The 55 Cancri planetary system: fully self-consistent N-body constraints and a dynamical analysis

Nelson, Benjamin E.; Ford, Eric B.; Wright, Jason T.; Fischer, Debra A.; Braun, Kaspar von; Howard, Andrew W.; Payne, Matthew J.; Dindar, Saleh

doi:10.1093/mnras/stu450

Cited by 86 publications

(41 citation statements)

References 40 publications

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“…Notably, the three complementary methods all yielded the same conclusions, resulting in a mass measurement for the innermost planet that is not only precise but also robust. Demory et al 2011Demory et al , 2016Winn et al 2011;Nelson et al 2014), CoRoT-7b (Léger et al 2009;Queloz et al 2009;Haywood et al 2014), WASP-47e (Becker et al 2015;Dai et al 2015;Sinukoff et al 2017b;Vanderburg et al 2017), Kepler-78b (Howard et al 2013;Pepe et al 2013;Sanchis-Ojeda et al 2013;Hatzes 2014;Grunblatt et al 2015), Kepler-10b (Batalha et al 2011;Dumusque et al 2014;Weiss et al 2016;Rajpaul et al 2017), K2-131b , HD 3167b (Vanderburg et al 2016a;Christiansen et al 2017;Gandolfi et al 2017, respectively labeled as C17 and G17 in the plot), K2-106b (Guenther et al 2017;Sinukoff et al 2017a, G17 and S17 respectively). Notably, the last two planets have two independent density measurements that are not consistent with each other, resulting in a disagreement in the interpretation of the internal composition.…”

Section: Discussionmentioning

confidence: 99%

An Ultra-short Period Rocky Super-Earth with a Secondary Eclipse and a Neptune-like Companion around K2-141

et al. 2018

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Ultra-short period (USP) planets are a class of low-mass planets with periods shorter than one day. Their origin is still unknown, with photo-evaporation of mini-Neptunes and in situ formation being the most credited hypotheses. Formation scenarios differ radically in the predicted composition of USP planets, and it is therefore extremely important to increase the still limited sample of USP planets with precise and accurate mass and density measurements. We report here the characterization of a USP planet with a period of 0.28 days around K2-141 (EPIC 246393474), and the validation of an outer planet with a period of 7.7 days in a grazing transit configuration. We derived the radii of the planets from the K2 light curve and used high-precision radial velocities gathered with the HARPS-N spectrograph for mass measurements. For K2-141b, we thus inferred a radius of 1.51±0.05R Å and a mass of 5.08±0.41M Å , consistent with a rocky composition and lack of a thick atmosphere. K2-141c is likely a Neptune-like planet, although due to the grazing transits and the non-detection in the RV data set, we were not able to put a strong constraint on its density. We also report the detection of secondary eclipses and phase curve variations for K2-141b. The phase variation can be modeled either by a planet with a geometric albedo of 0.30±0.06 in the Kepler bandpass, or by thermal emission from the surface of the planet at ∼3000 K. Only follow-up observations at longer wavelengths will allow us to distinguish between these two scenarios.

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Section: Discussionmentioning

confidence: 99%

An Ultra-short Period Rocky Super-Earth with a Secondary Eclipse and a Neptune-like Companion around K2-141

et al. 2018

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“…Again, we keep forward and reverse scans separated as their initial scanning positions are close to the two vertically opposite edges of the frame. Nelson et al (2014). e Dragomir et al (2014).…”

Section: Extracting the Spectro-photometric Light Curvesmentioning

confidence: 99%

Detection of an Atmosphere Around the Super-Earth 55 Cancri E

Tsiaras

Rocchetto

Waldmann

et al. 2016

ApJ

258

238

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We report the analysis of two new spectroscopic observations in the near-infrared of the super-Earth 55 Cancri e, obtained with the WFC3 camera on board the Hubble Space Telescope. 55 Cancri e orbits so close to its parent star that temperatures much higher than 2000 K are expected on its surface. Given the brightness of 55 Cancri, the observations were obtained in scanning mode, adopting a very long scanning length and a very high scanning speed. We use our specialized pipeline to take into account systematics introduced by these observational parameters when coupled with the geometrical distortions of the instrument. We measure the transit depth per wavelength channel with an average relative uncertainty of 22 ppm per visit and find modulations that depart from a straight line model with a 6σ confidence level. These results suggest that 55 Cancri e is surrounded by an atmosphere, which is probably hydrogen-rich. Our fully Bayesian spectral retrieval code,  -REx, has identified HCN to be the most likely molecular candidate able to explain the features at 1.42 and 1.54 μm. While additional spectroscopic observations in a broader wavelength range in the infrared will be needed to confirm the HCN detection, we discuss here the implications of such a result. Our chemical model, developed with combustion specialists, indicates that relatively high mixing ratios of HCN may be caused by a high C/O ratio. This result suggests this super-Earth is a carbon-rich environment even more exotic than previously thought.

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“…Integrating one of the best-fit solutions with high eccentricities for b, c and d at 0.23, 0.20 and 0.18 respectively, we confirmed that the orbits were stable for over 1 Gyr; the apsidal lock was maintained with periapses of all three planets closely aligned. Although rare in the Solar System, apsidal alignment has been observed and studied in the Uranian ring system 47,48 and it has been detected in exoplanetary systems, including υ Andromedae 49 , GJ 876 50 and possibly 55 Cancri 51 .…”

Section: Orbital Eccentricitymentioning

confidence: 99%

The mass of the Mars-sized exoplanet Kepler-138 b from transit timing

Jontof-Hutter¹,

Rowe²,

Lissauer³

et al. 2015

Nature

Self Cite

122

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Extrasolar planets that pass in front of their host star (transit) cause a temporary decrease in the apparent brightness of the star once per orbit, providing a direct measure of the planet's size and orbital period. In some systems with multiple transiting planets, the times of the transits are measurably affected by the gravitational interactions between neighbouring planets 1,2 . In favorable cases, the departures from Keplerian orbits implied by the observed transit times permit planetary masses to be measured, which is key to determining bulk densities 3 . Characterizing rocky planets is particularly difficult, since they are generally smaller and less massive than gaseous planets. Thus, few exoplanets near Earth's size have had their masses measured. Here we report the sizes and masses of three planets orbiting Kepler-138, a star much fainter and cooler than the Sun. We measure the mass of the Mars-sized inner planet based on on the transit times of its neighbour and thereby provide the first density measurement for an exoplanet smaller than Earth. The middle and outer planets are both slightly larger than Earth. The middle planet's density is similar to that of Earth, while the outer planet is less than half as dense, implying that it contains a greater portion of low density components such as H 2 O and/or H 2 .NASA's Kepler mission has discovered thousands of candidate transiting exoplanets, with a wide range of planetary sizes 4,5,6 . A small fraction of these planets have had their masses characterized, by either radial velocity spectroscopy (RV) or via transit timing. The latter probes the gravitational perturbations between planets in multi-planet systems by precisely measuring transit times and fitting dynamical models to the observed transit timing variations (TTV) 1,2 . Both RV and TTV signals are larger for more massive planets, improve with greater planetary masses, although the two techniques sample different populations of exoplanets. The RV technique measures the motion of a host star induced by its planet's gravity, and hence the signal declines with increasing orbital distance. The majority of planets with mass determinations via RV from Kepler's dataset have orbital periods shorter than one week. For Kepler-discovered planets characterized as rocky by this method, the orbital periods are all less than one day. Of the RV detections, Kepler-78 b has the lowest mass, (1.7 M Earth ), and the shortest orbital period-0.35 days 7,8 . Characterizing planets by transit timing is quite complementary to RV because transit timing is very sensitive to perturbations between planets that are closely spaced or near orbital resonances 3,9 . Note that most systems with detected TTVs are not in resonance, but rather near enough to resonance for the perturbations to be coherent for many orbital periods, while also far enough from resonance that the planetary """""""""""""""""""""""""""""""""""""""""""""""""""""""" 1 "Department"of"Astronomy,"Pennsylvania"State"University,"Davey"Lab,"University"Park," PA"1680...

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The 55 Cancri planetary system: fully self-consistent N-body constraints and a dynamical analysis

Cited by 86 publications

References 40 publications

An Ultra-short Period Rocky Super-Earth with a Secondary Eclipse and a Neptune-like Companion around K2-141

An Ultra-short Period Rocky Super-Earth with a Secondary Eclipse and a Neptune-like Companion around K2-141

Detection of an Atmosphere Around the Super-Earth 55 Cancri E

The mass of the Mars-sized exoplanet Kepler-138 b from transit timing

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