Beyond the exoplanet mass-radius relation

Ulmer-Moll, S.; Santos, N. C.; Figueira, P.; Brinchmann, Jarle; Faria, J. P.

doi:10.1051/0004-6361/201936049

Cited by 25 publications

(19 citation statements)

References 44 publications

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“…Before fitting for the planet's albedo, we first used the posterior mass estimate from the orbit fit and radial velocity semi-amplitude, and then inferred the planet's radius from an empirical mass-radius relationship along with the approximate equilibrium temperature of planet d. 19 A simple least-squares optimization finds the albedo that minimizes the distance between the 4 epochs of photometry and the Lambertian phase curve associated with the orbit posteriors. The result, in Figure 6, illustrates the four photometric data points, the best-fit flux curve, and the flux curve of the true planet parameters.…”

Section: Photometry and Phase Curve Analysismentioning

confidence: 99%

Community exoplanet imaging data challenge for Roman CGI and starshade rendezvous

Turnbull

Zimmerman

Girard

et al. 2021

J. Astron. Telesc. Instrum. Syst.

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Operating in an unprecedented contrast regime (10 −7 to 10 −9 ), the Roman Coronagraph Instrument (CGI) will serve as a pathfinder for key technologies needed for future Earth-finding missions such as HabEx and LUVOIR. The Roman Exoplanet Imaging Data Challenge (Roman EIDC) was a community engagement effort that tasked participants with extracting exoplanets and their orbits for a 47-UMa-like target star given: (1) 15 years of simulated precursor radial velocity (RV) data and (2) six epochs of simulated imaging taken over the course of the Roman mission. Led by the Turnbull CGI Science Investigation Team, the Roman EIDC was preceded by four tutorial "hack-a-thon" events in Baltimore, Pasadena, New York City, and Tokyo. The Roman EIDC officially launched in October 2019 and ran for 8 months, offering a unique opportunity for exoplanet scientists of all experience levels to get acquainted with realistic near-future imaging data. The Roman EIDC simulated images include four epochs with CGI's Hybrid Lyot Coronagraph (HLC) plus two epochs with a starshade (SS) assumed to arrive as part of a Starshade Rendezvous later in the mission. We focus on our in-house analysis of the outermost planet "d," for which the SS's higher throughput and lower noise floor present a factor of ∼4 improvement in the signal-to-noise ratio over the narrow-field HLC. We find that, although the RV detection was marginal for planet d, the precursor RV data enabled the mass and orbit to be constrained with only two epochs of SS imaging. Including the HLC images in the analysis results in improved measurements over RV + SS alone, with the greatest gains resulting from images taken at epochs near maximum elongation. Combining the two epochs of SS imaging with the RV + HLC data resulted in a factor of ∼2 better orbit and mass determinations over RV + HLC alone. In summary, the Roman CGI, combined with precursor RV data and latermission SS imaging, forms a powerful trifecta in detecting exoplanets and determining their masses, albedos, and system configurations. While the Roman CGI will break new scientific and technological ground with direct imaging of giant exoplanets within ∼5 AU of V5 and brighter stars, a Roman Starshade Rendezvous mission would additionally enable the detection of planets out to ∼8 AU in those systems.

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Section: Photometry and Phase Curve Analysismentioning

confidence: 99%

Community exoplanet imaging data challenge for Roman CGI and starshade rendezvous

Turnbull

Zimmerman

Girard

et al. 2021

J. Astron. Telesc. Instrum. Syst.

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“…We then compared the available measurements of mass and radius contained in Exo-MerCat with the verification sample used in Ulmer-Moll et al (2019), as shown in Figure 6.…”

Section: Performancementioning

confidence: 99%

“…Unsurprisingly, the theoretical relation appears to be in agreement with both the data belonging to Exo-MerCat, as well as the validation sample. The sample produced by Exo-MerCat, however, contains more elements, with a few candidates covering regions in the mass-radius parameter space which are not included in the verification sample used by Ulmer-Moll et al (2019). It could be therefore possible that, when repeating similar analyses, small differences in the theoretical relations would appear.…”

Section: Performancementioning

confidence: 99%

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Exo-MerCat: A merged exoplanet catalog with Virtual Observatory connection

Alei

Claudi

Bignamini

et al. 2020

Astronomy and Computing

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The heterogeneity of papers dealing with the discovery and characterization of exoplanets makes every attempt to maintain a uniform exoplanet catalog almost impossible. Four sources currently available online (NASA Exoplanet Archive, Exoplanet Orbit Database, Exoplanet Encyclopaedia, and Open Exoplanet Catalogue) are commonly used by the community, but they can hardly be compared, due to discrepancies in notations and selection criteria. Exo-MerCat is a Python code that collects and selects the most precise measurement for all interesting planetary and orbital parameters contained in the four databases, accounting for the presence of multiple aliases for the same target. It can download information about the host star as well by the use of Virtual Observatory ConeSearch connections to the major archives such as SIMBAD and those available in VizieR. A Graphical User Interface is provided to filter data based on the user's constraints and generate automatic plots that are commonly used in the exoplanetary community. With Exo-MerCat, we retrieved a unique catalog that merges information from the four main databases, standardizing the output and handling notation differences issues. Exo-MerCat can correct as many issues that prevent a direct correspondence between multiple items in the four databases as possible, with the available data. The catalog is available as a VO resource for everyone to use and it is periodically updated, according to the update rates of the source catalogs.

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“…Using the sample of known transiting planets, several studies have been conducted to investigate the mass-radius relation for exoplanets, taking into account the role of the flux received from the star (Enoch et al 2012;Kane & Gelino 2012;Weiss et al 2013;Chen & Kipping 2017;Bashi et al 2017;Ulmer-Moll et al 2019) and also their bulk composition (Swift et al 2012;Dorn et al 2015Dorn et al , 2017. These studies about the formation and evolution of exoplanetary systems have shown that planet radii increase with the mass in the case of low-mass planets, while these two quantities present a constant or even negative relation for high-mass planets (higher than 100 M ⊕ ).…”

Section: Introductionmentioning

confidence: 99%

Characterization of the K2-38 planetary system

Toledo-Padrón

Mascareño

Barros

et al. 2020

A&A

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Context. An accurate characterization of the known exoplanet population is key to understanding the origin and evolution of planetary systems. Determining true planetary masses through the radial velocity (RV) method is expected to experience a great improvement thanks to the availability of ultra-stable echelle spectrographs. Aims. We took advantage of the extreme precision of the new-generation echelle spectrograph ESPRESSO to characterize the transiting planetary system orbiting the G2V star K2-38 located at 194 pc from the Sun with V ~ 11.4. This system is particularly interesting because it could contain the densest planet detected to date. Methods. We carried out a photometric analysis of the available K2 photometric light curve of this star to measure the radius of its two known planets, K2-38b and K2-38c, with Pb = 4.01593 ± 0.00050 d and Pc = 10.56103 ± 0.00090 d, respectively. Using 43 ESPRESSO high-precision RV measurements taken over the course of 8 months along with the 14 previously published HIRES RV measurements, we modeled the orbits of the two planets through a Markov chain Monte Carlo analysis, significantly improving their mass measurements. Results. Using ESPRESSO spectra, we derived the stellar parameters, Teff = 5731 ± 66, log g = 4.38 ± 0.11 dex, and [Fe/H] = 0.26 ± 0.05 dex, and thus the mass and radius of K2-38, M⋆ = 1.03−0.02+0.04 M⊕ and R⋆ = 1.06−0.06+0.09 R⊕. We determine new values for the planetary properties of both planets. We characterize K2-38b as a super-Earth with RP = 1.54 ± 0.14 R⊕ and Mp = 7.3−1.0+1.1 M⊕, and K2-38c as a sub-Neptune with RP = 2.29 ± 0.26 R⊕ and Mp = 8.3−1.3+1.3 M⊕. Combining the radius and mass measurements, we derived a mean density of ρp = 11.0−2.8+4.1 g cm−3 for K2-38b and ρp = 3.8−1.1+1.8 g cm−3 for K2-38c, confirming K2-38b as one of the densest planets known to date. Conclusions. The best description for the composition of K2-38b comes from an iron-rich Mercury-like model, while K2-38c is better described by a rocky-model with H2 envelope. The maximum collision stripping boundary shows how giant impacts could be the cause for the high density of K2-38b. The irradiation received by each planet places them on opposite sides of the radius valley. We find evidence of a long-period signal in the RV time-series whose origin could be linked to a 0.25–3 MJ planet or stellar activity.

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Beyond the exoplanet mass-radius relation

Cited by 25 publications

References 44 publications

Community exoplanet imaging data challenge for Roman CGI and starshade rendezvous

Community exoplanet imaging data challenge for Roman CGI and starshade rendezvous

Exo-MerCat: A merged exoplanet catalog with Virtual Observatory connection

Characterization of the K2-38 planetary system

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