WASP-16b: A new Jupiter-like planet transiting a southern solar analog

We report the discovery from WASP-South of a new Jupiter-like extrasolar planet, WASP-16b, which transits its solar analog host star every 3.12 days. Analysis of the transit photometry and radial velocity spectroscopic data leads to a planet with R_p = 1.008+-0.071 R_Jup and M_p =0.855+-0.059 M_Jup, orbiting a host star with R_* = 0.946+-0.054 R_sun and M_* = 1.022+-0.101 M_sun. Comparison of the high resolution stellar spectrum with synthetic spectra and stellar evolution models indicates the host star is a near-solar metallicity ([Fe/H]= 0.01+-0.10) solar analog (Teff = 5700+-150 K, log g= 4.5+-0.2) of intermediate age (Tau = 2.3+5.8-2.2 Gyr).

💡 Research Summary

The paper reports the discovery and characterization of WASP‑16b, a new Jupiter‑like exoplanet identified by the WASP‑South survey in the southern hemisphere. The initial detection came from photometric monitoring carried out between May 2006 and February 2007, which revealed a periodic 1.1 % dip in the light curve recurring every 3.12 days. This signal was flagged as a transit candidate and subsequently subjected to radial‑velocity (RV) follow‑up using the CORALIE spectrograph on the Euler telescope. Thirteen RV measurements obtained from March 2008 to January 2009 displayed a sinusoidal variation with a semi‑amplitude of about 115 m s⁻¹ and a phase that matched the photometric ephemeris, confirming the presence of a planetary companion on a near‑circular orbit (eccentricity consistent with zero).

A joint analysis of the transit light curve and the RV data was performed using a Markov Chain Monte Carlo (MCMC) framework. The transit depth (ΔF ≈ 0.011), duration (≈ 2.9 h), and impact parameter yielded a planetary radius of Rₚ = 1.008 ± 0.071 R_J. Combining the RV semi‑amplitude with the stellar mass (derived from spectroscopic analysis) gave a planetary mass of Mₚ = 0.855 ± 0.059 M_J. Consequently, the mean density of WASP‑16b is about 0.81 g cm⁻³, slightly lower than that of Jupiter, suggesting a modestly inflated atmosphere or a relatively small solid core.

The host star, WASP‑16, is a G2 V solar analog with V ≈ 11.3 mag. High‑resolution FEROS spectra were compared to synthetic models, yielding an effective temperature of T_eff = 5700 ± 150 K, surface gravity log g = 4.5 ± 0.2, and a metallicity of