The galactic unclassified B[e] star HD 50138. II. Interferometric constraints on the close circumstellar environment

TL;DR

This paper uses interferometric observations to resolve and model the circumstellar environment of the B[e] star HD 50138, revealing a dusty disk structure and its orientation.

Contribution

First detailed interferometric modeling of HD 50138's circumstellar environment, determining disk geometry and orientation.

Findings

Detected a dusty circumstellar disk with a 71±7 degree orientation.

Determined the star is viewed at an intermediate angle of 56±4 degrees.

Discussed the flux contributions of gas and dust in the disk.

Abstract

HD 50138 is a southern star that presents the B[e] phenomenon, but its evolutionary stage is still not well known. This object presents spectral variability, which can be explained by outbursts or shell phases and spectropolarimetric observations have shown the presence of a non-spherically symmetric circumstellar environment that is responsible for the B[e] phenomenon. Based on recent optical long baseline interferometric observations from the VLTI/MIDI and VLTI/AMBER, and also from the Keck segment-tilting experiment, we study the structure of the circumstellar environment of HD 50138, through a geometrical analytical modeling, also using the recent LITpro software and considering a large space of parameters. We resolve and describe its circumstellar geometry for the first time in detail. The presence of a dusty circumstellar disk with an orientation onto the sky-plane of 71+-7 degrees, which is perpendicular to the polarimetric measurements from the literature, was derived. We also derived that HD 50138 is seen under an intermediate angle related to the line of sight, 56+-4 degrees. In addition, the structure of the disk and the flux contributions of the gas and dust components is discussed.