Forecast of strongly lensed supernovae rates in the China Space Station Telescope surveys

¹ Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210023, PR China
² School of Astronomy and Space Science, University of Science and Technology of China, Hefei, Anhui 230026, PR China
³ South-Western Institute for Astronomy Research, Yunnan University, Kunming, Yunnan 650504, PR China
⁴ Institute for Frontier in Astronomy and Astrophysics, Beijing Normal University, Beijing 102206, PR China
⁵ Department of Astronomy, Beijing Normal University, Beijing 100875, PR China
⁶ National Astronomical Observatories, Beijing 100101, PR China

Received: 23 May 2024
Accepted: 27 June 2024

Abstract

Strong gravitationally lensed supernovae (SNe) are a powerful probe for cosmology and stellar physics. The relative time delays between lensed SN images provide an independent way of measuring a fundamental cosmological parameter – the Hubble constant –, the value of which is currently under debate. The time delays also serve as a “time machine”, offering a unique opportunity to capture the extremely early phase of the SN explosion, which can be used to constrain the SN progenitor and explosion mechanism. Although there are only a handful of strongly lensed SN discoveries so far, which greatly hinders scientific applications, the sample size is expected to grow substantially with next-generation surveys. In this work, we investigate the capability of detecting strongly lensed SNe with the China Space Station Telescope (CSST), a two-meter space telescope to be launched around 2026. Through Monte Carlo simulations, we predict that CSST can detect 1008.53 and 51.78 strongly lensed SNe from its Wide Field Survey (WFS, covering 17 500 deg²) and Deep Field Survey (DFS, covering 400 deg²) over the course of ten years. In both surveys, about 35% of the events involve Type Ia SNe as the background sources. Our results suggest that the WFS and DFS of CSST, although not designed or optimized for discovering transients, can still make a great contribution to the strongly lensed SNe studies.