Discovery of magnetic A supergiants: the descendants of magnetic main-sequence B stars

Abstract : In the context of the high resolution, high signal-to-noise ratio, high sensitivity, spectropolarimetric survey BritePol, which complements observations by the BRITE constellation of nanosatellites for asteroseismology, we are looking for and measuring the magnetic field of all stars brighter than V = 4. In this paper, we present circularly polarized spectra obtained with HarpsPol at ESO in La Silla (Chile) and ESPaDOnS at CFHT (Hawaii) for three hot evolved stars: ι Car, HR 3890 and ε CMa. We detected a magnetic field in all three stars. Each star has been observed several times to confirm the magnetic detections and check for variability. The stellar parameters of the three objects were determined and their evolutionary status was ascertained employing evolution models computed with the Geneva code. ε CMa was already known and is confirmed to be magnetic, but our modelling indicates that it is located near the end of the main sequence, i.e. it is still in a core hydrogen burning phase. ι Car and HR 3890 are the first discoveries of magnetic hot supergiants located well after the end of the main sequence on the Hertzsprung–Russell diagram. These stars are probably the descendants of main-sequence magnetic massive stars. Their current field strength (a few G) is compatible with magnetic flux conservation during stellar evolution. These results provide observational constraints for the development of future evolutionary models of hot stars including a fossil magnetic field.
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Article dans une revue
Monthly Notices of the Royal Astronomical Society, Oxford University Press (OUP): Policy P - Oxford Open Option A, 2017, 471 (2), pp.1926 - 1935. 〈10.1093/mnras/stx1549〉
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Soumis le : mardi 19 septembre 2017 - 11:30:28
Dernière modification le : jeudi 11 janvier 2018 - 06:19:07

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Coralie Neiner, Mary E. Oksala, Cyril Georgy, Norbert Przybilla, Stéphane Mathis, et al.. Discovery of magnetic A supergiants: the descendants of magnetic main-sequence B stars. Monthly Notices of the Royal Astronomical Society, Oxford University Press (OUP): Policy P - Oxford Open Option A, 2017, 471 (2), pp.1926 - 1935. 〈10.1093/mnras/stx1549〉. 〈hal-01589948〉

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