Scalar-tensor theories of gravity can lead to modifications of the gravitational force inside astrophysical objects. We exhibit that compact stars such as white dwarfs provide a unique setup to test beyond Horndeski theories of $G^3$ type. We obtain stringent and independent constraints on the parameter $\mathrm{\Upsilon }$ characterizing the deviations from Newtonian gravity using the mass-radius relation, the Chandrasekhar mass limit, and the maximal rotational frequency of white dwarfs. We find that white dwarfs impose stronger constraints on $\mathrm{\Upsilon }$ than red and brown dwarfs.

• Received 14 January 2016

DOI:https://doi.org/10.1103/PhysRevLett.116.151103