We announce the discovery of KELT-16b , a highly irradiated , ultra-short period hot Jupiter transiting the relatively bright ( V = 11.7 ) star TYC 2688-1839-1/KELT-16 .
A global analysis of the system shows KELT-16 to be an F7V star with T _ { \textrm { eff } } = 6236 \pm 54 K , \log { g _ { \star } } = 4.253 _ { -0.036 } ^ { +0.031 } , \left [ { Fe } / { H } \right ] = -0.002 _ { -0.085 } ^ { +0.086 } , M _ { \star } = 1.211 _ { -0.046 } ^ { +0.043 } M _ { \odot } , and R _ { \star } = 1.360 _ { -0.053 } ^ { +0.064 } R _ { \odot } .
The planet is a relatively high mass inflated gas giant with M _ { \textrm { P } } = 2.75 _ { -0.15 } ^ { +0.16 } M _ { \textrm { J } } , R _ { \textrm { P } } = 1.415 _ { -0.067 } ^ { +0.084 } R _ { \textrm { J } } , density \rho _ { \textrm { P } } = 1.20 \pm 0.18 g cm ^ { -3 } , surface gravity \log { g _ { \textrm { P } } } = 3.530 _ { -0.049 } ^ { +0.042 } , and T _ { \textrm { eq } } = 2453 _ { -47 } ^ { +55 } K. The best-fitting linear ephemeris is T _ { \textrm { C } } = 2457247.24791 \pm 0.00019 BJD _ { \textrm { TDB } } and P = 0.9689951 \pm 0.0000024 d. KELT-16b joins WASP-18b , -19b , -43b , -103b , and HATS-18b as the only giant transiting planets with P < 1 day .
Its ultra-short period and high irradiation make it a benchmark target for atmospheric studies by HST , Spitzer , and eventually JWST .
For example , as a hotter , higher mass analog of WASP-43b , KELT-16b may feature an atmospheric temperature-pressure inversion and day-to-night temperature swing extreme enough for TiO to rain out at the terminator .
KELT-16b could also join WASP-43b in extending tests of the observed mass-metallicity relation of the Solar System gas giants to higher masses .
KELT-16b currently orbits at a mere \sim 1.7 Roche radii from its host star , and could be tidally disrupted in as little as a few \times 10 ^ { 5 } years ( for a stellar tidal quality factor of Q _ { * } ^ { \prime } = 10 ^ { 5 } ) .
Finally , the likely existence of a widely separated bound stellar companion in the KELT-16 system makes it possible that Kozai-Lidov oscillations played a role in driving KELT-16b inward to its current precarious orbit .