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Centro de Astrofísica da Universidade do Porto
Impact of the occultation of stellar active regions on transmission spectra: Do HD189733b and GJ3470b have blue skies?

Mahmoudreza Oshagh
CAUP

Abstract
Transmission spectroscopy during planetary transits is a powerful technique to explore exoplanetary atmospheres. It consists in measuring the variations of the planet-to-star radius ratio as a function of wavelength. One of the main limitation of this technique is stellar activity, which is usually taken into account only by assessing the effect of non-occulted stellar spots on the planet-to-star radius estimation. In this talk, I present our recent study on the impact of the occultation of stellar active regions, such as spots and plages, on the transmission spectra of transiting exoplanets. We found that the anomalies inside the transit light curve can lead to a significant underestimation or overestimation of the planet-to-star radius ratio as a function of wavelength. At short wavelengths, the effect can reach up to a maximum difference of 10% in the planet-to-star radius ratio, mimicking the signature of light scattering in the planetary atmosphere. Atmospheric scattering has been proposed to interpret the increasing slopes of transmission spectra toward the blue for exoplanets HD 189733b and GJ 3470b. We showed that these signatures can be alternatively interpreted by stellar activity, if the planets transit across stellar plages with sun-like properties.

15 May 2014, 13:30

Centro de Astrofísica
Rua das Estrelas
4150-762 Porto

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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