Characterization of the HD 17156 planetary system

TL;DR

This study refines the parameters of the HD 17156 system, including stellar and planetary radii, orbital elements, and spin-orbit alignment, while also confirming the absence of stellar companions within a certain range.

Contribution

It provides improved measurements of the HD 17156 system's parameters and confirms the system's spin-orbit alignment and lack of stellar companions, using combined photometric, spectroscopic, and imaging data.

Findings

Star radius: 1.43 R_sun

Planet radius: 1.02 R_jup

Spin-orbit alignment angle: 4.8 degrees

Abstract

AIMS : To improve the parameters of the HD 17156 system (peculiar due to the eccentric and long orbital period of its transiting planet) and constrain the presence of stellar companions. METHODS : Photometric data were acquired for 4 transits, and high precision radial velocity measurements were simultaneously acquired with SARG@TNG for one transit. The template spectra of HD 17156 was used to derive effective temperature, gravity, and metallicity. A fit of the photometric and spectroscopic data was performed to measure the stellar and planetary radii, and the spin-orbit alignment. Planet orbital elements and ephemeris were derived from the fit. Near infrared adaptive optic images was acquired with ADOPT@TNG. RESULTS: We have found that the star has a radius of R_S = 1.43+/-0.03 R_sun and the planet R_P =1.02+/-0.08 R_jup. The transit ephemeris is T_c = 2454\756.73134+/-0.00020+N*21.21663+/-0.00045 BJD. The analysis of the Rossiter-Mclaughlin effect shows that the system is spin orbit aligned with an angle lambda = 4.8 +/- 5.3 deg. The analysis of high resolution images has not revealed any stellar companion with projected separation between 150 and 1000 AU from HD 17156.