Full polarization study of SiO masers at 86 GHz

Herpin, Fabrice; Baudry, A.; Thum, C.; Morris, D.; Wiesemeyer, H.

doi:10.1051/0004-6361:20054255

Cited by 102 publications

(155 citation statements)

References 52 publications

(86 reference statements)

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“…Blackman et al (2001) argue that some remnant field anchored in the core will survive even without a convection zone, although the convective envelope may not be removed completely. The idea that magnetic fields are important ingredients shaping PNe has been supported by the detection of SiO, H 2 O, and OH maser emission in circumstellar envelopes of AGB stars pointing at milliGauss fields in these nebula (Kemball & Diamond 1997;Szymczak & Cohen 1997;Miranda et al 2001;Vlemmings et al 2002Vlemmings et al , 2005Vlemmings et al , 2006Herpin et al 2006;Sabin et al 2007;Kemball et al 2009;Gómez et al 2009;Vlemmings 2011). Moreover, using an idea of Pascoli (1985), Huggins & Manley (2005) connected the extreme filamentary structures seen in high-resolution optical images of certain PNe to magnetic fields consistent with those measured in the maser from the precursor circumstellar envelopes.…”

Section: Introductionmentioning

confidence: 91%

Magnetic fields in central stars of planetary nebulae?

Jordan

Bagnulo

Werner

et al. 2012

A&A

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Context. Most planetary nebulae have bipolar or other non-spherically symmetric shapes. Magnetic fields in the central star may be responsible for this lack of symmetry, but observational studies published to date have reported contradictory results. Aims. We search for correlations between a magnetic field and departures from the spherical geometry of the envelopes of planetary nebulae. Methods. We determine the magnetic fields from spectropolarimetric observations of ten central stars of planetary nebulae. The results of the analysis of the observations of four stars were previously presented and discussed in the literature, while the observations of six stars, plus additional measurements of a star previously observed, are presented here for the first time.Results. All our determinations of magnetic field in the central planetary nebulae are consistent with null results. Our field measurements have a typical error bar of 150-300 G. Previous spurious field detections using data acquired with FORS1 (FOcal Reducer and low dispersion Spectrograph) of the Unit Telescope 1 (UT1) of the Very Large Telescope (VLT) were probably due to the use of different wavelength calibration solutions for frames obtained at different position angles of the retarder waveplate. Conclusions. There is currently no observational evidence of magnetic fields with a strength of the order of hundreds Gauss or higher in the central stars of planetary nebulae.

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Section: Introductionmentioning

confidence: 91%

Magnetic fields in central stars of planetary nebulae?

Jordan

Bagnulo

Werner

et al. 2012

A&A

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“…they are not the source of localized magnetic fields unrelated to the global field issued from the central star. Fig.4 includes previous measurements of SiO masers (Kemball et al 2009;Herpin et al 2006), H2O masers (Vlemmings et al 2002(Vlemmings et al , 2005 and OH masers (Rudnitski et al 2010) giving us an overview of the maser and magnetic field strength distributions in evolved stars. Thus, Vlemmings (2011) summarised the results of the aforementioned studies related to the characteristics of masers in AGB stars (the behaviour is similar in PAGB stars) and noted some correlations through the different investigations in terms of strength and location of each masers.…”

Section: Prediction Of Maser Strengths In the Envelope Of U Monmentioning

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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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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“…Both single-dish and interferometric observations have revealed that silicon monoxide (SiO), water (H 2 O), hydrogen cyanide (HCN), hydroxyl (OH), and methanol (CH 3 OH), among others, can naturally generate polarized maser emission in these enviroments (e.g. Vlemmings et al 2006b;Surcis et al 2011;Fish & Reid 2007b;Herpin et al 2006;Kemball et al 2009). In particular, interferometric observations of the masers at radio wavelengths have become a useful tool for studying the magnetic field in and around SFRs and late-type stars (e.g.…”

Section: Introductionmentioning

confidence: 99%

Linear polarization of submillimetre masers

Pérez-Sánchez

Vlemmings

2013

A&A

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Context. Once ALMA full polarization capabilities are offered, it will become possible to perform detailed studies of polarized maser emission towards star-forming regions and late-type stars, such as (post-) asymptotic giant branch stars and young planetary nebulae. To derive the magnetic field orientation from maser linear polarization, a number of conditions involving the rate of stimulated emission R, the decay rate of the molecular state Γ, and the Zeeman frequency gΩ need to be satisfied. Aims. The goal of this work is to investigate if SiO, H 2 O and HCN maser emission within the ALMA frequency range can be detected with observable levels of fractional linear polarization in the regime where the Zeeman frequency is greater than the stimulated emission rate. Methods. We used a radiative transfer code to calculate the fractional linear polarization as a function of the emerging brightness temperature for a number of rotational transition of SiO, H 2 O and HCN that have been observed to display maser emission at submillimetre wavelengths. We assumed typical magnetic field strengths measured towards galactic star-forming regions and circumstellar envelopes of late-type stars from previous VLBI observations. Since the Landé g-factors have not been reported for the different rotational transitions we modelled, we performed our calculations assuming conservative values of the Zeeman frequency for the different molecular species. Results. Setting a lower limit for the Zeeman frequency that still satisfies the criteria gΩ > R and gΩ > Γ, we find fractional polarization levels of up to 13%, 14% and 19% for the higher J transitions analysed for SiO, H 2 O and HCN, respectively, without considering anisotropic pumping or any other non-Zeeman effect. These upper limits were calculated assuming a magnetic field oriented perpendicular to the direction of propagation of the maser radiation. Conclusions. According to our results, SiO, H 2 O, and HCN maser emission within the ALMA frequency range can be detected with suitable linear polarization to trace the magnetic field structure towards star-forming regions and late-type stars even if the detected polarization has been enhanced by non-Zeeman effects.

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Full polarization study of SiO masers at 86 GHz

Cited by 102 publications

References 52 publications

Magnetic fields in central stars of planetary nebulae?

Magnetic fields in central stars of planetary nebulae?

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

Linear polarization of submillimetre masers

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