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Centro de Astrofísica da Universidade do Porto

An Ultra-short Period Rocky Super-Earth with a Secondary Eclipse and a Neptune-like Companion around K2-141

L. Malavolta, A. W. Mayo, T. Louden, V. M. Rajpaul, A. S. Bonomo, L. A. Buchhave, L. Kreidberg, M. H. Kristiansen, M. López-Morales, A. Mortier, A. Vanderburg, A. Coffinet, D. Ehrenreich, C. Lovis, F. Bouchy, D. Charbonneau, D. Ciardi, A. C. Cameron, R. Cosentino, I. J. M. Crossfield, M. Damasso, C. D. Dressing, X. Dumusque, M. Everett, P. Figueira, A. F. M. Fiorenzano, E. J. Gonzales, R. D. Haywood, A. Harutyunyan, L. A. Hirsch, S. B. Howell, J. A. Johnson, D. W. Latham, E. Lopez, M. Mayor, G. Micela, E. Molinari, V. Nascimbeni, F. Pepe, D. F. Phillips, G. Piotto, K. Rice, D. Sasselov, D. Ségransan, A. Sozzetti, S. Udry, C. A. Watson

Ultra-short period (USP) planets are a class of low-mass planets with periods shorter than one day. Their origin is still unknown, with photo-evaporation of mini-Neptunes and in situ formation being the most credited hypotheses. Formation scenarios differ radically in the predicted composition of USP planets, and it is therefore extremely important to increase the still limited sample of USP planets with precise and accurate mass and density measurements. We report here the characterization of a USP planet with a period of 0.28 days around K2-141 (EPIC 246393474), and the validation of an outer planet with a period of 7.7 days in a grazing transit configuration. We derived the radii of the planets from the K2 light curve and used high-precision radial velocities gathered with the HARPS-N spectrograph for mass measurements. For K2-141b, we thus inferred a radius of 1.51 ± 0.05 R ${}_{oplus }$ and a mass of 5.08 ± 0.41 M ${}_{oplus }$, consistent with a rocky composition and lack of a thick atmosphere. K2-141c is likely a Neptune-like planet, although due to the grazing transits and the non-detection in the RV data set, we were not able to put a strong constraint on its density. We also report the detection of secondary eclipses and phase curve variations for K2-141b. The phase variation can be modeled either by a planet with a geometric albedo of 0.30 ± 0.06 in the Kepler bandpass, or by thermal emission from the surface of the planet at ~3000 K. Only follow-up observations at longer wavelengths will allow us to distinguish between these two scenarios.

planetary systems; planets and satellites: composition; planets and satellites: individual: K2-141b; K2-141c; planets and satellites: interiors; stars: individual: K2-141; techniques: photometric; techniques: radial velocities; Astrophysics - Earth and Pl

The Astronomical Journal
Volume 155
March 2018

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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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