2017ApJ...837...46P

We present unique NUV observations of a well-observed X-class flare from NOAA 12087 obtained at the Ondrejov Observatory. The flare shows a strong white-light continuum but no detectable emission in the higher Balmer and Lyman lines. Reuven Ramaty High-Energy Solar Spectroscopic Imager and Fermi observations indicate an extremely hard X-ray spectrum and γ-ray emission. We use the RADYN radiative hydrodynamic code to perform two types of simulations: one where an energy of 3 x 10¹¹ erg cm^–2 s^–1 is deposited by an electron beam with a spectral index of ≃3, and a second where the same energy is applied directly to the photosphere. The combination of observations and simulations allows us to conclude that the white-light emission and the suppression or complete lack of hydrogen emission lines is best explained by a model where the dominant energy deposition layer is located in the lower layers of the solar atmosphere, rather than the chromosphere.