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

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 κ Tuc with a significance of 3σ to 6σ at wavelengths between 3.37 and 3.85 μm and a dust-to-star flux ratio of 5 to $7\,\mathrm{\%}$. 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 μm grains of amorphous carbon to fit the κ 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 1σ uncertainty dust location and temperature are confined to 0.032 − 1.18 au and 600 − 2000 K.

A near-infrared interferometric survey of debris-disk stars. VII. The hot/warm dust connection

“…At best, we could reject the hypothesis that the detected excess are due to the thermal emission of grains at temperature below 1000 K, which is not expected as such grains would not produce a significant H-band emission anyway. A possible way to circumvent this limitation would be to follow up our detections at other wavelengths, for instance using the second generation interferometric instruments of the VLTI (GRAVITY in the near-infrared and MATISSE in the mid-infrared, see e.g., Kirchschlager et al 2020).…”

“…Our current understanding is that near-infrared excesses around main sequence stars are related to the thermal emission from hot dust grains close to their sublimation temperature (∼1500 K for silicate dust grains). The contribution of scattered light cannot be excluded in some cases (di Folco et al 2007;Mennesson et al 2011;Defrère et al 2012;Ertel et al 2014), although recent polarimetric, interferometric, and theoretical studies argue against scattered light as a prominent contributor to the detected excesses (Kennedy & Piette 2015;Marshall et al 2016;Kirchschlager et al 2017Kirchschlager et al , 2020. These previous studies have highlighted a tentative correlation between spectral type and near-infrared excess detection rate, but could not formally identify any correlation between the presence of hot dust and of cold, distant dust reservoirs detected by far-infrared and submillimeter photometry.…”

Review and scientific prospects of high-contrast optical stellar interferometry

“…VLTI/MATISSE is not designed for high-contrast observations and will be limited to the characterisation of the brightest systems already detected in the near-infrared. 55 With Hi-5, it will be possible to carry out the first large survey of habitable zone dust in the Southern hemisphere.…”

Commissioning MATISSE: operation and performances

“…Above that limit, the incoherent addition of quadratic quantities has the advantage to be nearly unsensitive to tracking errors. The phase of the coherent flux has a precision 6 the closure phase error has a more complex expression based on the analysis of the bispectrum SNR. This analysis is beyond the scope of this paper.…”

“…Observations in open time started in April 2019. The first science results have just been published [6,7] and many others are in the final steps of redaction. The commissioning of MATISSE has started in March 2018 and was scheduled to be concluded in May 2020.…”