A search for magnetic fields on central stars in planetary nebulae

Leone, F.; Corradi, R. L. M.; González, M. J. Martínez; Ramos, A. Asensio; Sainz, R. Manso

doi:10.1051/0004-6361/201322753

Cited by 30 publications

(29 citation statements)

References 29 publications

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“…Table 2 presents the log of our Stokes V observations with the target ID, the date of observation, the number of collected V sequences, the total exposure time (in sec) for a single Stokes V sequence and the peak signal to noise ratio (S/N) of a single Stokes V sequence per 2.6 km.s −1 spectral bin, around 680 nm. As mentioned by Leone et al (2014), our ability to detect any magnetic field is strongly linked to the high S/N achieved. In our case, the mean S/N per spectral bin per Stokes V sequence is typically greater than ∼500.…”

Section: The Samplementioning

confidence: 95%

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First detection of surface magnetic fields in post-AGB stars: the cases of U Monocerotis and R Scuti

Sabin¹,

Wade²,

Lèbre³

2014

Monthly Notices of the Royal Astronomical Society

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While several observational investigations have revealed the presence of magnetic fields in the circumstellar envelopes, jets and outflows of post-Asymptotic Giant Branch stars (PAGBs) and planetary nebulae (PNe), none has clearly demonstrated their presence at the stellar surface. The lack of information on the strength of the surface magnetic fields prevents us from performing any thorough assessment of their dynamic capability (i.e. material mixing, envelope shaping, etc). We present new high resolution spectropolarimetric (Stokes V ) observations of a sample of PAGB stars, realised with the instruments ESPaDOnS and Narval, where we searched for the presence of photospheric magnetic fields. Out of the seven targets investigated the RV Tauri stars U Mon and R Sct display a clear Zeeman signature and return a definite detection after performing a least squares deconvolution (LSD) analysis. The remaining five PAGBs show no significant detection. We derived longitudinal magnetic fields of 10.2 ± 1.7 G for U Mon and 0.6 ± 0.6 G for R Sct. In both cases the Stokes profiles point towards an interaction of the magnetic field with the atmosphere dynamics. This first discovery of weak magnetic fields (i.e. ∼10 gauss level) at the stellar surface of PAGB stars opens the door to a better understanding of magnetism in evolved stars.

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Section: The Samplementioning

confidence: 95%

“…Historically however, for objects located beyond the AGB, different investigations conducted with this technique, principally targeting PNe, led to null or inconclusive detections (Leone et al 2011;Jordan et al 2012;Leone et al 2014;Steffen et al 2014). The limited number of suitable spectral lines are often to blame when analysing PNe.…”

Section: Introductionmentioning

confidence: 99%

First detection of surface magnetic fields in post-AGB stars: the cases of U Monocerotis and R Scuti

Sabin¹,

Wade²,

Lèbre³

2014

Monthly Notices of the Royal Astronomical Society

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“…The detections of synchrotron emission (Pérez-Sánchez et al 2013), Faraday rotation (Ransom et al 2010), maser emission (Leal-Ferreira et al 2013;Wolak et al 2012;Amiri et al 2011), dust continuum polarisation (Sabin et al 2007), and molecular line polarisation (Girart et al 2012;Vlemmings et al 2012) have allowed us to determine the configuration and/or strength of the magnetic field 1 . All these discoveries are leading to a better understanding of the ⋆ E-mail:lsabin@astro.iam.udg.mx (LS) † Jansky Fellow of the National Radio Astronomy Observatory, which is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. 1 It is worth mentioning that in PNe, contrary to the case of AGB stars (see the work by Lèbre et al 2014), there is still no conspicuous and definite measurements indicating the presence of a B-field at the stellar surface (Jordan et al 2012; Leone et al 2011Leone et al , 2014Steffen et al 2014). …”

Section: Introductionmentioning

confidence: 99%

Millimetre polarization of the protoplanetary nebula OH 231.8+4.2: a follow-up study with CARMA

Sabin¹,

Hull²,

Plambeck³

et al. 2015

Monthly Notices of the Royal Astronomical Society

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In order to investigate the characteristics and influence of the magnetic field in evolved stars, we performed a follow-up investigation of our previous submillimeter analysis of the proto-planetary nebula (PPN) OH 231.8+4.2 (Sabin et al. 2014), this time at 1.3 mm with the CARMA facility in polarisation mode for the purpose of a multi-scale analysis. OH 231.8+4.2 was observed at ∼ 2.5 ′′ resolution and we detected polarised emission above the 3σ threshold (with a mean polarisation fraction of 3.5%). The polarisation map indicates an overall organised magnetic field within the nebula. The main finding in this paper is the presence of a structure mostly compatible with an ordered toroidal component that is aligned with the PPN's dark lane. We also present some alternative magnetic field configuration to explain the structure observed. These data complete our previous SMA submillimeter data for a better investigation and understanding of the magnetic field structure in OH 231.8+4.2.

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“…than 600 G, or that the field has a complex structure. The most recent search for magnetic fields in central stars of planetary nebulae by Leone et al (2014), based on spectropolarimetric observations of 19 central stars with WHT/ISIS and VLT/FORS 2, is partly affected by large measurement uncertainties and reports no positive detection either. Thus, convincing evidence for the presence of significant magnetic fields in the central stars of PNe is still missing.…”

Section: Introductionmentioning

confidence: 99%

Weak magnetic fields in central stars of planetary nebulae?

Steffen

Hubrig

Todt

et al. 2014

A&A

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Context. It is not yet clear whether magnetic fields play an essential role in shaping planetary nebulae (PNe), or whether stellar rotation alone and/or a close binary companion, stellar or substellar, can account for the variety of the observed nebular morphologies. Aims. In a quest for empirical evidence verifying or disproving the role of magnetic fields in shaping planetary nebulae, we follow up on previous attempts to measure the magnetic field in a representative sample of PN central stars. Methods. We obtained low-resolution polarimetric spectra with FORS 2 installed on the Antu telescope of the VLT for a sample of 12 bright central stars of PNe with different morphologies, including two round nebulae, seven elliptical nebulae, and three bipolar nebulae. Two targets are Wolf-Rayet type central stars.Results. For the majority of the observed central stars, we do not find any significant evidence for the existence of surface magnetic fields. However, our measurements may indicate the presence of weak mean longitudinal magnetic fields of the order of 100 Gauss in the central star of the young elliptical planetary nebula IC 418 as well as in the Wolf-Rayet type central star of the bipolar nebula Hen 2-113 and the weak emission line central star of the elliptical nebula Hen 2-131. A clear detection of a 250 G mean longitudinal field is achieved for the A-type companion of the central star of NGC 1514. Some of the central stars show a moderate night-to-night spectrum variability, which may be the signature of a variable stellar wind and/or rotational modulation due to magnetic features. Conclusions. Since our analysis indicates only weak fields, if any, in a few targets of our sample, we conclude that strong magnetic fields of the order of kG are not widespread among PNe central stars. Nevertheless, simple estimates based on a theoretical model of magnetized wind bubbles suggest that even weak magnetic fields below the current detection limit of the order of 100 G may well be sufficient to contribute to the shaping of the surrounding nebulae throughout their evolution. Our current sample is too small to draw conclusions about a correlation between nebular morphology and the presence of stellar magnetic fields.

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A search for magnetic fields on central stars in planetary nebulae

Cited by 30 publications

References 29 publications

First detection of surface magnetic fields in post-AGB stars: the cases of U Monocerotis and R Scuti

First detection of surface magnetic fields in post-AGB stars: the cases of U Monocerotis and R Scuti

Millimetre polarization of the protoplanetary nebula OH 231.8+4.2: a follow-up study with CARMA

Weak magnetic fields in central stars of planetary nebulae?

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