ) dependence on gravity. The Lyman transitions of H2, observed with the Hubble Space Telescope towards white dwarf stars that underwent a gravitational collapse, are compared to accurate laboratory spectra taking into account the high temperature conditions (T∼13 000  K) of their photospheres. We derive sensitivity coefficients Ki which define how the individual H2 transitions shift due to μ dependence. The spectrum of white dwarf star GD133 yields a Δμ/μ constraint of (-2.7±4.7stat±0.2syst)×10(-5) for a local environment of a gravitational potential ϕ∼10(4) ϕEarth, while that of G29-38 yields Δμ/μ=(-5.8±3.8stat±0.3syst)×10(-5) for a potential of 2×10(4) ϕEarth.
authors.affiliation: Department of Physics and Astronomy, and LaserLaB, VU University, De Boelelaan 1081, 1081 HV Amsterdam, Netherlands.
authors.forename: J
authors.initials: J
authors.lastname: Bagdonaite
authors.affiliation: Department of Physics and Astronomy, and LaserLaB, VU University, De Boelelaan 1081, 1081 HV Amsterdam, Netherlands and Department of Physics, University of San Carlos, Cebu City 6000, Philippines.
authors.forename: E J
authors.initials: EJ
authors.lastname: Salumbides
authors.affiliation: Department of Physics and Astronomy, University of Leicester, University Road, Leicester LEI 7RH, United Kingdom.
authors.forename: S P
authors.initials: SP
authors.lastname: Preval
authors.affiliation: Department of Physics and Astronomy, University of Leicester, University Road, Leicester LEI 7RH, United Kingdom.
authors.forename: M A
authors.initials: MA
authors.lastname: Barstow
authors.affiliation: DAMTP, Centre for Mathematical Sciences, University of Cambridge, Cambridge CB3 0WA, United Kingdom.
authors.forename: J D
authors.initials: JD
authors.lastname: Barrow
authors.affiliation: Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Melbourne, Victoria 3122, Australia.
authors.forename: M T
authors.initials: MT
authors.lastname: Murphy
authors.affiliation: Department of Physics and Astronomy, and LaserLaB, VU University, De Boelelaan 1081, 1081 HV Amsterdam, Netherlands.
authors.forename: W
authors.initials: W
authors.lastname: Ubachs