Planetesimals around stars with TESS (PAST) – I. Transient dimming of a binary solar analogue at the end of the planet accretion era

Creators: Gaidos, E.; Jacobs, T.; LaCourse, D.; Vanderburg, A.; Rappaport, S.; Berger, T.; Pearce, L.; Mann, A. W.; Weiss, L.; Fulton, B.; Behmard, A.; Howard, A. W.; Ansdell, M.; Ricker, G. R.; Vanderspek, R. K.; Latham, D. W.; Seager, S.; Winn, J. N.; Jenkins, J. M.

Abstract

We report detection of quasi-periodic (1.5-d) dimming of HD 240779, the solar-mass primary in a 5 arcsec visual binary (also TIC 284730577), by the Transiting Exoplanet Survey Satellite. This dimming, as has been shown for other 'dipper' stars, is likely due to occultation by circumstellar dust. The barycentric space motion, lithium abundance, rotation, and chromospheric emission of the stars in this system point to an age of ≈125 Myr, and possible membership in the AB Doradus moving group. As such it occupies an important but poorly explored intermediate regime of stars with transient dimming between young stellar objects in star-forming regions and main-sequence stars, and between UX Orionis-type Ae/Be stars and M-type 'dippers'. HD 240779, but not its companion BD+10 714B, has Wide-field Infrared Survey Explorer (WISE)-detected excess infrared emission at 12 and 22 μm indicative of circumstellar dust. We propose that infrared emission is produced by collisions of planetesimals during clearing of a residual disc at the end of rocky planet formation, and that quasi-periodic dimming is produced by the rapid disintegration of a ≳100 km planetesimal near the silicate evaporation radius. Further studies of this and similar systems will illuminate a poorly understood final phase of rocky planet formation like that which produced the inner Solar system.

Additional Information

© 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model). Accepted 2019 July 5. Received 2019 July 3; in original form 2019 May 23. Published: 12 July 2019. The authors thank Jonathan Gagné for discussion of young moving group identifications. TJ and DL gratefully acknowledge Allan R. Schmitt for making his light curve-examining software LcTools freely available. This paper includes data collected by the TESS mission and archived by the MAST at the Space Telescope Science Institute. Funding for TESS is provided by the NASA Explorer Program. We acknowledge support by the NASA High-End Computing (HEC) Program through the NASA Advanced Supercomputing Division at Ames Research Center for the production of the SPOC data products. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. This research has made use of the NASA/ IPAC Infrared Science Archive, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.

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