KELT-1b: A Strongly Irradiated, Highly Inflated, Short Period, 27 Jupiter-mass Companion Transiting a Mid-F Star

We present the discovery of KELT-1b, the first transiting low-mass companion from the wide-field Kilodegree Extremely Little Telescope-North (KELT-North) transit survey. A joint analysis of the spectroscopic, radial velocity, and photometric data indicates that the V = 10.7 primary is a mildly evolved mid-F star with T eff = 6516 ± 49 K, log g = 4.228^(+0.014)_(–0.021), and [Fe/H] = 0.052 ± 0.079, with an inferred mass M_* = 1.335 ± 0.063 M_☉ and radius R_* = 1.471^(+0.045)_(–0.035) R_☉. The companion is a low-mass brown dwarf or a super-massive planet with mass M_P = 27.38 ± 0.93 M_(Jup) and radius R_P = 1.116^(+0.038)_(–0.029) R_(Jup). The companion is on a very short (~29 hr) period circular orbit, with an ephemeris T_c (BJD_(TDB)) = 2455909.29280 ± 0.00023 and P = 1.217501 ± 0.000018 days. KELT-1b receives a large amount of stellar insolation, resulting in an estimated equilibrium temperature assuming zero albedo and perfect redistribution of T_(eq) = 2423^(+34)_(–27) K. Comparison with standard evolutionary models suggests that the radius of KELT-1b is likely to be significantly inflated. Adaptive optics imaging reveals a candidate stellar companion to KELT-1 with a separation of 588 ± 1 mas, which is consistent with an M dwarf if it is at the same distance as the primary. Rossiter-McLaughlin measurements during transit imply a projected spin-orbit alignment angle λ = 2 ± 16 deg, consistent with a zero obliquity for KELT-1. Finally, the v sin I_* = 56 ± 2 km ^(s–1) of the primary is consistent at ~2σ with tidal synchronization. Given the extreme parameters of the KELT-1 system, we expect it to provide an important testbed for theories of the emplacement and evolution of short-period companions, as well as theories of tidal dissipation and irradiated brown dwarf atmospheres

The KELT-South Telescope

The Kilodegree Extremely Little Telescope (KELT) project is a survey for new transiting planets around bright stars. KELT-South is a small-aperture, wide-field automated telescope located at Sutherland, South Africa. The telescope surveys a set of 26 degree by 26 degree fields around the southern sky, and targets stars in the range of 8 < V < 10 mag, searching for transits by Hot Jupiters. This paper describes the KELT-South system hardware and software and discusses the quality of the observations. We show that KELT-South is able to achieve the necessary photometric precision to detect transits of Hot Jupiters around solar-type main-sequence stars.Comment: 26 pages, 13 figure

The Hawaii Infrared Parallax Program. V. New T-Dwarf Members and Candidate Members of Nearby Young Moving Groups

We present a search for new planetary-mass members of nearby young moving groups (YMGs) using astrometry for 694 T and Y dwarfs, including 447 objects with parallaxes, mostly produced by recent large parallax programs from UKIRT and Spitzer. Using the BANYAN $\Sigma$ and LACEwING algorithms, we identify 30 new candidate YMG members, with spectral types of T0$-$T9 and distances of $10-43$ pc. Some candidates have unusually red colors and/or faint absolute magnitudes compared to field dwarfs with similar spectral types, providing supporting evidence for their youth, including 4 early-T dwarfs. We establish one of these, the variable T1.5 dwarf 2MASS J21392676$+$0220226, as a new planetary-mass member ($14.6^{+3.2}_{-1.6}$ M$_{\rm Jup}$) of the Carina-Near group ($200\pm50$ Myr) based on its full six-dimensional kinematics, including a new parallax measurement from CFHT. The high-amplitude variability of this object is suggestive of a young age, given the coexistence of variability and youth seen in previously known YMG T dwarfs. Our four latest-type (T8$-$T9) YMG candidates, WISE J031624.35$+$430709.1, ULAS J130217.21$+$130851.2, WISEPC J225540.74$-$311841.8, and WISE J233226.49$-$432510.6, if confirmed, will be the first free-floating planets ($\approx2-6$ M$_{\rm Jup}$) whose ages and luminosities are compatible with both hot-start and cold-start evolutionary models, and thus overlap the properties of the directly-imaged planet 51 Eri b. Several of our early/mid-T candidates have peculiar near-infrared spectra, indicative of heterogenous photospheres or unresolved binarity. Radial velocity measurements needed for final membership assessment for most of our candidates await upcoming 20$-$30 meter class telescopes. In addition, we compile all 15 known T7$-$Y1 benchmarks and derive a homogeneous set of their effective temperatures, surface gravities, radii, and masses.Comment: ApJ, in press. 27 pages including 6 figures and 5 table