Intricate visibility effects from resolved emission of young stellar objects: the case of MWC158 observed with the VLTI

TL;DR

This paper investigates visibility chromatic dependency effects in young stellar objects observed with VLTI, introduces correction methods for imaging, and applies them to the star MWC158 to improve image reconstruction accuracy.

Contribution

It presents a novel correction method for visibility chromatic effects and demonstrates its application to imaging the star MWC158.

Findings

Visibility rise effect linked to emission from the star and disk transition.

Effective correction method enables accurate broadband image reconstruction.

Comparison with parametric models validates the imaging approach.

Abstract

In the course of our VLTI young stellar object PIONIER imaging program, we have identified a strong visibility chromatic dependency that appeared in certain sources. This effect, rising value of visibilities with decreasing wavelengths over one base, is also present in previous published and archival AMBER data. For Herbig AeBe stars, the H band is generally located at the transition between the star and the disk predominance in flux for Herbig AeBe stars. We believe that this phenomenon is responsible for the visibility rise effect. We present a method to correct the visibilities from this effect in order to allow "gray" image reconstruction software, like Mira, to be used. In parallel we probe the interest of carrying an image reconstruction in each spectral channel and then combine them to obtain the final broadband one. As an illustration we apply these imaging methods to MWC158, a (possibly Herbig) B[e] star intensively observed with PIONIER. Finally, we compare our result with a parametric model fitted onto the data.