Препринт

Interferometric Detection and Orbit Modeling of the Subcomponent in the Hot-dust System $κ$ Tuc A: A Low-mass Star on an Eccentric Orbit in a Hierarchical-quintuple System

Stuber, T. A.Department of Astronomy and Steward Observatory, The University of ArizonaMérand, A.European Southern Observatory HeadquarterKirchschlager, F.Sterrenkundig Observatorium, Ghent UniversityWolf, S.Institute of Theoretical Physics and Astrophysics, Kiel UniversityWeible, G.Department of Astronomy and Steward Observatory, The University of ArizonaAbsil, O.STAR Institute, Université de LiègePearce, T. D.Department of Physics, University of WarwickGarreau, G.Institute of Astronomy, KU LeuvenAugereau, J. -C.Univ. Grenoble Alpes, CNRS, IPAGDanchi, W. C.NASA Goddard Space Flight CenterDefrère, D.Institute of Astronomy, KU LeuvenFaramaz-Gorka, V.Department of Astronomy and Steward Observatory, The University of ArizonaIsbell, J. W.Department of Astronomy and Steward Observatory, The University of ArizonaKobus, J.Institute of Theoretical Physics and Astrophysics, Kiel UniversityKrivov, A. V.Astrophysikalisches Institut und Universitätssternwarte, Friedrich-Schiller-Universität JenaLaugier, R.Institute of Astronomy, KU LeuvenOllmann, K.Institute of Theoretical Physics and Astrophysics, Kiel UniversityPetrov, R. G.Université Côte d'Azur, Observatoire de la Côte d'Azur, CNRS, Laboratoire LagrangePriolet, P.Univ. Grenoble Alpes, CNRS, IPAGScott, J. P.Department of Astronomy and Steward Observatory, The University of ArizonaTsishchankava, K.Institute of Theoretical Physics and Astrophysics, Kiel UniversityErtel, S.Department of Astronomy and Steward Observatory, The University of Arizona

arXiv (Cornell University)repository2025

ABI

Аннотация

The system $κ$ Tuc A is part of a hierarchical-quintuple system and is a prime target for studies of hot-exozodiacal dust, because a time-variable near-infrared excess has been detected. We observed the system with the Multi Aperture mid-Infrared Spectroscopic Experiment (MATISSE) and GRAVITY at the Very Large Telescope Interferometer, and detected the stellar companion to the primary $κ$ Tuc Aa that was previously inferred by astrometry, $κ$ Tuc Ab. Its $L$-band flux ratio to the primary is 1.32% and its signature in the MATISSE closure phases is mostly smaller than +/- 2°, which makes $κ$ Tuc Ab the highest-contrast companion ever detected with MATISSE closure phases. We verified with GRAVITY that relative astrometry with milliarcsecond precision can be retrieved from MATISSE closure phases. Using multiple epochs of observations, we obtain a full orbital solution for $κ$ Tuc Ab. Its orbit has an eccentricity of 0.94 and a semi-major axis of 4.8au. The orbit of $κ$ Tuc Ab and the orbit of the wider separation companion $κ$ Tuc B are mutually inclined. Based on the measured flux ratio of $κ$ Tuc Ab to Aa and their dynamical mass, we estimate the spectral type of $κ$ Tuc Ab to be M3.5V to M4.5V. While the then unknown star $κ$ Tuc Ab might have caused the putative detection of hot-exozodiacal dust around $κ$ Tuc Aa in 2012 and 2014, this cannot be for the detection in 2019, giving rise to an intriguing system architecture. This motivates studies investigating the interplay of the low-mass star on an eccentric orbit, the hot-exozodiacal dust, and a possible planetesimal reservoir.

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Astrophysics and Star Formation Studies Stellar, planetary, and galactic studies Astro and Planetary Science

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DOI: 10.48550/arxiv.2512.03209

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