Publication: Magnetic activity and differential rotation in the young Sun-like stars KIC 7985370 and KIC 7765135
Loading...
Official URL
Full text at PDC
Publication Date
2012-07
Advisors (or tutors)
Editors
Journal Title
Journal ISSN
Volume Title
Publisher
EDP Sciencies
Citations
Exportar
Abstract
Aims. We present a detailed study of the two Sun-like stars KIC 7985370 and KIC 7765135, to determine their activity level, spot distribution, and differential rotation. Both stars were previously discovered by us to be young stars and were observed by the NASA Kepler mission.
Methods. The fundamental stellar parameters (vsini, spectral type, T_eff, log g, and [Fe/H]) were derived from optical spectroscopy by comparison with both standard-star and synthetic spectra. The spectra of the targets allowed us to study the chromospheric activity based on the emission in the core of hydrogen Hα and Ca ii infrared triplet (IRT) lines, which was revealed by the subtraction of inactive templates. The high-precision Kepler photometric data spanning over 229 days were then fitted with a robust spot model. Model selection and parameter estimation were performed in a Bayesian manner, using a Markov chain Monte Carlo method.
Results. We find that both stars are Sun-like (of G1.5 V spectral type) and have an age of about 100–200 Myr, based on their lithium content and kinematics. Their youth is confirmed by their high level of chromospheric activity, which is comparable to that displayed by the early G-type stars in the Pleiades cluster. The Balmer decrement and flux ratio of their Ca ii-IRT lines suggest that the formation of the core of these lines occurs mainly in optically thick regions that are analogous to solar plages. The spot model applied to the Kepler photometry requires at least seven persistent spots in the case of KIC 7985370 and nine spots in the case of KIC 7765135 to provide a satisfactory fit to the data. The assumption of the longevity of the star spots, whose area is allowed to evolve with time, is at the heart of our spot-modelling approach. On both stars, the surface differential rotation is Sun-like, with the high-latitude spots rotating slower than the low-latitude ones. We found, for both stars, a rather high value of the equator-to-pole differential rotation (dΩ ≈ 0.18 rad d^-1), which disagrees with the predictions of some mean-field models of differential rotation for rapidly rotating stars. Our results agree instead with previous works on solar-type stars and other models that predict a higher latitudinal shear, increasing with equatorial angular velocity, that can vary during the magnetic cycle.
Description
© ESO, 2012.
We would like to thank the Kepler project and the team who created the MAST Kepler web site and search interfaces. We also thank an anonymous referee for helpful and constructive comments. This work has been partly supported by the Italian Ministero dell'Istruzione, Universita e Ricerca (MIUR), which is gratefully acknowledged. JMZ acknowledges the Polish Ministry grant No. NN203 405139. D.M. and A.K. acknowledge the Universidad Complutense de Madrid (UCM), the Spanish Ministerio de Ciencia e Innovación (MCINN) under grants AYA2008-000695 and AYA2011-30147-C03-02, and the Comunidad de Madrid under PRICIT project S2009/ESP-1496 (AstroMadrid). This research made use of SIMBAD and VIZIER databases, operated at the CDS, Strasbourg, France. This publication makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation.
UCM subjects
Unesco subjects
Keywords
Citation
Andersen, J., Gustafson, B., & Lambert, D. L. 1984, A&A, 136, 65
Barnes, J. R., Collier Cameron, A., Unruh, Y. C., Donati, J.-F., & Hussain, G. A. J. 1998, MNRAS, 299, 904
Barnes, J. R., Collier Cameron, A., Donati, J.-F., et al. 2005, MNRAS, 357, L1
Barrado y Navascués, D., Stauffer, J. R., & Jayawardhana, R. 2004, ApJ, 614, 386
Bonanno, A. 2012, Geophysical & Fluid Dynamics, in press
Bonanno, A., Elstner, D., Rüdiger, G., & Belvedere, G. 2002, A&A, 390, 673
Borucki, W. J., Koch, D., Basri, G., et al. 2010, Science, 327, 977
Brown, A., Korhonen, H., Berdyugina, S., et al. 2011, AAS Meeting Abstracts #218, 205.02
Buzasi, D. L. 1989, Ph.D. Thesis, Pennsylvania State Univ.
Cardelli, J. A., Clayton, G. C., & Mathis, J. S. 1989, ApJ, 345, 245
Castelli, F., & Hubrig, S. 2004, A&A, 425, 263
Catanzaro, G., Frasca, A., Molenda-Żakowicz, J., & Marilli, E. 2010, A&A, 517, A3
Chester, M. M. 1991, Ph.D. Thesis, Pennsylvania State Univ.
Claret, A., & Bloemen, S. 2011, A&A, 529, 75
Collier Cameron, A. 1995, MNRAS, 275, 534
Covas, E., Moss, D., & Tavakol, R. 2005, A&A, 429, 657
Croll, B. 2006, PASP, 118, 1351
Croll, B., Walker, G. A. H., Kuschnig, R., et al. 2006, ApJ, 648, 607
Cutri, R. M., Skrutskie, M. F., van Dyk, S., et al. 2003, 2MASS All-Sky Catalog of Point Sources, University of Massachusetts and Infrared Processing and Analysis Center (IPAC/California Institute of Technology)
Dikpati, M., & Gilman, P. A. 2001, ApJ, 559, 428
Donati, J.-F., Collier Cameron, A., & Petit, P. 2003, MNRAS, 345, 1187
Dorren, J. D. 1987, ApJ, 320, 756
Eggen, O. J. 1984, ApJS, 55, 597
Eggen, O. J. 1989, PASP, 101, 366
Fleming, T. A., Molendi, S., Maccacaro, T., & Wolter, A. 1995, ApJS, 99, 701
Frasca, A., & Catalano, S. 1994, A&A, 284, 883
Frasca, A., Alcalá, J. M., Covino, E., et al. 2003, A&A, 405, 149
Frasca, A., Guillout, P., Marilli, E., et al. 2006, A&A, 454, 301
Frasca, A., Biazzo, K., Kővári, Zs., Marilli, E., & Çakırlı, Ö. 2010, A&A, 518, A48
Frasca, A., Fröhlich, H.-E., Bonanno, A., et al. 2011, A&A, 532, A81 (Paper I)
Fröhlich, H.-E. 2007, Astron. Nachr., 328, 1037
Glebocki, R., & Gnacinski, P. 2005, The Catalogue of Rotational Velocities of Stars, ESA, SP-560, 571
Gorlova, N., Rieke, G. H., Muzerolle, J., et al. 2006, ApJ, 649, 1028
Grevesse, N., Asplund, M., Sauval, A. J., & Scott, P. 2010, Ap&SS, 328, 179
Guillout, P., Klutsch, A., Frasca, A., et al. 2009, A&A, 504, 829
Hall, J. C., & Ramsey, L. W. 1992, AJ, 104, 1942
Hatzes, A. P. 1995, ApJ, 451, 784
Hauschildt, P. H., Allard, F., & Baron, E. 1999, ApJ, 512, 377
Høg, E., Fabricius, C., Makarov, V. V., et al. 2000, A&A, 355, L27
Hotta, H., & Yokoyama, T. 2011, ApJ, 740, 12
Huber, K. F., Wolter, U., Czesla, S., et al. 2009, A&A, 501, 715
Järvinen, S. P., Korhonen, H., Berdyugina, S. V., et al. 2008, A&A, 488, 1047
Jeffers, S. D., & Donati, J.-F. 2008, MNRAS, 390, 635
Jenkins, J. M., Caldwell, D. A., Chandrasekaran, H., et al. 2010, ApJ, 713, L120
Kass, R. E., & Wassermann, L. 1996, J. Am. Stat. Assoc., 91, 1343
Klutsch, A., Guillout, P., Frasca, A., et al. 2010, in Highlights of Spanish Astrophysics VI, Proc. IX Scientific Meeting of the Spanish Astronomical Society, eds. M. R. Zapatero Osorio, J. Gorgas, J. Maíz Apellániz, J. R. Pardo, & A. Gil de Paz, 534
Koch, D. G., Borucki, W. J., Basri, G., et al. 2010, ApJ, 713, L79
Korhonen, H., & Elstner, D. 2011, A&A, 532, 106
Kővári, Zs., Frasca, A., Biazzo, K., et al. 2011, Physics of Sun and Star Spots, eds. D. P. Choudhary, & K. G. Strassmeier (Cambridge Univ. Press), Proc. IAU Symp., 273, 121
Küker, M., Rüdiger, G., & Kitchatinov, L. L. 2011, A&A, 530, A48
Kurucz, R. L. 1993, A new opacity-sampling model atmosphere program for arbitrary abundances, in Peculiar versus normal phenomena in A-type and related stars, IAU Colloq., 138, eds. M. M. Dworetsky, F. Castelli, & R. Faraggiana, ASP Conf. Ser., 44, 87
Kurucz, R. L., & Avrett, E. H. 1981, SAO Spec. Rep., 391
Kurucz, R. L., & Bell, B. 1995, Kurucz CD-ROM No. 23, Cambridge, Mass.: Smithsonian Astrophysical Observatory
Landman, D. A., & Mongillo, M. 1979, ApJ, 230, 581
Lanza, A. F. 2006, MNRAS, 373, 819
Lanza, A. F., Rodonò, M., & Zappala, R. A. 1994, A&A, 290, 861
Lanza, A. F., Bonomo, A. S., Pagano, I., et al. 2011, A&A, 525, A14
Lindborg, M., Korpi, M. J., Hackman, T., et al. 2011, A&A, 526, A44
Lüftinger, T., Fröhlich, H.-E., Weiss, W. W., et al. 2010, A&A, 509, A43
Marino, A., Micela, G., Peres, G., & Sciortino, S. 2003, A&A, 406, 629
Marsden, S. C., Donati, J.-F., Semel, M., Petit, P., & Carter, B. D. 2006, MNRAS, 370, 468
Marsden, S. C., Carter, B. D., & Donati, J.-F. 2009, MNRAS, 399, 888
Marsden, S. C., Jardine, M. M., Ramírez Vélez, J. C., et al. 2011, MNRAS, 413, 1939
Martínez Arnáiz, R., Maldonado, J., Montes, D., Eiroa, C., & Montesinos, B. 2010, A&A, 520, A79
Messina, S., & Guinan, E. F. 2003, A&A, 409, 1017
Mikolajewska, J., & Mikolajewski, M. 1980, Acta Astron., 30, 347
Montes, D., Fernández Figueroa, M. J., De Castro, E., & Cornide, M. 1995, A&AS, 109, 135
Montes, D., López Santiago, J., Gálvez, M. C., et al. 2001a, MNRAS, 328, 45
Montes, D., López Santiago, J., Fernández Figueroa, M. J., & Gálvez, M. C. 2001b, A&A, 379, 976
Mosser, B., Baudin, F., Lanza, A. F., et al. 2009, A&A, 506, 245
Nelson, N. J., Brown, B. P., Brun, S., Miesch, M. S., & Toomre, J. 2011, 217th AAS Meeting, #155.12, BAAS, 43
Nordström, B., Mayor, M., Andersen, J., et al. 2004, A&A, 418, 989
Parker, E. N. 1955, ApJ, 122, 293
Pavlenko, Y. V., & Magazzù, A. 1996, A&A, 311, 961
Perryman, M. A. C., Lindegren, L., Kovalevsky, J., et al. 1997, A&A, 323, L49
Pfeiffer, M. J., Frank, C., Baumueller, D., et al. 1998, A&AS, 130, 381
Pigulski, A., Pojmański, G., Pilecki, B., & Szczygieł, D. M. 2009, Acta Astron., 59, 33
Pinsonneault, M. H., An, D., Molenda-Żakowicz, J., et al. 2012, ApJS, 199, 30
Pizzolato, N., Maggio, A., Micela, G., Sciortino, S., & Ventura, P. 2003, A&A, 397, 147
Press, W. H., Teulkolsky, S. A., Vetterling, W. T., & Flannery, B. P. 2007, Numerical Recipes, 3rd edn. (Cambridge: Cambridge Univ. Press)
Reiners, A. 2006, A&A, 446, 267
Reiners, A., & Schmitt, J. H. M. M. 2003, A&A, 398, 647
Roberts, D. H., Lehar, J., & Dreher, J. W. 1987, AJ, 93, 968
Rodonò, M., Messina, S., Lanza, A. F., Cutispoto, G., & Teriaca, L. 2000, A&A, 358, 624
Schwarz, G. 1978, The Annals of Statistics, 6, 461
Sestito, P., & Randich, S. 2005, A&A, 442, 615
Siess, L., Dufour, E., & Forestini, M. 2000, A&A, 358, 593
Soderblom, D. R., Jones, B. F., Balachandran, S., et al. 1993a, AJ, 106, 1059
Soderblom, D. R., Stauffer, J. R., Hudon, J. D., & Jones, B. F. 1993b, ApJS, 85, 315
Stauffer, J. R., Caillault, J.-P., Gagne, M., Prosser, C. F., & Hartmann, L. W. 1994, ApJS, 91, 625
Stauffer, J. R., Rebull, L. M., Carpenter, J., et al. 2005, AJ, 130, 1834
Steenbeck, M., Krause, F., & Rädler, K.-H. 1966, Z. Naturforsch. 21a, 369
Stetson, P. B. 2000, PASP, 112, 925
Udry, S., Mayor, M., & Queloz, D. 1999, Precise Stellar Radial Velocities, in IAU Colloq., 170, eds. J. B. Hearnshaw, & C. D. Scarfe, ASP Conf. Ser., 185, 367
Uytterhoeven, K., Moya, A., Grigahcène, A., et al. 2011, A&A, 534, A125
Voges, W., Aschenbach, B., Boller, T., et al. 1999, A&A, 349, 389
Voges, W., Aschenbach, B., Boller, T., et al. 2000, IAU Circ., 7432
Waite, I. A., Marsden, S. C., Carter, B. D., et al. 2011, MNRAS, 413, 1949