In this work we investigate the equilibrium configurations of white dwarfs in a modified gravity theory, namely, f(R, T) gravity, for which R and T stand for the Ricci scalar and trace of the energy-momentum tensor, respectively. Considering the functional form f(R, T) = R+ 2 λT, with λ being a constant, we obtain the hydrostatic equilibrium equation for the theory. Some physical properties of white dwarfs, such as: mass, radius, pressure and energy density, as well as their dependence on the parameter λ are derived. More massive and larger white dwarfs are found for negative values of λ when it decreases. The equilibrium configurations predict a maximum mass limit for white dwarfs slightly above the Chandrasekhar limit, with larger radii and lower central densities when compared to standard gravity outcomes. The most important effect of f(R, T) theory for massive white dwarfs is the increase of the radius in comparison with GR and also f(R) results. By comparing our results with some observational data of massive white dwarfs we also find a lower limit for λ, namely, λ> - 3 × 10 - 4.
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Acknowledgements GAC would like to thank CAPES (Coordenação de Aperfeiçoamento de Pessoal de Nível Superior) for financial support. RVL thanks CNPq (Conselho Nacional de Desenvolvimeno Cien-tífico e Tecnológico) process 141157/2015-1 and CAPES/PDSE/88881. 134089/2016-01 for financial support. He is also sincerely grateful to staff of ICRANet, Pescara, Italy, for kind hospitality during his visit. PHRSM would like to thank São Paulo Research Foundation (FAPESP), grant 2015/08476-0, for financial support. JDVA, RMM and MM acknowledge CAPES, CNPq and FAPESP thematic project 13/26258-4. All computations were performed in open source software and the authors are sincerely thankful to open source community [68– 71].