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Source I in the Orion-KL nebula is believed to be the nearest example of amassive star still in the main accretion phase. It is thus one of the bestcases for studying the properties of massive protostars to constrain high-massstar formation theories. Near-infrared radiation from source I escapes throughthe cavity opened by the OMC1 outflow and is scattered by dust towards our lineof sight. The reflected spectrum offers a unique possibility of observing theemission from the innermost regions of the system and probing the nature ofsource I and its immediate surroundings. We obtained moderately highspectral-resolution (R~9000) observations of the near-infrared diffuse emissionin several locations around source I/Orion-KL. We observed a widespread richabsorption line spectrum that we compare with cool stellar photospheres andprotostellar accretion disk models. The spectrum is broadly similar to stronglyveiled, cool, low-gravity stellar photospheres in the range Teff~3500-4500 K,luminosity class I-III. An exact match explaining all features has not beenfound, and a plausible explanation is that a range of different temperaturescontribute to the observed absorption spectrum. The 1D velocity dispersionsimplied by the absorption spectra, sigma~30 km/s, can be explained by theemission from a disk around a massive, mstar~10 Msun, protostar that isaccreting at a high rate, mdot~3x10^{-3} Msun/yr. Our observations suggest thatthe near-infrared reflection spectrum observed in the Orion-KL region isproduced close to source I and scattered to our line of sight in the OMC1outflow cavity. The spectrum allows us to exclude source I being a very large,massive protostar rotating at breakup speed. We suggest that the absorptionspectrum is produced in a disk surrounding a ~10 Msun protostar, accreting fromits disk at a high rate of a few 10^{-3} Msun/yr.

The near-infrared reflected spectrum of source I in Orion-KL