Multisite spectroscopic seismic study of the beta Cep star V2052 Oph: inhibition of mixing by its magnetic field

BRIQUET, M; NEINER, C.; AERTS, C.; MOREL, T. ; MATHIS, S.; REESE, D.; LEHMAN, H.; COSTERO, R.; ECHEVARRIA, J.; HANDLER, G; KAMBE, E.; HIRATA, R. ; MASUDA, S. ; WRIGTH, D.; YOUNG, S.; PINTADO, O. ; MKRTICHIANI, D.; LEE, C.; HAN, I.; BRUCH, A.; DE CAT, P. ; UYTTERHOEVEN, K.; LEFEVER, K.; VANAUTGAERDEN, J. ; DE BATZ, B.; FREMAT, Y.; HENRICHS, H.; GEERS, V.; MARTAYANS, C.; HUBERT, A.; THYZI, O.; TIJANI, A.

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2012 vol. 424 p. 2380 - 2391

0035-8711

We used extensive ground-based multisite and archival spectroscopy to derive observational constraints for a seismic modelling of the magnetic beta Cep star V2052 Ophiuchi. The line-profile variability is dominated by a radial mode (f_1=7.14846 d^{-1}) and by rotational modulation (P_rot=3.638833 d). Two non-radial low-amplitude modes (f_2=7.75603 d^{-1} and f_3=6.82308 d^{-1}) are also detected. The four periodicities that we found are the same as the ones discovered from a companion multisite photometric campaign (Handler et al. 2012) and known in the literature. Using the photometric constraints on the degrees l of the pulsation modes, we show that both f_2 and f_3 are prograde modes with (l,m)=(4,2) or (4,3). These results allowed us to deduce ranges for the mass (M in [8.2,9.6] M_o) and central hydrogen abundance (X_c in [0.25,0.32]) of V2052 Oph, to identify the radial orders n_1=1, n_2=-3 and n_3=-2, and to derive an equatorial rotation velocity v_eq in [71,75] km s^{-1}. The model parameters are in full agreement with the effective temperature and surface gravity deduced from spectroscopy. Only models with no or mild core overshooting (alpha_ov in [0,0.15] local pressure scale heights) can account for the observed properties. Such a low overshooting is opposite to our previous modelling results for the non-magnetic beta Cep star theta Oph having very similar parameters, except for a slower surface rotation rate. We discuss whether this result can be explained by the presence of a magnetic field in V2052 Oph that inhibits mixing in its interior.