Why Magnetic Fields Cannot Be the Main Agent Shaping Planetary Nebulae

Soker, Noam

doi:10.1086/498829

Cited by 84 publications

(82 citation statements)

References 39 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It has been argued that at least one highly collimated pre-PN can be shaped by magnetic fields (Vlemmings et al 2006). Although pre-PN central stars are not likely descendants from common envelopes, it is highly likely that wider binary interactions caused the magnetic fields in the first place (for theoretical arguments against shaping of PNe by single star, global magnetic fields see Soker (2006); see also Sect. 3.3.6).…”

Section: Planetary Nebulae As a Constraint On Ejecta Velocities And Tmentioning

confidence: 99%

Common envelope evolution: where we stand and how we can move forward

Іванова

Justham

Chen

et al. 2013

Astron Astrophys Rev

921

587

View full text Add to dashboard Cite

This work aims to present our current best physical understanding of common-envelope evolution (CEE). We highlight areas of consensus and disagree- ment, and stress ideas which should point the way forward for progress in this important but long-standing and largely unconquered problem. Unusually for CEE-related work, we mostly try to avoid relying on results from population synthesis or observations, in order to avoid potentially being misled by previous misunderstandings. As far as possible we debate all the relevant issues starting from physics alone, all the way from the evolution of the binary system immediately before CEE begins to the processes which might occur just after the ejection of the envelope. In particular, we include extensive discussion about the energy sources and sinks operating in CEE, and hence examine the foundations of the standard energy formalism. Special attention is also given to comparing the results of hydrodynamic simulations from different groups and to discussing the potential effect of initial conditions on the differences in the outcomes. We compare current numerical techniques for the problem of CEE and also whether more appropriate tools could and should be produced (including new formulations of computational hydrodynamics, and attempts to include 3D processes within 1D codes). Finally we explore new ways to link CEE with observations. We compare previous simulations of CEE to the recent outburst from V1309 Sco, and discuss to what extent post-common-envelope binaries and nebulae can provide information, e.g. from binary eccentricities, which is not currently being fully exploited.

show abstract

Section: Planetary Nebulae As a Constraint On Ejecta Velocities And Tmentioning

confidence: 99%

Common envelope evolution: where we stand and how we can move forward

Іванова

Justham

Chen

et al. 2013

Astron Astrophys Rev

921

587

View full text Add to dashboard Cite

show abstract

“…In the single-star scenario, magnetic fields and stellar rotation have been deemed sufficient to achieve most of the observed shapes (e.g., García-Segura et al 1999). However, recently we have appreciated that a single asymptotic giant branch (AGB) star cannot sustain largescale magnetic fields long enough for it to act on the mass-loss geometry (Nordhaus et al 2007;Soker 2006). A rotating AGB star can produce a large-scale magnetic field, but this field will drain angular momentum from the star, slow down the rotation that sustains it, and therefore switch itself off.…”

Section: Introductionmentioning

confidence: 99%

Binary Central Stars of Planetary Nebulae Discovered Through Photometric Variability. I. What We Know and What We Would Like to Find Out

Marco

Hillwig

Smith

2008

The Astronomical Journal

106

View full text Add to dashboard Cite

Shaping axisymmetric planetary nebulae is easier if a companion interacts with a primary at the top of the asymptotic giant branch. To determine the impact of binarity on planetary nebula formation and shaping, we need to determine the central star of planetary nebula binary fraction and period distribution. The short-period binary fraction has been known to be 10-15% from a survey of ∼100 central stars for photometric variability indicative of irradiation effects, ellipsoidal variability, or eclipses. This survey technique is known to be biased against binaries with long periods and this fact is used to explain why the periods of all the binaries discovered by this survey are smaller than 3 days. In this paper we assess the status of knowledge of binary central stars discovered because of irradiation effects. We determine that, for average parameters, this technique should be biased against periods longer than 1-2 weeks, so it is surprising that no binaries were found with periods longer than 3 days. Even more puzzling is the fact that 9 out of 12 of the irradiated binaries have periods smaller than 1 day, a fact that is starkly at odds with post-common envelope predictions. We suggest that either all common envelope models tend to overestimate post-common envelope periods or this binary survey might have suffered from additional, unquantified biases. If the latter hypothesis is true, the currently known short-period binary fraction is put in serious doubt. We also introduce a new survey for binary-related variability, which will enable us to better quantify biases and determine an independent value for the short-period binary fraction.

show abstract

“…Blackman et al (2001) showed that AGB stars can generate a magnetic field by dynamo action at the interface between the rapidly rotating core and the extended convection zone. However, the importance of the magnetic field for global envelope dynamics remains a matter of debate (e.g., Soker 2006).…”

Section: Introductionmentioning

confidence: 99%

Precessing planetary magnetospheres in SiO stars?

Wiesemeyer¹,

Thum²,

Baudry

et al. 2009

A&A

View full text Add to dashboard Cite

Context. The origin of magnetism around asymptotic giant branch (AGB) stars remains an uncertainty. These stars may drive an important dynamo, but if the magnetic energy dissipates entirely into X-rays, the observed X-ray luminosities are too low to maintain a strong, dynamically important global field. Other explanations of the circular polarization in SiO masers in AGB atmospheres may thus be required. Aims. The interaction of the AGB wind with both previously ejected matter and planets is expected to produce complex magnetohydrodynamic phenomena on a short timescale, such that strong magnetic fields can be maintained locally. Here, we provide observational evidence of the corresponding magnetic fluctuations. Methods. We use the circular polarization of the v = 1, J = 2-1 SiO masers as a tracer of magnetic activity. A correlation polarimeter allows us to record simultaneously all Stokes parameters. An SiO maser survey of 77 AGB stars was performed from which eight sources of the strongest circular polarization were selected for further monitoring. Results. In two AGB stars, V Cam and R Leo, we find evidence of pseudo-periodic fluctuations in the fractional circular polarization on a timescale of a few hours, from which we infer magnetic fluctuations of ∼1 G. The phenomenon is rare and, if detected in an SiO star, restricted to a narrow range of velocities. It seems to be associated with planetary wake flows suggested by VLBI maps. Conclusions. While scenarios involving magnetic activity in the extended stellar atmosphere have problems explaining all observed features, precessing Jovian magnetospheres predict all of them without difficulty. For the case of R Leo, we constrain the orbit of the planet (estimated period 5.2 years), derive a stellar mass estimate of 0.7 M from it, and discuss the impact of planetary magnetism on the survival of planets. Smooth velocity variations in the fluctuating circular polarization feature are predicted as the planet moves along its orbit.

show abstract

Why Magnetic Fields Cannot Be the Main Agent Shaping Planetary Nebulae

Cited by 84 publications

References 39 publications

Common envelope evolution: where we stand and how we can move forward

Common envelope evolution: where we stand and how we can move forward

Binary Central Stars of Planetary Nebulae Discovered Through Photometric Variability. I. What We Know and What We Would Like to Find Out

Precessing planetary magnetospheres in SiO stars?

Contact Info

Product

Resources

About