摘要
We search for isotropic stochastic gravitational-wave background(SGWB)in the International Pulsar Timing Array second data release.By modeling the SGWB as a power-law,we find very strong Bayesian evidence for a common-spectrum process,and further this process has scalar transverse(ST)correlations allowed in general metric theory of gravity as the Bayes factor in favor of the ST-correlated process versus the spatially uncorrelated common-spectrum process is 30±2.The median and the 90%equal-tail amplitudes of ST mode are A_(ST)=1.29^(+0.51)_(−0.44)×10^(−15),or equivalently the energy density parameter per logarithm frequency isΩSTGW=2.31^(+2.19)_(−1.30)×10^(−9),at frequency of 1 year−1.However,we do not find any statistically significant evidence for the tensor transverse(TT)mode and then place the 95%upper limits as A_(TT)<3.95×10^(−15),or equivalentlyΩ^(TT)_(GW)<2.16×10^(−9),at frequency of 1 year^(−1).
基金
This work is supported by the National Key Research and Development Program of China Grant No.2020YFC2201502, grants from NSFC (Grant No.11 975 019,11 991 052,12 047 503)
Key Research Program of Frontier Sciences, CAS, Grant NO. ZDBS-LY-7009
CAS Project for Young Scientists in Basic Research YSBR-006
the Key Research Program of the Chinese Academy of Sciences (Grant NO. XDPB15)。
