## Physics & Astronomy Faculty Works

Article

3-1-2017

#### Published In

Astronomical Journal

#### Abstract

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 ${T}_{\mathrm{eff}}=6236\pm 54$ K, $\mathrm{log}{g}_{\star }={4.253}_{-0.036}^{+0.031}$, $[\mathrm{Fe}/{\rm{H}}]=-{0.002}_{-0.085}^{+0.086}$, ${M}_{\star }={1.211}_{-0.046}^{+0.043}\,{M}_{\odot }$, and ${R}_{\star }\,={1.360}_{-0.053}^{+0.064}{R}_{\odot }$. The planet is a relatively high-mass inflated gas giant with ${M}_{{\rm{P}}}={2.75}_{-0.15}^{+0.16}{M}_{{\rm{J}}}$, ${R}_{{\rm{P}}}={1.415}_{-0.067}^{+0.084}{R}_{{\rm{J}}}$, density ${\rho }_{{\rm{P}}}=1.20\pm 0.18$ g cm−3, surface gravity $\mathrm{log}\,{g}_{{\rm{P}}}={3.530}_{-0.049}^{+0.042}$, and ${T}_{\mathrm{eq}}={2453}_{-47}^{+55}$ K. The best-fitting linear ephemeris is ${T}_{{\rm{C}}}=2457247.24791\pm 0.00019$ ${\mathrm{BJD}}_{\mathrm{TDB}}\$and $P=0.9689951\pm 0.0000024$ day. 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 the Hubble Space Telescope, Spitzer, and eventually the James Webb Space Telescope. 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 ~1.7 Roche radii from its host star, and could be tidally disrupted in as little as a few ×105 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 (KL) oscillations played a role in driving KELT-16b inward to its current precarious orbit.

#### Keywords

planets and satellites: detection, planets and satellites: gaseous planets, methods: observational, techniques: photometric, techniques: radial velocities