Abstract

During its orbit around the four million solar mass black hole Sagittarius A∗ the star S2 experiences significant changes in gravitational potential. We use this change of potential to test one part of the Einstein equivalence principle: the local position invariance (LPI). We study the dependency of different atomic transitions on the gravitational potential to give an upper limit on violations of the LPI. This is done by separately measuring the redshift from hydrogen and helium absorption lines in the stellar spectrum during its closest approach to the black hole. For this measurement we use radial velocity data from 2015 to 2018 and combine it with the gravitational potential at the position of S2, which is calculated from the precisely known orbit of S2 around the black hole. This results in a limit on a violation of the LPI of |βHe-βH|=(2.4±5.1)×10-2. The variation in potential that we probe with this measurement is six magnitudes larger than possible for measurements on Earth, and a factor of 10 larger than in experiments using white dwarfs. We are therefore testing the LPI in a regime where it has not been tested before.

Original languageEnglish
Article number101102
JournalPhysical Review Letters
Volume122
Issue number10
DOIs
StatePublished - 14 Mar 2019

Funding

FundersFunder number
Seventh Framework Programme
Centre National de la Recherche Scientifique
Bundesministerium für Bildung und Forschung
Deutsche Forschungsgemeinschaft
Fundação para a Ciência e Tecnologia
Alexander von Humboldt-Stiftung
European Research Council306311
European Commission610058
FCT-PortugalUID/FIS/00099/2013

    Fingerprint

    Dive into the research topics of 'Test of the Einstein Equivalence Principle near the Galactic Center Supermassive Black Hole'. Together they form a unique fingerprint.

    Cite this