A Tale of Two Herbig Ae stars -MWC275 and AB Aurigae: Comprehensive Models for SED and Interferometry

TL;DR

This paper develops comprehensive models for Herbig Ae stars MWC275 and AB Aur, integrating spectral energy distribution and interferometry data, revealing the importance of gas emission and dust composition in their inner disk regions.

Contribution

The study introduces a combined dust and gas emission model that successfully explains NIR and interferometry observations, highlighting differences in outer disk structures of the two stars.

Findings

Gas emission inside sublimation radius is crucial for fitting NIR data.

Outer disk structures differ significantly between MWC275 and AB Aur.

Highly refractory dust is necessary in the gas-dust transition region.

Abstract

We present comprehensive models for the Herbig Ae stars MWC275 and AB Aur that aim to explain their spectral energy distribution (from UV to millimeter) and long baseline interferometry (from near-infrared to millimeter) simultaneously. Data from the literature, combined with new mid-infrared (MIR) interferometry from the Keck Segment Tilting Experiment, are modeled using an axisymmetric Monte Carlo radiative transfer code. Models in which most of the near-infrared (NIR) emission arises from a dust rim fail to fit the NIR spectral energy distribution (SED) and sub-milli-arcsecond NIR CHARA interferometry. Following recent work, we include an additional gas emission component with similar size scale to the dust rim, inside the sublimation radius, to fit the NIR SED and long-baseline NIR interferometry on MWC275 and AB Aur. In the absence of shielding of star light by gas, we show that the gas-dust transition region in these YSOs will have to contain highly refractory dust, sublimating at ~1850K. Despite having nearly identical structure in the thermal NIR, the outer disks of MWC275 and AB Aur differ substantially. In contrast to the AB Aur disk, MWC275 lacks small grains in the disk atmosphere capable of producing significant 10-20micron emission beyond ~7AU, forcing the outer regions into the "shadow" of the inner disk