[Paper Review] EPIC210957318b and EPIC212110888b: two inflated hot-Jupiters around Solar-type stars

J. Lillo-Box, O. D. S. Demangeon+24 more|arXiv (Cornell University)|Jan 28, 2016

Stellar, planetary, and galactic studies3 citations

TL;DR

This paper reports the discovery of two inflated hot-Jupiters, EPIC210957318b and EPIC212110888b, transiting Solar-type stars during K2 campaigns 4 and 5. Radial velocity follow-up with SOPHIE, HARPS-N, and CAFE confirmed their planetary nature, and atmospheric and orbital characterization reveal their large radii (1.25 and 1.33 R_Jup) and potential for obliquity and atmospheric studies due to their bright host stars.

ABSTRACT

We report the discovery of the two hot-Jupiters EPIC210957318b and EPIC212110888b (hereafter EPIC-318b and EPIC-888b, respectively). The two planets were detected transiting their main-sequence star with periods $\sim$ 4.099 and $\sim$ 2.996 days, in campaigns 4 and 5 of the extension of the Kepler mission, K2. Subsequent ground-based radial velocity follow-up with SOPHIE, HARPS-N and CAFE, established the planetary nature of the transiting objects. We analyzed the transit signal, radial velocity and spectral energy distributions of the two systems to characterize their properties. Both planets (EPIC-318b and EPIC-888b) are bloated hot-Jupiters (1.25 $R_{ m Jup}$ and 1.33 $R_{ m Jup}$) around relatively bright (V =13.5 and V=11.5), slow rotating main-sequence (G8 and F9) stars. Thus, these systems are good candidates for detecting the Rossiter-MacLaughlin effect to measure their obliquity and for atmospheric studies.

Motivation & Objective

• To identify and confirm transiting exoplanets in K2 campaigns 4 and 5 using transit photometry and radial velocity follow-up.
• To characterize the physical and orbital properties of newly discovered hot-Jupiters, particularly their inflated radii.
• To assess the potential of these systems for detecting the Rossiter-MacLaughlin effect and conducting atmospheric studies.
• To determine the stellar parameters of the host stars using spectral energy distribution and radial velocity data.
• To confirm the planetary nature of the transiting objects through multi-instrument radial velocity monitoring.

Proposed method

• Transit photometry from K2 campaigns 4 and 5 was used to detect periodic dimming indicative of planetary transits.
• Ground-based radial velocity measurements were obtained using SOPHIE, HARPS-N, and CAFE to confirm planetary mass and exclude stellar false positives.
• Stellar parameters were derived from spectral energy distribution modeling and radial velocity analysis of the host stars.
• Orbital inclination and planetary radius were constrained via transit light curve modeling.
• The Rossiter-MacLaughlin effect was assessed as a potential observable due to the systems' bright host stars and favorable orbital geometry.
• Planetary mass and radius were derived from radial velocity amplitude and transit depth measurements.

Experimental results

Research questions

• RQ1 What are the physical and orbital parameters of the two newly discovered transiting planets, EPIC-318b and EPIC-888b?
• RQ2 To what extent are these planets inflated compared to typical hot-Jupiters, and what does this imply about their internal structure or irradiation?
• RQ3 Can the Rossiter-MacLaughlin effect be detected in these systems, and what would this reveal about their orbital obliquity?
• RQ4 What is the potential for atmospheric characterization of these planets given their host star brightness?
• RQ5 How do the stellar properties of the host stars (spectral type, rotation, brightness) influence the detectability of planetary signals?

Key findings

• EPIC210957318b is a hot-Jupiter with a radius of 1.25 R_Jup, orbiting a G8-type main-sequence star with a 4.099-day period.
• EPIC212110888b is a larger hot-Jupiter with a radius of 1.33 R_Jup, orbiting an F9-type main-sequence star with a 2.996-day period.
• Both host stars are relatively bright (V = 13.5 and V = 11.5), slow-rotating, and suitable for high-precision radial velocity and atmospheric studies.
• The planets' inflated radii suggest enhanced irradiation or internal heating mechanisms, though no detailed modeling of these effects is provided in the abstract.
• The systems are strong candidates for detecting the Rossiter-MacLaughlin effect due to their bright stars and favorable orbital inclinations.
• Radial velocity follow-up with multiple instruments confirmed the planetary nature of both transiting objects and constrained their masses.