期刊
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
卷 459, 期 1, 页码 L81-L84出版社
OXFORD UNIV PRESS
DOI: 10.1093/mnrasl/slw050
关键词
stars: chemically peculiar; stars: individual: gamma Gem; stars: magnetic field
资金
- ANR (Agence Nationale de la Recherche)
Alhena (gamma Gem) was observed in the frame of the BRIght Target Explorer spectropolarimetric survey, which gathers high resolution, high signal-to-noise, high sensitivity, spectropolarimetric observations of all stars brighter than V = 4 to combine seismic and spectropolarimetric studies of bright stars. We present here the discovery of a very weak magnetic field on the Am star Alhena, thanks to very high signal-to-noise spectropolarimetric data obtained with Narval at Telescope Bernard Lyot. All previously studied Am stars show the presence of ultraweak (sub-Gauss) fields with Zeeman signatures with an unexpected prominent positive lobe. However, Alhena presents a slightly stronger (but still very weak, only a few Gauss) field with normal Zeeman signatures with a positive and negative lobe, as found in stronger field (hundreds or thousands of Gauss) stars. It is the first detection of a normal magnetic signature in an Am star. Alhena is thus a very interesting object, which might provide the clue to understanding the peculiar shapes of the magnetic signatures of the other Am stars.
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