학술논문
Finding magnetic north: an extraordinary magnetic field detection in Polaris and first results of a magnetic survey of classical Cepheids.
Document Type
Article
Author
Source
Subject
*MAGNETIC fields
*CEPHEIDS
*STELLAR evolution
*CIRCULAR polarization
*STELLAR magnetic fields
*MAGNETIC properties
*POLARIMETRY
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Language
ISSN
0035-8711
Abstract
Classical Cepheids are essential objects in the study of stellar evolution and cosmology; however, we know little about their magnetic properties. We report the detection of Stokes V features interpreted as Zeeman signatures in four classical Cepheids using high-resolution spectropolarimetric observations obtained with ESPaDOnS at the Canada–France–Hawaii Telescope. Eight observations of η Aql were acquired in 2017 covering its 7.2 d pulsation period, and single observations of Polaris, ζ Gem, δ Cep, and RT Aur were obtained in 2020 as part of our ongoing systematic survey. We use mean circular polarization Stokes V profiles generated using the least-squares deconvolution procedure to diagnose Zeeman signatures and measure mean longitudinal field strengths 〈 Bz 〉. We detect magnetic signatures across all pulsation phases of η Aql (−0.89 ± 0.47 G |$\, \lt \langle B_{z}\rangle \lt 1.27\pm 0.40$| G), as well as in the single observations of Polaris (0.59 ± 0.16 G), ζ Gem (0.41 ± 0.16 G), and δ Cep (0.43 ± 0.19 G). The Stokes V profile of Polaris is detected at extremely high signal-to-noise ratio and implies a complex magnetic field topology. It stands in stark contrast to all other detected Stokes V profiles, which show unusual approximately unipolar positive circular polarization lobes analogous to those observed in some Am stars. [ABSTRACT FROM AUTHOR]