تقرير
Measuring surface magnetic fields of red supergiant stars
| العنوان: | Measuring surface magnetic fields of red supergiant stars |
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| المؤلفون: | Tessore, Benjamin, Lèbre, Agnès, Morin, Julien, Mathias, Philippe, Josselin, Eric, Aurière, Michel |
| المصدر: | A&A 603, A129 (2017) |
| سنة النشر: | 2017 |
| المجموعة: | Astrophysics |
| مصطلحات موضوعية: | Astrophysics - Solar and Stellar Astrophysics |
| الوصف: | RSG stars are very massive cool evolved stars. Recently, a weak magnetic field was measured at the surface of $\alpha$ Ori and this is so far the only M-type supergiant for which a direct detection of a surface magnetic field has been reported. By extending the search for surface magnetic field in a sample of late-type supergiants, we want to determine whether the surface magnetic field detected on $\alpha$ Ori is a common feature among the M-type supergiants. With the spectropolarimeter Narval at TBL we undertook a search for surface magnetic fields in a sample of cool supergiant stars, and we analysed circular polarisation spectra using the least-squares deconvolution technique. We detect weak Zeeman signatures of stellar origin in the targets CE Tau, $\alpha^1$ Her and $\mu$ Cep. For the latter star, we also show that cross-talk from the strong linear polarisation signals detected on this star must be taken into account. For CE Tau and $\mu$ Cep, the longitudinal component of the detected surface fields is at the Gauss-level, such as in $\alpha$~Ori. We measured a longitudinal field almost an order of magnitude stronger for $\alpha^1$ Her. We also report variability of the longitudinal magnetic field of CE Tau and $\alpha^1$ Her, with changes in good agreement with the typical atmospheric dynamics time-scales. We also report a non-detection of magnetic field at the surface of the yellow supergiant star $\rho$ Cas. The two RSG stars of our sample, CE Tau and $\mu$ Cep, display magnetic fields very similar to that of $\alpha$ Ori. The non-detection of a magnetic field on the post-RSG star $\rho$ Cas suggests that the magnetic field disappears, or at least becomes undetectable with present methods, at later evolutionary stages. Our analysis of $\alpha^1$ Her supports the proposed reclassification of the star as an AGB star. Comment: Accepted for publication in Astronomy and Astrophysics (2017 April 19) |
| نوع الوثيقة: | Working Paper |
| DOI: | 10.1051/0004-6361/201730473 |
| URL الوصول: | http://arxiv.org/abs/1704.07761 |
| رقم الأكسشن: | edsarx.1704.07761 |
| قاعدة البيانات: | arXiv |
| DOI: | 10.1051/0004-6361/201730473 |
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