Magellan/PFS Radial Velocities of GJ 9827, a Late K dwarf at 30 pc with Three Transiting Super-Earths

Teske, Johanna; Wang, Sharon X.; Wolfgang, Angie; Dai, Fei; Shectman, Stephen; Butler, R. Paul; Crane, Jeffrey D.; Thompson, I. B.

doi:10.3847/1538-3881/aaab56

Cited by 19 publications

(28 citation statements)

References 67 publications

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“…This mass and radius would suggest that GJ 9827 b has an iron core that makes up a significant fraction of its mass, and could indicate that it has undergone a mantle-stripping collision with another body of a similar mass (Marcus et al 2010). A more recent analysis (Prieto-Arranz et al 2018), however, suggests that the mass of GJ 9827 b is not as high as suggested by Teske et al (2018) and, in fact, may have a composition similar to that of the Earth. This analysis also suggests that GJ 9827 c is also rocky, but that GJ 9827 d may retain a substantial, extended atmosphere.…”

Section: Introductionmentioning

confidence: 89%

“…In addition to the HARPS-N and HARPS spectra, we also include in our analysis the Magellan/PFS observations first presented by Teske et al (2018). Thirty-six PFS observations were taken between January 2010 and August 2016, using the Planet Finder Spectrograph (PFS: Crane et al 2006) on the Magellan II (Clay) Telescope.…”

Section: Previously Published Magellan/pfs and Not/fies Spectroscopymentioning

confidence: 99%

“…A recent radial velocity analysis (Teske et al 2018) has, however, presented mass estimates for the GJ 9827 planets. This analysis was unable to place strong constraints on the masses of GJ 9827 c and d, but suggests that GJ 9827 b has a mass of ∼ 8.2 ± 1.53M⊕.…”

Section: Introductionmentioning

confidence: 99%

“…We also use the K2 lightcurve to constrain the stellar activity (Section 5). We then carry out a radial velocity analysis using the same radial velocity data as used by Teske et al (2018), Niraula et al (2017) and Prieto-Arranz et al (2018), but with an additional 41 new radial velocities from the HARPS-N spectrograph (Cosentino et al 2012(Cosentino et al , 2014. As we will discuss in Section 7, we were able to constrain the masses of GJ 9827 b and d to better than "10%" and about "20%", but were not able to place a strong constraint on the mass of GJ 9827 c. We also discuss what these results imply about the typical composition of planets below the radius gap (Fulton et al 2017), a particular science goal of the HARPS-N Collaboration.…”

Section: Introductionmentioning

confidence: 99%

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Masses and radii for the three super-Earths orbiting GJ 9827, and implications for the composition of small exoplanets

Rice

Malavolta

Mayo

et al. 2019

Monthly Notices of the Royal Astronomical Society

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Super-Earths belong to a class of planet not found in the Solar System, but which appear common in the Galaxy. Given that some super-Earths are rocky, while others retain substantial atmospheres, their study can provide clues as to the formation of both rocky planets and gaseous planets, and -in particular -they can help to constrain the role of photo-evaporation in sculpting the exoplanet population. GJ 9827 is a system already known to host 3 super-Earths with orbital periods of 1.2, 3.6 and 6.2 days. Here we use new HARPS-N radial velocity measurements, together with previously published radial velocities, to better constrain the properties of the GJ 9827 planets. Our analysis can't place a strong constraint on the mass of GJ 9827 c, but does indicate that GJ 9827 b is rocky with a composition that is probably similar to that of the Earth, while GJ 9827 d almost certainly retains a volatile envelope. Therefore, GJ 9827 hosts planets on either side of the radius gap that appears to divide super-Earths into pre-dominantly rocky ones that have radii below ∼ 1.5R ⊕ , and ones that still retain a substantial atmosphere and/or volatile components, and have radii above ∼ 2R ⊕ . That the less heavily irradiated of the 3 planets still retains an atmosphere, may indicate that photoevaporation has played a key role in the evolution of the planets in this system.

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Section: Introductionmentioning

confidence: 89%

Section: Previously Published Magellan/pfs and Not/fies Spectroscopymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Masses and radii for the three super-Earths orbiting GJ 9827, and implications for the composition of small exoplanets

Rice

Malavolta

Mayo

et al. 2019

Monthly Notices of the Royal Astronomical Society

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“…K2-133 is comparable to the GJ-9827 system -three super-Earths orbiting a late K star with radii 1.6, 1.2 and 2.0 R ⊕ (Niraula et al 2017), which has been studied in great detail with precise radial velocity measurements (Teske et al 2018;Prieto-Arranz et al 2018;Rice et al 2019). A similar follow-up study of K2-133 would be interesting as a comparison to the GJ 9827 system.…”

Section: Radius Gapmentioning

confidence: 97%

Validation of a temperate fourth planet in the K2-133 multiplanet system

Wells

Poppenhaeger

Watson

2019

Monthly Notices of the Royal Astronomical Society

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We present follow-up observations of the K2-133 multi-planet system. Previously, we announced that K2-133 contained three super-Earths orbiting an M1.5V host starwith tentative evidence of a fourth outer-planet orbiting at the edge of the temperate zone. Here we report on the validation of the presence of the fourth planet, determining a radius of 1.73 +0.14 −0.13 R ⊕ . The four planets span the radius gap of the exoplanet population, meaning further follow-up would be worthwhile to obtain masses and test theories of the origin of the gap. In particular, the trend of increasing planetary radius with decreasing incident flux in the K2-133 system supports the claim that the gap is caused by photo-evaporation of exoplanet atmospheres. Finally, we note that K2-133 e orbits on the edge of the stars temperate zone, and that our radius measurement allows for the possibility that this is a rocky world. Additional mass measurements are required to confirm or refute this scenario.

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Mass determination of the 1:3:5 near-resonant planets transiting GJ 9827 (K2-135)

Prieto-Arranz

Πάλλη

Gandolfi

et al. 2018

A&A

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Context. Multi-planet systems are excellent laboratories to test planet formation models, since all planets are formed under the same initial conditions. In this context, systems transiting bright stars can play a key role, since planetary masses, radii, and bulk densities can be accurately measured. Aims. GJ 9827 (K2-135) has recently been found to host a tightly packed system consisting of three transiting small planets whose orbital periods of 1.2, 3.6, and 6.2 days are near the 1:3:5 ratio. GJ 9827 hosts the nearest planetary system (d = 30.32 ± 1.62 pc) detected by Kepler and K2. Its brightness (V = 10.35 mag) makes the star an ideal target for detailed studies of the properties of its planets. Methods. Combining the K2 photometry with high-precision radial-velocity measurements gathered with the FIES, HARPS, and HARPS-N spectrographs we revise the system parameters and derive the masses of the three planets.Results. We find that GJ 9827 b has a mass of M b = 3.74 +0.50 −0.48 M ⊕ and a radius of R b = 1.62 +0.17 −0.16 R ⊕ , yielding a mean density of ρ b = 4.81 +1.97 −1.33 g cm −3 . GJ 9827 c has a mass of M c = 1.47 +0.59 −0.58 M ⊕ , radius of R c = 1.27 +0.13 −0.13 R ⊕ , and a mean density of ρ c = 3.87 +2.38 −1.71 g cm −3 . For GJ 9827 d we derive M d = 2.38 +0.71 −0.69 M ⊕ , R d = 2.09 +0.22 −0.21 R ⊕ , and ρ d = 1.42 +0.75 −0.52 g cm −3. Conclusions. GJ 9827 is one of the few known transiting planetary systems for which the masses of all planets have been determined with a precision better than 30%. This system is particularly interesting because all three planets are close to the limit between super-Earths and mini-Neptunes. We also find that the planetary bulk compositions are compatible with a scenario where all three planets formed with similar core/atmosphere compositions, and we speculate that while GJ 9827 b and GJ 9827 c lost their atmospheric envelopes, GJ 9827 d maintained its atmosphere, owing to the much lower stellar irradiation. This makes GJ 9827 one of the very few systems where the dynamical evolution and the atmospheric escape can be studied in detail for all planets, helping us to understand how compact systems form and evolve.

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Magellan/PFS Radial Velocities of GJ 9827, a Late K dwarf at 30 pc with Three Transiting Super-Earths

Cited by 19 publications

References 67 publications

Masses and radii for the three super-Earths orbiting GJ 9827, and implications for the composition of small exoplanets

Masses and radii for the three super-Earths orbiting GJ 9827, and implications for the composition of small exoplanets

Validation of a temperate fourth planet in the K2-133 multiplanet system

Mass determination of the 1:3:5 near-resonant planets transiting GJ 9827 (K2-135)

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