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Description
Cataclysmic variables (CVs) are a type of interacting binary stars with a white dwarf primary and a low-mass donor star. In weakly magnetic systems, an accretion disk is formed around the primary star. Current evolutionary models predict the orbital period of CVs to shorten, until the donor has lost enough mass to become a degenerate brown dwarf. This happens at orbital periods of around ~70-80 minutes. Now the donor star responds to mass loss by expanding its radius, and the orbital periods start to lengthen again. Objects at the period minimum or evolved beyond it are called period bouncers, and they are classified as WZ Sge-type CVs.
The evolutionary status of WZ Sge, the prototype of WZ Sge-type CVs, has been a topic of discussion for over the past two decades. Its donor is extremely faint and thus determining its mass and spectral type has proven to be a difficult task. However, we observed it in June 2025 with ESO VLT/X-SHOOTER and received the best available near-infrared observations of WZ Sge. We present our observations and findings on the question of whether WZ Sge is a period bouncer or not.