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Published online: 10 September 2008 | doi:10.1038/nchina.2008.214

Symbiotic stars: Chemical clues

Tim Reid

Introduction

© (2008) NASA/STScI

Two-star systems called symbiotic stars provide unique stellar laboratories for investigating nebulae, star interactions and explosions. The abundances of chemicals in symbiotic stars have been measured and found to be quite variable across different systems. Now numerical simulations performed by Guoliang Lv at Xinjiang University in Urumqi and co-workers¹ have shed light on the processes that cause these changes in chemical composition.

Symbiotic stars comprise a cool star that is constantly shedding mass, such as a red giant, to a companion hot star that collects and burns the ejected material, such as a white dwarf (pictured). Hydrogen usually burns up on the hot star, but can accumulate until there is a thermonuclear blast that throws material out, forming a nebula.

Lv and co-workers used population simulations to estimate the amounts of hydrogen, helium, carbon, nitrogen, oxygen and neon in symbiotic stars. Their model took into account the dredge-up of chemicals from the star centres and the transfer of mass between the stars.

Their simulations showed that the efficiency of the chemical dredge-up and interactions of stellar winds (outflows of gas and plasma) greatly affect the ratio of oxygen-rich to carbon-rich stars. The chemical abundances in the nebula are mainly modified by materials blasted out from the hot star.

The authors of this work are from:
Department of Physics, Xinjiang University, Urumqi, China; School of Science, Xi'an Jiaotong University, Xi'an, China; National Astronomical Observatories Yunnan Observatory, Chinese Academy of Sciences, Kunming, China.

Reference

1. Lü, G., Zhu, C., Han, Z. & Wang, Z. Chemical abundances in symbiotic stars. Astrophys. J. 683, 990–1005 (2008).  | Article |