Faint debris disk peering through superflare light echo

TL;DR

This paper explores the potential to detect mid-infrared light echoes from faint debris disks around M-dwarf stars caused by superflares, suggesting observational strategies for nearby systems.

Contribution

It models the detectability of MIR light echoes from faint debris disks illuminated by superflares, proposing observational methods for nearby M-dwarf systems.

Findings

MIR echoes from debris disks with masses comparable to zodiacal dust are detectable at >10 μm.

Echos from inner debris disks irradiated by energetic superflares are observable within 3 parsecs.

High-speed optical and ground-based MIR observations can detect these light echoes.

Abstract

We present the detectability of strong mid-infrared (MIR) light echoes from faint debris disks illuminated by bright superflares of M-dwarf stars. Circumstellar dust grains around an M-dwarf star are simultaneously heated by superflare radiation. One can thus expect their re-emission in the MIR wavelength regime. According to our model calculations for the Proxima Centauri system, the nearest M-dwarf star system, thermal emission echos from an inner ($r < 1~{\rm au}$) debris disk with a total mass down to that of the solar system's zodiacal dust are expected to emerge at wavelengths longer than $\sim 10~{\rm \mu m}$ with a strength comparable to or greater than a white-light superflare. Also, observable echos from inner- ($r \lesssim 0.5~{\rm au}$) debris disks irradiated by energetic ($\gtrsim 10^{33.5}~{\rm ergs}$) superflares of nearby ($D < 3~{\rm pc}$) M-dwarfs are expected. Our simulation results indicate that superflare monitoring using high-speed optical instruments like OASES and its prompt follow-up using ground-based MIR instruments, such as TAO/MIMIZUKU, can detect these MIR light echoes from debris disks around solar neighborhood flare stars.