The discovery of new warm debris disks around F-type stars

TL;DR

This paper reports the discovery of four warm debris disks around F-type stars, including one with transient dust production, and discusses implications for dust evolution and replenishment mechanisms.

Contribution

It presents the discovery of new warm debris disks around F-stars, including a transient system, and analyzes dust properties and evolution models.

Findings

Three disks align with steady state evolution models.

One disk shows evidence of recent transient dust production.

Small grains are continuously produced over several years.

Abstract

We report the discovery of four rare debris disks with warm excesses around F-stars, significantly increasing the number of such systems known in the solar neighborhood. Three of the disks are consistent with the predictions of steady state planetesimal disk evolution models. The oldest source, HD 169666, displays a dust fractional luminosity too high to be in steady state and we suggest that this system recently underwent a transient event of dust production. In addition, two spectra of this star separated by ~three years show silicate emission features, indicative of submicron- to micron-sized grains. We argue that such small grains would be rapidly depleted and their presence in both spectra suggests that the production of small dust is continuous over at least on few years timescale. We predict that systems showing variable mid-infrared spectra, if exist, will provide valuable help in distinguishing the possible scenarios proposed for dust replenishment.