Details

Autor(en) / Beteiligte

• Blazère, A
• Neiner, C
• Petit, P

Titel

Discovery of a very weak magnetic field on the Am star Alhena

Ist Teil von

• Monthly notices of the Royal Astronomical Society. Letters, 2016-06, Vol.459 (1), p.L81-L84

Ort / Verlag

Oxford University Press

Erscheinungsjahr

2016

Link zum Volltext

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• Alhena (γ 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 Télescope 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.