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Published October 2021 | Accepted Version + Published
Journal Article Open

The mass of β Pictoris c from β Pictoris b orbital motion

Abstract

Aims. We aim to demonstrate that the presence and mass of an exoplanet can now be effectively derived from the astrometry of another exoplanet. Methods. We combined previous astrometry of β Pictoris b with a new set of observations from the GRAVITY interferometer. The orbital motion of β Pictoris b is fit using Markov chain Monte Carlo simulations in Jacobi coordinates. The inner planet, β Pictoris c, was also reobserved at a separation of 96 mas, confirming the previous orbital estimations. Results. From the astrometry of planet b only, we can (i) detect the presence of β Pictoris c and (ii) constrain its mass to 10.04_(−3.10)^(+4.53) M_(Jup). If one adds the astrometry of β Pictoris c, the mass is narrowed down to 9.15_(−1.06)^(+1.08) M_(Jup). The inclusion of radial velocity measurements does not affect the orbital parameters significantly, but it does slightly decrease the mass estimate to 8.89_(−0.75)^(+0.75) M_(Jup). With a semimajor axis of 2.68 ± 0.02 au, a period of 1221 ± 15 days, and an eccentricity of 0.32 ± 0.02, the orbital parameters of β Pictoris c are now constrained as precisely as those of β Pictoris b. The orbital configuration is compatible with a high-order mean-motion resonance (7:1). The impact of the resonance on the planets' dynamics would then be negligible with respect to the secular perturbations, which might have played an important role in the eccentricity excitation of the outer planet.

Additional Information

© S. Lacour et al. 2021. Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Received 28 July 2021; Accepted 26 August 2021; Published online 08 October 2021. Letter based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere, ID 1104.C-0651. This research has made use of the Jean-Marie Mariotti Center Aspro service (http://www.jmmc.fr/aspro). This research also made use of Astropy (http://www.astropy.org), a community-developed core Python package for Astronomy (Astropy Collaboration 2018). J.J.W. is supported by the Heising-Simons Foundation 51 Pegasi b Fellowship. The development of orbitize! is supported by the Heising-Simons Foundation through grant 2019-1698. We acknowledge support from the European Research Council under the Horizon 2020 Framework Program via the ERC grants 832428 (T.H.) and 757561 (A.V. and G.P.P.O.). A.A. and P.G. were supported by Fundação para a Ciência e a Tecnologia, with grants reference UIDB/00099/2020 and PTDC/FIS-AST/7002/2020.

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Accepted Version - 2109.10671.pdf

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Additional details

Created:
August 20, 2023
Modified:
October 23, 2023