stars: early-type; stars: fundamental parameters; stars: abundances; stars: atmospheres; stars: magnetic fields
Abstract :
[en] Evolutionary models for massive stars, accounting for rotational mixing effects, do not predict any core-processed material at the surface of B dwarfs with low rotational velocities. Contrary to theoretical expectations, we present a detailed and fully-homogeneous, NLTE abundance analysis of 20 early B-type dwarfs and (sub)giants that reveals the existence of a population of nitrogen-rich and boron-depleted, yet intrinsically slowly-rotating objects. The low-rotation rate of several of these stars is firmly established, either from the occurrence of phase-locked UV wind line-profile variations, which can be ascribed to rotational modulation, or from theoretical modelling in the pulsating variables. The observational data presently available suggest a higher incidence of chemical peculiarities in stars with a (weak) detected magnetic field. This opens the possibility that magnetic phenomena are important in altering the photospheric abundances of early B dwarfs, even for surface field strengths at the one hundred Gauss level. However, further spectropolarimetric observations are needed to assess the validity of this hypothesis.
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Morel, Thierry ; Katholieke Universiteit Leuven, Departement Natuurkunde en Sterrenkunde, Instituut voor Sterrenkunde, Celestijnenlaan 200D, 3001 Leuven, Belgium
Hubrig, S.; European Southern Observatory, Casilla 19001, Santiago, Chile
Briquet, Maryline ; Katholieke Universiteit Leuven, Departement Natuurkunde en Sterrenkunde, Instituut voor Sterrenkunde, Celestijnenlaan 200D, 3001 Leuven, Belgium
Language :
English
Title :
Nitrogen enrichment, boron depletion and magnetic fields in slowly-rotating B-type dwarfs
Briquet, M., Morel, T., Thoul, A., et al. 2007, MNRAS, 381, 1482
Brooks, A. M., Venn, K. A., Lambert, D. L., et al. 2002, ApJ, 573, 584
Butkovskaya, V. V., & Plachinda, S. I. 2007, A&A, 469, 1069
Bychkov, V. D., Bychkova, L. V., & Madej, J. 2003, A&A, 407, 631
Cassinelli, J. P., Cohen, D. H., MacFarlane, J. J., et al. 1995, ApJ, 438, 932
Crowther, P. A. 1998, in Fundamental Stellar Properties: The Interaction between Observation and Theory, ed. T. R. Bedding et al. (Dordrecht: Reidel), IAU Symp., 189, 137
Cunha, K., Hubeny, I., & Lanz, T. 2006, ApJ, 647, L143
Daflon, S., & Cunha, K. 2004, ApJ, 617, 1115
Daflon, S., Cunha, K., & Butler, K. 2004, ApJ, 604, 362
Donati, J.-F., Wade, G. A., Babel, J., et al. 2001, MNRAS, 326, 1265
Donati, J.-F., Howarth, I. D., Bouret, J.-C., et al. 2006a, MNRAS, 365, L6
Donati, J.-F., Howarth, I. D., Jardine, M. M., et al. 2006b, MNRAS, 370, 629
Drew, J. E., Denby, M., & Hoare, M. G. 1994, MNRAS, 266, 917
Dupret, M.-A., Thoul, A., Scuflaire, R., et al. 2004, A&A, 415, 251
Ebbets, D. 1979, ApJ, 227, 510
Fliegner, J., Langer, N., & Venn, K. A. 1996, A&A, 308, L13
Flower, P. J. 1996, ApJ, 469, 355
Gies, D. R., & Lambert, D. L. 1992, ApJ, 387, 673
Grevesse, N., & Sauval, A. J. 1998, Space Sci. Rev., 85, 161
Gummersbach, C. A., Kaufer, A., Schäfer, D. R., Szeifert, T., & Wolf, B. 1998, A&A, 338, 881
Hanbury Brown, R., Davis, J., & Allen, L. R. 1974, MNRAS, 167, 121
Heger, A., & Langer, N. 2000, ApJ, 544, 1016
Heger, A., Woosley, S. E., & Spruit, H. C. 2005, ApJ, 626, 350
Henrichs, H. F., de Jong, J. A., Verdugo, E., et al. 2007, A&A, submitted
Huang, W., & Gies, D. R. 2006, ApJ, 648, 591
Hubrig, S., Briquet, M., Schöller, M., et al. 2006, MNRAS, 369, L61
Hunter, I., Dufton, P. L., Smartt, S. J., et al. 2007a, A&A, 466, 277
Hunter, I., Brott, I., Lennon, D. J., et al. 2007b, ApJ, submitted [arXiv:0711.2267]
Kilian, J. 1992, A&A, 262, 171
Kilian-Montenbrack, J., Gehren, T., & Nissen, P. E. 1994, A&A, 291, 757
Korn, A. J., Nieva, M. F., Daflon, S., & Cunha, K. 2005, ApJ, 633, 899
Kurucz, R. L. 1993, ATLAS9 Stellar Atmosphere Programs and 2 km. s -1 grid, Kurucz CD-ROM (Cambridge, Mass.: Smithsonian Astrophysical Observatory), 13
Leckrone, D. S. 1980, Highlights Astron., 5, 277
Lefever, K. 2007, Ph.D. Thesis, Katholieke Universiteit Leuven, Belgium
Mikulášek, Z., Krtička, J., Henry, G. W., et al. 2007, A&A, submitted
Morel, T., & Aerts, C. 2007, CoAst, 150, 201
Morel, T., Butler, K., Aerts, C., Neiner, C., & Briquet, M. 2006, A&A, 457, 651 (M06)
Neiner, C., Geers, V. C., Henrichs, H. F., et al. 2003a, A&A, 406, 1019
Neiner, C., Henrichs, H. F., Floquet, M., et al. 2003b, A&A, 411, 565
Nieva, M. F., & Przybilla, N. 2008, A&A, 481, 199
Pamyatnykh, A. A., Handler, G., & Dziembowski, W. A. 2004, MNRAS, 350, 1022
Pigulski, A., & Boratyn, D. A. 1992, A&A, 253, 178
Popper, D. M. 1968, ApJ, 151, L51
Pourbaix, D., Tokovinin, A. A., Batten, A. H., et al. 2004, A&A, 424, 727 (the 9th catalogue of spectroscopic binary orbits is available online at: http://sb9.astro.ulb.ac.be/)
Proffitt, C. R., & Quigley, M. F. 200.1, ApJ, 548, 429
Puls, J., Urbaneja, M. A., Venero, R., et al. 2005, A&A, 435, 669
Roberts, L. C., Jr., Turner, N. H., & Ten Brammelaar, T. A. 2007, AJ, 133, 545
Roby, S. W., & Lambert, D. L. 1990, ApJS, 73, 67
Rudy, R. J., & Kemp, J. C. 1978, MNRAS, 183, 595
Schnerr, R. S. 2007, Ph.D. Thesis, University of Amsterdam, The Netherlands
Schaller, G., Schaerer, D., Meynet, G., & Maeder, A. 1992, A&AS, 96, 269
Schnerr, R. S., Verdugo, E., Henrichs, H. F., & Neiner, C 2006a, A&A, 452, 969
Schnerr, R. S., Henrichs, H. F., Oudmaijer, R. D., & Telling, J. H. 2006b, A&A, 459, L21
Schönberner, D., Herrero, A., Becker, S., et al. 1988, A&A, 197, 209
Simón-Díaz, S., & Herrero, A. 2007, A&A, 468, 1063
Spruit, H. C. 2002, A&A, 381, 923
Stankov, A., & Handler, G. 2005, ApJS, 158, 193
Stȩpień, K. 2002, A&A, 383, 218
Trigilio, C., Leto, P., Umana, G., Buemi, C. S., & Leone, F. 2007, MNRAS, in press [arXiv:0710.0817]
Trundle, C., Lennon, D. J., Puls, J., & Dufton, P. L. 2004, A&A, 417, 217
Trundle, C., Dufton, P. L., Hunter, I., et al. 2007, A&A, 471, 625
ud-Doula, A., & Owocki, S. P. 2002, ApJ, 576, 413
Vanbeveren, D. 1989, A&A, 224, 93
Venn, K. A. 1999, ApJ, 518, 405
Venn, K. A., Brooks, A. M., Lambert, D. L., et al. 2002, ApJ, 565, 571
Wade, G. A., Fullerton, A. W., Donati, J.-F., et al. 2006, A&A, 451, 195
Walborn, N. R., Howarth, I. D., Herrero, A., & Lennon, D. J. 2003, ApJ, 588, 1025
Wolff, S. C., Strom, S. E., Dror, D., & Venn, K. 2007, AJ, 133, 1092
Zahn, J.-P., Brun, A. S., & Mathis, S. 2007, A&A, 474, 145
Zboril, M., & North, P. 1999, A&A, 345, 244
Zhai, M., & Shaw, D. M. 1994, Meteoritics, 29, 607