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Centro de Astrofísica da Universidade do Porto

New Light on Alpha Centauri B

X. Dumusque, F. Pepe, C. Lovis, D. Ségransan, W. Benz, F. Bouchy, M. Mayor, D. Queloz, N. C. Santos, S. Udry

Abstract.
Since a long time, Alpha Cen B (HD128621) has been qualified as the best target to search for an habitable Earth-like planet. The brightness of the star (V = 1.3) allowing to reach a very high signal-to-noise ratio, its low activity, its spectral type (K1V) and the proximity of it have made of Alpha Cen B the holy grail of exoplanet astronomers.
However, recent HARPS measurements of Alpha Cen B have show that the star is not as quiet as expected. Since 4 years, the activity level of the star has raise, increasing strongly the stellar jitter due to the presence of magnetic spots on the stellar surface.
Due to a high frequency sampling (2 to 3 measurements per night every night) and the very high-precision of the HARPS spectrograph (below 80 cm/s), it is possible to see the magnetic cycle and the day-by-day variation of the spot induced noise. The high quality of these data allows us to correct radial velocities (RVs) from these noises.

Extreme Solar Systems II
Moran, Wyoming, U.S.A.
September 2011

Type: Poster

Institute of Astrophysics and Space Sciences

Institute of Astrophysics and Space Sciences (IA) is a new but long anticipated research infrastructure with a national dimension. It embodies a bold but feasible vision for the development of Astronomy, Astrophysics and Space Sciences in Portugal, taking full advantage and fully realizing the potential created by the national membership of the European Space Agency (ESA) and the European Southern Observatory (ESO). IA resulted from the merging the two most prominent research units in the field in Portugal: the Centre for Astrophysics of the University of Porto (CAUP) and the Center for Astronomy and Astrophysics of the University of Lisbon (CAAUL). It currently hosts more than two-thirds of all active researchers working in Space Sciences in Portugal, and is responsible for an even greater fraction of the national productivity in international ISI journals in the area of Space Sciences. This is the scientific area with the highest relative impact factor (1.65 times above the international average) and the field with the highest average number of citations per article for Portugal.

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