# A compact gaseous accretion disk in Keplerian rotation around MWC147

## TL;DR

This study provides direct evidence of a compact, gaseous accretion disk in Keplerian rotation around MWC147, observed through high-resolution interferometry and spectroscopy, revealing that both continuum and line emissions originate from the same inner disk region.

## Contribution

First direct spatially and spectrally resolved detection of a gaseous accretion disk in Keplerian rotation around a Herbig Be star, combining VLTI/AMBER and CRIRES data.

## Key findings

- The continuum disk is compact and close to face-on.
- No significant visibility change across Br-gamma line suggests co-location of gas and dust.
- Br-gamma emission originates from the same region as the continuum, indicating a gaseous accretion disk.

## Abstract

The disks around some Herbig Be stars have been observed to be more compact than the expected dust sublimation radius for such objects, with highly refractory dust grains and optically thick gas emission having been proposed as possible explanations for this phenomenon. Our aim is to search for direct evidence for the presence of hot gas inside of the expected dust sublimation radius of MWC147. By combining VLTI/AMBER spectro-interferometry (R=12,000) with CRIRES spectroscopy (R=100,000) we can both spectrally and spatially resolve the Br-gamma line-emitting gas around MWC147. Our interferometric visibility modelling of MWC147 indicates the presence of a compact continuum disk with a close to face-on orientation. We model the continuum with an inclined Gaussian, as well as a ring with a radius of 0.60mas (0.39au) which is well within the expected dust sublimation radius of 1.52au. We detect no significant change in the measured visibilities across the Br-gamma line, indicating that the line-emitting gas is located in the same region as the continuum-emitting disk. We fit our AMBER spectro-interferometry data with a kinematic model of a disk in Keplerian rotation, with both the line-emitting and continuum-emitting components of the disk originating from the same compact region close to the central star. The presence of line-emitting gas in the same region as the K-band continuum supports the interpretation that the K-band continuum traces an optically-thick gas disk. Our spatially and spectrally resolved observations of MWC147 reveal that the K-band continuum and Br-gamma emission both originate from a similar compact region, with Br-gamma emitted from the accretion disk or disk wind region and exhibiting a rotational velocity profile. We conclude that we detect the presence of a compact, gaseous accretion disk in Keplerian rotation around MWC147.