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Register a new userThe 3-dimensional architecture of the Upsilon Andromedae planetary system
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The Upsilon Andromedae system is the first exoplanetary system to have the relative inclination of two planets orbital planes directly measured, and therefore offers our first window into the 3-dimensional configurations of planetary systems. We present, for the first time, full 3-dimensional, dynamically stable configurations for the 3 planets of the system consistent with all observational constraints. While the outer 2 planets, c and d, are inclined by about 30 degrees, the inner planets orbital plane has not been detected. We use N-body simulations to search for stable 3-planet configurations that are consistent with the combined radial velocity and astrometric solution. We find that only 10 trials out of 1000 are robustly stable on 100 Myr timescales, or about 8 billion orbits of planet b. Planet bs orbit must lie near the invariable plane of planets c and d, but can be either prograde or retrograde. These solutions predict bs mass is in the range 2 - 9 $M_{Jup}$ and has an inclination angle from the sky plane of less than 25 degrees. Combined with brightness variations in the combined star/planet light curve (phase curve), our results imply that planet bs radius is about 1.8 $R_{Jup}$, relatively large for a planet of its age. However, the eccentricity of b in several of our stable solutions reaches values greater than 0.1, generating upwards of $10^{19}$ watts in the interior of the planet via tidal dissipation, possibly inflating the radius to an amount consistent with phase curve observations.
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Upsilon Andromedae is an F8V star known to have an extrasolar system of at least 3 planets in orbit around it. Here we report the discovery of a low-mass stellar companion to this system. The companion shares common proper motion, lies at a projected separation of ~750 AU, and has a spectral type of M4.5V. The effect of this star on the radial velocity of the brighter primary is negligible, but this system provides an interesting testbed for stellar planetary formation theory and understanding dynamical stability since it is the first multiple planetary system known in a multiple stellar system.
The bright star $pi$ Men was chosen as the first target for a radial velocity follow-up to test the performance of ESPRESSO, the new high-resolution spectrograph at the ESOs Very-Large Telescope (VLT). The star hosts a multi-planet system (a transiting 4 M$_oplus$ planet at $sim$0.07 au, and a sub-stellar companion on a $sim$2100-day eccentric orbit) which is particularly appealing for a precise multi-technique characterization. With the new ESPRESSO observations, that cover a time span of 200 days, we aim to improve the precision and accuracy of the planet parameters and search for additional low-mass companions. We also take advantage of new photometric transits of $pi$ Men c observed by TESS over a time span that overlaps with that of the ESPRESSO follow-up campaign. We analyse the enlarged spectroscopic and photometric datasets and compare the results to those in the literature. We further characterize the system by means of absolute astrometry with Hipparcos and Gaia. We used the spectra of ESPRESSO for an independent determination of the stellar fundamental parameters. We present a precise characterization of the planetary system around $pi$ Men. The ESPRESSO radial velocities alone (with typical uncertainty of 10 cm/s) allow for a precise retrieval of the Doppler signal induced by $pi$ Men c. The residuals show an RMS of 1.2 m/s, and we can exclude companions with a minimum mass less than $sim$2 M$_oplus$ within the orbit of $pi$ Men c). We improve the ephemeris of $pi$ Men c using 18 additional TESS transits, and in combination with the astrometric measurements, we determine the inclination of the orbital plane of $pi$ Men b with high precision ($i_{b}=45.8^{+1.4}_{-1.1}$ deg). This leads to the precise measurement of its absolute mass $m_{b}=14.1^{+0.5}_{-0.4}$ M$_{Jup}$, and shows that the planetary orbital planes are highly misaligned.
We evaluate the orbital evolution and several plausible origins scenarios for the mutually inclined orbits of Upsilon Andromedae c and d. These two planets have orbital elements that oscillate with large amplitudes and lie close to the stability boundary. This configuration, and in particular the observed mutual inclination, demands an explanation. The planetary system may be influenced by a nearby low-mass star, Upsilon And B, which could perturb the planetary orbits, but we find it cannot modify two coplanar orbits into the observed mutual inclination of ~30 deg. However, it could incite ejections or collisions between planetary companions that subsequently raise the mutual inclination to >30 deg. Our simulated systems with large mutual inclinations tend to be further from the stability boundary than Upsilon And, but we are able to produce similar systems. We conclude that scattering is a plausible mechanism to explain the observed orbits of Upsilon And c and d, but we cannot determine whether the scattering was caused by instabilities among the planets themselves or by perturbations from Upsilon And B. We also develop a procedure to quantitatively compare numerous properties of the observed system to our numerical models. Although we only implement this procedure to Upsilon And, it may be applied to any exoplanetary system.
We perform numerical simulations to study the secular orbital evolution and dynamical structure in the quintuplet planetary system 55 Cancri with the self-consistent orbital solutions by Fischer and coworkers (2008). In the simulations, we show that this system can be stable at least for $10^{8}$ yr. In addition, we extensively investigate the planetary configuration of four outer companions with one terrestrial planet in the wide region of 0.790 AU $leq a leq $ 5.900 AU to examine the existence of potential asteroid structure and Habitable Zones (HZs). We show that there are unstable regions for the orbits about 4:1, 3:1 and 5:2 mean motion resonances (MMRs) with the outermost planet in the system, and several stable orbits can remain at 3:2 and 1:1 MMRs, which is resemblance to the asteroidal belt in solar system. In a dynamical point, the proper candidate HZs for the existence of more potential terrestrial planets reside in the wide area between 1.0 AU and 2.3 AU for relatively low eccentricities.
Simulations of exoplanet albedo profiles are key to planning and interpreting future direct imaging observations. In this paper we demonstrate the use of the Planetary Spectrum Generator to produce simulations of reflected light exoplanet spectra. We use PSG to examine multiple issues relevant to all models of directly imaged exoplanet spectra and to produce sample spectra of the bright, nearby exoplanet $upsilon$ Andromedae d, a potential direct imaging target for next-generation facilities. We introduce a new, fast, and accurate subsampling technique that enables calculations of disk-integrated spectra one order of magnitude faster than Chebyshev-Gauss sampling for moderate- to high-resolution sampling. Using this method and a first-principles-derived atmosphere for $upsilon$ And d, we simulate phase-dependent spectra for a variety of different potential atmospheric configurations. The simulated spectra for $upsilon$ And d inclu
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