[en] Aims. The main-sequence B-type star zeta Cassiopeiae is known as a N-rich star with a magnetic field discovered with the Musicos spectropolarimeter. We model the magnetic field of the star by means of 82 new spectropolarimetric observations of higher precision to investigate the field strength, topology, and effect. Methods. We gathered data with the Narval spectropolarimeter installed at Télescope Bernard Lyot (TBL; Pic du Midi, France) and applied the least-squares deconvolution technique to measure the circular polarisation of the light emitted from zeta Cas. We used a dipole oblique rotator model to determine the field configuration by fitting the longitudinal field measurements and by synthesizing the measured Stokes V profiles. We also made use of the Zeeman-Doppler imaging technique to map the stellar surface and to deduce the difference in rotation rate between the pole and equator. Results. zeta Cas exhibits a polar field strength B_pol of 100-150 G, which is the weakest polar field observed so far in a massive main-sequence star. Surface differential rotation is ruled out by our observations and the field of zeta Cas is strong enough to enforce rigid internal rotation in the radiative zone according to theory. Thus, the star rotates as a solid body in the envelope. Conclusions. We therefore exclude rotationally-induced mixing as the cause of the surface N-enrichment. We discuss that the transport of chemicals from the core to the surface by internal gravity waves is the most plausible explanation for the nitrogen overabundance at the surface of zeta Cas.
Aerts, C., Molenberghs, G., Kenward, M. G., & Neiner, C. 2014, ApJ, 781, 88
Alecian, E., Kochukhov, O., Neiner, C. et al., 2011, A&A, 536, L6
Aurière, M., Wade, G. A., Lignières, F. et al., 2010, A&A, 523, A40
Blazère, A., Neiner, C., Bouret, J.-C., & Tkachenko, A. 2015a, in IAU Symp. 307, eds. G. Meynet, C. Georgy, J. Groh, & P. Stee, 367
Blazère, A., Neiner, C., Tkachenko, A., Bouret, J.-C., & Rivinius, T. 2015 b, A&A, 582, A110
Blazère, A., Petit, P., Lignières, F. et al., 2016, A&A, 586, A97
Blomme, R., Mahy, L., Catala, C. et al., 2011, A&A, 533, A4
Borra, E. F., & Landstreet, J. D. 1980, ApJS, 42, 421
Braithwaite, J. 2008, MNRAS, 386, 1947
Briquet, M. 2015, EPJ, 101, 5001
Briquet, M., & Morel, T. 2007, Comm. Asteroseismol., 150, 183
Briquet, M., Aerts, C., Baglin, A. et al., 2011, A&A, 527, A112
Briquet, M., Neiner, C., Aerts, C. et al., 2012, MNRAS, 427, 483
Briquet, M., Neiner, C., Leroy, B., Pápics, P. I., & MiMeS collaboration 2013, A&A, 557, L16
Donati, J.-F., & Brown, S. F. 1997, A&A, 326, 1135
Donati, J.-F., Semel, M., Carter, B. D., Rees, D. E., & Collier Cameron, A. 1997, MNRAS, 291, 658
Donati, J.-F., Howarth, I. D., Jardine, M. M. et al., 2006, MNRAS, 370, 629
Fossati, L., Castro, N., Morel, T. et al., 2015, A&A, 574, A20
Gies, D. R., & Lambert, D. L. 1992, ApJ, 387, 673
Goldreich, P., & Nicholson, P. D. 1989, ApJ, 342, 1075
Henrichs, H. F., de Jong, J. A., Donati, D.-F., et al. 2000, in Magnetic Fields of Chemically Peculiar and Related Stars, eds. Y. V. Glagolevskij, & I. I. Romanyuk, 57
Henrichs, H. F., Neiner, C., Schnerr, R. S., et al. 2009, in IAU Symp. 259, eds. K. G. Strassmeier, A. G. Kosovichev, & J. E. Beckman, 393
Henrichs, H. F., Kolenberg, K., Plaggenborg, B. et al., 2012, A&A, 545, A119
Hubrig, S., Briquet, M., Schöller, M. et al., 2006, MNRAS, 369, L61
Hubrig, S., Briquet, M., De Cat, P. et al., 2009, Astron. Nachr., 330, 317
Hubrig, S., Ilyin, I., Schöller, M. et al., 2011, ApJ, 726, L5
Langer, N. 2008, in IAU Symp. 252, eds. L. Deng, & K. L. Chan, 467
Lignières, F., Petit, P., Aurière, M., Wade, G. A., & Böhm, T. 2014, in IAU Symp. 302, eds. P. Petit, M. Jardine, & H. C. Spruit, 338
Maeder, A., & Meynet, G. 2015, in IAU Symp. 307, eds. G. Meynet, C. Georgy, J. Groh, & P. Stee, 9
Martins, F., Escolano, C., Wade, G. A. et al., 2012, A&A, 538, A29
Mathis, S. 2013, in EAS PS 63, eds. G. Alecian, Y. Lebreton, O. Richard, & G. Vauclair, 269
Mathis, S., & Alvan, L. 2013, in Progress in Physics of the Sun and Stars: A New Era in Helio-and Asteroseismology, eds. H. Shibahashi, & A. E. Lynas-Gray, ASP Conf. Ser., 479, 295
Mathis, S., & de Brye, N. 2012, A&A, 540, A37
Mathis, S., & Neiner, C. 2015, in IAU Symp. 307, eds. G. Meynet, C. Georgy, J. Groh, & P. Stee, 420
Neiner, C., Geers, V. C., Henrichs, H. F. et al., 2003 a, A&A, 406, 1019
Neiner, C., Henrichs, H. F., Floquet, M. et al., 2003 b, A&A, 411, 565
Neiner, C., Alecian, E., Briquet, M. et al., 2012 a, A&A, 537, A148
Neiner, C., Floquet, M., Samadi, R. et al., 2012 b, A&A, 546, A47
Neiner, C., Folsom, C. P., & Blazere, A. 2014a, in SF2A-2014: Proceedings of the Annual meeting of the French Society of Astronomy and Astrophysics, eds. J. Ballet, F. Martins, F. Bournaud, R. Monier, & C. Reylé, 163
Neiner, C., Monin, D., Leroy, B., Mathis, S., & Bohlender, D. 2014 b, A&A, 562, A59
Petit, P., Lignières, F., Wade, G. A. et al., 2010, A&A, 523, A41
Press, W. H. 1981, ApJ, 245, 286
Rees, D. E., & Semel, M. D. 1979, A&A, 74, 1
Rogers, T. M., Lin, D. N. C., McElwaine, J. N., & Lau, H. H. B. 2013, ApJ, 772, 21
Sadsaoud, H., Le Contel, J. M., Chapellier, E., Le Contel, D., & Gonzalez-Bedolla, S. 1994, A&A, 287, 509
Schatzman, E. 1996, Sol. Phys., 169, 245
Scuflaire, R., Théado, S., Montalbán, J. et al., 2008, Ap&SS, 316, 83
Shiode, J. H., Quataert, E., Cantiello, M., & Bildsten, L. 2013, MNRAS, 430, 1736
Silvester, J., Neiner, C., Henrichs, H. F. et al., 2009, MNRAS, 398, 1505
Smith, M. A. 1980, in Nonradial and Nonlinear Stellar Pulsation, eds. H. A. Hill, & W. A. Dziembowski (Berlin: Springer Verlag), Lect. Notes Phys., 125, 60
Sódor, Á., De Cat, P., Wright, D. J. et al., 2014, MNRAS, 438, 3535
Spruit, H. C. 1999, A&A, 349, 189
Vidotto, A. A., Gregory, S. G., Jardine, M. et al., 2014, MNRAS, 441, 2361
Wade, G. A., Donati, J.-F., Landstreet, J. D., & Shorlin, S. L. S. 2000, MNRAS, 313, 851
Wade, G. A., Folsom, C. P., Petit, P. et al., 2014, MNRAS, 444, 1993
Zahn, J.-P. 2011, in IAU Symp. 272, eds. C. Neiner, G. Wade, G. Meynet, & G. Peters, 14
