Mid-infrared interferometry towards the massive young stellar object CRL 2136: inside the dust rim

TL;DR

This study uses mid-infrared interferometry to analyze the dust and potential compact sources around the massive young stellar object CRL 2136, revealing complex structures including dust sublimation zones and possible gaseous disks or bloated stars.

Contribution

First detailed mid-infrared interferometric modeling of CRL 2136, identifying dust sublimation radii and exploring origins of compact emission beyond dust envelope models.

Findings

Dust emission peaks at ~170 AU from the star.

Compact mid-infrared emission could originate from a gaseous disk or a bloated star.

The dust envelope is truncated at several times the sublimation radius.

Abstract

We apply mid-infrared spectro-interferometry to the massive young stellar object CRL2136. The observations were performed with the Very Large Telescope Interferometer and the MIDI instrument at a 42m baseline probing angular scales of 50 milli-arcseconds. We model the observed visibilities in parallel with diffraction-limited images at both 24.5micron and in the N-band (with resolutions of 0.6" and 0.3", respectively), as well as the spectral energy distribution. The arcsec-scale spatial information reveals the well-resolved emission from the dusty envelope. By simultaneously modelling the spatial and spectral data, we find that the bulk of the dust emission occurs at several dust sublimation radii (approximately 170 AU). This reproduces the high mid-infrared fluxes and at the same time the low visibilities observed in the MIDI data for wavelengths longward of 8.5micron. However, shortward of this wavelength the visibility data show a sharp up-turn indicative of compact emission. We discuss various potential sources of this emission. We exclude a dust disk being responsible for the observed spectral imprint on the visibilities. A cool supergiant star and an accretion disk are considered and both shown to be viable origins of the compact mid-infrared emission. We propose that CRL2136 is embedded in a dusty envelope, which truncates at several times the dust sublimation radius. A dust torus is manifest in the equatorial region. We find that the spectro-interferometric N-band signal can be reproduced by either a gaseous disk or a bloated central star. If the disk extends to the stellar surface, it accretes at a rate of 3.0 10^(-3) Msun/yr.