[en] We report a multisite photometric campaign for the β Cep stars V2052 Oph and V986 Oph. 670 h of high-quality differential photoelectric Strömgren, Johnson and Geneva time-series photometry was obtained with eight telescopes on five continents during 182 nights. Frequency analyses of the V2052 Oph data enabled the detection of three pulsation frequencies, the first harmonic of the strongest signal, and the rotation frequency with its first harmonic. Pulsational mode identification from analysing the colour amplitude ratios confirms the dominant mode as being radial, whereas the other two oscillations are most likely l = 4. Combining seismic constraints on the inclination of the rotation axis with published magnetic field analyses we conclude that the radial mode must be the fundamental mode. The rotational light modulation is in phase with published spectroscopic variability, and consistent with an oblique rotator for which both magnetic poles pass through the line of sight. The inclination of the rotation axis is 54° < i < 58° and the magnetic obliquity 58° < β < 66°. The possibility that V2052 Oph has a magnetically confined wind is discussed. The photometric amplitudes of the single oscillation of V986 Oph are most consistent with an l = 3 mode, but this identification is uncertain. Additional intrinsic, apparently temporally incoherent light variations of V986 Oph are reported. Different interpretations thereof cannot be distinguished at this point, but this kind of variability appears to be present in many OB stars. The prospects of obtaining asteroseismic information for more rapidly rotating β Cep stars, which appear to prefer modes of higher l, are briefly discussed.
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Handler, G.; Copernicus Astronomical Center, Bartycka 18, 00-716, Warsaw, Poland
Shobbrook, R. R.; Research School of Astronomy and Astrophysics, Australian National University, Canberra, ACT Australia
Uytterhoeven, K.; Instituto de Astrofísica de Canarias (IAC), E-38200 La Laguna, Tenerife, Spain, ; Departamento de Astrofísica, Universidad de La Laguna (ULL), E-38206 La Laguna, Tenerife, Spain
Briquet, Maryline ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Astrophysique stellaire théorique et astérosismologie
Neiner, C.; LESIA, Observatoire de Paris, CNRS UMR 8109, UPMC, Université Paris Diderot, 5 place Jules Janssen, 92190, Meudon, France
Tshenye, T.; Department of Physics, University of the North-West, Private Bag X2046, Mmabatho, 2735, South Africa
Ngwato, B.; Department of Physics, University of the North-West, Private Bag X2046, Mmabatho, 2735, South Africa
van Winckel, H.; Instituut voor Sterrenkunde, K. U. Leuven, Celestijnenlaan 200D, B-3001, Leuven, Belgium
Guggenberger, E.; Institut für Astronomie, Universität Wien, Türkenschanzstrasse 17, A-1180, Wien, Austria
Raskin, G.; Instituut voor Sterrenkunde, K. U. Leuven, Celestijnenlaan 200D, B-3001, Leuven, Belgium
Rodríguez, E.; Instituto de Astrofisica de Andalucia, C.S.I.C., Apartado 3004, 18080, Granada, Spain
Mazumdar, A.; Homi Bhabha Centre for Science Education (TIFR), V. N. Purav Marg, Mumbai, 400088, India
Barban, C.; LESIA, Observatoire de Paris, CNRS UMR 8109, UPMC, Université Paris Diderot, 5 place Jules Janssen, 92190, Meudon, France
Lorenz, D.; Institut für Astronomie, Universität Wien, Türkenschanzstrasse 17, A-1180, Wien, Austria
Vandenbussche, B.; Instituut voor Sterrenkunde, K. U. Leuven, Celestijnenlaan 200D, B-3001, Leuven, Belgium
Şahin, T.; Faculty of Science, Space Science and Technologies Department, Akdeniz University, 07058, Antalya, Turkey, ; TUBITAK National Observatory, Akdeniz University Campus, 07058, Antalya, Turkey
Medupe, R.; Department of Physics, University of the North-West, Private Bag X2046, Mmabatho, 2735, South Africa
Aerts, C.; Instituut voor Sterrenkunde, K. U. Leuven, Celestijnenlaan 200D, B-3001, Leuven, Belgium)
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