# Science with the TianQin observatory: Preliminary results on massive black hole binaries

## TL;DR

This paper assesses TianQin's potential to detect gravitational waves from massive black hole mergers, estimating detection rates, parameter accuracy, and early warning capabilities for multi-messenger astronomy.

## Contribution

It provides the first comprehensive preliminary analysis of TianQin's detection prospects for massive black hole binaries across different astrophysical models.

## Key findings

- TianQin could detect up to 60 mergers per year in optimistic scenarios.
- The observatory can estimate luminosity distances within 10% for high-redshift events.
- Early warnings with sky localization are feasible for nearby mergers, enabling multi-messenger follow-up.

## Abstract

We investigate the prospects of detecting gravitational waves from coalescing massive black hole binaries in the Universe with the TianQin observatory, a space-based gravitational wave interferometer proposed to be launched in the 2030s. To frame the scientific scope of the mission, in this paper, we carry out a preliminary estimation of the signal-to-noise ratio, detection rate and parameter estimation precision of massive black hole binaries detectable by TianQin. In order to make our results as robust as possible, we consider several models of the growth history of massive black holes, exploring the effect of some key astrophysical prescriptions as well the impact of the employed computational methods. In the most optimistic model, TianQin can detect as many as approximately 60 mergers per year. If TianQin detects a merger at redshift of 15, it will be capable of estimating its luminosity distance to within an accuracy of 10%; for a nearby event at redshift approximately 2, TianQin can issue early warnings 24 hours before coalescence, with a timing accuracy of around three hours and a sky localization ability of approximately 80 deg$^2$, thus enabling multi-messenger observations.