| The successful detection of GW150914 by the ground-based gravitational wave detector LIGO opens a new gate of gravitational wave astronomy.Because sensitive frequency bands of ground-based detectors are restricted by factors such as arm length and gravitational gradient noise,the future space gravitational wave detectors will become an important instrument of detecting gravitational waves in the millihertz band.TianQin is a space gravitational wave detection program proposed by China and it is expected to be on orbit around 2035.Compared with ground-based detectors,the inter-satellite lasers of the space gravitational wave detector need to travel a long distance of hundreds of thousands to millions of kilometers.As a result,the laser frequency noise caused by the unequal arm length of the propagation optical path in the Doppler data is about 7 to 8 orders larger than the frequency shift signal caused by the gravitational wave on magnitude.The data preprocessing method,Time Delay Interference(TDI),can effectively suppress laser frequency noise.The basic idea of this method is to time delay the data and then combine it to construct interferometric data with the same arm length.Only the detector configuration with the static arm length was considered in the beginning,then the Sagnac effect caused by the rotation of the detector,finally the deteriorated symmetry of the optical path caused by the change of the arm length was considered.Correspondingly,the TDI method has also undergone three versions upgrade of TDI 1.0,TDI 1.5 and TDI 2.0.In this paper,based on the design of geocentric high orbit of TianQin,the influence of the eccentricity of the geocentric orbit on the residual laser frequency noise is studied based on the TDI method through analytical orbit expression.The results suggest that the eccentricity of the geocentric orbit is set to e1=0.01,the TDI 1.5 combinations cannot meet the requirement of suppressing the laser frequency noise below the secondary noise,and the TDI 2.0 combinations can meet this requirement,providing a reference for future orbit parameter design.The paper also considers the residual laser frequency noise of each TDI combination to modify the all-sky response sensitivity curve.Compared with the other combinations,the X2.0 combination has the highest sensitivity.There are a large number of double white dwarfs(DWDs)in the Milky Way,and they are one of the important wave sources of space gravitational wave detectors.The detection of such sources can deepen our understanding of the evolution of stars and the formation of dense binary stars,etc.Firstly,the paper gives a detailed expression of the gravitational wave signal expression about the detached DWD for TianQin under the quadrupole moment radiation approximation.Then combined with TDI optimal combination(AET combination),the gravitational wave data of 41 pairs of detached DWDs that have been discovered through electromagnetic wave observations in the Milky Way are simulated.Finally,based on the maximum likelihood estimation and Particle Swarm Optimization(PSO)algorithm,the multi-source search process is established.In order to reduce the calculation time and improve the accuracy of the parameter search results,a fast search template is established in the multi-source search process,and the methods of sub-band processing data,down sampling and F statistics are adopted.Through this set of data processing process,all four wave sources with a signal-to-noise ratio of 5 or higher are searched out.The matching degree of the recovered gravitational wave signal and the injected gravitational wave signal is above 99.9%and the location error of the wave source is in(0.0005,0.21)square degrees,which proves the feasibility of the data processing process. |
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