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 \pm 43 K, log(g_*)=4.07_{-0.07}^{+0.04} and Fe/H=-0.28 \pm 0.04, with an inferred mass M_*=1.09 \pm 0.04 M_sun and radius R_star=1.58_{-0.09}^{+0.16} R_sun. The planetary companion has mass M_P=0.43 \pm 0.05 M_J, radius R_P=1.19_{-0.08}^{+0.13} R_J, surface gravity log(g_P)=2.86_{-0.08}^{+0.06}, and density rho_P=0.31_{-0.08}^{+0.07} g~cm^{-3}. The planet is on an orbit with semimajor axis a=0.079 \pm 0.001 AU and eccentricity e=0.22_{-0.10}^{+0.12}, which is roughly consistent with circular, and has ephemeris of T_c(BJD_TDB)=2456347.79679 \pm 0.00036 and P=7.845631 \pm 0.000046 d. 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 HD209458b, but orbits a host that is more metal poor than HD209458 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.
We report the discovery of KELT-3b, a moderately inflated transiting hot Jupiter with a mass of 1.477 (-0.067, +0.066) M_J, and radius of 1.345 +/- 0.072 R_J, with 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 (-0.061, +0.063) M_sun, R_* = 1.472 (-0.067, +0.065) R_sun, T_eff = 6306 (-49, +50) K, log(g) = 4.209 (-0.031, +0.033), and Fe/H = 0.044 (-0.082, +0.080), 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 & Seager (2011).
T-type dwarfs present a broad and shallow absorption feature centred around 6950 A in the blue wing of the K doublet at 0.77 micron which resembles in depth and shape the satellite absorption ...predicted by detailed collisional broadening profiles. In our previous work, the predicted line satellite position was however somewhat too blue compared to the observed feature. In this paper we investigate whether new calculations of the energy surfaces of the potentials in the K-H_2 system, including spin-orbit coupling, result in a closer coincidence of the satellite with the observed position. We also investigate the extent to which CaH absorption bands contribute to the feature. We present model atmospheres and synthetic spectra, including gravitational settling for an improved description of depth-dependent abundances of refractory elements, and based on new K-H_2 line profiles using improved interaction potentials. By comparison with a high signal-to-noise optical spectrum of the T1 dwarf epsilon Indi Ba, we find that these new models do reproduce the observed feature, while CaH does not contribute for the atmospheric parameters considered. We also find that CaH is settled out so deep into the atmosphere that even turbulent vertical mixing would appear insufficient to bring significant amounts of CaH to the photosphere in dwarfs later than ~L5. We conclude that previous identification of the feature at this location in T and late L dwarf spectra with CaH was erroneous, as expected on physical grounds: calcium condenses onto grains in early L dwarfs and thus should have settled out of the photosphere in cooler brown dwarfs. This finding revokes one observational verification for the cloud-clearing theory: a gradual clearing of the cloud cover in early T dwarfs.
We report the discovery of KELT-2Ab, a hot Jupiter transiting the bright (V=8.77) primary star of the HD 42176 binary system. The host is a slightly evolved late F-star likely in the very short-lived ..."blue-hook" stage of evolution, with \(\teff=6148\pm48{\rm K}\), \(\log{g}=4.030_{-0.026}^{+0.015}\) and \(\feh=0.034\pm0.78\). The inferred stellar mass is \(M_*=1.314_{-0.060}^{+0.063}\)\msun\ and the star has a relatively large radius of \(R_*=1.836_{-0.046}^{+0.066}\)\rsun. The planet is a typical hot Jupiter with period \(4.11379\pm0.00001\) days and a mass of \(M_P=1.524\pm0.088\)\mj\ and radius of \(R_P=1.290_{-0.050}^{+0.064}\)\rj. This is mildly inflated as compared to models of irradiated giant planets at the \(\sim\)4 Gyr age of the system. KELT-2A is the third brightest star with a transiting planet identified by ground-based transit surveys, and the ninth brightest star overall with a transiting planet. KELT-2Ab's mass and radius are unique among the subset of planets with \(V<9\) host stars, and therefore increases the diversity of bright benchmark systems. We also measure the relative motion of KELT-2A and -2B over a baseline of 38 years, robustly demonstrating for the first time that the stars are bound. This allows us to infer that KELT-2B is an early K-dwarf. We hypothesize that through the eccentric Kozai mechanism KELT-2B may have emplaced KELT-2Ab in its current orbit. This scenario is potentially testable with Rossiter-McLaughlin measurements, which should have an amplitude of \(\sim\)44 m s\(^{-1}\).
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 \(T_{\rm eff} = 6278 \pm 51\) K, \(\log{g_\star} = 3.89^{+0.054}_{-0.051}\), and Fe/H = \(0.19^{+0.083}_{-0.085}\), with an inferred mass \(M_{\star} = 1.59^{+0.071}_{-0.091} M_\odot\) and radius \(R_\star = 2.37 \pm 0.18 R_\odot\). The planetary companion has \(M_{\rm P} = 0.95 \pm 0.14 M_{\rm J}\), \(R_{\rm P} = 1.79^{+0.18}_{-0.17} R_{\rm J}\), \(\log{g_{\rm P}} = 2.87^{+0.097}_{-0.098}\), and density \(\rho_{\rm P} = 0.21^{+0.075}_{-0.054}\) g cm\(^{-3}\), making it one of the most inflated giant planets known. The time of inferior conjunction in \({\rm BJD_{TDB}}\) is \(2457088.692055 \pm 0.0009\) and the period is \(P = 5.0316144 \pm 0.0000306\) days. Despite the relatively large separation of \(\sim0.07\) AU implied by its \(\sim 5.03\)-day orbital period, KELT-12b receives significant flux of \(2.93^{+0.33}_{-0.30} \times 10^9\) erg s\(^{-1}\) cm\(^{-2}\) from its host. We compare the radii and insolations of transiting gas-giant planets around hot (\(T_{\rm eff} \geq 6250\) 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.
We present the discovery of KELT-1b, the first transiting low-mass companion from the wide-field Kilodegree Extremely Little Telescope-North (KELT-North) survey. The V=10.7 primary is a mildly ...evolved, solar-metallicity, mid-F star. The companion is a low-mass brown dwarf or super-massive planet with mass of 27.23+/-0.50 MJ and radius of 1.110+0.037-0.024 RJ, on a very short period (P=1.21750007) circular orbit. KELT-1b receives a large amount of stellar insolation, with an equilibrium temperature assuming zero albedo and perfect redistribution of 2422 K. Upper limits on the secondary eclipse depth indicate that either the companion must have a non-zero albedo, or it must experience some energy redistribution. Comparison with standard evolutionary models for brown dwarfs suggests that the radius of KELT-1b is significantly inflated. Adaptive optics imaging reveals a candidate stellar companion to KELT-1, which is consistent with an M dwarf if bound. The projected spin-orbit alignment angle is consistent with zero stellar obliquity, and the vsini of the primary is consistent 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, and theories of tidal dissipation and irradiated brown dwarf atmospheres.
Astrophys.J. 601 (2004) L183-L186 We present new FUV observations of the pulsating DA white dwarf G226-29
obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE). This ZZ Ceti
star is the ...brightest one of its class and the coolest white dwarf observed by
FUSE. We report the first detection of the broad quasi-molecular
collision-induced satellite of Ly-beta at 1150 A, an absorption feature that is
due to transitions which take place during close collisions of hydrogen atoms.
The physical interpretation of this feature is based on recent progress of the
line broadening theory of the far wing of Ly-beta. This predicted feature had
never been observed before, even in laboratory spectra.
European Physical Journal D 12, 263 (2000) We present a theoretical profile of the Lyman Beta line of atomic hydrogen
perturbed by collisions with neutral hydrogen atoms and protons. We use a
general ...unified theory in which the electric dipole moment varies during a
collision. A collision-induced satellite appears on Lyman Beta, correlated to
the B''\barB 1Sigma+u - X 1Sigma+g asymptotically forbidden transition of H_2.
As a consequence, the appearance of the line wing between Lyman Alpha and Lyman
Beta is shown to be sensitive to the relative abundance of hydrogen ions and
neutral atoms, and thereby to provide a temperature diagnostic for stellar
atmospheres and laboratory plasmas.
We present new FUV observations of the pulsating DA white dwarf G226-29 obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE). This ZZ Ceti star is the brightest one of its class and the ...coolest white dwarf observed by FUSE. We report the first detection of the broad quasi-molecular collision-induced satellite of Ly-beta at 1150 A, an absorption feature that is due to transitions which take place during close collisions of hydrogen atoms. The physical interpretation of this feature is based on recent progress of the line broadening theory of the far wing of Ly-beta. This predicted feature had never been observed before, even in laboratory spectra.
We present a theoretical profile of the Lyman Beta line of atomic hydrogen perturbed by collisions with neutral hydrogen atoms and protons. We use a general unified theory in which the electric ...dipole moment varies during a collision. A collision-induced satellite appears on Lyman Beta, correlated to the B''\barB 1Sigma+u - X 1Sigma+g asymptotically forbidden transition of H_2. As a consequence, the appearance of the line wing between Lyman Alpha and Lyman Beta is shown to be sensitive to the relative abundance of hydrogen ions and neutral atoms, and thereby to provide a temperature diagnostic for stellar atmospheres and laboratory plasmas.
