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Sonoita, AZ, United States

Bieryla A.,Harvard - Smithsonian Center for Astrophysics | Collins K.,University of Louisville | Beatty T.G.,Pennsylvania State University | Eastman J.,Harvard - Smithsonian Center for Astrophysics | And 33 more authors.
Astronomical Journal | Year: 2015

We report the discovery of KELT-7b, a transiting hot Jupiter with a mass of 1.28 ± 0.18MJ, radius of 1.533 0.047 0.046RJ, and an orbital period of 2.7347749 ± 0.0000039 days. The bright host star (HD 33643; KELT-7) is an F-star with V = 8.54, Teff= 6789 49 50 K, [Fe/H] 0.139 0.081 = -0.075, and log g = 4.149 ± 0.019. It has a mass of 1.535 0.054 0.066 Me, a radius of 1.732 0.045 0.043 Re, and is the fifth most massive, fifth hottest, and the ninth brightest star known to host a transiting planet. It is also the brightest star around which Kilodegree Extremely Little Telescope (KELT) has discovered a transiting planet. Thus, KELT-7b is an ideal target for detailed characterization given its relatively low surface gravity, high equilibrium temperature, and bright host star. The rapid rotation of the star (73 ± 0.5 km s-1) results in a RossiterMcLaughlin effect with an unusually large amplitude of several hundred m s-1. We find that the orbit normal of the planet is likely to be well-aligned with the stellar spin axis, with a projected spin orbit alignment of = 9.7 ± 5. 2. This is currently the second most rapidly rotating star to have a reflex signal (and thus mass determination) due to a planetary companion measured. © 2015. The American Astronomical Society. All rights reserved.

Siverd R.J.,Vanderbilt University | Beatty T.G.,Ohio State University | Pepper J.,Vanderbilt University | Eastman J.D.,Las Cumbres Observatory Global Telescope Network | And 34 more authors.
Astrophysical Journal | Year: 2012

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 MP= 27.38 ± 0.93 M⊙Jup and radius RP= 1.116+0.038 -0.029RJup. The companion is on a very short (∼29 hr) period circular orbit, with an ephemeris Tc(BJDTDB) = 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 vsin 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. © 2012. The American Astronomical Society. All rights reserved..

Pepper J.,Lehigh University | Pepper J.,Vanderbilt University | Siverd R.J.,Vanderbilt University | Beatty T.G.,Ohio State University | And 35 more authors.
Astrophysical Journal | Year: 2013

We report the discovery of KELT-3b, a moderately inflated transiting hot Jupiter with a mass of 1.477?0.067+0.066 MJ, radius of 1.345 ± 0.072RJ, and an orbital period of 2.7033904 ± 0.000010 days. The host star, KELT-3, is a V = 9.8 late F star with M* = 1.278+0.063?0.061M⊙, R* = 1.472+0.065?0.067 R *, Teff = 6306+50?49 K, log(g) = 4.209+0.033?0.031, and [Fe/H] = 0.044 +0.080?0.082, and has a likely proper motion companion. KELT-3b is the third transiting exoplanet discovered by the KELT survey, and is orbiting one of the 20 brightest known transiting planet host stars, making it a promising candidate for detailed characterization studies. Although we infer that KELT-3 is significantly evolved, a preliminary analysis of the stellar and orbital evolution of the system suggests that the planet has likely always received a level of incident flux above the empirically identified threshold for radius inflation suggested by Demory and Seager. © 2013. The American Astronomical Society. All rights reserved. Printed in the U.S.A.

Eastman J.D.,Harvard - Smithsonian Center for Astrophysics | Beatty T.G.,Pennsylvania State University | Siverd R.J.,Las Cumbres Observatory Global Telescope Network | Antognini J.M.O.,Ohio State University | And 44 more authors.
Astronomical Journal | Year: 2016

We report the discovery of KELT-4Ab, an inflated, transiting Hot Jupiter orbiting the brightest component of ahierarchical triple stellar system. The host star is an F star with Teff =6206 ± 75 K, log g =4.108 ± 0.014, [Fe/H]= -0.116+0.069 +0.065, M∗ = 1.201-0.061 +0.067 M⊙, and R∗ = 1.603-0.038 +0.039 R⊙. The best-fit linear ephemeris is BJDTDB =2456193.29157±0.00021 + E(2.9895936±0.0000048). With a magnitude of V∼10, a planetary radius of 1.699-0.045 +0.046 RJ, and a mass of 0.902-0.059 +0.060 MJ, it is the brightest host among the population of inflated Hot Jupiters (RP > 1.5RJ), making it a valuable discovery for probing the nature of inflated planets. In addition, its existence within a hierarchical triple and its proximity to Earth (210 pc) provide a unique opportunity for dynamical studies with continued monitoring with high resolution imaging and precision radial velocities. The projected separation between KELT-4A and KELT-4BC is 328±16 AU and the projected separation between KELT-4B and KELT-4C is 10.30±0.74 AU. Assuming face-on, circular orbits, their respective periods would be 3780±290 and 29.4±3.6 years and the astrometric motions relative to the epoch in this work of both the binary stars around each other and of the binary around the primary star would be detectable now and may provide meaningful constraints on the dynamics of the system. © 2016. The American Astronomical Society. All rights reserved.

Collins K.A.,University of Louisville | Eastman J.D.,Las Cumbres Observatory Global Telescope Network | Eastman J.D.,University of California at Santa Barbara | Beatty T.G.,Ohio State University | And 44 more authors.
Astronomical Journal | Year: 2014

We report the discovery of KELT-6b, a mildly inflated Saturn-mass planet transiting a metal-poor host. The initial transit signal was identified in KELT-North survey data, and the planetary nature of the occulter was established using a combination of follow-up photometry, high-resolution imaging, high-resolution spectroscopy, and precise radial velocity measurements. The fiducial model from a global analysis including constraints from isochrones indicates that the V = 10.38 host star (BD+31 2447) is a mildly evolved, late-F star with T eff = 6102 ± 43 K, log g* = 4.07 +0.04 -0.07, and [Fe/H] = -0.28 ± 0.04, with an inferred mass M· = 1.09 ± 0.04M· and radius R· = 1.58+0.16 -0.09 R ·. The planetary companion has mass MP = 0.43 ± 0.05MJup, radius RP = 1.19+0.13 -0.08 RJup, surface gravity log gP = 2.86+0.06 -0.08, and density .P = 0.31+0.07 -0.08 g cm-3. The planet is on an orbit with semimajor axis a = 0.079 ± 0.001 AU and eccentricity e = 0.22+0.12 -0.10, which is roughly consistent with circular, and has ephemeris of Tc(BJDTDB) = 2456347.79679 ± 0.00036 and P = 7.845631 ± 0.000046 days. Equally plausible fits that employ empirical constraints on the host-star parameters rather than isochrones yield a larger planet mass and radius by ∼4}-7}. KELT-6b has surface gravity and incident flux similar to HD 209458b, but orbits a host that is more metal poor than HD 209458 by ∼0.3 dex. Thus, the KELT-6 system offers an opportunity to perform a comparative measurement of two similar planets in similar environments around stars of very different metallicities. The precise radial velocity data also reveal an acceleration indicative of a longer-period third body in the system, although the companion is not detected in Keck adaptive optics images. © 2014. The American Astronomical Society. All rights reserved.

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