Theoretical Spectra and Light Curves of Close-in Extrasolar Giant Planets and Comparison with Data

We present theoretical atmosphere, spectral, and light-curve models for extrasolar giant planets (EGPs) undergoing strong irradiation for which {\it Spitzer} planet/star contrast ratios or light curves have been published (circa June 2007). These include HD 209458b, HD 189733b, TrES-1, HD 149026b, HD 179949b, and $\upsilon$ And b. By comparing models with data, we find that a number of EGP atmospheres experience thermal inversions and have stratospheres. This is particularly true for HD 209458b, HD 149026b, and $\upsilon$ And b. This finding translates into qualitative changes in the planet/star contrast ratios at secondary eclipse and in close-in EGP orbital light curves. Moreover, the presence of atmospheric water in abundance is fully consistent with all the {\it Spitzer} data for the measured planets. For planets with stratospheres, water absorption features invert into emission features and mid-infrared fluxes can be enhanced by a factor of two. In addition, the character of near-infrared planetary spectra can be radically altered. We derive a correlation between the importance of such stratospheres and the stellar flux on the planet, suggesting that close-in EGPs bifurcate into two groups: those with and without stratospheres. From the finding that TrES-1 shows no signs of a stratosphere, while HD 209458b does, we estimate the magnitude of this stellar flux breakpoint. We find that the heat redistribution parameter, P$_n$, for the family of close-in EGPs assumes values from $\sim$0.1 to $\sim$0.4. This paper provides a broad theoretical context for the future direct characterization of EGPs in tight orbits around their illuminating stars.Comment: Accepted to Ap. J., provided here in emulateapj format: 28 pages, 8 figures, many with multiple panel

Pregnancy diagnosis using ultrasound

Few Western Australian ewe flocks are diagnosed for pregnancy despite the precence of high numbers of barren ewes. Surveys of farm flocks in the early 1970s recorded that between 14 and 29 per cent of ewes failed to lamb each year. Techniques for diagnosing pregnant ewes have been available for many years, but ultrasonic devices and computer technology have made it possible for skilled operators to determine whether ewes are pregnant and more importantly, whether they have one, two or more foetuses. Once the number of pregnant ewes is known farmers can use labour more efficiently. They can minimise the cost of supplementary feeding, particularily if the use of diagnostic techniques identifies ewes bearing twin lambs. Failure to carefully manage a flock with multiple lambs could lead to reduced wool production per head, reduced lamb growth and morre ewe and lamb deaths

Non-detection of the OH Meinel system in comet P/Swift-Tuttle

We report a search for emissions from the OH Meinel system in high-resolution near-infrared spectra of comet P/Swift-Tuttle. Because of the large cometary heliocentric velocity and high resolution of the spectrograph, the cometary lines should be well separated from the bright OH sky lines. Contrary to the findings of Tozzi et al. (1994) - who report seeing cometary OH at intensities comparable to the sky emissions in their low-resolution spectra - we find no OH in these spectra with an upper limit of 5% the value of the night sky lines. The non-detection of these cometary lines is consistent with theoretical calculations of expected emission strengths from prompt and fluorescent emission from cometary OH

Eddy Impacts on the Florida Current

The Gulf Stream in the Atlantic carries warm water northwards and forms both the return closure of the subtropical gyre as well as the upper limb of the meridional overturning circulation. Recent time series recorded east of the Bahamas at 26°N indicate that from May 2009 to April 2011, in contrast with past observations, the northward flowing Antilles Current covaried with the Gulf Stream in the Florida Straits—the Florida Current—even though the Florida and Antilles Currents are separated by banks and islands spanning 150?km. The peak-to-trough amplitude of transport variations during this period was 15?×?106?m3?s?1 for the Florida Current and 12?×?106?m3?s?1 for the Antilles Current, at time scales of 50?days to a year. From satellite observations, we show that the fluctuations in both the Florida and Antilles Currents between May 2009 and April 2011 are driven by eddy activity east of the Bahamas. Since the Florida Current time series is a critical time series for the state of the oceans, and often compared to climate models, this newly identified source of variability needs careful consideration when attributing the variability of the Florida Current to changes in the larger-scale circulations (e.g., gyre and overturning) or wind forcing.<br/

A high-Resolution Catalog of Cometary Emission Lines

Using high-resolution spectra obtained with the Hamilton echelle spectrograph at Lick Observatory, we have constructed a catalog of emission lines observed in comets Swift-Tuttle and Brorsen-Metcalf. The spectra cover the range between 3800 Å and 9900 Å with a spectral resolution of λ/Δλ~42000. In the spectra, we catalog 2997 emission lines of which we identify 2438. We find cometary lines due to H, O, C_2, CN, NH_2, C_3, H_2O^+, CH, and CH^+. We list 559 unidentified lines compiled from the two spectra and comment on possibilities for their origins

Magnetic fields of intermediate mass T Tauri stars

Aims. In this paper, we aim to measure the strength of the surface magnetic fields for a sample of five intermediate mass T Tauri stars and one low mass T Tauri star from late-F to mid-K spectral types. While magnetic fields of T Tauri stars at the low mass range have been extensively characterized, our work complements previous studies towards the intermediate mass range; this complementary study is key to evaluate how magnetic fields evolve during the transition from a convective to a radiative core. Methods. We studied the Zeeman broadening of magnetically sensitive spectral lines in the H-band spectra obtained with the CRIRES high-resolution near-infrared spectrometer. These data are modelled using magnetic spectral synthesis and model atmospheres. Additional constraints on non-magnetic line broadening mechanisms are obtained from modelling molecular lines in the K band or atomic lines in the optical wavelength region. Results. We detect and measure mean surface magnetic fields for five of the six stars in our sample: CHXR 28, COUP 107, V2062 Oph, V1149 Sco, and Par 2441. Magnetic field strengths inferred from the most magnetically sensitive diagnostic line range from 0.8 to 1.8 kG. We also estimate a magnetic field strength of 1.9 kG for COUP 107 from an alternative diagnostic. The magnetic field on YLW 19 is the weakest in our sample and is marginally detected, with a strength of 0.8 kG. Conclusions. We populate an uncharted area of the pre-main-sequence HR diagram with mean magnetic field measurements from high-resolution near-infrared spectra. Our sample of intermediate mass T Tauri stars in general exhibits weaker magnetic fields than their lower mass counterparts. Our measurements will be used in combination with other spectropolarimetric studies of intermediate mass and lower mass T Tauri stars to provide input into pre-main-sequence stellar evolutionary models.Comment: 8 pages, 8 figures, accepted for publication in Astronomy and Astrophysic

Accretion-powered Stellar Winds as a Solution to the Stellar Angular Momentum Problem

We compare the angular momentum extracted by a wind from a pre-main-sequence star to the torques arising from the interaction between the star and its Keplerian accretion disk. We find that the wind alone can counteract the spin-up torque from mass accretion, solving the mystery of why accreting pre-main-sequence stars are observed to spin at less than 10% of break-up speed, provided that the mass outflow rate in the stellar winds is ~10% of the accretion rate. We suggest that such massive winds will be driven by some fraction $\epsilon$ of the accretion power. For observationally constrained typical parameters of classical T-Tauri stars, $\epsilon$ needs to be between a few and a few tens of percent. In this scenario, efficient braking of the star will terminate simultaneously with accretion, as is usually assumed to explain the rotation velocities of stars in young clusters.Comment: Accepted by ApJ Letter

Stratigraphic Studies of the Palo Duro Basin: An Update

Stratigraphic studies of the Palo Duro Basin are now in their 8th year. Although the emphasis in these studies now lies in the San Andres Formation (possible repository host rock) and the Wolfcamp Series (sub-repository aquifer), investigations of other units (fig. 1) continue to be carried out as well. This report includes work that was not available for inclusion in last year's (1983) CSR on stratigraphy (Open File Report No. OF-WTWI-1984-30). The section on pre-Pennsylvanian stratigraphy represents the final stages of study of those units. The report detailing structural controls on deposition of the San Andres is part of an ongoing effort to recognize indications of structural or tectonic controls on sedimentation throughout the stratigraphic column in the Palo Duro Basin area. Studies of the Dockum Group are revealing similar controls during the Triassic. Core studies of the Dockum are increasing our resolution of depositional settings in the area.Bureau of Economic Geolog

The Far-Ultraviolet Spectra of TW Hya. II. Models of H2 Fluorescence in a Disk

We measure the temperature of warm gas at planet-forming radii in the disk around the classical T Tauri star (CTTS) TW Hya by modelling the H2 fluorescence observed in HST/STIS and FUSE spectra. Strong Ly-alpha emission irradiates a warm disk surface within 2 AU of the central star and pumps certain excited levels of H2. We simulate a 1D plane-parallel atmosphere to estimate fluxes for the 140 observed H2 emission lines and to reconstruct the Ly-alpha emission profile incident upon the warm H2. The excitation of H2 can be determined from relative line strengths by measuring self-absorption in lines with low-energy lower levels, or by reconstructing the Ly-alpha profile incident upon the warm H2 using the total flux from a single upper level and the opacity in the pumping transition. Based on those diagnostics, we estimate that the warm disk surface has a column density of log N(H2)=18.5^{+1.2}_{-0.8}, a temperature T=2500^{+700}_{-500} K, and a filling factor of H2, as seen by the source of Ly-alpha emission, of 0.25\pm0.08 (all 2-sigma error bars). TW Hya produces approximately 10^{-3} L_\odot in the FUV, about 85% of which is in the Ly-alpha emission line. From the H I absorption observed in the Ly-alpha emission, we infer that dust extinction in our line of sight to TW Hya is negligible.Comment: Accepted by ApJ. 26 pages, 17 figures, 6 table

Chemical spots in the absence of magnetic field in the binary HgMn star 66 Eridani

According to our current understanding, a subclass of the upper main sequence chemically peculiar stars, called mercury-manganese (HgMn), is non-magnetic. Nevertheless, chemical inhomogeneities were recently discovered on their surfaces. At the same time, no global magnetic fields stronger than 1-100 G are detected by modern studies. The goals of our study are to search for magnetic field in the HgMn binary system 66 Eri and to investigate chemical spots on the stellar surfaces of both components. Our analysis is based on high quality spectropolarimetric time-series observations obtained during 10 consecutive nights with the HARPSpol instrument at the ESO 3.6-m telescope. To increase the sensitivity of the magnetic field search we employed a least-squares deconvolution (LSD). We used spectral disentangling to measure radial velocities and study line profile variability. Chemical spot geometry was reconstructed using multi-line Doppler imaging. We report a non-detection of magnetic field in 66 Eri, with error bars 10-24 G for the longitudinal field. Circular polarization profiles also do not indicate any signatures of complex surface magnetic fields. For a simple dipolar field configuration we estimated an upper limit of the polar field strength to be 60-70 G. For the HgMn component we found variability in spectral lines of Ti, Ba, Y, and Sr with the rotational period equal to the orbital one. The surface maps of these elements reconstructed with the Doppler imaging technique, show relative underabundance on the hemisphere facing the secondary component. The contrast of chemical inhomogeneities ranges from 0.4 for Ti to 0.8 for Ba.Comment: 13 pages, 14 figure