Long-period Giant Companions to Three Compact, Multiplanet Systems

π Men hosts a transiting super Earth (P ≈ 6.27 d, m ≈ 4.82 M⊕, R ≈ 2.04 R⊕) discovered by TESS and a cold Jupiter (P ≈ 2093 d, msin I ≈ 10.02 MJup, e ≈ 0.64) discovered from radial velocity. We use Gaia DR2 and Hipparcos astrometry to derive the star’s velocity caused by the orbiting planets and constrain the cold Jupiter’s sky-projected inclination (Ib = 41 − 65○). From this we derive the mutual inclination (ΔI) between the two planets, and find that 49○ < ΔI < 131○ (1σ), and 28○ < ΔI < 152○ (2σ). We examine the dynamics of the system using N-body simulations, and find that potentially large oscillations in the super Earth’s eccentricity and inclination are suppressed by General Relativistic precession. However, nodal precession of the inner orbit around the invariable plane causes the super Earth to only transit between 7-22 per cent of the time, and to usually be observed as misaligned with the stellar spin axis. We repeat our analysis for HAT-P-11, finding a large ΔI between its close-in Neptune and cold Jupiter and similar dynamics. π Men and HAT-P-11 are prime examples of systems where dynamically hot outer planets excite their inner planets, with the effects of increasing planet eccentricities, planet-star misalignments, and potentially reducing the transit multiplicity. Formation of such systems likely involves scattering between multiple giant planets or misaligned protoplanetary discs. Future imaging of the faint debris disc in π Men and precise constraints on its stellar spin orientation would provide strong tests for these formation scenarios.

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“…For example, dedicated RV monitoring of Kepler systems in search for outer CJs would help increase the sample size (e.g. Mills et al 2019).…”

Section: Dynamically Linked Inner and Outer Systemsmentioning

confidence: 99%

Evidence for a high mutual inclination between the cold Jupiter and transiting super Earth orbiting π Men

Xuan

Wyatt

2020

Monthly Notices of the Royal Astronomical Society

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“…The authors argue that if the giant planet has an eccentric orbit, it is very unlikely that the system harbors any inner super-Earths (making the HD 137496 system a counter example). Nevertheless, the presence of a low-mass inner planet together with a cold Jupiter in eccentric and/or mutually inclined orbits has been the object of recent studies (Hansen 2017;Mills et al 2019;Carrera et al 2019;Masuda et al 2020;Poon & Nelson 2020;Pu & Lai 2021). This highlights the need for accurate characterization of such systems for our understanding of planet formation and evolution and stresses the importance of the HD 137496 system.…”

Section: A Low-mass Inner Planet With a Cold Distant Companionmentioning

confidence: 99%

The HD 137496 system: A dense, hot super-Mercury and a cold Jupiter

Silva

Barros

Otegi

et al. 2022

A&A

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Context. Most of the currently known planets are small worlds with radii between that of the Earth and that of Neptune. The characterization of planets in this regime shows a large diversity in compositions and system architectures, with distributions hinting at a multitude of formation and evolution scenarios. However, many planetary populations, such as high-density planets, are significantly under-sampled, limiting our understanding of planet formation and evolution. Aims. NCORES is a large observing program conducted on the HARPS high-resolution spectrograph that aims to confirm the planetary status and to measure the masses of small transiting planetary candidates detected by transit photometry surveys in order to constrain their internal composition. Methods. Using photometry from the K2 satellite and radial velocities measured with the HARPS and CORALIE spectrographs, we searched for planets around the bright (Vmag = 10) and slightly evolved Sun-like star HD 137496. Results. We precisely estimated the stellar parameters, M* = 1.035 ± 0.022 M⊙, R* = 1.587 ± 0.028 R⊙, Teff = 5799 ± 61 K, together with the chemical composition (e.g. [Fe/H] = −0.027 ± 0.040 dex) of the slightly evolved star. We detect two planets orbiting HD 137496. The inner planet, HD 137496 b, is a super-Mercury (an Earth-sized planet with the density of Mercury) with a mass of Mb = 4.04 ± 0.55 M⊕, a radius of Rb = 1.31−0.05+0.06 R⊕, and a density of ρb = 10.49−1.82+2.08 g cm-3. With an interior modeling analysis, we find that the planet is composed mainly of iron, with the core representing over 70% of the planet’s mass (Mcore / Mtotal = 0.73−0.12+0.11). The outer planet, HD 137496 c, is an eccentric (e = 0.477 ± 0.004), long period (P = 479.9−1.1+1.0 days) giant planet (Mc sinic = 7.66 ± 0.11 MJup) for which we do not detect a transit. Conclusions. HD 137496 b is one of the few super-Mercuries detected to date. The accurate characterization reported here enhances its role as a key target to better understand the formation and evolution of planetary systems. The detection of an eccentric long period giant companion also reinforces the link between the presence of small transiting inner planets and long period gas giants.

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“…To improve upon the RV + TTV solution, we used an iterative photodynamical forward-model to simultaneously fit the photometry and RVs of the Kepler-88 system. We used the code Phodymm, which has previously been used to model and fit photometry from the Kepler prime mission in Kepler-223, (Mills et al 2016), Kepler-444 (Mills & Fabrycky 2017a), and Kepler-108 (Mills & Fabrycky 2017b), and the combined Kepler prime photometry and Keck-HIRES RVs in Kepler-25, Kepler-65, and Kepler-68 (Mills et al 2019). Phodymm is a Runge-Kutta N-body integrator that can simultaneously forward-model photometry and RVs for N planets and one star.…”

Section: Photodynamical Fit To Transits and Rvsmentioning

confidence: 99%

“…Giant planets are present around a large number of the Kepler systems that host small, transiting planets (Marcy et al 2014;Mills et al 2019), and perhaps at greater frequency than giant planets occur around field stars (Zhu & Wu 2018;Bryan et al 2019). Kepler-88 joins their ranks.…”

Section: Comparison To Other Planetary Systemsmentioning

confidence: 99%

The Discovery of the Long-Period, Eccentric Planet Kepler-88 d and System Characterization with Radial Velocities and Photodynamical Analysis

Weiss

Fabrycky

Agol

et al. 2020

Self Cite

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We present the discovery of Kepler-88 d (= P d  1403 14 days, =  =  Å M i M M sin 965 44 3.04 0.13 d J , =  e 0.41 0.03 d) based on six years of radial velocity (RV) follow-up from the W. M. Keck Observatory High Resolution Echelle Spectrometer spectrograph. Kepler-88 has two previously identified planets. Kepler-88 b (KOI-142.01) transits in the NASA Kepler photometry and has very large transit timing variations (TTVs). Nesvorný et al. performed a dynamical analysis of the TTVs to uniquely identify the orbital period and mass of the perturbing planet (Kepler-88 c), which was later was confirmed with RVs from the Observatoire de Haute-Provence (OHP). To fully explore the architecture of this system, we performed photodynamical modeling on the Kepler photometry combined with the RVs from Keck and OHP and stellar parameters from spectroscopy and Gaia. Planet d is not detectable in the photometry, and long-baseline RVs are needed to ascertain its presence. A photodynamical model simultaneously optimized to fit the RVs and Kepler photometry yields the most precise planet masses and orbital properties yet for b and c:

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Long-period Giant Companions to Three Compact, Multiplanet Systems

Cited by 51 publications

References 78 publications

Evidence for a high mutual inclination between the cold Jupiter and transiting super Earth orbiting π Men

Evidence for a high mutual inclination between the cold Jupiter and transiting super Earth orbiting π Men

The HD 137496 system: A dense, hot super-Mercury and a cold Jupiter

The Discovery of the Long-Period, Eccentric Planet Kepler-88 d and System Characterization with Radial Velocities and Photodynamical Analysis

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