John F. Kielkopf

New approximation to the Voigt function with applications to spectral-line profile analysis

An approximation to the Voigt function is described, which is valid over the entire domain of the independent variables that characterize it and which is accurate to the order of 0.0001 of the peak value of the function. Relations between the parameters of the function are also given. The approximation is used to develop a procedure for fitting observed lines with Voigt functions; the class of asymmetric lines that arise from the superposition of two Voigt functions is considered in some detail, and methods for extracting the Voigt parameters of the components from the observed contour of the envelope are given. The measurement of the width and shape of a single line with a Fabry–Perot interferometer is also discussed. All of the calculations described here can be handled by programmable calculators or small computers.

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 Teff = 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 MJup and radius RP = 1.116 +0.038 −0.029 RJup. 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 Teq = 2423 +3427 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 ± 2k m 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.

A new model for brown dwarf spectra including accurate unified line shape theory for the Na I and K I resonance line profiles

We present the first brown dwarf atmosphere models based on theoretical calculations of absorption profiles of sodium and potassium perturbed by helium and molecular hydrogen. The synthetic spectra have been compared to previous calculations with Lorentz profiles and the classic van der Waals approximation, and to the observed spectrum of the T dwarf SDSS 1624. The new profiles provide increased opacities in the optical spectra of methane brown dwarfs. However, the potas- sium and sodium far wings alone cannot explain the missing opacity in the 0.85 to 1.1m range.

K-H2 quasi-molecular absorption detected in the T-dwarf ε Indi Ba

Context. 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 μm which resembles in depth and shape the satellite absorption predicted by detailed collisional broadening profiles. In our previous work, the position of the predicted line satellite was however somewhat too blue compared to the observed feature. Aims. 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 and at what T eff these respective opacity sources predominate. Methods. 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. Results. By comparison with a high signal-to-noise optical spectrum of the Tl dwarf sIndiBa, 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 observable photosphere in dwarfs of later type than ∼L5. Conclusions. We conclude that previous identification of the feature at this location in the spectra of T dwarfs as well as the latest L dwarfs with CaH was erroneous, as expected on physical grounds: calcium has already condensed onto grains in early L dwarfs and thus should have settled out of the photosphere in cooler brown dwarfs. This finding revokes one of the observational verifications for the cloud-clearing theory assumption: a gradual clearing of the cloud cover in early T dwarfs.

ASTROIMAGEJ: IMAGE PROCESSING AND PHOTOMETRIC EXTRACTION FOR ULTRA-PRECISE ASTRONOMICAL LIGHT CURVES

ImageJ is a graphical user interface (GUI) driven, public domain, Java-based, software package for general image processing traditionally used mainly in life sciences fields. The image processing capabilities of ImageJ are useful and extendable to other scientific fields. Here we present AstroImageJ (AIJ), which provides an astronomy specific image display environment and tools for astronomy specific image calibration and data reduction. Although AIJ maintains the general purpose image processing capabilities of ImageJ, AIJ is streamlined for time-series differential photometry, light curve detrending and fitting, and light curve plotting, especially for applications requiring ultra-precise light curves (e.g., exoplanet transits). AIJ reads and writes standard FITS files, as well as other common image formats, provides FITS header viewing and editing, and is World Coordinate System (WCS) aware, including an automated interface to the astrometry.net web portal for plate solving images. AIJ provides research grade image calibration and analysis tools with a GUI driven approach, and easily installed cross-platform compatibility. It enables new users, even at the level of undergraduate student, high school student, or amateur astronomer, to quickly start processing, modeling, and plotting astronomical image data with one tightly integrated software package.

KELT-7b: A Hot Jupiter Transiting A Bright V = 8.54 Rapidly Rotating F-Star

United States. National Aeronautics and Space Administration (Origins Program Grant NNX11AG85G)

Theoretical profiles of light alkali resonance lines for brown dwarf atmosphere conditions

The analysis of the far wings of resonance lines of alkali elements in brown dwarf spectra requires their accurate determination. A unified theory of collisional line profiles has been applied for the evaluation of absorption profiles of alkalis perturbed by helium and molecular hydrogen. The study of the dependence on temperature of the far wings of Li-He and Li-H2 collisional profiles is reported.

KELT-3b: A HOT JUPITER TRANSITING A V = 9.8 LATE-F STAR

We report the discovery of KELT-3b, a moderately inflated transiting hot Jupiter with a mass of 1.477 +0.066 −0.067 MJ, radius of 1.345 ± 0.072 RJ, 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 −0.061 M� , R∗ = 1.472 +0.065 −0.067 R� , Teff = 6306 +5049 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 & Seager.

Predicted alkali collision broadening by noble gases based on semiempirical potentials

The collision broadening and shift of lithium, sodium, potassium, rubidium and caesium principal series lines by helium, neon, argon, krypton and xenon perturbers is tabulated based on the impact approximation and semiempirical interatomic potentials. Comparisons are made with available experimental data. The temperature dependence of the line broadening and shift rates is also estimated.

A giant planet undergoing extreme-ultraviolet irradiation by its hot massive-star host

The amount of ultraviolet irradiation and ablation experienced by a planet depends strongly on the temperature of its host star. Of the thousands of extrasolar planets now known, only six have been found that transit hot, A-type stars (with temperatures of 7,300–10,000 kelvin), and no planets are known to transit the even hotter B-type stars. For example, WASP-33 is an A-type star with a temperature of about 7,430 kelvin, which hosts the hottest known transiting planet, WASP-33b (ref. 1); the planet is itself as hot as a red dwarf star of type M (ref. 2). WASP-33b displays a large heat differential between its dayside and nightside, and is highly inflated–traits that have been linked to high insolation. However, even at the temperature of its dayside, its atmosphere probably resembles the molecule-dominated atmospheres of other planets and, given the level of ultraviolet irradiation it experiences, its atmosphere is unlikely to be substantially ablated over the lifetime of its star. Here we report observations of the bright star HD 195689 (also known as KELT-9), which reveal a close-in (orbital period of about 1.48 days) transiting giant planet, KELT-9b. At approximately 10,170 kelvin, the host star is at the dividing line between stars of type A and B, and we measure the dayside temperature of KELT-9b to be about 4,600 kelvin. This is as hot as stars of stellar type K4 (ref. 5). The molecules in K stars are entirely dissociated, and so the primary sources of opacity in the dayside atmosphere of KELT-9b are probably atomic metals. Furthermore, KELT-9b receives 700 times more extreme-ultraviolet radiation (that is, with wavelengths shorter than 91.2 nanometres) than WASP-33b, leading to a predicted range of mass-loss rates that could leave the planet largely stripped of its envelope during the main-sequence lifetime of the host star.