Constraints on fourth order gravity from binary pulsar and gravitational   waves
  We have earlier proposed a fourth order gravity model as a possible explanation for late time cosmic acceleration, and for flattened galaxy rotation curves. The model has a free length parameter whose value depends on the scale of the system under study (e.g. the whole Universe, a galaxy, or a compact binary pulsar). In the present work, we investigate the constraints imposed on the free model parameter by Hulse-Taylor binary pulsar data: periastron advance; and emission of gravitational waves and consequent period decay. It is shown that the model is consistent with these observations, provided the length parameter is bounded from above. 
Shreya Banerjee, Sayantani Bera, Srimanta Banerjee and Tejinder P.   Singh
gr-qc astro-ph.HE