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Hydrogen-line emission from an accretion shock has recently been observed atplanetary-mass objects. Our previous work predicted the shock spectrum andluminosity for a shock on the circumplanetary disc. We extend this to theplanet-surface shock. We calculate the global spectral energy distribution(SED) of accreting planets by combining our model emission spectra withphotospheric SEDs, and predict the line-integrated flux for several hydrogenlines, especially H alpha, but also H beta, Pa alpha, Pa beta, Pa gamma, Bralpha, and Br gamma. We apply our non-equilibrium emission model to the surfaceaccretion shock for a wide range of accretion rates Mdot and masses M_p . Fitsto formation calculations provide radii and effective temperatures. Extinctionby the surrounding material is neglected, which is arguably often relevant. Wefind that the line luminosity increases monotonically with Mdot and M_p ,depending mostly on Mdot and weakly on M_p for the relevant range ofparameters. The Lyman, Balmer, and Paschen continua can exceed the photosphere.The H beta line is fainter by 0 to 1 dex than H alpha, whereas other lines areweaker (by 1 to 3 dex). Shocks on the planet or the CPD surface aredistinguishable at very high spectral resolution, but the planet surface shocklikely dominates if both are present. Applied to recent non-detections of Halpha, our models imply looser constraints on the Mdot of putative planets thanwhen extrapolating fits from the stellar regime. These hydrogen-line luminositypredictions are useful for interpreting (non-)detections of accreting planets.

Spectral appearance of the planetary-surface accretion shock: Global spectra and hydrogen-line profiles and fluxes