Magnetic fields during the evolution towards planetary nebulae

Vlemmings, Wouter

doi:10.1017/s1743921312010903

Cited by 7 publications

(5 citation statements)

References 14 publications

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“…Also note that in this very mass range, near the MS, about 10% of stars possess large magnetic fields. Using the method of measuring circular polarization of maser lines, magnetic fields were also detected in a number of their far evolved descendants, PPN and PN [3,4].…”

Section: Introductionmentioning

confidence: 99%

Spectroscopy of Supergiants with Infrared Excess: Results of 1998–2018

Клочкова

2019

Astrophys. Bull.

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The results of our second stage of the detailed spectroscopy of peculiar supergiants identified with galactic infrared sources, performed at the 6-meter BTA telescope are summarized. The main aspect of the program is a search for the evolutionary variations in the chemical composition of stars, past the AGB stage and the TDU, as well as an analysis of spectral manifestations of kinematic processes in their extended, often unstable, atmospheres and in the envelopes. The most significant result is detection of the s-process element excesses in seven single post-AGB stars, which confirms the theory of evolution of this type of stars. In three of these stars we for the first time discovered the ejection of the s-process heavy metals to the circumstellar envelopes. A Li excess was found in the atmospheres of peculiar supergiants V2324 Cyg and V4334 Sgr. The results of investigation of the kinematical parameters of atmospheres and envelopes will clarify the equilibrium of matter produced by stars in the AGB and post-AGB stages and delivered to the interstellar medium.

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Section: Introductionmentioning

confidence: 99%

Spectroscopy of Supergiants with Infrared Excess: Results of 1998–2018

Клочкова

2019

Astrophys. Bull.

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“…Models and explanations range from single stars with particular magnetic fields arrangements (Chevalier & Luo 1994;García-Segura et al 1999;Pascoli & Lahoche 2008;Vlemmings 2011Vlemmings , 2012Jordan et al 2012) to the view that almost all planetary nebulae are caused by binary companions (Yungelson et al 1993;Soker & Rappaport 2001;De Marco 2009;Jones et al 2010Jones et al , 2012Douchin et al 2012). The discovery that hot Jupiter exoplanets are common around stars means that large planetary mass companions can also be considered amongst the shaping mechanisms (Nordhaus & Blackman 2006).…”

Section: Introductionmentioning

confidence: 99%

VLT observations of the asymmetric Etched Hourglass Nebula, MyCn 18

Clyne

Redman

Lloyd

et al. 2014

A&A

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Context. The mechanisms that form extreme bipolar planetary nebulae remain unclear. Aims. The physical properties, structure, and dynamics of the bipolar planetary nebula, MyCn 18, are investigated in detail with the aim of understanding the shaping mechanism and evolutionary history of this object. Methods. VLT infrared images, VLT ISAAC infrared spectra, and long-slit optical Echelle spectra are used to investigate MyCn 18. Morpho-kinematic modelling was used to firmly constrain the structure and kinematics of the source. A timescale analysis was used to determine the kinematical age of the nebula and its main components. Results. A spectroscopic study of MyCn 18's central and offset region reveals the detailed make-up of its nebular composition. Molecular hydrogen, atomic helium, and Bracket gamma emission are detected from the central regions of MyCn 18. ISAAC spectra from a slit position along the narrow waist of the nebula demonstrate that the ionised gas resides closer to the centre of the nebula than the molecular emission. A final reconstructed 3D model of MyCn 18 was generated, which provides kinematical information on the expansion velocity of its nebular components by means of position-velocity (P-V) arrays. A kinematical age of the nebula and its components were obtained by the P-V arrays and timescale analysis. Conclusions. The structure and kinematics of MyCn 18 are better understood using an interactive 3D modelling tool called SHAPE. A dimensional and timescale analysis of MyCn 18's major components provides a possible mechanism for the nebula's asymmetry. The putative central star is somewhat offset from the geometric centre of the nebula, which is thought to be the result of a binary system. We speculate that the engulfing and destruction of an exoplanet during the asymptotic giant branch phase may have been a key event in shaping MyCn 18 and generating of its hypersonic knotty outflow.

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“…On the other hand, in the hybrid MHD dust-driven wind model for Mira of Thirumalai & Heyl (2012) the role of a surface field of ∼4 G is dynamically important in the star's mass-loss process. Moreover, Vlemmings (2011) has shown, based on the measured magnetic field found in the literature in SiO and H 2 O, that the magnetic field dominates at and close to the photosphere. This is not the case in the OH/CN region, or at least the field energy is comparable to the kinetic energy.…”

Section: Impact On the Stellar Evolutionmentioning

confidence: 90%

Magnetic field in IRC+10216 and other C-rich evolved stars

Duthu

Herpin

Wiesemeyer

et al. 2017

A&A

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Context. During the transition from the asymptotic giant branch (AGB) to planetary nebulae (PN), the circumstellar geometry and morphology change dramatically. Another characteristic of this transition is the high mass-loss rate, that can be partially explained by radiation pressure and a combination of various factors, such as the stellar pulsation, the dust grain condensation, and opacity in the upper atmosphere. The magnetic field can also be one of the main ingredients that shapes the stellar upper atmosphere and envelope. Aims. Our main goal is to investigate for the first time the spatial distribution of the magnetic field in the envelope of IRC+10216. More generally we intend to determine the magnetic field strength in the circumstellar envelope (CSE) of C-rich evolved stars, compare this field with previous studies for O-rich stars, and constrain the variation of the magnetic field with r the distance to the star's centre. Methods. We use spectropolarimetric observations of the Stokes V parameter, collected with Xpol on the IRAM-30 m radiotelescope, observing the Zeeman effect in seven hyperfine components of the CN J = 1-0 line. We use the Crutcher et al. (1996, ApJ, 456, 217) method to estimate the magnetic field. For the first time, the instrumental contamination is investigated, through dedicated studies of the power patterns in Stokes V and I in detail.Results. For C-rich evolved stars, we derive a magnetic field strength (B) between 1.6 and 14.2 mG while B is estimated to be 6 mG for the proto-PN (PPN) AFGL618, and an upper value of 8 mG is found for the PN NGC 7027. These results are consistent with a decrease of B as 1/r in the environment of AGB objects, that is, with the presence of a toroidal field. But this is not the case for PPN and PN stars. Our map of IRC+10216 suggests that the magnetic field is not homogeneously strong throughout or aligned with the envelope and that the morphology of the CN emission might have changed with time.

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Magnetic fields during the evolution towards planetary nebulae

Cited by 7 publications

References 14 publications

Spectroscopy of Supergiants with Infrared Excess: Results of 1998–2018

Spectroscopy of Supergiants with Infrared Excess: Results of 1998–2018

VLT observations of the asymmetric Etched Hourglass Nebula, MyCn 18

Magnetic field in IRC+10216 and other C-rich evolved stars

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