摘要：Context.HD 50138is a Herbig B[e] star with a circumstellar disc detected at infrared and millimeter wavelength. Its brightness makes it a good candidate for near-infrared interferometry observations.Aims.We aim to resolve, spatially and spectrally, the continuum and hydrogen emission lines in the 2.12–2.47 micron region, to shed light on the immediate circumstellar environment of the star.Methods.VLTI/AMBERK-band observations provide spectra, visibilities, differential phases, and closure phases along three long baselines for the continuum, and HIemission in Brγand five high-nPfund lines. By computing the pure line visibilities, we derive the angular size of the different line-emitting regions. A simple local thermodynamic equilibrium (LTE) model was created to constrain the physical conditions of HIemitting region.Results.The continuum region cannot be reproduced by a geometrical two-dimensional (2D) elongated Gaussian fitting model. We estimate the size of the region to be 1 au. We find the detected hydrogen lines (Brγand Pfund lines) come from a more compact region of size 0.4 au. The Brγline exhibits an S-shaped differential phase, indicative of rotation. The continuum and Brγline closure phases show offsets of ~ −25 ± 5° and 20 ± 10° respectively. This is evidence of an asymmetry in their origin, but with opposing directions. We find that we cannot converge on constraints for the HI physical parameters without a more detailed model.Conclusions.Our analysis reveals thatHD 50138hosts a complex circumstellar environment. Its continuum emission cannot be reproduced by a simple disc brightness distribution. Similarly, several components must be evoked to reproduce the interferometric observables within the Brγline. Combining the spectroscopic and interferometric data of the Brγand Pfund lines favours an origin in a wind region with a large opening angle. Finally, although we cannot exclude the possibility thatHD 50138is a young star our results point to an evolved source.
