Evidence for an accretion bridge in the DX Cha circumbinary system from VLTI/MATISSE observations

Tímea Juhász; József Varga; Péter Ábrahám; Ágnes Kóspál; Foteini Lykou; Lei Chen; Attila Moór; Fernando Cruz-Sáenz de Miera; Bruno Lopez; Alexis Matter; Roy van Boekel; Michiel Hogerheijde; Margaux Abello; Jean-Charles Augereau; Paul Boley; William C. Danchi; Thomas Henning; Mathis Letessier; Jie Ma; Philippe Priolet; Marten Scheuck; Gerd Weigelt; Sebastian Wolf

arXiv · 2502.11722

Evidence for an accretion bridge in the DX Cha circumbinary system from VLTI/MATISSE observations

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Abstract

DX Cha (HD 104237) is a spectroscopic binary consisting of a Herbig A7.5Ve-A8Ve primary star and a K3-type companion. Here we report on new $3.55$ micrometer interferometric observations of this source with the Multi Aperture Mid-Infrared Spectroscopic Experiment (MATISSE) at the Very Large Telescope Interferometer (VLTI). To model the four MATISSE observations obtained between 2020 and 2023, we constructed a time-dependent interferometric model of the system, using the oimodeler software. The model consists of an asymmetric ring and two point sources on a Keplerian orbit. Our best-fit model consists of a circumbinary ring with a diameter of $0.86$ au ($8.1$ mas), featuring a strong azimuthal asymmetry. We found that the position angle of the asymmetry changes tens of degrees between the MATISSE epochs. The ring is relatively narrow, with a full width at half maximum (FWHM) of $\sim$$0.13$ au ($1.23$ mas). The presence of circumstellar dust emission so close to the binary is unexpected, as previous hydrodynamic simulations predicted an inner disk cavity with a diameter of $\sim$$4$ au ($\sim$$37.5$ mas). Thus, we argue that the narrow envelope of material we detected is probably not a gravitationally stable circumbinary ring, but may be part of tidal accretion streamers channeling material from the inner edge of the disk toward the stars.

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Tímea Juhász, József Varga, Péter Ábrahám, Ágnes Kóspál, Foteini Lykou, Lei Chen, Attila Moór, Fernando Cruz-Sáenz de Miera, Bruno Lopez, Alexis Matter, Roy van Boekel, Michiel Hogerheijde, Margaux Abello, Jean-Charles Augereau, Paul Boley, William C. Danchi, Thomas Henning, Mathis Letessier, Jie Ma, Philippe Priolet, Marten Scheuck, Gerd Weigelt, Sebastian Wolf. 2025-02-17. Evidence for an accretion bridge in the DX Cha circumbinary system from VLTI/MATISSE observations. https://arxiv.org/abs/2502.11722

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