Variable warm dust around the Herbig Ae star HD~169142: Birth of a ring?

TL;DR

This study tracks the formation and fading of a dust ring around the Herbig Ae star HD 169142 over six years, suggesting secondary dust production inside a protoplanetary disk, with implications for disk evolution.

Contribution

First direct detection of secondary dust production inside a protoplanetary disk through multi-epoch interferometric and photometric observations.

Findings

A dust ring formed between 2013 and 2018 at ~0.3 au.

The dust ring faded by 2019 but did not disappear.

Short-term variability resembles that of extreme debris disks.

Abstract

The Herbig Ae star HD 169142 is known to have a gaseous disk with a large inner hole, and also a photometrically variable inner dust component in the sub-au region. Following up our previous analysis, we further studied the temporal evolution of inner dust around HD 169142, which may provide information on the evolution from late-stage protoplanetary disks to debris disks. We used near-infrared interferometric observations obtained with VLTI/PIONIER to constrain the dust distribution at three epochs spanning six years. We also studied the photometric variability of HD 169142 using our optical-infrared observations and archival data. Our results indicate that a dust ring at ~0.3 au formed at some time between 2013 and 2018, and then faded (but did not completely disappear) by 2019. The short-term variability resembles that observed in extreme debris disks, and is likely related to short-lived dust of secondary origin, though variable shadowing from the inner ring could be an alternative interpretation. If confirmed, this is the first direct detection of secondary dust production inside a protoplanetary disk.