ALBERT

Description: We report interferometric observations of the semiregular variable star RS CrB, a red giant with strong silicate emission features. The data were among the first long-baseline mid-infrared stellar fringes obtained between the Keck telescopes, using parts of the new nulling beam combiner.

Description: We report an orbital characterization of GJ1108Aab that is a low-mass binary system in the pre-main-sequence phase. Via the combination of astrometry using adaptive optics and radial velocity measurements, an eccentric orbital solution of e = 0.63 is obtained, which might be induced by the KozaiLidov mechanism with a widely separated GJ1108B system. Combined with several observed properties, we conrm that the system is indeed young. Columba is the most probable moving group, to which the GJ1108A system belongs, although its membership to the group has not been established. If the age of Columba is assumed for GJ1108A, the dynamical masses of both GJ1108Aa and GJ1108Ab (M(sub dynamical,GJ1108Aa) = 0.72 0.04 Solar Mass and M(sub dynamical,GJ1108Ab) = 0.30 0.03 Solar Mass) are more massive than what an evolutionary model predicts based on the age and luminosities. We consider that the discrepancy in mass comparison can be attributed to an age uncertainty; the system is likely older than stars in Columba, and effects that are not implemented in classical models such as accretion history and magnetic activity are not preferred to explain the mass discrepancy. We also discuss the performance of the evolutionary model by compiling similar low-mass objects in the evolutionary state based on the literature. Consequently, it is suggested that the current model on average reproduces the mass of resolved low-mass binaries without any signicant offsets.

Description: The Hunt for Observable Signatures of Terrestrial Systems survey searches for dust near the habitable zones (HZs) around nearby, bright main-sequence stars. We use nulling interferometry in the N band to suppress the bright stellar light and to probe for low levels of HZ dust around the 30 stars observed so far. Our overall detection rate is 18%, including four new detections, among which are the first three around Sun-like stars and the first two around stars without any previously known circumstellar dust. The inferred occurrence rates are comparable for early-type and Sun-like stars, but decrease from 60(sup +16)(sub -21)% for stars with previously detected cold dust to 8(sup +10)(sub -3)% for stars without such excess, confirming earlier results at higher sensitivity. For completed observations on individual stars, our sensitivity is five to ten times better than previous results. Assuming a lognormal excess luminosity function, we put upper limits on the median HZ dust level of 13 zodis (95% confidence) for a sample of stars without cold dust and of 26 zodis when focusing on Sun-like stars without cold dust. However, our data suggest that a more complex luminosity function may be more appropriate. For stars without detectable Large Binocular Telescope Interferometer (LBTI) excess, our upper limits are almost reduced by a factor of two, demonstrating the strength of LBTI target vetting for future exo-Earth imaging missions. Our statistics are limited so far, and extending the survey is critical to informing the design of future exo-Earth imaging surveys.

Description: We present the direct imaging discovery of an extrasolar planet, or possible low-mass brown dwarf, at a projected separation of 55 plus or minus 2 AU (1."058 plus or minus 0."007) from the B9-type star K And. The planet was detected with Subaru/HiCIAO (Subaru/High Contrast Instrument for the Subaru Next Generation Adaptive Optics) during the SEEDS (Strategic Exploration of Exoplanets and Disks with Subaru Telescope/HiCIAO) survey and confirmed as a bound companion via common proper motion measurements. Observed near-infrared magnitudes of J equals 16.3 plus or minus 0.3, H equals 15.2 plus or minus 0.2, K (sub s) = 14.6 plus or minus 0.4, and L prime equals 13.12 plus or minus 0.09 indicate a temperature of approximately 1700 degrees Kelvin. The galactic kinematics of the host star are consistent with membership in the Columba Association, implying a corresponding age of 30 (exp from plus 20 to minus10) Myr. The systems age, combined with the companion photometry, points to a model-dependent companion mass approximately 12.8 times the mass of Jupiter. The host stars estimated mass of 2.4 to 2.5 times the mass of the sun places it among the most massive stars ever known to harbor an extrasolar planet or low-mass brown dwarf. While the mass of the companion is close to the deuterium burning limit, its mass ratio, orbital separation, and likely planet-like formation scenario imply that it may be best defined as a super-Jupiter with properties similar to other recently discovered companions to massive stars.

Description: We report observations of the nova RS 0phiuchi using the Keck Interferometer Nuller (KIN) taken approximately 3.8 days following the most recent outburst that occurred on 2006 February 12. The KIN operates in N-band from approx. 8 to 12.5 microns in a nulling mode - the sparse aperture equivalent of the conventional coronagraphic technique used in filled aperture te1escopes. In this mode the stellar light is suppressed by a destructive fringe, effectively enhancing the contrast of the circumstellar material located near the star. In a second, constructive-fringe mode, the instrument detects primarily the light from the central, bright source. These are the outer and inner spatial regimes, resprectively. We will describe the capabilities of the KIN, including these unique modes, and outline how they were key in our discovery that dust does not appear to be created in the outburst as in previous models, but instead was created between nova events. We also show how these first results from the KIN are consistent with Spitzer data. The KIN data show evidence of enhanced neutral atomic hydrogen emission and atomic metals including silicon located in the inner spatial regime near the white dwarf (WD) relative to the outer regime. There are also nebular emission lines and evidence of hot silicate dust in the outer spatial region, centered at approximately 17 AU from the WD, that are not found in the inner regime. The KIN and Spitzer data suggest that these emissions were excited by the nova flash in the outer spatial regime before the blast wave reached these regions. We describe the present results in terms of a new model for dust creation in recurrent novae that includes an increase in density in the plane of the orbit of the two stars created by a spiral shock wave caused by the motion of the stars through the cool wind of the red giant star. These data show the power and potential of the nulling technique which has been developed for the detection of Earth-like planets around nearby stars for the Terrestrial Planet Finder and Darwin missions.

Description: The Keck interferometer currently under development will include a midinfrared nulling experiment that is designed to search for extrazodiacal dust around nearby stars. The potential of this technique, as wel1 as the basic experimental approach, will be discussed. The initial goal is to search for extrazodiacal emission around nearby stars at the 10-solar zodi-equivalent level, with a long-term goal of I solar zodi.

Description: We have used the Long Wavelength Spectrometer (LWS) aboard the Infrared Space Observatory (ISO) to map the far-infrared continuum emission (45-175 micrometer) toward several massive Giant Molecular Cloud (GMC) cores located near the Galactic center. The observed far-infrared and submillimeter spectral energy distributions imply low temperatures (approx. 15 - 22 K) for the bulk of the dust in all the sources, consistent with external heating by the diffuse ISRF and suggest that these GMCs do not harbor high- mass star-formation sites, in spite of their large molecular mass. Observations of FIR atomic fine structure lines of C(sub II) and O(sub I) indicate an ISRF enhancement of approx. 10(exp 3) in the region. Through continuum radiative transfer modeling we show that this radiation field strength is in agreement with the observed FIR and submillimeter spectral energy distributions, assuming primarily external heating of the dust with only limited internal luminosity (approx. 2 x 10(exp 5) solar luminosity). Spectroscopic observations of millimeter-wave transitions of H2CO, CS, and C-34S carried out with the Caltech Submillimeter Observatory (CSO) and the Institut de Radio Astronomie Millimetrique (IRAM) 30-meter telescope indicate a gas temperature of approx. 80 K, significantly higher than the dust temperatures, and density of approx. 1 x 10(exp 5)/cc in GCM0.25 + 0.01, the brightest submillimeter source in the region. We suggest that shocks caused by cloud collisions in the turbulent interstellar medium in the Galactic center region are responsible for heating the molecular gas. This conclusion is supported by the presence of wide-spread emission from molecules such as SiO, SO, and CH3OH, which are considered good shock tracers. We also suggest that the GMCs studied here are representative of the "typical", pre-starforming cloud population in the Galactic center.

Description: Far-infrared Fourier-transform spectrometer measurements of the 1-0 and 3-2 PH3 transitions in Saturn's disk near 267 and 800 GHz (8.9 and 26.7/cm), respectively, were analyzed simultaneously to derive a global mean profile for the PH3 vertical mixing ratio between 100 and 600 mbar total pressure. The far-infrared spectrum is relatively free from spectral interlopers, suffers minimal absorption or scattering by atmospheric particulates, and contains intrinsically weak PH3 lines that are sensitive to a range of atmospheric depths. The combined spectra are inconsistent with a uniform tropospheric mixing ratio, even with a stratospheric cut-off. They are consistent with a volume mixing ratio of PH3 that drops from 1.2 x 10(exp -5) at 645 mbar pressure to a value of 4.1 x 10(exp -7) at 150 mbar pressure, a decrease that is linear is log abundance vs log pressure. The mixing ratio could drop even more quickly at atmospheric pressures below 150 mbar and still be consistent with the data. The mixing ratio may well remain constant with depth for pressures above 630 mbar. The maximum PH3 mixing ratio in this model is consistent with a [P]/[H] ratio in the deep atmosphere that is about a factor of 10 higher than solar composition. Such a model is consistent with rapid mixing up to the radiative-convective boundary and transport by, for example, vertical waves just above this boundary. In the best fitting model, the eddy diffusion coefficient is approximately 10(exp 4) sq cm near 630 mbar, and it must increase with altitude. The predominant PH3 loss mechanisms are direct photolysis by UV radiation and scavenging by H atoms produced by the photolysis.

Description: Hi-5 is a high-contrast (or high dynamic range) infrared imager project for the VLTI. Its main goal is to characterize young extra-solar planetary systems and exozodiacal dust around southern main-sequence stars. In this paper, we present an update of the project and key technology pathways to improve the contrast achieved by the VLTI. In particular, we discuss the possibility to use integrated optics, proven in the near-infrared, in the thermal near-infrared (L and M bands, 3-5 m) and advanced fringe tracking strategies. We also address the strong exoplanet science case (young exoplanets, planet formation, and exozodiacal disks) offered by this wavelength regime as well as other possible science cases such as stellar physics (fundamental parameters and multiplicity) and extragalactic astrophysics (active galactic nuclei and fundamental constants). Synergies and scientific preparation for other potential future instruments such as the Planet Formation Imager are also briefly discussed.