A near-infrared interferometric survey of debris-disc stars

VI. Extending the exozodiacal light survey with CHARA/JouFLU

¹ NASA Postdoctoral Program Fellow, Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA
e-mail: paul.nunez@jpl.nasa.gov
² NASA Ames Research Center, Moffett Field, CA 94035, USA
³ Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA
⁴ Space Sciences, Technologies and Astrophysics Research (STAR) Institute, Université de Liège, 19c allée du Six Août, 4000 Liège, Belgium
⁵ Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
⁶ The CHARA Array of Georgia State University, Mount Wilson Observatory, Mount Wilson, CA 91023, USA
⁷ Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85719, USA
⁸ Observatoire de Paris-Meudon, 5 place Jules Janssen, 92195 Meudon Cedex, France
⁹ National Optical Astronomy Observatories, 950 North Cherry Avenue, Tucson, AZ 85719, USA

Received: 23 March 2017
Accepted: 24 August 2017

Abstract

We report the results of high-angular-resolution observations that search for exozodiacal light in a sample of main sequence stars and sub-giants. Using the “jouvence” of the fiber linked unit for optical recombination (JouFLU) at the center for high angular resolution astronomy (CHARA) telescope array, we have observed a total of 44 stars. Out of the 44 stars, 33 are new stars added to the initial, previously published survey of 42 stars performed at CHARA with the fiber linked unit for optical recombination (FLUOR). Since the start of the survey extension, we have detected a K-band circumstellar excess for six new stars at the ~ 1% level or higher, four of which are known or candidate binaries, and two for which the excess could be attributed to exozodiacal dust. We have also performed follow-up observations of 11 of the stars observed in the previously published survey and found generally consistent results. We do however detect a significantly larger excess on three of these follow-up targets: Altair, υ And and κ CrB. Interestingly, the last two are known exoplanet host stars. We perform a statistical analysis of the JouFLU and FLUOR samples combined, which yields an overall exozodi detection rate of 21.7^+5.7_-4.1%. We also find that the K-band excess in FGK-type stars correlates with the existence of an outer reservoir of cold (≲100 K) dust at the 99% confidence level, while the same cannot be said for A-type stars.