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arXiv · 2610.02783

Joint RV-Astrometric Analysis of two-planet system HD 65216: Prospects for Gaia DR4

Alexander L. Wallace·Robert A. Wittenmyer·Jonathan Horner
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Abstract

We provide updated mass and orbital constraints on the planetary system around HD 65216, consisting of at least two giant planets on eccentric orbits. We first analyse new RV data to constrain the periods and eccentricities of both planets, before applying the Hipparcos-Gaia proper motion anomaly to constrain the inclination of HD 65216 c. From this joint analysis, we find that HD 65216 c is most likely in an eccentric orbit ($e$ = 0.42$\pm$0.05) with a longer period (7007$^{+192}_{-161}$ days) than previously determined. The proper motion anomaly is consistent with a bimodal distribution of inclinations, with peaks at sin$i\sim$0.5, producing true masses of 2.23$^{+0.96}_{-0.77}$ M$_{\mathrm{J}}$ and 3.32$^{+1.40}_{-1.16}$ M$_{\mathrm{J}}$ for HD 65216 b and c respectively, assuming the planets are co-planar. Finally, we simulate Gaia DR4 epoch astrometry and the DR3-DR4 proper motion anomaly. We find that these methods will be sensitive enough to further constrain orbital parameters and true mass.

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Alexander L. Wallace, Robert A. Wittenmyer, Jonathan Horner. 2026-10-02. Joint RV-Astrometric Analysis of two-planet system HD 65216: Prospects for Gaia DR4. https://doi.org/10.1017/pasa.2026.10270

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