Miszalski, Brent; Boffin, Henri M. J.; Corradi, R. L. M.
Bibliographical reference
Monthly Notices of the Royal Astronomical Society: Letters, Volume 428, Issue 1, p.L39-L43
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1
2013
Citations
60
Refereed citations
49
Description
The formation of collimated outflows or jets in planetary nebulae (PNe)
is not well understood. There is no evidence for active accretion discs
in PNe, making it difficult to decide which of the several proposed jet
formation scenarios may be correct. A handful of wide binary central
stars of PNe are known to have accreted carbon and slow neutron capture
(s-process) enhanced material, the immediate progenitors of barium
stars; however, no close binary analogues are known to have passed
through a common-envelope (CE) phase. Here we present spectroscopy of
the Necklace taken near light-curve minimum that for the first time
reveals a carbon-rich (C/O > 1) companion, a carbon dwarf, in a
post-CE central star. As unevolved stars do not produce carbon, the
chemical enhancement of the secondary can only be explained by accretion
from the primary. Accretion most likely happened prior to the CE phase
via wind accretion as not enough material can be accreted during the
short CE phase. The pair of jets in the Necklace, which are observed to
be older than the PN, are therefore likely to have been launched from an
accretion disc around the companion during this early accretion phase.
This discovery adds significant weight to the emerging scenario that
jets in post-CE PNe are primarily launched by an accretion disc around a
main-sequence companion before the CE phase.
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