Navegando por Autor "Meibom, S."
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Artigo Magnetic field and wind of kappa ceti: toward the planetary habitability of the young sun when life arose on earth(The American Astronomical Society, 2016-03-20) Nascimento Júnior, José Dias do; Vidotto, A. A.; Petit, P.; Folsom, C.; Castro, M.; Marsden, S. C.; Morin, J.; Mello, G. F. Porto de; Meibom, S.; Jeffers, S. V.; Guinan, E.; Ribas, I.We report magnetic field measurements for κ1 Cet, a proxy of the young Sun when life arose on Earth. We carry out an analysis of the magnetic properties determined from spectropolarimetric observations and reconstruct the large-scale surface magnetic field to derive the magnetic environment, stellar winds, and particle flux permeating the interplanetary medium around k1 Cet. Our results show a closer magnetosphere and mass-loss rate of M˙ = 9.7 ´ 10-13 M yr-1 , i.e., a factor of 50 times larger than the current solar wind mass-loss rate, resulting in a larger interaction via space weather disturbances between the stellar wind and a hypothetical young-Earth analogue, potentially affecting the planet’s habitability. Interaction of the wind from the young Sun with the planetary ancient magnetic field may have affected the young Earth and its life conditionsArtigo Rotation periods and ages of solar analogs and solar twins revealed by the kepler mission(IOP Publishing, 2014-08-01) Costa, Jefferson Soares da; Nascimento, José Dias do; Garcia, R. A.; Mathur, S.; Anthony, F.; Barnes, S. A.; Meibom, S.; Castro, Matthieu Sebastien; Salabert, D.; Ceillier, T.A new sample of solar analogs and twin candidates has been constructed and studied, paying particular attention to their light curves from NASA’s Kepler mission. This Letter aims to assess their evolutionary status, derive their rotation and ages, and identify those which are solar analogs or solar twin candidates. We separate out the subgiants that compose a large fraction of the asteroseismic sample, and which show an increase in the average rotation period as the stars ascend the subgiant branch. The rotation periods of the dwarfs, ranging from 6 to 30 days and averaging 19 days, allow us to assess their individual evolutionary states on the main sequence and to derive their ages using gyrochronology. These ages are found to be in agreement with a correlation coefficient of r = 0.79 with independent asteroseismic ages, where available. As a result of this investigation, we are able to identify 34 stars as solar analogs and 22 of them as solar twin candidates