Vol. 603
In section 8. Stellar atmospheres

The full spectral radiative properties of Proxima Centauri

by I. Ribas, M. D. Gregg, T. S. Boyajian, and E. Bolmont A&A 603, A58


The discovery of Proxima Centauri b, a terrestrial temperate planet, presents the opportunity of studying a nearby, potentially habitable world. Understanding the radiation environment of the planet is a prerequisite for modeling its habitability. In this paper, the authors derive top-of-atmosphere fluxes on the planet from the X-ray to the mid-IR spectral domains. They also also aim at constraining the fundamental properties of the star, namely its mass, radius, effective temperature, and luminosity. The top-of-atmosphere average XUV irradiance on Proxima b is 0.293 W m^-2, nearly 60 times higher than Earth, and the total irradiance is 877 ± 44 W m^-2 , or 64 ± 3% of the solar constant but with a significantly redder spectrum. The fundamental properties of Proxima Centuri are M = 0.120±0.003 solar mass, R = 0.146±0.007 solar radius, Teff = 2980±80K, L = 0.00151 ± 0.00008 solar luminosity. The analysis also reveals a 20% excess in the 3–30 μm range that is best interpreted as arising from warm dust in the system.