Program: GN-2024B-Q-221

The progenitor systems of gravitational wave mergers are believed to arise from a mass transfer process known as common envelope (CE) evolution. Although a large fraction of binary systems will undergo CE evolution at some point in their lives, modelling CE evolution is extremely difficult due to the lack of benchmark observed systems where both the pre-CE and post-CE conditions are known. While post-CE systems containing a white dwarf (WD) and main-sequence (MS) star have been observed, they are all located in the field and suffer from uncertainties in their cooling tracks, making it difficult to gain insights into their pre-CE parameters. Identifying post-CE systems in stellar clusters can circumvent this issue by providing an independent constraint on the age of the system, but only two WD+MS post-CE systems in a stellar cluster have been identified to date. Thus, we have undertaken a large effort to identify and characterize the first population of WD+MS post-CE systems in star clusters. Here, we request 7.80 hours with Gemini North and South to obtain initial spectra for 5 photometrically/kinematically selected post-CE candidates. These spectra will allow us to (i) confirm the WD+MS nature of the binary systems and (ii) perform an initial assessment of the properties of each component (e.g. effective temperature and surface gravity). These spectra are necessary to continue building the first catalogue of WD+MS post-CE binaries in star clusters.