Bounds on a change in α towards HE 2217-2818.
Abstract
Intervening absorption systems towards distant QSOs can be used to compare the value of dimensionless fundamental constants such as the fine-structure constant, α of remote regions of the Universe to their present value on Earth. We here report on the stringent bound for {Delta α/α} obtained for the absorber at mÅthrm zabs = 1.6919 towards HE 2217-2818. The absorption profile is complex and is modeled with 32 velocity components. The relative variation in α in this system is +1.3± 2.4mÅthrm stat ± 1.0mÅthrm sys ppm (parts per million) derived by means of Al II lambda 1670 Å and three Fe II transitions, and +1.1 ± 2.6mÅthrm stat ppm whith only Fe II transitions. This bound reveals no evidence for variation in α at the 3-ppm precision level (1-sigma confidence). At this sky position of the recently-reported dipolar variation of α is (3.2-5.4)±1.7 ppm. At face value this constraint is not supporting the spatial dipole model but not inconsistent with it at the 3sigma level. Beside, asteroid observations revealed the presence of a possible wavelength dependent velocity drift and of inter-order distortions. A systematic error which is a serious obstacle to improve the accuracy of this kind of measurements.
Based on observations obtained with UVES at the the 8.2m Kueyen ESO telescope programme L185.A-0745- Publication:
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Memorie della Societa Astronomica Italiana
- Pub Date:
- 2014
- Bibcode:
- 2014MmSAI..85...63W
- Keywords:
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- Cosmology: observations;
- Quasars: absorption lines