First L band detection of hot exozodiacal dust with VLTI/MATISSE

TL;DR

This study reports the first detection of hot exozodiacal dust in the L band using VLTI/MATISSE, revealing details about dust composition, location, and variability around $$ Tuc.

Contribution

It presents the first L band interferometric detection of hot exozodiacal dust and models its properties based on new and existing data, highlighting dust composition and spatial distribution.

Findings

Detected hot exozodiacal dust with 3-6 sigma significance in L band.

Best-fit models suggest dust located within 0.1 to 0.29 au from the star.

Dust temperature estimated between 600 and 2000 K.

Abstract

For the first time we observed the emission of hot exozodiacal dust in L band. We used the new instrument MATISSE at the Very Large Telescope Interferometer to detect the hot dust around $\kappa$ Tuc with a significance of 3$\sigma$ to 6$\sigma$ at wavelengths between 3.37 and 3.85 $\mu$m and a dust-to-star flux ratio of 5 to 7 %. We modelled the spectral energy distribution based on the new L band data alone and in combination with H band data published previously. In all cases we find 0.58 $\mu$m grains of amorphous carbon to fit the $\kappa$ Tuc observations the best, however, also nanometre or micrometre grains and other carbons or silicates reproduce the observations well. Since the H band data revealed a temporal variability, while our L band data were taken at a different epoch, we combine them in different ways. Depending on the approach, the best fits are obtained for a narrow dust ring at a stellar distance in the 0.1 to 0.29 au range and thus with a temperature between 940 and 1430 K. Within the 1$\sigma$ uncertainty dust location and temperature are confined to 0.032 - 1.18 au and 600 - 2000 K.