Abstract. We present Infrared Space Observatory (ISO) spectra of fourteen isolated Herbig Ae/Be (HAEBE) stars, to study the characteristics of their circumstellar dust. These spectra show large star-to-star differences, in the emission features of both carbon-rich and oxygen-rich dust grains. The IR spectra were combined with photometric data ranging from the UV through the optical into the sub-mm region. We defined two key groups, based upon the spectral shape of the infrared region. The derived results can be summarized as follows: (1) the continuum of the IR to sub-mm region of all stars can be reconstructed by the sum of a power-law and a cool component, which can be represented by a black body. Possible locations for these components are an optically thick, geometrically thin disc (power-law component) and an optically thin flared region (black body); (2) all stars have a substantial amount of cold dust around them, independent of the amount of mid-IR excess they show; (3) also the near-IR excess is unrelated to the mid-IR excess, indicating different composition/location of the emitting material; (4) remarkably, some sources lack the silicate bands; (5) apart from amorphous silicates, we find evidence for crystalline silicates in several stars, some of which are new detections; (6) PAH bands are present in at least 50% of our sample, and their appearance is slightly different from PAHs in the ISM; (7) PAH bands are, with one exception, not present in sources which only show a power-law continuum in the IR; their presence is unrelated to the presence of the silicate bands; (8) the dust in HAEBE stars shows strong evidence for coagulation; this dust processing is unrelated to any of the central star properties (such as age, spectral type and activity).

Silicate dust in the interstellar medium is observed to be amorphous, yet silicate dust in comets and interplanetary dust particles is sometimes partially crystalline. The dust in disks that are thought to be forming planets around some young stars also appears to be partially crystalline. These observations suggest that as the dust goes from the precursor clouds to a planetary system, it must undergo some processing, but the nature and extent of this processing remain unknown. Here we report observations of highly crystalline silicate dust in the disks surrounding binary red-giant stars. The dust was created in amorphous form in the outer atmospheres of the red giants, and therefore must be processed in the disks to become crystalline. The temperatures in these disks are too low for the grains to anneal; therefore, some low-temperature process must be responsible. As the physical properties of the disks around young stars and red giants are similar, our results suggest that low-temperature crystallization of silicate grains also can occur in protoplanetary systems.

3 Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries: France, Germany, the Netherlands and the United Kingdom) with the participation of ISAS and NASA. ABSTRACTWe combine spectra of VY CMa obtained with the short-and long-wavelength spectrometers, SWS and LWS, on the Infrared Space Observatory to provide a first detailed continuum spectrum of this highly luminous star. The circumstellar dust cloud through which the star is observed is partially self-absorbing, which makes for complex computational modeling. We review previous work and comment on the range of uncertainties about the physical traits and mineralogical composition of the modeled disk. We show that these uncertainties significantly affect the modeling of the outflow and the estimated mass loss. In particular, we demonstrate that a variety of quite diverse models can produce good fits to the observed spectrum. If the outflow is steady, and the radiative repulsion on the dust cloud dominates the star's gravitational attraction, we show that the total dust mass-loss rate is ∼ 4 × 10 −6 M ⊙ yr −1 , assuming that the star is at a distance of 1.5 kpc. Several indications, however, suggest that the outflow from the star may be spasmodic. We discuss this and other problems facing the construction of a physically coherent model of the dust cloud and a realistic mass-loss analysis.

We present a detailed analysis of SWS (2.35-45 µm) and LWS (43-200 µm) spectra obtained with the Infrared Space Observatory (ISO) (Kessler et al. 1996) of the dusty circumstellar disk surrounding the isolated young Fe star HD 142527. Two dust populations can be clearly discriminated: a warm component which is dominated by very strong silicate emission at 10 µm, but in which C-rich dust is observable as well, and a cool component, of which the spectrum is dominated by O-rich dust features (C-rich dust not cause obvious features in the far infrared). Besides silicates, crystalline water-ice and hydrous silicates-which are also found in interplanetary dust particlesare present in the cold circumstellar environment. The ISO spectrum of HD 142527 differs markedly from that of HD 100546 (Malfait et al. 1998b) and other objects in a similar evolutionary stage and with a similar broad-band energy distribution. No clear correlations between the spectral dust signatures and the stellar parameters can be found at the present stage.

During the last years, a trend to replace commonly used short arc lamps in projection systems with alternative light sources is seen. Next to LEDs for low light output products, lasers try to enter the projection area and have the ambition to infiltrate from low (picoprojection) towards high light output systems (digital cinema).One of the benefits of lasers is their narrow spectral bandwidth. As a consequence, the display can have a very large colour gamut, if the lasers are carefully selected. Another benefit is the very low intrinsic étendue of the source. One can imagine using less complex, more efficient, smaller but more powerful optical systems. This not only for scanning projectors, but also for 2D light valve based projectors (LCOS, LCD, DLP). In addition, the limited lifetime of lamps has serious impact on a system's cost of ownership, and puts light source reliability/lifetime high on the list of priorities for future developments. For this reason, Barco entered the European FP6-project OSIRIS, in a subtask where a 300 lm laser projector demonstrator has to be developed and evaluated.So far, we found out that next to obvious challenges such as laser cost and laser power, the most critical issue regarding image quality is speckle interference which counteracts the beneficial nature of the light source. This phenomenon is a direct consequence of the coherent nature of a laser and cannot be solved as easily as is often claimed. We will describe laser speckle in the context of laser projection and the theoretical limits of several reduction techniques. This leads to guidelines which can make laser projection worth considering.