Evidence of a discontinuous disk structure around the Herbig Ae star HD 139614

A Matter,A Matter,A Matter,A Matter,A Matter,B Lopez,W C Danchi,A Kreplin,G Weigelt,J.-U Pott,L Labadie,S Wolf,S Ertel,S Ertel,S Ertel,S Ertel

doi:10.1051/0004-6361/201322042

Abstract

A new class of pre-main sequence objects has been recently identified as pre-transitional disks. They present near-infrared excess coupled to a flux deficit at about 10 microns and a rising mid-infrared and far-infrared spectrum. These features suggest a disk structure with inner and outer dust components, separated by a dust-depleted region (or gap). We here report on the first interferometric observations of the disk around the Herbig Ae star HD 139614. Its infrared spectrum suggests a flared disk, and presents pre-transitional features,namely a substantial near-infrared excess accompanied by a dip around 6 microns and a rising mid-infrared part. In this framework, we performed a study of the spectral energy distribution (SED) and the mid-infrared VLTI/MIDI interferometric data to constrain thespatial structure of the inner dust disk region and assess its possibly multi-component structure. We based our work on a temperature-gradient disk model that includes dust opacity. While we could not reproduce the SED and interferometric visibilities with a one-component disk, a better agreement was obtained with a two-component disk model composed of an optically thin inner disk extending from 0.22 to 2.3 au, a gap, and an outer temperature-gradient disk starting at 5.6 au. Therefore, our modeling favors an extended and optically thin inner dust component and in principle rules out the possibility that the near-infrared excess originates only from a spatially confined region. Moreover, the outer disk is characterized by a very steep temperature profile and a temperature higher than 300 K at its inner edge. This suggests the existence of a warm component corresponding to a scenario where the inner edge of the outer disk is directly illuminated by the central star. This is an expected consequence of the presence of a gap, thus indicative of a pre-transitional structure.

Highlights

The formation and evolution of planetary systems around young stars are intrinsically linked to the evolution of the primordial accretion disk on a timescale of about 10 Myr
We performed a study of the spectral energy distribution (SED) and the mid-infrared VLTI/MIDI interferometric data to constrain the spatial structure of the inner dust disk region and assess its possibly multi-component structure
While we could not reproduce the SED and interferometric visibilities with a one-component disk, a better agreement was obtained with a two-component disk model composed of an optically thin inner disk extending from 0.22 to 2.3 AU, a gap, and an outer temperature-gradient disk starting at 5.6 AU

Summary

Introduction

The formation and evolution of planetary systems around young stars are intrinsically linked to the evolution of the primordial accretion disk on a timescale of about 10 Myr. Various disk morphologies have been observed and described, such as transitional disks that correspond to pre-main sequence objects with a large centrally-evacuated inner region in the disk, which implies a near-infrared emission deficit This suggests that dust dissipation has begun (Calvet et al 2002), possibly due to various physical processes such as photoevaporation, grain growth, or dynamical interactions. This is in contrast with the SED of the so-called transitional disks, like TW Hya, which only presents photospheric near-infrared flux (Calvet et al 2002) These pre-transitional objects are thought to represent disks whose inner and outer optically thick dust components are separated by a dust-depleted optically thin region (or gap) (see e.g., Benisty et al 2010b; Espaillat et al 2010). Considering the typical subarcsecond angular sizes of the planet-forming regions in young disks, Article published by EDP Sciences

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