The GAPS programme at TNG LXVIII. Characterization of the outer substellar companion around HD 72659 with a multitechnique approach

ABSTRACT Before discovering the first exoplanets, the radial velocity (RV) method had been used for decades to discover binary stars. Despite significant advancements in this technique, it is limited by the intrinsic mass-inclination degeneracy that can be broken when combining RVs with astrometry, which allows us to determine the orbital inclination, or direct imaging, from which we can estimate the true mass of the target. HD 72659 is a solar analogue known to host a gas giant on a $\sim 10$-yr orbit and a massive outer companion. This work aims to confirm HD 72659 c, which was recently announced using data from HIRES and HARPS spectrographs in combination with Gaia’s astrometric data. We monitored HD 72659 with HARPS-N in the framework of the GAPS project since 2012. We now combined our 91 spectra with literature data and Gaia DR3 high-precision astrometry to constrain the mass and the orbit of this object ($M_{\rm c} \sim 19$ $M_{\rm J}$, $a \sim 21$ au) that falls in the Brown Dwarf desert. Moreover, we analysed our high-resolution imaging observation taken with SPHERE, but since the target was not detected, we could only derive upper limits on its mass. We characterize the orbital parameters of HD 72659 c, confirming the literature mass of this object but finding a period twice as high as previously reported, and we also refine the parameters of planet b with reduced uncertainties compared to previous works. Finally, we analyse and discuss the dynamic configuration of this system, finding that the Kozai–Lidov mechanism may be at work.

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Journal
Monthly Notices of the Royal Astronomical Society
Published
2025-07-30
DOI
https://doi.org/10.1093/mnras/staf1251
Primary Topic
Stellar, planetary, and galactic studies
Type
article
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article

The GAPS programme at TNG LXVIII. Characterization of the outer substellar companion around HD 72659 with a multitechnique approach

Markus R. Meyer, L. Malavolta, D. Barbato, S. Desidera et al.
Monthly Notices of the Royal Astronomical Society
Stellar, planetary, and galactic studies
article

The GAPS programme at TNG LXVIII. Characterization of the outer substellar companion around HD 72659 with a multitechnique approach

Markus R. Meyer, L. Malavolta, D. Barbato, S. Desidera, M. Pinamonti, V. D’Orazi, R. Claudi, A. F. Lanza, D. Mesa, F. Marzari, T. Zingales, Alessandro Sozzetti, A. F. Martínez Fiorenzano, K. Biazzo, M. Bonavita, Luca Naponiello, C. Lazzoni, C. Ginski, G. Scandariato, R. Cosentino, M. Rainer, P. Giacobbe, R. Gratton, D. Nardiello, Luigi Mancini, A. Ruggieri
article en

Abstract

ABSTRACT Before discovering the first exoplanets, the radial velocity (RV) method had been used for decades to discover binary stars. Despite significant advancements in this technique, it is limited by the intrinsic mass-inclination degeneracy that can be broken when combining RVs with astrometry, which allows us to determine the orbital inclination, or direct imaging, from which we can estimate the true mass of the target. HD 72659 is a solar analogue known to host a gas giant on a $\sim 10$-yr orbit and a massive outer companion. This work aims to confirm HD 72659 c, which was recently announced using data from HIRES and HARPS spectrographs in combination with Gaia’s astrometric data. We monitored HD 72659 with HARPS-N in the framework of the GAPS project since 2012. We now combined our 91 spectra with literature data and Gaia DR3 high-precision astrometry to constrain the mass and the orbit of this object ($M_{\rm c} \sim 19$ $M_{\rm J}$, $a \sim 21$ au) that falls in the Brown Dwarf desert. Moreover, we analysed our high-resolution imaging observation taken with SPHERE, but since the target was not detected, we could only derive upper limits on its mass. We characterize the orbital parameters of HD 72659 c, confirming the literature mass of this object but finding a period twice as high as previously reported, and we also refine the parameters of planet b with reduced uncertainties compared to previous works. Finally, we analyse and discuss the dynamic configuration of this system, finding that the Kozai–Lidov mechanism may be at work.

Monthly Notices of the Royal Astronomical SocietyVol. 542(2)
University of Rome Tor Vergata (IT), Roma Tre University (IT), Leiden University (NL), University of Padua (IT), Ollscoil na Gaillimhe – University of Galway (IE), University of Michigan (US), Astronomical Observatory of Rome (IT), Brera Astronomical Observatory (IT), Osservatorio Astrofisico di Torino (IT), Royal Observatory (GB), Osservatorio Astrofisico di Catania (IT), Astronomical Institute of the Slovak Academy of Sciences (SK), COPE Galway (IE), Osservatorio Astronomico di Padova (IT), Telescopio Nazionale Galileo (ES), University of Amsterdam (NL), University of Edinburgh (GB)
Nvidia, Dipartimenti di Eccellenza, European Commission, Istituto Nazionale di Astrofisica
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Stellar, planetary, and galactic studies
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