Formation of Extremely Low-mass White Dwarfs Binaries

Understand

Motivated by the discovery of a handful of pulsating, extremely low mass white dwarfs (ELM WDs, mass $M \lesssim 0.17\, M_\odot$) which likely have WD companions, this paper discusses binary formation models for these systems.

• Formation of an ELM WD by unstable mass transfer (MT) or a common envelope (CE) event is unlikely.
• Stable Roche-lobe overflow with conservative MT produces only $M \gtrsim 0.2\, M_\odot$.
• This paper discusses the formation of ELM WD using angular momentum losses by magnetic braking.