Constraints on common envelope magnetic fields from observations of jets in planetary nebulae

• DOI: 10.1093/mnras/stu079
• Publication Date: 2014-02-10T23:51:37Z
• Authors: James Tocknell; Orsola De Marco; Mark Wardle
• Keywords: Astrophysics - Solar and Stellar Astrophysics; 0103 physical sciences; FOS: Physical sciences; 01 natural sciences; Solar and Stellar Astrophysics (astro-ph.SR)

The common envelope (CE) interaction describes the swallowing of a nearby companion by a growing, evolving star. CEs that take place during the asymptotic giant branch phase of the primary and may lead to the formation of a planetary nebula (PN) with a post-CE close binary in the middle. We have used published observations of masses and kinematics of jets in four post-CE PN to infer physical characteristics of the CE interaction. In three of the four systems studied, Abell 63, ETHOS 1 and the Necklace PN, the kinematics indicate that the jets were launched a few thousand years before the CE and we favour a scenario where this happened before Roche lobe overflow, although better models of wind accretion and wind Roche lobe overflow are needed. The magnetic fields inferred to launch pre-CE jets are of the order of a few Gauss. In the fourth case, NGC 6778, the kinematics indicate that the jets were launched about 3000 years after the CE interaction. Magnetic fields of the order of a few hundreds to a few thousands Gauss are inferred in this case, approximately in line with predictions of post-CE magnetic fields. However, we remark that in the case of this system, it is impossible to find a reasonable scenario for the formation of the two jet pairs observed: the small orbital separation would preclude the formation of even one accretion disk able to supply the necessary accretion rate to cause the observed jets.<br/>9 pages, accepted by MNRAS, Key words: Magnetic Fields, ISM: Jets and Outflows, Planetary Nebulae: Individual: Necklace, Planetary Nebulae: Individual: Abell 63, Planetary Nebulae: Individual: ETHOS 1, Planetary Nebulae: Individual: NGC 6778<br/>