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Centro de Astrofísica da Universidade do Porto

Detecting ring systems around exoplanets using high resolution spectroscopy: the case of 51 Pegasi b

N. C. Santos, J. H. C. Martins, G. Boué, A. C. M. Correia, M. Oshagh, P. Figueira, A. Santerne, S. G. Sousa, C. Melo, M. Montalto, I. Boisse, D. Ehrenreich, C. Lovis, F. Pepe, S. Udry, A. Garcia Muñoz

Abstract

Aims. In this paper we explore the possibility that the recently detected reflected light signal of 51 Peg b could be caused by a ring system around the planet.
Methods. We use a simple model to compare the observed signal with the expected signal from a short-period giant planet with rings. We also use simple dynamical arguments to understand the possible geometry of such a system.
Results. We provide evidence that, to a good approximation, the observations are compatible with the signal expected from a ringed planet, assuming that the rings are non-coplanar with the orbital plane. However, based on dynamical arguments, we also show that this configuration is unlikely. In the case of coplanar rings we then demonstrate that the incident flux on the ring surface is about 2% the value received by the planet, a value that renders the ring explanation unlikely.
Conclusions. The results suggest that the signal observed cannot in principle be explained by a planet+ring system. We discuss, however, the possibility of using reflected light spectra to detect and characterize the presence of rings around short-period planets. Finally, we show that ring systems could have already been detected by photometric transit campaigns, but their signal could have been easily misinterpreted by the expected light curve of an eclipsing binary.

Keywords
techniques: spectroscopic, planets and satellites: dynamical evolution and stability, planets and satellites: rings, planetary systems

Astronomy and Astrophysics
Volume 583, Page A50
November 2015

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