1,509 research outputs found

    Updated Spitzer Emission Spectroscopy of Bright Transiting Hot Jupiter HD189733b

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    We analyze all existing secondary eclipse time series spectroscopy of hot Jupiter HD189733b acquired with the now defunct Spitzer/IRS instrument. We describe the novel approaches we develop to remove the systematic effects and extract accurate secondary eclipse depths as a function of wavelength in order to construct the emission spectrum of the exoplanet. We compare our results to a previous study by Grillmair et al. that did not examine all data sets available to us. We are able to confirm the detection of a water feature near 6{\mu}m claimed by Grillmair et al. We compare the planetary emission spectrum to three model families -- based on isothermal atmosphere, gray atmosphere, and two realizations of the complex radiative transfer model by Burrows et al., adopted in Grillmair et al.'s study. While we are able to reject the simple isothermal and gray models based on the data at the 97% level just from the IRS data, these rejections hinge on eclipses measured within relatively narrow wavelength range, between 5.5 and 7{\mu}m. This underscores the need for observational studies with broad wavelength coverage and high spectral resolution, in order to obtain robust information on exoplanet atmospheres.Comment: 16 pages, 13 figures and 3 tables. Accepted for publication in Ap

    Pension Plans and Public Policy

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    High signal-to-noise spectral characterization of the planetary-mass object HD 106906 b

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    We spectroscopically characterize the atmosphere of HD 106906b, a young low-mass companion near the deuterium burning limit. The wide separation from its host star of 7.1" makes it an ideal candidate for high S/N and high-resolution spectroscopy. We aim to derive new constraints on the spectral type, effective temperature, and luminosity of HD106906b and also to provide a high S/N template spectrum for future characterization of extrasolar planets. We obtained 1.1-2.5 μ\mum integral field spectroscopy with the VLT/SINFONI instrument with a spectral resolution of R~2000-4000. New estimates of the parameters of HD 106906b are derived by analyzing spectral features, comparing the extracted spectra to spectral catalogs of other low-mass objects, and fitting with theoretical isochrones. We identify several spectral absorption lines that are consistent with a low mass for HD 106906b. We derive a new spectral type of L1.5±\pm1.0, one subclass earlier than previous estimates. Through comparison with other young low-mass objects, this translates to a luminosity of log(L/L⊙L/L_\odot)=−3.65±0.08-3.65\pm0.08 and an effective temperature of Teff=1820±2401820\pm240 K. Our new mass estimates range between M=11.9−0.8+1.7MJupM=11.9^{+1.7}_{-0.8} M_{\rm Jup} (hot start) and M=14.0−0.5+0.2MJupM=14.0^{+0.2}_{-0.5} M_{\rm Jup} (cold start). These limits take into account a possibly finite formation time, i.e., HD 106906b is allowed to be 0--3 Myr younger than its host star. We exclude accretion onto HD 106906b at rates M˙>4.8×10−10MJup\dot{M}>4.8\times10^{-10} M_{\rm Jup}yr−1^{-1} based on the fact that we observe no hydrogen (Paschen-β\beta, Brackett-γ\gamma) emission. This is indicative of little or no circumplanetary gas. With our new observations, HD 106906b is the planetary-mass object with one of the highest S/N spectra yet. We make the spectrum available for future comparison with data from existing and next-generation (e.g., ELT and JWST) spectrographs.Comment: 11 pages, 5 figures. Accepted for publication in Astronomy & Astrophysics. Fully reduced spectra will be made available for download on CD

    Detection of phosphotyrosine, insulin receptor substrate-1 and growth factor receptor-bound protein-2 in the magnocellular forebrain system and hypothalamus of cat and man

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    Insulin action initiated by insulin binding to its cognate receptor is performed via phosphorylation of tyrosines on substrate proteins by the receptor tyrosine kinase domain. This process involves autophosphorylation of tyrosine residues in the cytoplasmic domain of the receptor. A comparable action is mediated by nerve growth factor (NGF) and epidermal growth factor (EGF) receptors. Few articles have been directed to the morphological regional distribution in the brain of phosphotyrosine, using antibodies. The first extensive description that proved a topographical distribution for phosphotyrosine in the rat brain was conducted by Marani and Maassen. It was shown that alternating areas positive and negative for phosphotyrosine could be described. These areas showed different localizations that were in good agreement with the biochemical results obtained by others. Moreover, fetal and postnatal series confirmed the results that phosphotyrosine content is extremely high in the developing brain as compared to the mature brain. In the mature brain, the phosphotyrosine localization is also found in the neuropil, not only in neurons. High concentrations of phosphotyrosine in a regional distribution are found in the rat rhinencephalon, the cortex, the basal ganglia (mainly in neostriatum and substantia nigra), hypothalamus and the habenular nuclei. In the hippocampus, the positivity for phosphotyrosine can be detected in the pyramidal cells and the neuropil. The hippocampal subdivisions of CA1 and CA3 can be weakly discerned. Topographical studies of the distribution of insulin receptor substrate-1 (IRS-1), growth factor receptor-bound protein-2 (GRB-2) or its adaptor molecule and substrate of insulin receptor kinase (She) that complexes to GRB-2 and conducts insulin action towards the Ras complex are absent for the brain.Biomedical Reviews 1996; 5: 73-82

    Ground-based optical transmission spectrum of the hot Jupiter HAT-P-1b

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    Time-series spectrophotometric studies of exoplanets during transit using ground-based facilities are a promising approach to characterize their atmospheric compositions. We aim to investigate the transit spectrum of the hot Jupiter HAT-P-1b. We compare our results to those obtained at similar wavelengths by previous space-based observations. We observed two transits of HAT-P-1b with the Gemini Multi-Object Spectrograph (GMOS) instrument on the Gemini North telescope using two instrument modes covering the 320 - 800 nm and 520 - 950 nm wavelength ranges. We used time-series spectrophotometry to construct transit light curves in individual wavelength bins and measure the transit depths in each bin. We accounted for systematic effects. We addressed potential photometric variability due to magnetic spots in the planet's host star with long-term photometric monitoring. We find that the resulting transit spectrum is consistent with previous Hubble Space Telescope (HST) observations. We compare our observations to transit spectroscopy models that marginally favor a clear atmosphere. However, the observations are also consistent with a flat spectrum, indicating high-altitude clouds. We do not detect the Na resonance absorption line (589 nm), and our observations do not have sufficient precision to study the resonance line of K at 770 nm. We show that even a single Gemini/GMOS transit can provide constraining power on the properties of the atmosphere of HAT-P-1b to a level comparable to that of HST transit studies in the optical when the observing conditions and target and reference star combination are suitable. Our 520 - 950 nm observations reach a precision comparable to that of HST transit spectra in a similar wavelength range of the same hot Jupiter, HAT-P-1b. However, our GMOS transit between 320 - 800 nm suffers from strong systematic effects and yields larger uncertainties.Comment: A&A, accepted, 16 pages, 8 figures, 5 table

    THE MORTALITY OF BACTERIOPHAGE CONTAINING ASSIMILATED RADIOACTIVE PHOSPHORUS

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    The bacteriophage T4 containing assimilated radioactive phosphorus is inactivated at a rate proportional to the specific radioactivity of the constituent phosphorus. The beta radiation from the phosphorus makes a negligible contribution to this effect. The inactivation is therefore a direct consequence of the nuclear reaction, which kills the phage with an efficiency of about 1/12. Several phages related to T4 behave similarly. When radioactive phage is grown from a seed of non-radioactive phage, all of the phage progeny are subject to killing by radioactive decay. The phage is killed by beta radiation from P32 with an efficiency of about 1/100 per ionization within the particle volume. Bacteriophage T4 and its relatives contain about 500,000 atoms of phosphorus per infective particle. Virtually all this phosphorus is adsorbed to bacteria with the specificity characteristic of the infective particles, and none of it can be removed from the particles by the enzyme desoxyribonuclease. The phosphorus content per particle, together with the published data on analytical composition, indicates a particle diameter close to 110 mµ for the varieties of phage studied

    Hydrogen Evolution by a Chloroplast-Ferredoxin-Hydrogenase System

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    Phase curves of WASP-33b and HD 149026b and a New Correlation Between Phase Curve Offset and Irradiation Temperature

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    We present new 3.6 and 4.5 μm\mu m Spitzer phase curves for the highly irradiated hot Jupiter WASP-33b and the unusually dense Saturn-mass planet HD 149026b. As part of this analysis, we develop a new variant of pixel level decorrelation that is effective at removing intrapixel sensitivity variations for long observations (>10 hours) where the position of the star can vary by a significant fraction of a pixel. Using this algorithm, we measure eclipse depths, phase amplitudes, and phase offsets for both planets at 3.6 μm\mu m and 4.5 μm\mu m. We use a simple toy model to show that WASP-33b's phase offset, albedo, and heat recirculation efficiency are largely similar to those of other hot Jupiters despite its very high irradiation. On the other hand, our fits for HD 149026b prefer a very high albedo and an unusually high recirculation efficiency. We also compare our results to predictions from general circulation models, and find that while neither are a good match to the data, the discrepancies for HD 149026b are especially large. We speculate that this may be related to its high bulk metallicity, which could lead to enhanced atmospheric opacities and the formation of reflective cloud layers in localized regions of the atmosphere. We then place these two planets in a broader context by exploring relationships between the temperatures, albedos, heat transport efficiencies, and phase offsets of all planets with published thermal phase curves. We find a striking relationship between phase offset and irradiation temperature--the former drops with increasing temperature until around 3400 K, and rises thereafter. Although some aspects of this trend are mirrored in the circulation models, there are notable differences that provide important clues for future modeling efforts

    Spitzer Secondary Eclipses of the Dense, Modestly-irradiated, Giant Exoplanet HAT-P-20b Using Pixel-Level Decorrelation

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    HAT-P-20b is a giant exoplanet that orbits a metal-rich star. The planet itself has a high total density, suggesting that it may also have a high metallicity in its atmosphere. We analyze two eclipses of the planet in each of the 3.6- and 4.5 micron bands of Warm Spitzer. These data exhibit intra-pixel detector sensitivity fluctuations that were resistant to traditional decorrelation methods. We have developed a simple, powerful, and radically different method to correct the intra-pixel effect for Warm Spitzer data, which we call pixel-level decorrelation (PLD). PLD corrects the intra-pixel effect very effectively, but without explicitly using - or even measuring - the fluctuations in the apparent position of the stellar image. We illustrate and validate PLD using synthetic and real data, and comparing the results to previous analyses. PLD can significantly reduce or eliminate red noise in Spitzer secondary eclipse photometry, even for eclipses that have proven to be intractable using other methods. Our successful PLD analysis of four HAT-P-20b eclipses shows a best-fit blackbody temperature of 1134 +/-29K, indicating inefficient longitudinal transfer of heat, but lacking evidence for strong molecular absorption. We find sufficient evidence for variability in the 4.5 micron band that the eclipses should be monitored at that wavelength by Spitzer, and this planet should be a high priority for JWST spectroscopy. All four eclipses occur about 35 minutes after orbital phase 0.5, indicating a slightly eccentric orbit. A joint fit of the eclipse and transit times with extant RV data yields e(cos{omega}) = 0.01352 (+0.00054, -0.00057), and establishes the small eccentricity of the orbit to high statistical confidence. Given the existence of a bound stellar companion, HAT-P-20b is another excellent candidate for orbital evolution via Kozai migration or other three-body mechanism.Comment: version published in ApJ, minor text and figure revision
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