Discovery of a magnetic field in the early B-type star sigma Lupi
Article
Article Title | Discovery of a magnetic field in the early B-type star sigma Lupi |
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ERA Journal ID | 1050 |
Article Category | Article |
Authors | Henrichs, H. F. (Author), Kolenberg, K. (Author), Plaggenborg, B. (Author), Marsden, S. C. (Author), Waite, I. A. (Author), Landstreet, J. D. (Author), Wade, G. A. (Author), Grunhut, J. H. (Author) and Oksala, M. E. (Author) |
Journal Title | Astronomy and Astrophysics: a European journal |
Journal Citation | 545, pp. 1-10 |
Number of Pages | 10 |
Year | 2012 |
Publisher | EDP Sciences |
Place of Publication | France |
ISSN | 0004-6361 |
1432-0746 | |
Digital Object Identifier (DOI) | https://doi.org/10.1051/0004-6361/201219632 |
Web Address (URL) | https://www.aanda.org/articles/aa/full_html/2012/09/aa19632-12/aa19632-12.html |
Abstract | Context: Magnetic early B-type stars are rare. Indirect indicators are needed to identify them before investing in time-intensive spectropolarimetric observations. Aims: We use the strongest indirect indicator of a magnetic field in B stars, which is periodic variability of ultraviolet (UV) stellar wind lines occurring symmetric about the approximate rest wavelength. Our aim is to identify probable magnetic candidates which would become targets for follow-up spectropolarimetry to search for a magnetic field. Methods: From the UV wind line variability the B1/B2V star σ Lupi emerged as a new magnetic candidate star. AAT spectropolarimetric measurements with SEMPOL were obtained. The longitudinal component of the magnetic field integrated over the visible surface of the star was determined with the least-squares deconvolution method. Results: The UV line variations of σ Lupi are similar to what is known in magnetic B stars, but no periodicity could be determined. We detected a varying longitudinal magnetic field with amplitude of about 100 G with error bars of typically 20 G, which supports an oblique magnetic-rotator configuration. The equivalent width variations of the UV lines, the magnetic and the optical-line variations are consistent with the photometric period of 3.02 d, which we identify with the rotation period of the star. Additional observations with ESPaDOnS attached to the CFHT confirmed this discovery, and allowed the determination of a precise magnetic period. Analysis revealed that σ Lupi is a helium-strong star, with an enhanced nitrogen abundance and an underabundance of carbon, and has a chemically spotted surface. |
Keywords | early-type stars; magnetic field; winds; outflows rotation; starspots |
ANZSRC Field of Research 2020 | 510109. Stellar astronomy and planetary systems |
519999. Other physical sciences not elsewhere classified | |
510903. Mesospheric, thermospheric, ionospheric and magnetospheric physics | |
Public Notes | File reproduced in accordance with the copyright policy of the publisher/author. |
Byline Affiliations | University of Amsterdam, Netherlands |
Center for Astrophysics Harvard and Smithsonian, United States | |
James Cook University | |
Centre for Astronomy, Solar Radiation and Climate | |
University of Western Ontario, Canada | |
Royal Military College of Canada, Canada | |
University of Delaware, United States | |
Institution of Origin | University of Southern Queensland |
https://research.usq.edu.au/item/q277q/discovery-of-a-magnetic-field-in-the-early-b-type-star-sigma-lupi
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