Constraints on the Orbit of the Young Substellar Companion GQ Lup B from High-resolution Spectroscopy and VLTI/GRAVITY Astrometry <sup>*</sup>

Abstract Understanding the orbits of giant planets is critical for testing planet formation models, particularly at wide separations (&gt;10 au) where traditional core accretion becomes inefficient. However, constraining orbits at these separations has historically been challenging due to sparse orbital coverage and related degeneracies in the orbital parameters. In this work, we use existing high-resolution ( R ∼ 100,000) spectroscopic measurements from CRIRES+, astrometric data from SPHERE, NACO, and Atacama Large Millimeter/submillimeter Array, and combine it with new high-precision GRAVITY astrometry data to refine the orbit of GQ Lup B, a ∼30 M J companion at ∼100 au, in a system that also hosts a circumstellar disk and a wide companion, GQ Lup C. Including radial velocity (RV) data significantly improves orbital constraints by breaking the degeneracy between inclination and eccentricity that plagues astrometry-only fits for long-period companions. Our work is one of the first to combine high-precision astrometry with the companion’s relative radial velocity measurements to achieve significantly improved orbital constraints. The eccentricity is refined from <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>e</mml:mi> <mml:mo>=</mml:mo> <mml:mn>0.4</mml:mn> <mml:msubsup> <mml:mrow> <mml:mn>7</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.16</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.14</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> (GRAVITY only) to <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>e</mml:mi> <mml:mo>=</mml:mo> <mml:mn>0.3</mml:mn> <mml:msubsup> <mml:mrow> <mml:mn>5</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.09</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.10</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> when RVs and GRAVITY data are combined. We also compute the mutual inclinations between the orbit of GQ Lup B, the circumstellar disk, the stellar spin axis, and the disk of GQ Lup C. The orbit is misaligned by <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>6</mml:mn> <mml:msubsup> <mml:mrow> <mml:mn>3</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>14</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>6</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> ° relative to the circumstellar disk, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>5</mml:mn> <mml:msubsup> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>24</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>19</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> ° with the host star’s spin axis, but appears more consistent ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>3</mml:mn> <mml:msubsup> <mml:mrow> <mml:mn>4</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>13</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>6</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> °) with the inclination of the wide tertiary companion GQ Lup C’s disk. These results support a formation scenario for GQ Lup B consistent with cloud fragmentation. They highlight the power of combining companion RV constraints with interferometric astrometry to probe the dynamics and formation of wide-orbit substellar companions.

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The Astrophysical Journal
Published
2025-10-24
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https://doi.org/10.3847/1538-4357/ae0c15
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1
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Stellar, planetary, and galactic studies
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article
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article

Constraints on the Orbit of the Young Substellar Companion GQ Lup B from High-resolution Spectroscopy and VLTI/GRAVITY Astrometry *

Jens Kammerer, Gabriel-Dominique Marleau, C. Straubmeier, A.-L. Maire et al.
1 citations
The Astrophysical Journal
Stellar, planetary, and galactic studies
1.15
article

Constraints on the Orbit of the Young Substellar Companion GQ Lup B from High-resolution Spectroscopy and VLTI/GRAVITY Astrometry *

Jens Kammerer, Gabriel-Dominique Marleau, C. Straubmeier, A.-L. Maire, S. Lacour, Sasha Hinkley, V. Lapeyrère, D. C. Ribeiro, C. Paladini, M. Houllé, Élodie Choquet, S. Hippler, William O. Balmer, A. Cridland, Jean-Philippe Berger, J. Shangguan, F. Cantalloube, A. Chomez, C. Mordasini, Emily Rickman, Laura Kreidberg, R. Genzel, N. Pourré, A. Eckart, T. Paumard, É. Gendron, Karl Wagner, H. Beust, T. Stolker, G. Bourdarot, J. Stadler, G. Heißel, Sarah Blunt, Vidya Venkatesan, J. H. Girard, A. Mérand, G. Perrin, Samuel R. Grant, D. Lutz, A. Boccaletti, N. T. Kurtovic, E. Sturm, Zafar Rustamkulov, Julien M. Woillez, L. Jocou, F. Widmann, G. P. P. L. Otten, Valentin Christiaens, G. Duvert, Ş. Yazıcı, A. Amorim, R. Asensio-Torres, E. Nasedkin, R. L. Davies, D. Mouillet, Thomas Shimizu, Aomawa L. Shields, S. Gillessen, O. Straub, Gavin A. L. Coleman, G. Chauvin, J.-B. Le Bouquin, David K. Sing, X. Haubois, Thomas Henning, B. Charnay, Simon Petrus, R. Dembet, Laurent Pueyo, L. J. Tacconi, S. D. von Fellenberg, M. Bonnefoy, R. Abuter, A. Vigan, M. Keppler, Thomas Ott, P. Caselli, T. O. Winterhalder, Jason Wang, R. Garcia Lopez, Frédéric E. Vincent, N. M. Förster Schreiber, J. Dexter, F. Eisenhauer, A. Drescher, Y. Clénet, K. Perraut, W. Brandner, O. Pfuhl, F. Mang, Mathias Nowak, P. Kervella, P. Garcia, A. Sivaramakrishnan, A.‐M. Lagrange, L. Guerrero, V. Coudé du Foresto, Z. Hubert, M. S. Bordoni, A. Chavez, H. Bonnet
article en
1 citations

Abstract

Abstract Understanding the orbits of giant planets is critical for testing planet formation models, particularly at wide separations (&gt;10 au) where traditional core accretion becomes inefficient. However, constraining orbits at these separations has historically been challenging due to sparse orbital coverage and related degeneracies in the orbital parameters. In this work, we use existing high-resolution ( R ∼ 100,000) spectroscopic measurements from CRIRES+, astrometric data from SPHERE, NACO, and Atacama Large Millimeter/submillimeter Array, and combine it with new high-precision GRAVITY astrometry data to refine the orbit of GQ Lup B, a ∼30 M J companion at ∼100 au, in a system that also hosts a circumstellar disk and a wide companion, GQ Lup C. Including radial velocity (RV) data significantly improves orbital constraints by breaking the degeneracy between inclination and eccentricity that plagues astrometry-only fits for long-period companions. Our work is one of the first to combine high-precision astrometry with the companion’s relative radial velocity measurements to achieve significantly improved orbital constraints. The eccentricity is refined from <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>e</mml:mi> <mml:mo>=</mml:mo> <mml:mn>0.4</mml:mn> <mml:msubsup> <mml:mrow> <mml:mn>7</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.16</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.14</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> (GRAVITY only) to <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>e</mml:mi> <mml:mo>=</mml:mo> <mml:mn>0.3</mml:mn> <mml:msubsup> <mml:mrow> <mml:mn>5</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.09</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.10</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> when RVs and GRAVITY data are combined. We also compute the mutual inclinations between the orbit of GQ Lup B, the circumstellar disk, the stellar spin axis, and the disk of GQ Lup C. The orbit is misaligned by <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>6</mml:mn> <mml:msubsup> <mml:mrow> <mml:mn>3</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>14</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>6</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> ° relative to the circumstellar disk, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>5</mml:mn> <mml:msubsup> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>24</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>19</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> ° with the host star’s spin axis, but appears more consistent ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>3</mml:mn> <mml:msubsup> <mml:mrow> <mml:mn>4</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>13</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>6</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> °) with the inclination of the wide tertiary companion GQ Lup C’s disk. These results support a formation scenario for GQ Lup B consistent with cloud fragmentation. They highlight the power of combining companion RV constraints with interferometric astrometry to probe the dynamics and formation of wide-orbit substellar companions.

The Astrophysical JournalVol. 993(1)
University College Dublin (IE), Northwestern University (US), University of Bern (CH), Leiden University (NL), Centre National de la Recherche Scientifique (FR), Space Telescope Science Institute (US), Goddard Space Flight Center (US), Institute of Astronomy and Astrophysics, Academia Sinica (TW), European Southern Observatory (DE), Joint Institute for Laboratory Astrophysics (US), University of Arizona (US), University of Lisbon (PT), Johns Hopkins University (US), University of Liège (BE), Queen Mary University of London (GB), University of Cologne (DE), Universidade do Porto (PT), University of California, Santa Cruz (US), Université Côte d'Azur (FR), Peking University (CN), University of California, Irvine (US), Université Paris Cité (FR), Aix-Marseille Université (FR), University of Exeter (GB), University of Cambridge (GB), Sorbonne Université (FR), Sorbonne Paris Cité (FR), Max Planck Institute for Extraterrestrial Physics (DE), Excellence Cluster Origins (DE), Max Planck Institute for Astrophysics (DE), Kavli Institute for Theoretical Sciences (CN), Max Planck Institute for Astronomy (DE), Université Bourgogne Franche-Comté (FR), Observatoire de la Côte d’Azur (FR), Institute of Applied Physics (MD), European Southern Observatory (CL), Max Planck Institute for Radio Astronomy (DE), European Space Research and Technology Centre (NL), University of Duisburg-Essen (DE), International Space Science Institute (CH), Université Grenoble Alpes (FR), University of California, Berkeley (US)
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