The HOSTS Survey—Exozodiacal Dust Measurements for 30 Stars

May 2018 • 2018AJ....155..194E

Authors • Ertel, S. • Defrère, D. • Hinz, P. • Mennesson, B. • Kennedy, G. M. • Danchi, W. C. • Gelino, C. • Hill, J. M. • Hoffmann, W. F. • Rieke, G. • Shannon, A. • Spalding, E. • Stone, J. M. • Vaz, A. • Weinberger, A. J. • Willems, P. • Absil, O. • Arbo, P. • Bailey, V. P. • Beichman, C. • Bryden, G. • Downey, E. C. • Durney, O. • Esposito, S. • Gaspar, A. • Grenz, P. • Haniff, C. A. • Leisenring, J. M. • Marion, L. • McMahon, T. J. • Millan-Gabet, R. • Montoya, M. • Morzinski, K. M. • Pinna, E. • Power, J. • Puglisi, A. • Roberge, A. • Serabyn, E. • Skemer, A. J. • Stapelfeldt, K. • Su, K. Y. L. • Vaitheeswaran, V. • Wyatt, M. C.

Abstract • The 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 the N band to suppress the bright stellar light and to probe for low levels of HZ dust around the 30 stars observed so far. Our overall detection rate is 18%, including four new detections, among which are the first three around Sun-like stars and the first two around stars without any previously known circumstellar dust. The inferred occurrence rates are comparable for early-type and Sun-like stars, but decrease from {60}-21+16% for stars with previously detected cold dust to {8}-3+10% for stars without 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 stars without cold dust and of 26 zodis when focusing on Sun-like stars without cold dust. However, our data suggest that a more complex luminosity function may be more appropriate. For stars without detectable Large Binocular Telescope Interferometer (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 limited so far, and extending the survey is critical to informing the design of future exo-Earth imaging surveys.


IPAC Authors

Chris Gelino

Associate Scientist