Since discovery of the binary pulsar PSR B1913+16 by Hulse and Taylor , binary pulsars promises an unprecedented opportunity to measure the effects of relativistic gravitation. Especially, the relativistic effects from binary pulsar are more remarkable than other celestial systems. By fitting the arrival time of pulsars, observational parameters of binary pulsar are obtained in high precision. It worthy of noted that the periastron advance for binary pulsars could reach several degrees per year, which is about 105 more than the perihelion advance of Mercury.   

  With this idea, the secular periastron precession  of binary pulsars has been investigated with a modified theory including the fifth force. The four binary pulsars data (PSR B1913 + 16, PSR B1534 + 12, PSR J0737 - 3039, and PSR B2127 + 11C) are used to constrain the Yukawa parameters for the modified theory (see Fig. 1): λ=(3.97±0.01)×108m and α=(2.40±0.02)×10-8. It has been shown that the limits of binary pulsars systems on the modified theory are basically consistent with the results from the Solar System such as the earth-satellite measurement of Earth gravity, the lunar orbiter measurement of lunar gravity, and lunar laser ranging measurement to constrain the fifth force. To solidify the existence of the Yukawa effects by binary pulsars systems in the future, the timing model should be constructed in the framework of the modified theory with the the fifth force.  

By with DENG Xuemei

  The plane of - constrained by !˙ of four double neutron star binaries. (a) Each curve is separated into two curves to show the bounds due to the observational 1 error. (b) Confidence 

  This work is done by Dr. Xue-Mei Deng of Purple Mountain Observatory who is collaborated with Dr. Yi Xie and Prof. Tian-Yi Huang of Department of Astronomy in Nanjing University. And this research is supported by the National Nature Science Foundation of China (Nos. 10973009, 1103085 and 11103010) and the Fundamental Research Program of Jiangsu Province of China (No. BK2011553). For more details, please see the following link: http://www.worldscientific.com/doi/abs/10.1142/9789814623995_0260  

level contours of 68:3% (red), 95:4% (green) and 99:73% (blue) in the plane of - constrained by four double neutron star binaries.