Context : The discovery of Proxima b , a terrestrial temperate planet , presents the opportunity of studying a potentially habitable world in optimal conditions .
A key aspect to model its habitability is to understand the radiation environment of the planet in the full spectral domain .

Aims : We characterize the X-rays to mid-IR radiative properties of Proxima with the goal of providing the top-of-atmosphere fluxes on the planet .
We also aim at constraining the fundamental properties of the star , namely its mass , radius , effective temperature and luminosity .

Methods : We employ observations from a large number of facilities and make use of different methodologies to piece together the full spectral energy distribution of Proxima .
In the high-energy domain , we pay particular attention to the contribution by rotational modulation , activity cycle , and flares so that the data provided are representative of the overall radiation dose received by the atmosphere of the planet .

Results : We present the full spectrum of Proxima covering 0.7 to 30000 nm .
The integration of the data shows that the top-of-atmosphere average XUV irradiance on Proxima b is 0.293 W m ^ { -2 } , i.e. , nearly 60 times higher than Earth , and that the total irradiance is 877 \pm 44 W m ^ { -2 } , or 64 \pm 3 % of the solar constant but with a significantly redder spectrum .
We also provide laws for the XUV evolution of Proxima corresponding to two scenarios , one with a constant XUV-to-bolometric luminosity value throughout its history and another one in which Proxima left the saturation phase at an age of about 1.6 Gyr and is now in a power-law regime .
Regarding the fundamental properties of Proxima , we find M = 0.120 \pm 0.003 M _ { \odot } , R = 0.146 \pm 0.007 R _ { \odot } , T _ { eff } = 2980 \pm 80 K , and L = 0.00151 \pm 0.00008 L _ { \odot } .
In addition , our analysis reveals a \sim 20 % excess in the 3–30 \mu m flux of the star that is best interpreted as arising from warm dust in the system .

Conclusions : The data provided here should be useful to further investigate the current atmospheric properties of Proxima b as well as its past history , with the overall aim of firmly establishing the habitability of the planet .