Abstract
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 $3.85\, {\mu {\rm m}}$ and a dust-to-star flux ratio of 5 to $7{{{\ \rm per\ cent}}}$. 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 $0.58\, {\mu {\rm m}}$ 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 Lband 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 0.1–029 au range and thus with a temperature between 940 and $1430\, {\rm K}$. Within the 1σ uncertainty dust location and temperature are confined to $0.032{\!-\!}1.18\, {\rm au}$ and $600{\!-\!}2000\, {\rm K}$.
Highlights
Since the first detection of hot exozodiacal dust (‘hot exozodi’) around Vega (Absil et al 2006), about two dozens hot exozodis have been discovered using optical long baseline interferometry (Di Folco et al 2007; Absil et al 2008, 2009, 2013; Defrere et al 2011, 2012; Ertel et al 2014, 2016; Nunez et al 2017)
We presented the first detection of hot exozodiacal dust emission in L band
We used the new instrument MATISSE at the Very Large Telescope Interferometer (VLTI) to observe the visibilities of κ Tuc at six baselines
Summary
Since the first detection of hot exozodiacal dust (‘hot exozodi’) around Vega (Absil et al 2006), about two dozens hot exozodis have been discovered using optical long baseline interferometry (Di Folco et al 2007; Absil et al 2008, 2009, 2013; Defrere et al 2011, 2012; Ertel et al 2014, 2016; Nunez et al 2017). To be detectable around ∼20 per cent of main-sequence stars of all spectral types from A to K at all ages (Ertel et al 2014), the dust has to be continuously replenished or to be trapped in the stellar vicinity for long times, yet the eliciting mechanism has still to be identified (van Lieshout et al 2014; Rieke, Gaspar & Ballering 2016; Kral et al 2017; Kimura et al 2020; Pearce, Krivov & Booth 2020). N band emission from more temperate (warm) dust near habitable zones has been detected (Millan-Gabet et al 2011; Mennesson et al 2014; Ertel et al 2018b, 2020) but observations at intermediate wavelengths (1.6 μm λ 10 μm) are required to study the potential connection of warm and hot dust.
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