Science with the TianQin Observatory: Preliminary results on Galactic double white dwarf binaries

We explore the prospects of detecting Galactic double white dwarf (DWD) binaries with the space-based gravitational wave (GW) observatory TianQin. In this work, we analyze both a sample of currently known DWDs and a realistic synthetic population of DWDs to assess the number of guaranteed detections and the full capacity of the mission. We find that TianQin can detect 12 out of $\ensuremath{\sim}100$ known DWDs; GW signals of these binaries can be modeled in detail ahead of the mission launch, and therefore they can be used as verification sources. Besides, we estimate that TianQin has a potential to detect as many as ${10}^{4}$ DWDs in the Milky Way. TianQin is expected to measure their orbital periods and amplitudes with accuracies of $\ensuremath{\sim}{10}^{\ensuremath{-}7}$ and $\ensuremath{\sim}0.2$, respectively, and to localize on the sky a large fraction (39%) of the detected population to better than $1\text{ }\text{ }{\mathrm{deg}}^{2}$. We conclude that TianQin has the potential to significantly advance our knowledge on Galactic DWDs by increasing the sample up to 2 orders of magnitude, and will allow their multimessenger studies in combination with electromagnetic telescopes. We also test the possibilities of different configurations of TianQin: (1) the same mission with a different orientation, (2) two perpendicular constellations combined into a network, and (3) the combination of the network with the ESA-led Laser Interferometer Space Antenna. We find that the network of detectors boosts the accuracy on the measurement of source parameters by 1--2 orders of magnitude, with the improvement on sky localization being the most significant.