Crystalline silicate dust around evolved stars: I. The sample stars

This is the first paper in a series of three where we present the first comprehensive inventory of solid state emission bands observed in a sample of 17 oxygen-rich circumstellar dust shells surrounding evolved stars. The data were taken with the Short and Long Wavelength Spectrographs on board of the Infrared Space Observatory (ISO) and cover the 2.4 to 195 μm wavelength range. The spectra show the presence of broad 10 and 18 μm bands that can be attributed to amorphous silicates. In addition, at least 49 narrow bands are found whose position and width indicate they can be attributed to crystalline silicates. Almost all of these bands were not known before ISO. The incredible richness of the crystalline silicate spectra observed by ISO allows detailed studies of the mineralogy of these dust shells, and is a telltale about the origin and evolution of the dust. We have measured the peak positions, widths and strengths of the individual, continuum subtracted bands. Based on these measurements, we were able to order the spectra in sequence of decreasing crystalline silicate band strength. We found that the strength of the emission bands correlates with the geometry of the circumstellar shell, as derived from direct imaging or inferred from the shape of the spectral energy distribution. This naturally divides the sample into objects that show a disk-like geometry (strong crystalline silicate bands), and objects whose dust shell is characteristic of an outflow (weak crystalline silicate bands). All stars with the 33.6 μm forsterite band stronger than 20 percent over continuum are disk sources. We define spectral regions (called complexes) where a concentration of emission bands is evident, at 10, 18, 23, 28, 33, 40 and 60 μm. We derive average shapes for these complexes and compare these to the individual band shapes of the programme stars. In an Appendix, we provide detailed comments on the measured band positions and strengths of individual sources

The circumstellar dust shell of the post-AGB star HD 161796

We have modeled the complete optical to millimeter spectrum of the Post-Asymptotic Giant Branch (Post-AGB) star HD 161796 and its circumstellar dust shell. A full 2–200 μm spectrum taken with the Infrared Space Observatory was used to constrain the dust properties. A good fit is achieved using only 4 dust components: amorphous silicates, the crystalline silicates forsterite and enstatite, and crystalline water ice, contributing respectively about 63, 4, 6 and 27% to the total dust mass. The different dust species were assumed to be co-spatial but distinct, resulting in different temperatures for the different grain populations. We find a temperature for the crystalline H2O ice of 70 K, which is higher than thermal equilibrium calculations of pure H2O ice would give. This implies that the ice must be formed as a mantle on top of an (amorphous) silicate core. In order to form H2O ice mantles the mass loss rate must exceed some yr-1. With a water-ice fraction of 27% a lower limit for the gas to dust mass ratio of 270 is found. At a distance of 1.2 kpc (Skinner et al. [CITE]) and adopting an outflow velocity of 15 km s-1 (Likkel et al. [CITE]) an AGB mass loss rate of ( yr-1) is found, which lasted 900 years and ended 430 years ago. During this phase a total of 0.46 was expelled. The mass loss rate was high enough to account for the presence of the H2O ice

Mineral cloud and hydrocarbon haze particles in the atmosphere of the hot Jupiter JWST target WASP-43b

Context: Having a short orbital period and being tidally locked makes WASP-43b an ideal candidate for the James Webb Space Telescope (JWST) phase curve measurements. Phase curve observations of an entire orbit will enable the mapping of the atmospheric structure across the planet, with different wavelengths of observation allowing different atmospheric depths to be seen. Aims: We provide insight into the details of the clouds that may form on WASP-43b and their impact on the remaining gas phase, in order to prepare the forthcoming interpretation of the JWST and follow-up data. Methods: We follow a hierarchical modelling strategy. We utilise 3D GCM results as input for a kinetic, non-equilibrium model for mineral cloud particles and for a kinetic model to study a photochemically-driven hydrocarbon haze component. Results: Mineral condensation seeds form throughout the atmosphere of WASP-43b. This is in stark contrast to the ultra-hot Jupiters, such as WASP-18b and HAT-P-7b. The dayside is not cloud free but it is loaded with few yet large mineral cloud particles in addition to hydrocarbon haze particles of a comparable abundance. Photochemically driven hydrocarbon haze appears on the dayside, but it does not contribute to the cloud formation on the nightside. The geometrical cloud extension differs across the globe due to the changing thermodynamic conditions. Day and night differ by 6000 km in pressure scale height. As reported for other planets, the C/O is not constant throughout the atmosphere and varies between 0.74 and 0.3. The mean molecular weight is approximately constant in a H2- dominated WASP-43b atmosphere because of the moderate day/night-temperature differences compared to the super-hot Jupiters. Conclusions: WASP-43b is expected to be fully covered in clouds which are not homogeneously distributed throughout the atmosphere. The dayside and the terminator clouds are a combination of mineral particles of locally varying size and composition as well as of hydrocarbon hazes. The optical depth of hydrocarbon hazes is considerably lower than that of mineral cloud particles such that a wavelength-dependent radius measurement of WASP-43b would be determined by the mineral cloud particles but not by hazes

A close halo of large transparent grains around extreme red giant stars

Intermediate-mass stars end their lives by ejecting the bulk of their envelope via a slow dense wind back into the interstellar medium, to form the next generation of stars and planets. Stellar pulsations are thought to elevate gas to an altitude cool enough for the condensation of dust, which is then accelerated by radiation pressure from starlight, entraining the gas and driving the wind. However accounting for the mass loss has been a problem due to the difficulty in observing tenuous gas and dust tens of milliarcseconds from the star, and there is accordingly no consensus on the way sufficient momentum is transferred from the starlight to the outflow. Here, we present spatially-resolved, multi-wavelength observations of circumstellar dust shells of three stars on the asymptotic giant branch of the HR diagram. When imaged in scattered light, dust shells were found at remarkably small radii (<~ 2 stellar radii) and with unexpectedly large grains (~300 nm radius). This proximity to the photosphere argues for dust species that are transparent to starlight and therefore resistant to sublimation by the intense radiation field. While transparency usually implies insufficient radiative pressure to drive a wind, the radiation field can accelerate these large grains via photon scattering rather than absorption - a plausible mass-loss mechanism for lower-amplitude pulsating stars.Comment: 13 pages, 1 table, 6 figure

Entangled-State Cycles of Atomic Collective-Spin States

We study quantum trajectories of collective atomic spin states of $N$ effective two-level atoms driven with laser and cavity fields. We show that interesting ``entangled-state cycles'' arise probabilistically when the (Raman) transition rates between the two atomic levels are set equal. For odd (even) $N$, there are $(N+1)/2$ ($N/2$) possible cycles. During each cycle the $N$-qubit state switches, with each cavity photon emission, between the states $(|N/2,m>\pm |N/2,-m>)/\sqrt{2}$, where $|N/2,m>$ is a Dicke state in a rotated collective basis. The quantum number $m$ ($>0$), which distinguishes the particular cycle, is determined by the photon counting record and varies randomly from one trajectory to the next. For even $N$ it is also possible, under the same conditions, to prepare probabilistically (but in steady state) the Dicke state $|N/2,0>$, i.e., an $N$-qubit state with $N/2$ excitations, which is of particular interest in the context of multipartite entanglement.Comment: 10 pages, 9 figure

Pompe disease in children and adults: natural course, disease severity and impact on daily life; results from an international patient survey

Pompe disease is a lysosomal storage disorder caused by deficiency of the enzyme acid alpha-glucosidase and mainly characterized by progressive skeletal muscle weakness. Research on this so far untreatable disease has long been directed towards unraveling the pathophysiological mechanisms and the development of a causal treatment. At the advent of enzyme replacement therapy, the research described in this thesis was intended to include the patientâ €™s perspective in the assessment of the consequences of the disease. The aims were to map out the health status of patients with non- classic or late-onset Pompe disease, to provide more insight in the natural course and rate of progression on a group level, and to evaluate the use of specific self-report measurement scales. These studies form the basis for further follow-up of patients before and after the start of therapy, and are examples of a successful cooperation between patients, patient organizations and universities

The complete ISO spectrum of NGC 6302

We present the combined Infrared Space Observatory Short-Wavelength Spectrometer and Long-Wavelength Spectrometer 2.4-197 μm spectrum of the Planetary Nebula NGC 6302 which contains in addition to strong atomic lines, a series of emission features due to solid state components. The broad wavelength coverage enables us to more accurately identify and determine the properties of both oxygen- and carbon-rich circumstellar dust. A simple model fit was made to determine the abundance and typical temperature of the amorphous silicates, enstatite and forsterite. Forsterite and enstatite do have roughly the same abundance and temperature. The origin and location of the dust in a toroidal disk around the central star are discussed

Infrared imaging and spectroscopy of the Luminous Blue Variables Wra 751 and AG Car

We present ground-based infrared imaging and ISO spectroscopy of the luminous blue variables Wra 751 and AG Car. The images show in both cases a detached shell with a roughly circular distribution of emission. The infrared images of AG Car coincide very well with the optical images. The optical (H[FORMULA]) image of Wra 751 is different from the infrared image; the H[FORMULA] nebula is suggested to be a scattering nebula containing cold dust particles. Fitting both the images and the spectra consistently with a 1-D radiative transfer model, we derive properties of their dust shells. Wra 751 is surrounded by a dust shell with inner and outer radii of 0.17 and 0.34 pc respectively and a dust mass of 0.017 [FORMULA]. The dust shell of AG Car has inner and outer radii of 0.37 and 0.81 pc respectively and a total dust mass of 0.25 [FORMULA]. Dust mass-loss rates during the formation of the shells are 2.7[FORMULA] and 3.4[FORMULA] [FORMULA] yr-1, respectively. The total dust mass and hence the derived dust mass-loss rates are uncertain by at least a factor of two. For AG Car, the derived dust mass and mass-loss rate are higher than previous estimates. This is mainly caused by the fact that a contribution of very large grains ([FORMULA] 10 µm) is needed to explain the flux levels at longer wavelengths. Dust models for both objects fail to explain the flux shortward of 15 to 20 µm: a population of small warm grains, not in thermal equilibrium with the central star is necessary to explain this excess. Similarities between dust shells around Wolf-Rayet stars and Wra 751 and AG Car (mass, grain size population, morphology) suggest a similar formation history and imply an evolutionary connection. A similar connection with red supergiants is suggested on the basis of the dust composition and derived time-averaged mass-loss rates

Herschel/HIFI observations of molecular emission in protoplanetary nebulae and young planetary nebulae

Aims. We aim to study the physical conditions, particularly the excitation state, of the intermediate-temperature gas in protoplanetary nebulae and young planetary nebulae (PPNe, PNe). The information that the observations of the different components deliver is of particular importance for understanding the evolution of these objects. Methods. We performed Herschel/HIFI observations of intermediate-excitation molecular lines in the far-infrared/submillimeter range in a sample of ten nebulae. The high spectral resolution provided by HIFI allows the accurate measurement of the line profiles. The dynamics and evolution of these nebulae are known to result from the presence of several gas components, notably fast bipolar outflows and slow shells (that often are the fossil AGB shells), and the interaction between them. Because of the diverse kinematic properties of the different components, their emissions can be identified in the line profiles. The observation of these high-energy transitions allows an accurate study of the excitation conditions, particularly in the warm gas, which cannot be properly studied from the low-energy lines. Results. We have detected FIR/sub-mm lines of several molecules, in particular of (CO)-C-12, (CO)-C-13, and H2O. Emission from other species, like NH3, OH, (H2O)-O-18, HCN, SiO, etc., has been also detected. Wide profiles showing sometimes spectacular line wings have been found. We have mainly studied the excitation properties of the high-velocity emission, which is known to come from fast bipolar outflows. From comparison with general theoretical predictions, we find that CRL 618 shows a particularly warm fast wind, with characteristic kinetic temperature T-k greater than or similar to 200 K. In contrast, the fast winds in OH 231.8+4.2 and NGC 6302 are cold, T-k similar to 30 K. Other nebulae, like CRL 2688, show intermediate temperatures, with characteristic values around 100 K. We also discuss how the complex structure of the nebulae can affect our estimates, considering two-component models. We argue that the differences in temperature in the different nebulae can be caused by cooling after the gas acceleration (that is probably caused by shocks); for instance, CRL 618 is a case of very recent acceleration, less than similar to 100 yr ago, while the fast gas in OH 231.8+4.2 was accelerated similar to 1000 yr ago. We also find indications that the densest gas tends to be cooler, which may be explained by the expected increase of the radiative cooling efficiency with the density