[en] The direct detection of photons emitted or reflected by extrasolar planets, spatially resolved from their parent star, is a major frontier in the study of other solar systems. Direct detection will provide statistical information on planets in 5-50 AU orbits, inaccessible to current Doppler searches, and allow spectral characterization of radius, temperature, surface gravity, and perhaps composition. Achieving this will require new dedicated high-contrast instruments. One such system under construction is the Gemini Planet Imager (GPI.) This combines a high-order/high-speed adaptive optics system to control wavefront errors from the Earth's atmosphere, an advanced coronagraph to block diffraction, ultrasmooth optics, a precision infrared interferometer to measure and correct systematic errors, and a integral field spectrograph/polarimeter to image and characterize target planetary systems. We predict that GPI will be able to detect planets with brightness less than 10^-7 of their parent star, sufficient to observe warm self-luminous planets around a large population of targets

[en] The evolution of a supernova buried in a molecular cloud is studied analytically and compared with preliminary numerical dynamical results. Such a supernova can disrupt a cloud of mass M< or approx. =10⁴ M/sub sun/, but will be assimilated by larger clouds. The rate of evolution of a buried supernova is considerably enhanced by the large ambient density n> or approx. =10³ cm^-3. For constant density n> or approx. =10⁵ cm^-3 and ejected mass approx.10 M/sub sun/ the system cannot relax into a true self-similar adiabatic solution because the radiative losses are already appreciable by the time a mass exceeding that of the supernova ejecta is swept up. With a density gradient the shock is accelerated while the emissivity decreases. This serves to prolong the adiabatic phase which may last until the remnant reaches the edge of the cloud. For a constant density n=10⁴ cm^-3 the luminosity rises during the adiabatic phase to a peak greater than 10⁶ lasting approx.100 years. It plummets rapidly thereafter in the radiative phase but may still be approx.10⁴ L/sub O/ after several thousand years when the radius is approx.1 pc. The spectrum will be characterized by a self-absorbed radio free-free tail and a large peak in the IR due to absorption and reradiation by dust grains of optical, UV, and soft X-ray photons. This peak is determined basically by flux balance and thus will qualitatively resemble the IR spectrum of a buried O star of the same luminosity. There will also be a characteristic X-ray signature in the free-free emission with conspicuous absorption edges in the range 1/2-1 keV

[en] Ground based adaptive optics is a potentially powerful technique for direct imaging detection of extrasolar planets. Turbulence in the Earth's atmosphere imposes some fundamental limits, but the large size of ground-based telescopes compared to spacecraft can work to mitigate this. We are carrying out a design study for a dedicated ultra-high-contrast system, the eXtreme Adaptive Optics Planet Imager (XAOPI), which could be deployed on an 8-10m telescope in 2007. With a 4096-actuator MEMS deformable mirror it should achieve Strehl >0.9 in the near-IR. Using an innovative spatially filtered wavefront sensor, the system will be optimized to control scattered light over a large radius and suppress artifacts caused by static errors. We predict that it will achieve contrast levels of 10⁷-10⁸ at angular separations of 0.2-0.8 inches around a large sample of stars (R<7-10), sufficient to detect Jupiter-like planets through their near-IR emission over a wide range of ages and masses. We are constructing a high-contrast AO testbed to verify key concepts of our system, and present preliminary results here, showing an RMS wavefront error of <1.3 nm with a flat mirror

[en] We present an analysis of the orbital motion of the four substellar objects orbiting HR 8799. Our study relies on the published astrometric history of this system augmented with an epoch obtained with the Project 1640 coronagraph with an integral field spectrograph (IFS) installed at the Palomar Hale telescope. We first focus on the intricacies associated with astrometric estimation using the combination of an extreme adaptive optics system (PALM-3000), a coronagraph, and an IFS. We introduce two new algorithms. The first one retrieves the stellar focal plane position when the star is occulted by a coronagraphic stop. The second one yields precise astrometric and spectrophotometric estimates of faint point sources even when they are initially buried in the speckle noise. The second part of our paper is devoted to studying orbital motion in this system. In order to complement the orbital architectures discussed in the literature, we determine an ensemble of likely Keplerian orbits for HR 8799bcde, using a Bayesian analysis with maximally vague priors regarding the overall configuration of the system. Although the astrometric history is currently too scarce to formally rule out coplanarity, HR 8799d appears to be misaligned with respect to the most likely planes of HR 8799bce orbits. This misalignment is sufficient to question the strictly coplanar assumption made by various authors when identifying a Laplace resonance as a potential architecture. Finally, we establish a high likelihood that HR 8799de have dynamical masses below $13M_{\mathrm{J}\mathrm{u}\mathrm{p}}$, using a loose dynamical survival argument based on geometric close encounters. We illustrate how future dynamical analyses will further constrain dynamical masses in the entire system.