Astronomy and Astrophysics, volume 559A, 91-91 (2013/11-1)
Limits on the spatial variations of the electron-to-proton mass ratio in the Galactic plane.
LEVSHAKOV S.A., REIMERS D., HENKEL C., WINKEL B., MIGNANO A., CENTURION M. and MOLARO P.
Abstract (from CDS):
We aim to validate the Einstein equivalence principle (local position invariance) by limiting the fractional changes in the electron-to-proton mass ratio, µ=me/mp, measured in Galactic plane objects. High-resolution spectral observations of dark clouds in the inversion line of NH3(1, 1) and pure rotational lines of other molecules (the so-called ammonia method) were performed at the Medicina 32-m and the Effelsberg 100-m radio telescopes to measure the radial velocity offsets, ΔRV=Vrot-Vinv, between the rotational and inversion transitions, which have different sensitivities to the value of µ. In our previous observations (2008-2010), a mean offset of <ΔRV≥0.027±0.010km/s (3σ confidence level (C.L.)) was measured. To test for possible hidden errors, we carried out additional observations of a sample of molecular cores in 2010-2013. As a result, a systematic error with an amplitude ∼0.02km/s in the radial velocities was revealed. The averaged offset between the radial velocities of the rotational transitions of HC3N(2-1), HC5N(9-8), HC7N(16-15), HC7N(21-20), and HC7N(23-22), and the inversion transition of NH3(1, 1) is <ΔRV≥0.003±0.018km/s (3σ C.L.). This value, when interpreted in terms of Δµ/µ=(µobs-µlab)/µlab, constraints the µ-variation at the level of Δµ/µ<2x10–8 (3σ C.L.), which is the most stringent limit on the fractional changes in µ based on astronomical observations.
line: profiles - ISM: molecules - radio lines: ISM - techniques: radial velocities - elementary particles
Status at CDS:
In ref list Kuiper et al 1996 is Kuiper et al. 1996ApJ...468..761K
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