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We analyse the main physical parameters and the circumstellar environment ofthe young Herbig Be star HD 98922. We present AMBER/VLTI high spectralresolution (R =12000) interferometric observations across the Br$\gamma$ line,accompanied by UVES high-resolution spectroscopy and SINFONI-AO assistednear-infrared integral field spectroscopic data. To interpret our observations,we develop a magneto-centrifugally driven disc-wind model. Our analysis of theUVES spectrum shows that HD 98922 is a young (~5x10^5 yr) Herbig Be star(SpT=B9V), located at a distance of 440(+60-50) pc, with a mass accretion rateof ~9+/-3x10^(-7) M_sun yr^(-1). SINFONI K-band AO-assisted imaging shows aspatially resolved circumstellar disc-like region (~140 AU in diameter) withasymmetric brightness distribution. Our AMBER/VLTI UT observations indicatethat the Br$\gamma$ emitting region (radius ~0.31+/-0.04 AU) is smaller thanthe continuum emitting region (inner dust radius ~0.7+/-0.2 AU), showingsignificant non-zero V-shaped differential phases (i.e. non S-shaped, asexpected for a rotating disc). The value of the continuum-corrected pureBr$\gamma$ line visibility at the longest baseline (89 m) is ~0.8+/-0.1, i.e.the Br$\gamma$ emitting region is partially resolved. Our modelling suggeststhat the observed Br$\gamma$ line-emitting region mainly originates from a discwind with a half opening angle of 30deg, and with a mass-loss rate of ~2x10(-7)M_sun yr^(-1). The observed V-shaped differential phases are reliablyreproduced by combining a simple asymmetric continuum disc model with ourBr$\gamma$ disc-wind model. The Br$\gamma$ emission of HD 98922 can be modelledwith a disc wind that is able to approximately reproduce all interferometricobservations if we assume that the intensity distribution of the dust continuumdisc is asymmetric.

astronomy and astrophysics

AMBER/VLTI high spectral resolution observations of the Br$\gamma$  emitting region in HD 98922. A compact disc wind launched from the inner disc  region