S22A0013

We propose to observe the COSMOS UltraDeep (UD) field with HSC in order to investigate the unexplored time domain of the variable Universe - the long and faint. To explore the long-timescale frontier of the variable Universe, we have been accumulating the time domain legacy data with HSC at the COSMOS UD field in the last 5 seasons in the i and z bands with the median limiting magnitudes of 26.0 mag and 25.5 mag, respectively. We propose to add the 6th season data as deep as the last 5 seasons. The proposed long-term survey can discover high-redshift pair-instability and superluminous SNe and intrinsically long-lasting SNe. Long-term AGN activities can also be investigated. Unknown long-timescale transients may be discovered. Obtaining the time domain data in this year is essential to identify long-lasting transient candidates to follow with JWST, which will be launched in late 2021. We have been discovering long-lasting faint transients in the last 5 seasons. The live long-lasting SNe to be observed with JWST will show up in 2022 and it is required to obtain the long-term time domain data in S22A to make full use of JWST.

This document was translated from L^AT_EX by H^EV^EA.