The Kepler-454 System: A Small, Not-Rocky Inner Planet, a Jovian World, and a Distant Companion

Gettel, Sara; Charbonneau, David; Dressing, Courtney D.; Buchhave, Lars A.; Dumusque, X.; Vanderburg, Andrew; Bonomo, A. S.; Malavolta, L.; Pepe, F.; Cameron, A. Collier; Latham, David W.; Udry, S.; Marcy, Geoffrey W.; Isaacson, Howard; Howard, Andrew W.; Davies, G. R.; Aguirre, V. Silva; Kjeldsen, H.; Bedding, Timothy R.; Lopez, Eric; Affer, L.; Cosentino, R.; Figueira, P.; Fiorenzano, A. F. Martínez; Harutyunyan, A.; Johnson, John Asher; López‐Morales, Mercedes; Lovis, C.; Mayor, M.; Micela, G.; Molinari, E.; Motalebi, F.; Phillips, David F.; Piotto, G.; Queloz, D.; Rice, Ken; Sasselov, Dimitar; Ségransan, D.; Sozzetti, A.; Watson, Chris; Basu, Sarbani; Campante, Tiago L.; Christensen‐Dalsgaard, J.; Kawaler, Steven D.; Metcalfe, T. S.; Handberg, R.; Lund, M. N.; Lundkvist, M.; Huber, Daniel; Chaplin, W. J.

doi:10.3847/0004-637x/816/2/95

Cited by 55 publications

(19 citation statements)

References 66 publications

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“…HARPS-N is an ultra-stable fiber-fed high-resolution (R=115,000) spectrograph with an optical wavelength coverage from 383 to 693 nm, designed specifically to provide precise radial velocities. The instrument has significantly improved our understanding of small transiting planets with several precise mass measurements of transiting planets (Pepe et al 2013;Bonomo et al 2014;Dumusque et al 2014;López-Morales et al 2014;Gettel et al 2016). We obtained 61 and 64 observations of Kepler-20 in the 2014 and 2015 observing seasons, respectively (125 observations in total).…”

Section: Observations and Data Reductionmentioning

confidence: 95%

A 1.9 Earth Radius Rocky Planet and the Discovery of a Non-Transiting Planet in the Kepler-20 System*

Buchhave

Dressing

Dumusque

et al. 2016

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Kepler-20 is a solar-type star (V = 12.5) hosting a compact system of five transiting planets, all packed within the orbital distance of Mercury in our own solar system. A transition from rocky to gaseous planets with a planetary transition radius of ∼1.6 Å R has recently been proposed by several articles in the literature. Kepler-20b (R p ∼1.9 Å R ) has a size beyond this transition radius; however, previous mass measurements were not sufficiently precise to allow definite conclusions to be drawn regarding its composition. We present new mass measurements of three of the planets in the Kepler-20 system that are facilitated by 104 radial velocity measurements from the HARPS-N spectrograph and 30 archival Keck/HIRES observations, as well as an updated photometric analysis of the Kepler data and an asteroseismic analysis of the host star

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Section: Observations and Data Reductionmentioning

confidence: 95%

A 1.9 Earth Radius Rocky Planet and the Discovery of a Non-Transiting Planet in the Kepler-20 System*

Buchhave

Dressing

Dumusque

et al. 2016

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“…The figure shows that most multi-planet systems have mass ratios below 10, and only very few cases present mass ratios above 200. Except for HD 219828, other systems with a mass ratio above 200 include our solar system (not included in the plot), with a Jupiter-to-Mercury mass ratio of almost 4000 7 , GJ 676 A, an M-dwarf where Anglada-Escudé & Tuomi (2012) announced the presence of 2 + 2 super-Earths+jovian planets (see also Forveille et al 2011;Bonfils et al 2013a) with the highest mass ratio of 353, Kepler-94, with a hot Neptune and a moderately long-period (P ∼ 820 days) jovian companion (Marcy et al 2014, a mass ratio of 288, assuming co-planar orbits), and Kepler-454, a system composed of a short-period transiting super-Earth, one jovian gas giant with a period of 524 days, and an additional possible longer period gas giant (Gettel et al 2016, mass ratio of 207 assuming co-planar orbits). We note, however, that at least one of the low-mass planets in the Gl 676 A system has recently been disputed (e.g.…”

Section: Statistics and The Formation Of Hot Neptunesmentioning

confidence: 99%

An extreme planetary system around HD 219828

Santos

Santerne

Faria

et al. 2016

A&A

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Context. With about 2000 extrasolar planets confirmed, the results show that planetary systems have a whole range of unexpected properties. This wide diversity provides fundamental clues to the processes of planet formation and evolution. Aims. We present a full investigation of the HD 219828 system, a bright metal-rich star for which a hot Neptune has previously been detected. Methods. We used a set of HARPS, SOPHIE, and ELODIE radial velocities to search for the existence of orbiting companions to HD 219828. The spectra were used to characterise the star and its chemical abundances, as well as to check for spurious, activity induced signals. A dynamical analysis is also performed to study the stability of the system and to constrain the orbital parameters and planet masses. Results. We announce the discovery of a long period (P = 13.1 yr) massive (m sin i = 15.1 M Jup ) companion (HD 219828 c) in a very eccentric orbit (e = 0.81). The same data confirms the existence of a hot Neptune, HD 219828 b, with a minimum mass of 21 M ⊕ and a period of 3.83 days. The dynamical analysis shows that the system is stable, and that the equilibrium eccentricity of planet b is close to zero. Conclusions. The HD 219828 system is extreme and unique in several aspects. First, ammong all known exoplanet systems it presents an unusually high mass ratio. We also show that systems like HD 219828, with a hot Neptune and a long-period massive companion are more frequent than similar systems with a hot Jupiter instead. This suggests that the formation of hot Neptunes follows a different path than the formation of their hot jovian counterparts. The high mass, long period, and eccentricity of HD 219828 c also make it a good target for Gaia astrometry as well as a potential target for atmospheric characterisation, using direct imaging or high-resolution spectroscopy. Astrometric observations will allow us to derive its real mass and orbital configuration. If a transit of HD 219828 b is detected, we will be able to fully characterise the system, including the relative orbital inclinations. With a clearly known mass, HD 219828 c may become a benchmark object for the range in between giant planets and brown dwarfs.

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“…The coupling of these two observations (the radial velocity and the transit) reveals that the mean density of super-Earths is quite diverse (e.g., Marcy et al 2014;Jontof-Hutter et al 2016;Gettel et al 2016, , see Figure 1). These discoveries in turn stimulate active investigations of super-Earths, since their formation mechanisms are uncertain.…”

Section: Introductionmentioning

confidence: 99%

Super-Earths as Failed Cores in Orbital Migration Traps

Hasegawa

2016

ApJ

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We explore whether close-in super-Earths were formed as rocky bodies that failed to grow fast enough to become the cores of gas giants before the natal protostellar disk dispersed. We model the failed cores' inward orbital migration in the low-mass or type I regime, to stopping points at distances where the tidal interaction with the protostellar disk applies zero net torque. The three kinds of migration traps considered are those due to the dead zone's outer edge, the ice line, and the transition from accretion to starlight as the disk's main heat source. As the disk disperses, the traps move toward final positions near or just outside 1 au. Planets at this location exceeding about 3 M ⊕ open a gap, decouple from their host trap, and migrate inward in the high-mass or type II regime to reach the vicinity of the star. We synthesize the population of planets formed in this scenario, finding that some fraction of the observed super-Earths can be failed cores. Most super-Earths formed this way have more than 4 M ⊕ , so their orbits when the disk disperses are governed by type II migration. These planets have solid cores surrounded by gaseous envelopes. Their subsequent photoevaporative mass loss is most effective for masses originally below about 6 M ⊕ . The failed core scenario suggests a division of the observed super-Earth mass-radius diagram into five zones according to the inferred formation history.

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The Kepler-454 System: A Small, Not-Rocky Inner Planet, a Jovian World, and a Distant Companion

Cited by 55 publications

References 66 publications

A 1.9 Earth Radius Rocky Planet and the Discovery of a Non-Transiting Planet in the Kepler-20 System*

A 1.9 Earth Radius Rocky Planet and the Discovery of a Non-Transiting Planet in the Kepler-20 System*

An extreme planetary system around HD 219828

Super-Earths as Failed Cores in Orbital Migration Traps

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