Burst of strongly polarized maser emission at 1612 MHz  
in the proto-planetary nebula OH17.7–2.0

Szymczak, M.; Gérard, E.

doi:10.1051/0004-6361:200500090

Cited by 8 publications

(16 citation statements)

References 24 publications

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“…Finally, I conclude in § 4, arguing that local magnetic fields are consistent with those observed, and that they can take a side role in the shaping of local regions inside the main nebula. The burst of strongly polarized OH maser emission in the proto-PN OH 17.7Ϫ2.0 supports a local nature of the polarized maser emission (Szymczak & Gerard 2005). The most likely primary shaping agent, however, remains the presence of companions.…”

Section: Introductionmentioning

confidence: 54%

“…Soker & Kastner (2003) suggest that the maser spots with strong magnetic fields that are observed around some AGB stars might be similar in nature to the magnetic clouds in the solar wind, in that they represent local enhancements of the magnetic field. The fast variation in the polarization of the OH maser emission in the proto-PN OH 17.7Ϫ2.0 (Szymczak & Gerard 2005) seems to support a local explanation for a strong magnetic field. This magnetic field topology is drawn schematically in Figure 1.…”

Section: The Detection Of Magnetic Fieldsmentioning

confidence: 68%

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Why Magnetic Fields Cannot Be the Main Agent Shaping Planetary Nebulae

Soker

2006

PUBL ASTRON SOC PAC

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ABSTRACT. An increasing amount of the literature reports the detection of magnetic fields in asymptotic giant branch (AGB) stars and in central stars of planetary nebulae (PNe). These detections lead to claims that the magnetic fields are the main agent shaping the PNe. In this paper, I examine the energy and angular momentum carried by magnetic fields expelled from AGB stars, as well as other physical phenomena that accompany the presence of large-scale fields, such as those claimed in the literature. I show that a single star cannot supply the energy and angular momentum if the magnetic fields have the large coherent structure required to shape the circumstellar wind. Therefore, the structure of nonspherical planetary nebulae cannot be attributed to dynamically important large-scale magnetic fields. I conclude that the observed magnetic fields around evolved stars can be understood with respect to locally enhanced magnetic loops, which can have a secondary role in the shaping of the PN. The primary role, I argue, rests with the presence of a companion.

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Section: Introductionmentioning

confidence: 54%

Section: The Detection Of Magnetic Fieldsmentioning

confidence: 68%

Why Magnetic Fields Cannot Be the Main Agent Shaping Planetary Nebulae

Soker

2006

PUBL ASTRON SOC PAC

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“…• 7 (Table 7) but the polarization angle of the eruptive feature near 73 km s −1 (Szymczak & Gérard 2005) is about −15 • and differs by about 64 • from the mean value for the extreme blue-and red-shifted velocities (Table 7).…”

Section: Polarization Angle Arrangementmentioning

confidence: 92%

“…We notice that in the sample are at least two bursting post-AGB stars; IRAS 16342-3814 and OH17.7-2.0 with m C > 80%. These objects sometimes experience OH bursts of highly polarized emission at 1612 MHz usually not associated with bursts at 1665 and 1667 MHz (Szymczak & Gérard 2005). In many post-AGB objects there is a disruption of detached AGB 1612 MHz shells that are no longer spherically symmetric and the appearance of a well-defined bipolar morphology at 1667 MHz is observed (Zijlstra et al 2001).…”

Section: Effect Of Depolarizationmentioning

confidence: 99%

“…The OH emission in the 1665 and 1667 MHz lines shows a substantial degree of circular polarization up to 50−80% Claussen & Fix 1982) but linear polarization occurs in only ∼10% of sources (Olnon et al 1980). Highly polarized OH maser features are observed in flaring Miras (Reid et al 1977;Fix 1979;Etoka & Le Squeren 1997), hypergiant IRC+10420 (Benson et al 1979) and post-AGB star OH17.7-2.0 (Szymczak & Gérard 2005). There is a general consensus that the polarization measurements of OH maser emission can Appendices are available in electronic form at http://www.aanda.org be properly explained with the classic model of Goldreich et al (1973) in which the magnetic field plays a key role (e.g., Gray & Field 1996;Elitzur 1996).…”

Section: Introductionmentioning

confidence: 98%

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Polarization properties of OH masers in AGB and post-AGB stars

Wolak

Szymczak

Gérard

2011

A&A

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Context. Ground-state OH maser emission from late-type stars is usually polarized and remains a powerful probe of the magnetic field structure in the outer regions of circumstellar envelopes if observed with high angular and spectral resolutions. Observations in all four Stokes parameters are quite sparse and this is the most thorough, systematic study published to date. Aims. We aim to determine polarization properties of OH masers in an extensive sample of stars that show copious mass loss and search for candidate objects that are well-suited for high angular resolution studies. Methods. Full-polarization observations of the OH 1612 and 1667 MHz maser transitions were carried out for a sample of 117 AGB and post-AGB stars. Several targets were also observed in the 1665 MHz line. Results. A complete set of full-polarization spectra together with the basic polarization parameters are presented. Polarized features occur in more than 75% of the sources in the complete sample and there is no intrinsic difference in the occurrence of polarized emission between the three classes of objects of different infrared characteristics. The highest fractional polarization occurs for the post-AGB+PN and the Mira+SR classes at 1612 and 1667 MHz, respectively. Differences in the fractional polarization between the sources at different evolutionary stages appear to be related to depolarization caused by blending. The alignment of the polarization angles at the extreme sides of the shell implies a regular structure of the magnetic field of a strength of 0.3-2.3 mG. Conclusions. Polarized OH maser features are widespread in AGB and post-AGB stars. The relationship between the circular and linear fractional polarizations for a representative sample are consistent with the standard models of polarization for the Zeeman splitting higher than the Doppler line width, whereas the polarized features are the σ components.

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Amplification by Stimulated Emission in Rydberg Matter Clusters as the Source of Intense Maser Lines in Interstellar Space

Holmlid

2006

Astrophys Space Sci

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The detailed processes giving maser line radiation from various molecules in space are not well understood, as can be seen from many recent detailed studies of maser line emission with high spatial and velocity resolution, and with polarization measurements. We now propose an improved maser mechanism based on amplification of the original molecular line emission by stimulated emission in Rydberg Matter (RM) clouds in HII regions, containing clusters H N and (H 2 ) N . This mechanism will amplify the molecular lines, depending on the position, velocity, cluster size and state of excitation of the clusters in the RM cloud. RM will only support certain frequencies, corresponding to rotational transitions of the clusters. The bond lengths in the RM clusters are known within 1% from radio frequency emission measurements in the laboratory, and it is now shown that all the commonly studied maser lines agree well with stimulated emission transitions in several types of RM clusters simultaneously. This may explain the strongly varying intensities of neighboring or related maser lines, an important effect that is not well understood previously. It is also pointed out that the magnetic field due to RM is of the same order of magnitude as observed from the Zeeman splitting in maser lines; thus, the molecules that are the original sources of the lines may be embedded in the RM clouds, for example in dense HII regions that are likely to be RM regions.

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Burst of strongly polarized maser emission at 1612 MHz in the proto-planetary nebula OH17.7–2.0

Cited by 8 publications

References 24 publications

Why Magnetic Fields Cannot Be the Main Agent Shaping Planetary Nebulae

Why Magnetic Fields Cannot Be the Main Agent Shaping Planetary Nebulae

Polarization properties of OH masers in AGB and post-AGB stars

Amplification by Stimulated Emission in Rydberg Matter Clusters as the Source of Intense Maser Lines in Interstellar Space

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