分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： This article summarizes the talks in the session GW2 of the Sixteenth Marcel Grossmann Meeting on Recent Developments in Theoretical and Experimental General Relativity, Gravitation, and Relativistic Field Theories, 5-10 July, 2021, on Mid-frequency (0.1-10 Hz) gravitational waves: Sources and detection methods with a review on strain power spectral density amplitude of various mid-frequency gravitational wave projects/concepts and with extended summaries on the progress of ZAIGA project and on the conceptual study of AMIGO.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： The space-borne gravitational wave (GW) detectors, LISA and TAIJI, are planned to be launched in the 2030s. The dual detectors with comparable sensitivities will form a network observing GW with significant advantages. In this work, we investigate the three possible LISA-TAIJI networks for the different location and orientation compositions of LISA orbit ($+60^\circ$ inclination and trailing the Earth by $20^\circ$) and alternative TAIJI orbit configurations including TAIJIp ($+60^\circ$ inclination and leading the Earth by $20^\circ$), TAIJIc ($+60^\circ$ inclination and co-located with LISA), TAIJIm ($-60^\circ$ inclination and leading the Earth by $20^\circ$). In the three LISA-TAIJI configurations, the LISA-TAIJIm network shows the best performance on the sky localization and polarization determination for the massive binary system due to their better complementary antenna pattern, and LISA-TAIJIc could achieve the best cross-correlation and observe the stochastic GW background with an optimal sensitivity.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： A large number of galactic binary systems emit gravitational waves (GW) continuously with frequencies below $\sim$10 mHz. The LISA mission could identify the tens of thousands of binaries over years of observation and will be subject to the confusion noise around 1 mHz yielded by the unresolved sources. Beyond LISA, there are several missions have been proposed to observe GWs in the sub-mHz range where the galactic foreground is expected to be overwhelming the instrumental noises. In this study, we investigate the detectability of sub-mHz GW missions to detect the galactic double white dwarf (DWD) binaries and evaluate the confusion noise produced by the undistinguished DWDs. This confusion noise could also be viewed as a stochastic GW foreground and be effectively observed in the sub-mHz band. The parameter determinations for the modeled foreground are examined by employing different detector sensitivities and population models. By assuming the determined foregrounds could be subtracted from the data, we evaluate the residuals which are expected to have power spectral densities two orders of magnitude lower than the originals data.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： We introduce a generic algorithm to determine the time delays and spacecraft (S/C) positions to compose any time-delay interferometry (TDI) channel in the dynamical case and evaluate its sensitivity by using a full numerical method. We select 11 second-generation TDI channels constructed from four approaches and investigate their gravitational wave responses, noise levels, and averaged sensitivities under a numerical LISA orbit. The sensitivities of selected channels are various especially for frequencies lower than 20 mHz. The optimal channel A$_2$ (or equivalently E$_2$) combined from second-generation Michelson TDI channels (X$_1$, X$_2$, and X$_3$) achieves the best sensitivity among the channels, while the Sagnac $\alpha_1$ channel shows the worse sensitivity. Multiple channels show better sensitivities at some characteristic frequencies compared to the fiducial X$_1$ channel. The joint $\mathrm{A_2+E_2+T_2}$ observation not only enhances the sensitivity of the X$_1$ channel by a factor of $\sqrt{2}$ to 2 but also improves the capacity of sky coverage.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： A large number of galactic binary systems emit gravitational waves (GW) continuously with frequencies below $\sim$10 mHz. The LISA mission could identify the tens of thousands of binaries over years of observation and will be subject to the confusion noise around 1 mHz yielded by the unresolved sources. Beyond LISA, there are several missions have been proposed to observe GWs in the sub-mHz range where the galactic foreground is expected to be overwhelming the instrumental noises. In this study, we investigate the detectability of sub-mHz GW missions to detect the galactic double white dwarf (DWD) binaries and evaluate the confusion noise produced by the undistinguished DWDs. This confusion noise could also be viewed as a stochastic GW foreground and be effectively observed in the sub-mHz band. The parameter determinations for the modeled foreground are examined by employing different detector sensitivities and population models. By assuming the determined foregrounds could be subtracted from the data, we evaluate the residuals which are expected to have power spectral densities two orders of magnitude lower than the originals data.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： AMIGO - The Astrodynamical Middle-frequency Interferometric GW (Gravitation-Wave) Observatory is a first-generation mid-frequency GW mission bridging the sensitivity gap between the high-frequency GW detectors and low-frequency space GW detectors. In our previous works, we have obtained appropriate heliocentric orbit formations of nominal arm length 10,000 km with their first-generation time-delay configurations satisfying frequency noise reduction requirement, and we have also worked out thrust-fuel friendly constant-arm heliocentric orbit formations. In this paper, we review and study noise requirements and present the corresponding GW sensitivities. From the design white position noises and acceleration noises, we obtain the GW sensitivities for the first-generation Michelson X TDI configuration of b-AMIGO (baseline AMIGO), AMIGO, and e-AMIGO (enhanced AMIGO). In view of the current technology development, we study and indicate steps to implement the AMIGO mission concept.
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