Ongoing surveys for close binary central stars and wider implications

Abstract

Abstract. Binary central stars have long been invoked to explain the vexing shapes of planetary nebulae (PNe) despite there being scant direct evidence to support this hypothesis. Modern large-scale surveys and improved observing strategies have allowed us to significantly boost the number of known close binary central stars and estimate at least 20% of PNe have close binary nuclei that passed through a common-envelope (CE) phase. The larger sample of post-CE nebulae appears to have a high proportion of bipolar nebulae, low-ionisation structures (especially in SN1987A-like rings) and polar outflows or jets. These trends are guiding our target selection in ongoing multi-epoch spectroscopic and photometric surveys for new binaries. Multiple new discoveries are being uncovered that further strengthen the connection between post-CE trends and close binaries. These ongoing surveys also have wider implications for understanding CE evolution, low-ionisation structure and jet formation, spectral classification of central stars, asymptotic giant branch (AGB) nucleosynthesis and dust obscuration events in PNe.

A search for magnetic fields on central stars in planetary nebulae

“…The binary scenario has been explored both theoretically (e.g., Soker & Rappaport 2001) and observationally (e.g., Miszalski 2012;Boffin et al 2012), and while it can explain a number of structures observed in the nebulae, it is unlike gravitational interactions are sufficient to explain all the variety of outflows found in the same nebula (see e.g., the case of Mz3 in Santander et al 2004, where four distinct flows with increasing collimation degree have been identified).…”