Exomoon search with VLTI/GRAVITY around the substellar companion HD 206893 B

Context. This study presents the first application of high-precision astrometry to search for exomoons around substellar companions, as this field remains largely unexplored. Aims. We investigate whether the orbital motion of the companion HD 206893 B exhibits astrometric residuals consistent with the gravitational influence of an exomoon or binary planet. Methods. Using the VLTI/GRAVITY instrument, we monitored the astrometric positions of HD 206893 B and c on short (days to months) and long (yearly) timescales. This enabled us to isolate potential residual wobbles in the motion of component B attributable to an orbiting moon. Results. Our analysis reveals tentative astrometric residuals in the HD 206893 B orbit. If interpreted as an exomoon signature, these residuals correspond to a candidate (HD 206893 B I) with an orbital period of approximately 0.76 years and a mass of ~0.4 Jupiter masses. However, the origin of these residuals remains ambiguous and could be due to systematics. Complementing the astrometry, our analysis of GRAVITY R = 4000 spectroscopy for HD 206893 B confirms a clear detection of water, but no CO was found using cross-correlation. We also found that AF Lep b, and β Pic b are the best short-term candidates to look for moons with GRAVITY+. Conclusions. Our observations demonstrate the transformative potential of high-precision astrometry in the search for exomoons and proves the feasibility of the technique to detect moons with masses lower than Jupiter and potentially down to less than Neptune in optimistic cases. Crucially, further high-precision astrometric observations with VLTI/GRAVITY are essential to verify the reality and nature of this signal and apply this technique to a range of planetary systems.

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Publication Details

Journal
Springer Link (Chiba Institute of Technology)
Published
2026-01-29
DOI
https://doi.org/10.1051/0004-6361/202557127/pdf
Primary Topic
Stellar, planetary, and galactic studies
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article
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article

Exomoon search with VLTI/GRAVITY around the substellar companion HD 206893 B

C. A. Perrot, Élise Choquet, F. Dérie, A. Drescher et al.
Springer Link (Chiba Institute of Technology)
Stellar, planetary, and galactic studies
article

Exomoon search with VLTI/GRAVITY around the substellar companion HD 206893 B

C. A. Perrot, Élise Choquet, F. Dérie, A. Drescher, Hervé Beust, A. Cridland, A. Chomez, Laura Kreidberg, R. Genzel, N. Pourré, D. Sing, Benjamin Charnay, T. Stolker, C. Sykes, D. Lutz, Zafar Rustamkulov, Ş. Yazıcı, Mathilde Mâlin, E. Nasedkin, Guillaume Bourdarot, L. Shao, M. Keppler, M. Accardo, D. Mouillet, Stefan Hippler, Yann Clénet, H. Bonnet, G.-D. Marleau, N. M. Förster Schreiber, G. P. P. L. Otten, V. Lapeyrère, T. Ott, F. Eisenhauer, P. Caselli, M. Houllé, E. Gendron, J. Kammerer, C. Paladini, C. Mordasini, S. Hinkley, E. Sturm, M. S. Bordoni, T. Shimizu, P. Mollière, T. Gardner, W. Brandner, K. Perraut, O. Straub, D. C. Ribeiro, S. D. von Fellenberg, A. Vigan, L. Jocou, F. Mang, Z. Hubert, S. Yazici, R. Davies, N. T. Kurtovic, H. Bonnet, A. Amorim, S. Gillessen, X. Haubois, W. O. Balmer, V. Christiaens, J. Dexter, E. Rickman, C. Straubmeier, J. D. Monnier, A.-M. Lagrange, S. Grant, A. Boccaletti, J. Stadler, J.-B. Le Bouquin, V. Coudé du Foresto, O. Pfuhl, G. Duvert, T. Paumard, F. Vincent, P. Garcia, R. Garcia López, M. Nowak, L. Pueyo, A. Eckart, J. Wang, J. H. Girard, A.-L. Maire, A. Chavez, G. Perrin, S. Lacour, P. Kervella, P. Huet, G. Chauvin, Q. Kral, T. Winterhalder, A. Mérand, F. Cantalloube, L. J. Tacconi, J.-P. Berger, M. Benisty, S. Blunt, Th. Henning
article en

Abstract

Context. This study presents the first application of high-precision astrometry to search for exomoons around substellar companions, as this field remains largely unexplored. Aims. We investigate whether the orbital motion of the companion HD 206893 B exhibits astrometric residuals consistent with the gravitational influence of an exomoon or binary planet. Methods. Using the VLTI/GRAVITY instrument, we monitored the astrometric positions of HD 206893 B and c on short (days to months) and long (yearly) timescales. This enabled us to isolate potential residual wobbles in the motion of component B attributable to an orbiting moon. Results. Our analysis reveals tentative astrometric residuals in the HD 206893 B orbit. If interpreted as an exomoon signature, these residuals correspond to a candidate (HD 206893 B I) with an orbital period of approximately 0.76 years and a mass of ~0.4 Jupiter masses. However, the origin of these residuals remains ambiguous and could be due to systematics. Complementing the astrometry, our analysis of GRAVITY R = 4000 spectroscopy for HD 206893 B confirms a clear detection of water, but no CO was found using cross-correlation. We also found that AF Lep b, and β Pic b are the best short-term candidates to look for moons with GRAVITY+. Conclusions. Our observations demonstrate the transformative potential of high-precision astrometry in the search for exomoons and proves the feasibility of the technique to detect moons with masses lower than Jupiter and potentially down to less than Neptune in optimistic cases. Crucially, further high-precision astrometric observations with VLTI/GRAVITY are essential to verify the reality and nature of this signal and apply this technique to a range of planetary systems.

Springer Link (Chiba Institute of Technology)
Openalex Percentile: Top 61%
Stellar, planetary, and galactic studies
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