HATS-59b,c: A Transiting Hot Jupiter and a Cold Massive Giant Planet Around a Sun-Like Star

We report the first discovery of a multi-planetary system by the HATSouth network, HATS-59b,c, a planetary system with an inner transiting hot Jupiter and an outer cold massive giant planet, which was detected via radial velocity. The inner transiting planet, HATS-59b, is on an eccentric orbit with $e = 0.129\pm0.049$,orbitinga$V=13.951\pm0.030$magsolar-likestar($M_* = 1.038\pm0.039 M_{\odot}$,and$R_* = 1.036\pm0.067 R_{\odot}$)withaperiodof$5.416077\pm0.000017$ days. The outer companion, HATS-59c is on a circular orbit with $m\sin i=12.8\pm 1.1M_{\mathrm{J}}$, and a period of $1422\pm 14$ days. The inner planet has a mass of $0.806\pm 0.069M_{\mathrm{J}}$ and a radius of $1.126\pm 0.077M_{\mathrm{J}}$, yielding a density of $0.70\pm0.16 {\rm g,cm^{-3}}$. Unlike most of the planetary systems that include only a single hot Jupiter, HATS-59b,c includes, in addition to the transiting hot Jupiter, a massive outer companion. The architecture of this system is valuable for understanding planet migration.