stars: variables: general; stars: early-type; stars: oscillations; stars: individual: HD 46223; stars: individual: HD 46150; stars: individual: HD 46966
Abstract :
[en] Context. The detection of pulsational frequencies in stellar photometry is required as input for asteroseismological modelling. The second short run (SRa02) of the CoRoT mission has provided photometric data of unprecedented quality and time-coverage for a number of O-type stars. <BR /> Aims: We analyse the CoRoT data corresponding to three hot O-type stars, describing the properties of their light curves and search for pulsational frequencies, which we then compare to theoretical model predictions. <BR /> Methods: We determine the amplitude spectrum of the data, using the Lomb-Scargle and a multifrequency HMM-like technique. Frequencies are extracted by prewhitening, and their significance is evaluated under the assumption that the light curve is dominated by red noise. We search for harmonics, linear combinations, and regular spacings among these frequencies. We use simulations with the same time sampling as the data as a powerful tool to judge the significance of our results. From the theoretical point of view, we use the MAD non-adiabatic pulsation code to determine the expected frequencies of excited modes. <BR /> Results: A substantial number of frequencies is listed, but none can be convincingly identified as being connected to pulsations. The amplitude spectrum is dominated by red noise. Theoretical modelling shows that all three O-type stars can have excited modes, but the relation between the theoretical frequencies and the observed spectrum is not obvious. <BR /> Conclusions: The dominant red noise component in the hot O-type stars studied here clearly points to a different origin than the pulsations seen in cooler O stars. The physical cause of this red noise is unclear, but we speculate on the possibility of sub-surface convection, granulation, or stellar wind inhomogeneities being responsible. The CoRoT space mission was developed and is operated by the French space agency CNES, with participation of ESA's RSSD and Science Programmes, Austria, Belgium, Brazil, Germany and Spain.Tables 2-4 are available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via <A href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/533/A4">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/533/A4</A>
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Blomme, R.; Royal Observatory of Belgium, Ringlaan 3, 1180, Brussel, Belgium
Mahy, Laurent ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Sciences spatiales
Catala, C.; LESIA, UMR 8109, Observatoire de Paris, 5 place Jules Janssen, 92195, Meudon Cedex, France
Cuypers, J.; Royal Observatory of Belgium, Ringlaan 3, 1180, Brussel, Belgium
Gosset, Eric ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Groupe d'astrophysique des hautes énergies (GAPHE)
Godart, Mélanie ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Astrophysique stellaire théorique et astérosismologie
Montalban Iglesias, Josefa ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Astrophysique stellaire théorique et astérosismologie
Ventura, P.; INAF, Osservatorio Astronomico di Roma, via Frascati 33, 00040, Monteporzio Catone (Roma), Italy
Rauw, Grégor ; Institut d'Astrophysique et de Géophysique, University of Liège, Bât. B5C, Allée du 6 Août 17, 4000, Liège, Belgium
Morel, Thierry ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Groupe d'astrophysique des hautes énergies (GAPHE)
Degroote, P.; Instituut voor Sterrenkunde, K.U. Leuven, Celestijnenlaan 200D, 3001, Leuven, Belgium
Aerts, C.; Instituut voor Sterrenkunde, K.U. Leuven, Celestijnenlaan 200D, 3001, Leuven, Belgium ; Department of Astrophysics, IMAPP, University of Nijmegen, PO Box 9010, 6500 GL, Nijmegen, The Netherlands
Noels-Grötsch, Arlette ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Département d'astrophys., géophysique et océanographie (AGO)
Aerts, C., Christensen-Dalsgaard, J., & Kurtz, D. W. 2010, Asteroseismology (Dordrecht: Springer)
Auvergne, M., Bodin, P., Boisnard, L., et al. 2009, A&A, 506, 411
Baglin, A., Auvergne, M., Barge, P., et al. 2006, in The CoRoT Mission Pre-Launch Status - Stellar Seismology and Planet Finding, ed. M. Fridlund, A. Baglin, J. Lochard, & L. Conroy (ESA, Noordwijk), ESA SP, 1306, 33
Bisiacchi, G. F., Lopez, J. A., & Firmani, C. 1982, A&A, 107, 252
Bonatto, C., & Bica, E. 2009, MNRAS, 394, 2127
Briquet, M., Aerts, C., Baglin, A., et al. 2011, A&A, 527, A112
Burderi, L. 1994, in Astronomical Society of the Pacific Conf. Ser., Vol. 61, Astronomical Data Analysis Software and Systems III, ed. D. R. Crabtree, R. J. Hanisch, & J. Barnes (California: ASP), 353
Cantiello, M., Langer, N., Brott, I., et al. 2009, A&A, 499, 279
Conti, P. S., & Ebbets, D. 1977, ApJ, 213, 438
Conti, P. S., & Leep, E. M. 1974, ApJ, 193, 113
Conti, P. S., Leep, E. M., & Lorre, J. J. 1977, ApJ, 214, 759
De Cat, P., Briquet, M., Aerts, C., et al. 2007, A&A, 463, 243
Degroote, P., Aerts, C., Ollivier, M., et al. 2009a, A&A, 506, 471
Degroote, P., Briquet, M., Catala, C., et al. 2009b, A&A, 506, 111
Degroote, P., Briquet, M., Auvergne, M., et al. 2010, A&A, 519, A38
Diago, P. D., Gutiérrez-Soto, J., Auvergne, M., et al. 2009, A&A, 506, 125
Dupret, M.-A., De Ridder, J., De Cat, P., et al. 2003, A&A, 398, 677
Garmany, C. D., Conti, P. S., & Massey, P. 1980, ApJ, 242, 1063
Gosset, E. 2007, Le calcul du niveau de signification du plus haut pic dans les périodogrammes de type Fourier par la formule de Horne-Baliunas est contreindiqué, Thèse d'Agrégation de l'Enseignement Supérieur, Seconde Thèse Annexe, University of Liège, Liège
Gosset, E., Royer, P., Rauw, G., Manfroid, J., & Vreux, J. 2001, MNRAS, 327, 435
Grevesse, N., & Noels, A. 1993, in Perfectionnement de l'Association Vaudoise des Chercheurs en Physique, AVCP, Lausanne, 205
Hakala, P., Ramsay, G., Wheatley, P., Harlaftis, E. T., & Papadimitriou, C. 2004, A&A, 420, 273
Hannan, E. J. 1980, Ann. Stat., 8, 1071
Hannan, E. J., & Quinn, B. 1979, J. Roy. Stat. Soc. Ser. B, 41, 190
Heck, A., Manfroid, J., & Mersch, G. 1985, A&AS, 59, 63, (HMM)
Hensberge, H., Pavlovski, K., & Verschueren, W. 2000, A&A, 358, 553
Hillier, D. J., & Miller, D. L. 1998, ApJ, 496, 407
Hiltner, W. A. 1956, ApJS, 2, 389
Howarth, I. D., & Reid, A. H. N. 1993, A&A, 279, 148
Mahy, L., Gosset, E., Baudin, F., et al. 2011, A&A, 525, A101
Maíz-Apellániz, J., Walborn, N. R., Galué, H. Á., & Wei, L. H. 2004, ApJS, 151, 103
Massey, P., Johnson, K. E., & Degioia-Eastwood, K. 1995, ApJ, 454, 151
Montgomery, M. H., & O'Donoghue, D. 1999, Delta Scuti Star Newsletter, 13, 28
Munari, U., & Tomasella, L. 1999, A&AS, 137, 521
Owocki, S. P., & Rybicki, G. B. 1984, ApJ, 284, 337
Perdang, J. 2009, in EAS Pub. Ser., 38, ed. M. Goupil, Z. Koláth, N. Nardetto, & P. Kervella (Les Ulis, France: EDP), 43
Pigulski, A., & Pojmański, G. 2008, A&A, 477, 917
Press, W. H., Teukolsky, S. A., Vetterling, W. T., & Flannery, B. P. 1992, Numerical recipes in FORTRAN. The art of scientific computing, 2nd edn. (Cambridge: University Press)
