We have constructed a comprehensive grid of 680 metal line-blanketed, non-LTE, plane-parallel, hydrostatic model atmospheres for the basic parameters appropriate to O-type stars. The OSTAR2002 considers 12 values effective temperatures, 27,500 K ≤ Teff 55,000 with 2500 steps, eight surface gravities, 3.0 log g 4.75 0.25 dex and 10 chemical compositions, from metal-rich relative Sun metal-free. lower limit given temperature is set by an approximate location Eddington limit. selected...

We show that under certain circumstances the differences between absorption mean and Planck opacities can lead to multiple solutions for an LTE atmospheric structure. Since are not expected differ significantly in usual case of radiative equilibrium, non-irradiated atmospheres, most interesting situations where effect may play a role strongly irradiated stars planets, also possibly structures there is significant deposition mechanical energy, such as stellar chromospheres accretion disks....

We calculate the theoretical evolution of radii all fourteen known transiting extrasolar giant planets (EGPs) for a variety assumptions concerning atmospheric opacity, dense inner core masses, and possible internal power sources. incorporate effects stellar irradiation customize such each EGP star. Looking collectively at family as whole, we find that there are in fact two radius anomalies to be explained. Not only subset EGPs larger than expected from previous theory, but many other objects...

Abstract Atmospheric compositions can provide powerful diagnostics of formation and migration histories planetary systems. We investigate constraints on atmospheric abundances H 2 O, Na, K, in a sample transiting exoplanets using the latest transmission spectra new broadened opacities Na K. Our 19 spans from cool mini-Neptunes to hot Jupiters, with equilibrium temperatures between ∼300 2700 Using homogeneous Bayesian retrievals we report their detection significances, confirming 6 planets...

We present the results of a detailed UV and optical spectral analysis properties 6 dwarf O-type stars in SMC H II region NGC 346. Stellar parameters, chemical abundances, wind parameters have been determined using NLTE line blanketed models calculated with photospheric code, Tlusty, CMFGEN. The results, particular iron obtained two codes compare very favorably, demonstrating that basic O dwarfs can be reliably static model atmospheres. require microturbulent velocity to match observed...

We present theoretical atmosphere, spectral, and light-curve models for extrasolar giant planets (EGPs) undergoing strong irradiation which {\it Spitzer} planet/star contrast ratios or light curves have been published (circa June 2007). These include HD 209458b, 189733b, TrES-1, 149026b, 179949b, $\upsilon$ And b. By comparing with data, we find that a number of EGP atmospheres experience thermal inversions stratospheres. This is particularly true finding translates into qualitative changes...

We find that a theoretical fit to all the HD 209458b data at secondary eclipse requires dayside atmosphere of have thermal inversion and stratosphere. This is caused by capture optical stellar flux an absorber uncertain origin resides altitude. One consequence stratospheric heating temperature flipping water absorption features into emission from near- mid-infrared we see evidence such feature in recent IRAC Knutson et al. In addition, upper-atmosphere may help explain both...

We present a comprehensive theory of the spectra and atmospheres irradiated extrasolar giant planets. explore dependences on stellar type, orbital distance, cloud characteristics, planet mass, surface gravity. Phase-averaged for specific known planets that span wide range relevant parameters are calculated, plotted, discussed. The connection between atmospheric composition emergent spectrum is explored in detail. Furthermore, we calculate effect insolation brown dwarfs. review variety...

We present new coronagraphic images of Beta Pictoris obtained with the Space Telescope Imaging Spectrograph (STIS) in September 1997. The high-resolution (0.1") clearly detect circumstellar disk as close 0.75" to star, corresponding a projected radius 15 AU. define warp greater precision and at closer radii Pic than do previous observations. They show that can be modelled by projection two components: main disk, fainter component, which is inclined component 4-5 degrees, extends only far ~4"...

Non-local Thermodynamic Equilibrium (NLTE) calculations of hot white dwarf (WD) model atmospheres are the cornerstone modern flux calibrations for Hubble Space Telescope (HST) and CALSPEC database. These theoretical spectral energy distributions (SEDs) provide relative vs. wavelength, only absolute level remains to be set by reconciling measured Vega in visible with Midcourse Experiment (MSX) values Sirius mid-IR. The most recent SEDs calculated \textsc{tlusty} \textsc{tmap} NLTE atmosphere...

We present a detailed study of AV 83, an O7 Iaf+ supergiant, and 69 [OC7.5 III((f))] in the SMC. The stars have similar effective temperatures luminosities but show very different wind signatures. For our we used non-LTE line-blanketed atmosphere code developed by Hillier Miller, which explicitly allows for line blanketing C, N, O, S, Ar, Ne, Fe, other elements. Our finds that 83 has temperature approximately 33,000 K log g ≈ 3.25. It extended photosphere as result "low" surface gravity much...

We present an ultraviolet color-magnitude diagram (CMD) spanning the hot horizontal branch (HB), blue straggler, and white dwarf populations of globular cluster NGC 2808. These data were obtained with far-UV near-UV cameras on Space Telescope Imaging Spectrograph (STIS). Although previous optical CMDs 2808 show a high-temperature gap within HB population, no such is evident in our UV CMD. Instead, we find population subluminous stars, anomaly only previously reported for ω Cen. Our...

We report on a systematic study of the most massive stars, in which we analyzed spectra four very luminous stars Large Magellanic Cloud. The lie 30 Doradus complex, three are located core compact cluster, R136a (R136a1, R136a3, and R136a5), fourth (Melnick 42), about 8'' north R136a. Low-resolution (<200 km s-1) these were obtained with GHRS FOS spectrographs Hubble Space Telescope. cover spectral range from 1200 to 1750 Å, 3200 6700 Å. derived fundamental parameters by fitting observations...

We present a systematic study of the spectral consequences departures from chemical equilibrium in atmospheres L and T dwarfs, for even cooler dwarfs. The temperature/pressure profiles nonequilibrium models are fully consistent with chemistry. Our grid includes spectra effective temperatures 200 to 1800 K, three surface gravities, four possible values coefficient eddy diffusion radiative zone, different CO/CH4 reaction prescriptions. also provide clear cloudy model variants. find, keeping...

Using a self-consistent atmosphere code, we construct new model of the transiting extrasolar giant planet HD 209458b to investigate disparity between observed strength sodium absorption feature at 589 nm and predictions previous models. For atmospheric temperature-pressure profile derive, silicate iron clouds reside pressure several millibars in planet's atmosphere. These have significant vertical extent optical depth because our slant viewing geometry lead increased bands directly adjacent...

Self-consistent vertical structure models together with non-LTE radiative transfer should produce spectra from accretion disks around black holes, which differ multitemperature blackbodies at levels that may be observed. High-resolution, high signal-to-noise observations warrant spectral modeling both accounts for relativistic effects and treats the physics of in detail. In Davis et al. we presented accounted effects, Compton scattering, opacities due to ions abundant metals. Using a...

We have created a general methodology for calculating the wavelength-dependent light curves of close-in extrasolar giant planets (EGPs) as they traverse their orbits. Focusing on transiting EGPs HD 189733b, TrES-1, and 209458b, we calculate planet/star flux ratios during secondary eclipse compare them with Spitzer data points obtained so far in mid-infrared. introduce simple parameterization redistribution heat to planet's night side, derive constraints this parameter (Pn), provide set...

We study the evolution, rotation, and surface abundances of O-type dwarfs in Small Magellanic Cloud. analyzed UV optical spectra twenty-three objects derived photospheric wind properties. The observed binary fraction sample is ~ 26%, which compatible with more systematic studies, if one considers that actual potentially larger owing to low-luminosity companions excluded obvious spectroscopic binaries. location fastest rotators H-R diagram indicates these could be several Myr old. offset...

We have constructed a grid of non-LTE disk models for wide range values black hole mass and accretion rate, several the viscosity parameter α, two extreme spin: maximum-rotation Kerr hole, Schwarzschild (nonrotating) hole. Our procedure calculates self-consistently vertical structure all annuli together with radiation field, without any approximations imposed on optical thickness disk, ad hoc to behavior intensity. The total spectrum is computed by summing spectra individual annuli, taking...

The ultraviolet spectrum (1145-1720 Å) of the distant quasar Q0302-003 (z = 3.286) was observed at 1.8 Å resolution with Space Telescope Imaging Spectrograph aboard Hubble Telescope. A total integration time 23,280 s obtained. clearly delineates Gunn-Peterson He II absorption trough, produced by Lyα along line sight over redshift range z 2.78-3.28. Its interpretation facilitated modeling based on Keck HIRES spectra H I forest (provided A. Songaila and M. Rauch W. Sargent). We find that near...

We present a large grid of computed far- and mid-ultraviolet spectra (850-2000 Å) the integrated light from steady-state accretion disks in luminous cataclysmic variables. The are tabulated at 0.25 Å intervals with an adopted FWHM resolution 1.0 Å, so they suitable for use observed variety modern space-borne observatories. Twenty-six different combinations white dwarf mass Mwd rate considered, presented six disk inclinations i. models self-consistently plane-parallel approximation, assuming...

We present a comprehensive analysis of high-resolution, far-ultraviolet HST STIS, FUSE, and optical spectra 18 O stars in the Small Magellanic Cloud. Our is based on OSTAR2002 grid NLTE metal-line-blanketed model atmospheres calculated with our code TLUSTY. systematically explore sensitivity various UV lines to different stellar parameters. have obtained consistent fits spectrum derive effective temperature, surface gravity, composition, microturbulent velocity each star. Stellar radii,...

Brief HST/STIS spectroscopic snapshot exposures of the cataclysmic variables 1RXSJ232953.9+062814, CE315, BZ UMa and EY Cyg reveal very large NV/CIV line flux ratios, similar to those observed in AE Aqr. Such anomalous ratios have so far been 10 systems, presumably reflect a different composition accreted material compared majority variables. We discuss properties this small sample context recent proposal by Schenker et al. (2002) that significant fraction present-day population may passed...

We have generated new, self-consistent spectral and atmosphere models for the effective temperature range 600-1300 K thought to encompass known T dwarfs. For first time, theoretical are compared with a family of measured dwarf spectra at wavelengths shortward ~1.0 μm. By defining indices standard colors in optical very near-infrared, we explore systematics Teff, gravity, metallicity. conclude that short-wavelength is rich diagnostics complement those near-infrared now used subtyping. also...