The HOSTS survey - Exozodiacal dust measurements for 30 stars
2018
The HOSTS (Hunt for Observable Signatures of Terrestrial Systems) survey searches for dust near the habitable zones (HZs) around nearby, bright main sequence
stars. We use nulling interferometry in N band to suppress the bright stellar light and to probe for low levels of HZ dust around the 30
starsobserved so far. Our overall detection rate is 18%, including four new detections, among which are the first three around Sun-like
starsand the first two around
starswithout any previously known
circumstellar dust. The inferred occurrence rates are comparable for early type and Sun-like
stars, but decrease from 60 (+16/-21)% for
starswith previously detected cold dust to 8 (+10/-3)% for
starswithout such excess, confirming earlier results at higher sensitivity. For completed observations on individual
stars, our sensitivity is five to ten times better than previous results. Assuming a lognormal excess
luminosity function, we put upper limits on the median HZ dust level of 13 zodis (95% confidence) for a sample of
starswithout cold dust and of 26 zodis when focussing on Sun-like
starswithout cold dust. However, our data suggest that a more complex
luminosity functionmay be more appropriate. For
starswithout detectable LBTI excess, our upper limits are almost reduced by a factor of two, demonstrating the strength of LBTI target vetting for future exo-Earth imaging missions. Our statistics are so far limited and extending the survey is critical to inform the design of future exo-Earth imaging surveys.
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