KELT-12b: A $P\sim 5$ Day, Highly Inflated Hot Jupiter Transiting a Mildly Evolved Hot Star

Abstract

We report the discovery of KELT-12b, a highly inflated Jupiter-mass planet transiting a mildly evolved host star. We identified the initial transit signal in the KELT-North survey data and established the planetary nature of the companion through precise follow-up photometry, high-resolution spectroscopy, precise radial velocity measurements, and high-resolution adaptive optics imaging. Our preferred best-fit model indicates that the $V=10.64$ host, TYC 2619-1057-1, has $T_{\mathrm{eff}}=6278\pm 51$ K, $\log g_{\star }=3.89_{-0.051}^{+0.054}$, and [Fe/H] = $0.19_{-0.085}^{+0.083}$, with an inferred mass $M_{\star }=1.59_{-0.091}^{+0.071}{M}_{\odot }$ and radius $R_{\star }=2.37\pm 0.18R_{\odot }$. The planetary companion has $M_{\mathrm{P}}=0.95\pm 0.14M_{\mathrm{J}}$, $R_{\mathrm{P}}=1.79_{-0.17}^{+0.18}{R}_{\mathrm{J}}$, $\log g_{\mathrm{P}}=2.87_{-0.098}^{+0.097}$, and density ${\rho }_{\mathrm{P}}=0.21_{-0.054}^{+0.075}$ g cm${}^{-3}$, making it one of the most inflated giant planets known. The time of inferior conjunction in $\mathrm{BJ}{\mathrm{D}}_{\mathrm{TDB}}$ is $2457088.692055\pm 0.0009$ and the period is $P=5.0316144\pm 0.0000306$ days. Despite the relatively large separation of $\sim 0.07$ AU implied by its $\sim 5.03$-day orbital period, KELT-12b receives significant flux of $2.93_{-0.30}^{+0.33}\times 10^9$ erg s${}^{-1}$ cm${}^{-2}$ from its host. We compare the radii and insolations of transiting gas-giant planets around hot ($T_{\mathrm{eff}}\ge 6250$ K) and cool stars, noting that the observed paucity of known transiting giants around hot stars with low insolation is likely due to selection effects. We underscore the significance of long-term ground-based monitoring of hot stars and space-based targeting of hot stars with the Transiting Exoplanet Survey Satellite (TESS) to search for inflated giants in longer-period orbits.

arXiv comment16 pages, 14 figures, 6 tables. Submitted to AAS Journals

References in corpus (42)

• The Wide-field Infrared Survey Explorer (WISE): Mission Description and Initial On-orbit Performance
• The Transiting Exoplanet Survey Satellite
• The Galaxy Evolution Explorer: A Space Ultraviolet Survey Mission
• The K2 Mission: Characterization and Early results
• The VizieR database of Astronomical Catalogues
• Accurate masses and radii of normal stars: modern results and applications
• A method for optimal image subtraction
• The WASP Project and the SuperWASP Cameras
• A box-fitting algorithm in the search for periodic transits
• A continuum from clear to cloudy hot-Jupiter exoplanets without primordial water depletion
• EXOFAST: A fast exoplanetary fitting suite in IDL
• Defining and cataloging exoplanets: The exoplanet.eu database
• The effect of red noise on planetary transit detection
• Wide-field millimagnitude photometry with HAT: A Tool for Extra-solar Planet Detection
• The Transiting Exoplanet Survey Satellite: Simulations of planet detections and astrophysical false positives
• The NextGen Model Atmosphere grid: II. Spherically symmetric model atmospheres for giant stars with effective temperatures between 3000 and 6800~K
• Exoplanet Atmospheres
• The Kilodegree Extremely Little Telescope (KELT): A Small Robotic Telescope for Large-Area Synoptic Surveys
• HAT-P-16b: A 4 Mj Planet Transiting A Bright Star On An Eccentric Orbit
• Efficient identification of exoplanetary transit candidates from SuperWASP light curves
• Selection, Prioritization, and Characteristics of Kepler Target Stars
• The Mass of KOI-94d and a Relation for Planet Radius, Mass, and Incident Flux
• KELT-1b: A Strongly Irradiated, Highly Inflated, Short Period, 27 Jupiter-mass Companion Transiting a mid-F Star
• A Trend Filtering Algorithm for wide field variability surveys
• Lack of Inflated Radii for Kepler Giant Planet Candidates Receiving Modest Stellar Irradiation
• Expected Detection and False Alarm Rates for Transiting Jovian Planets
• The KELT-South Telescope
• Local Stellar Kinematics from RAVE Data: I. Local Standard of Rest
• HAT-P-3b: A heavy-element rich planet transiting a K dwarf star
• Testing blend scenarios for extrasolar transiting planet candidates. II. -- OGLE-TR-56
• Three Super-Earths Orbiting HD 7924
• Predicting the Yields of Photometric Surveys for Transiting Extrasolar Planets
• Searching for Transiting Planets in Stellar Systems
• Spitzer and z' Secondary Eclipse Observations of the Highly Irradiated Transiting Brown Dwarf KELT-1b
• Transit Target Selection Using Reduced Proper Motions
• Jupiter will become a hot Jupiter: Consequences of Post-Main-Sequence Stellar Evolution on Gas Giant Planets
• Detecting Transits of Planetary Companions to Giant Stars
• On the Size Distribution of Close-In Extrasolar Giant Planets
• KELT-6b: A P~7.9 d Hot Saturn Transiting a Metal-Poor Star with a Long-Period Companion
• Interpreting and predicting the yield of transit surveys: Giant planets in the OGLE fields
• KELT-4Ab: An inflated Hot Jupiter transiting the bright (V~10) component of a hierarchical triple
• The Amateur Sky Survey Mark III Project

Cited by in corpus (12)

• A library of ATMO forward model transmission spectra for hot Jupiter exoplanets
• TESS Transit Timing of Hundreds of Hot Jupiters
• Variability Properties of 4 Million Sources in the $TESS$ Input Catalog Observed with the Kilodegree Extremely Little Telescope Survey
• ExoClock Project III: 450 new exoplanet ephemerides from ground and space observations
• TESS Delivers Five New Hot Giant Planets Orbiting Bright Stars from the Full Frame Images
• KELT-21b: A Hot Jupiter Transiting the Rapidly-Rotating Metal-Poor Late-A Primary of a Likely Hierarchical Triple System
• A Discrete Set of Possible Transit Ephemerides for Two Long Period Gas Giants Orbiting HIP 41378
• Another Shipment of Six Short-Period Giant Planets from TESS
• KELT-24b: A 5M${}_{\mathrm{J}}$ Planet on a 5.6 day Well-Aligned Orbit around the Young V=8.3 F-star HD 93148
• Measuring Model-independent Masses and Radii of Single-Lined Eclipsing Binaries: Analytic Precision Estimates
• KELT-18b: Puffy Planet, Hot Host, Probably Perturbed
• Techniques for Finding Close-in, Low-mass Planets around Subgiants