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We have obtained FUSE and HST STIS spectra of HR 4796A, a nearby 8 Myr old main sequence star that possesses a dusty circumstellar disk whose inclination has been constrained from high resolution near-infrared observations to be ∼17◦ from edge-on. We searched for circumstellar absorption in the ground states of C II λ1036.3, O I λ1039.2, Zn II λ2026.1,(More)
The λ Boötis stars are Population I, late B to early F-type stars, with moderate to extreme (up to a factor 100) surface underabundances of most Fe-peak elements and solar abundances of lighter elements (C, N, O, and S). To put constraints on the various existing theories that try to explain these peculiar stars, we investigate the observational properties(More)
We discuss the chemical pre-conditions for planet formation, in terms of gas and ice abundances in a protoplanetary disk, as function of time and position, and the resulting chemical composition and cloud properties in the atmosphere when young gas giant planets form, in particular discussing the effects of unusual, non-solar carbon and oxygen abundances.(More)
Context. Emission lines from protoplanetary disks originate mainly from the irradiated surface layers, where the gas is generally warmer than the dust. Therefore, the interpretation of emission lines requires detailed thermo-chemical models, which are essential to convert line observations into understanding disk physics. Aims. We aim at hydrostatic disk(More)
Inga Kamp1, Cornelis P. Dullemond2, Michiel Hogerheijde3, Jesus Emilio Enriquez4 Space Telescope Division of ESA, STScI, 3700 San Martin Drive, Baltimore, MD 21218, USA email: kamp@stsci.edu Max-Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg, Germany Leiden Observatory, PO Box 9513, NL-3200 RA Leiden, The Netherlands University of Texas(More)
LkCa15 is an extensively studied star in the Taurus region, known for its pre-transitional disk with a large inner cavity in the dust continuum and normal gas accretion rate. The most popular hypothesis to explain the LkCa15 data invokes one or more planets to carve out the inner cavity, while gas continues to flow across the gap from the outer disk onto(More)
Models for the structure of protoplanetary disks have so far been based on the assumption that the gas and the dust temperature are equal. The gas temperature , an essential ingredient in the equations of hydrostatic equilibrium of the disk, is then determined from a continuum radiative transfer calculation, in which the continuum opacity is provided by the(More)
The λ Bootis stars, a group of late B to early F-type population I stars, have surface abundances that resemble the general metal depletion pattern found in the interstellar medium. Inspired by the recent result that the fundamental parameters of these peculiar stars differ in no respect from a comparison sample of normal stars, the hypothesis of an(More)
Planets are formed in disks around young stars. With an age of ∼10 Myr, TW Hya is one of the nearest T Tauri stars that is still surrounded by a relatively massive disk. In addition a large number of molecules has been found in the TW Hya disk, making TW Hya the perfect test case in a large survey of disks with Herschel–PACS to directly study their gaseous(More)