| 1. |
- Weigelt, G., et al.
(author)
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VLTI-MATISSE chromatic aperture-synthesis imaging of eta Carinae's stellar wind across the Br alpha line Periastron passage observations in February 2020
- 2021
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 652
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Journal article (peer-reviewed)abstract
- Context. Eta Carinae is a highly eccentric, massive binary system (semimajor axis similar to 15.5 au) with powerful stellar winds and a phase-dependent wind-wind collision (WWC) zone. The primary star, eta Car A, is a luminous blue variable (LBV); the secondary, eta Car B, is a Wolf-Rayet or O star with a faster but less dense wind. Aperture-synthesis imaging allows us to study the mass loss from the enigmatic LBV eta Car. Understanding LBVs is a crucial step toward improving our knowledge about massive stars and their evolution. Aims. Our aim is to study the intensity distribution and kinematics of eta Car's WWC zone. Methods. Using the VLTI-MATISSE mid-infrared interferometry instrument, we perform Br alpha imaging of eta Car's distorted wind. Results. We present the first VLTI-MATISSE aperture-synthesis images of eta Car A's stellar windin several spectral channels distributed across the Br alpha 4.052 mu m line (spectral resolving power R similar to 960). Our observations were performed close to periastron passage in February 2020 (orbital phase similar to 14.0022). The reconstructed iso-velocity images show the dependence of the primary stellar wind on wavelength or line-of-sight (LOS) velocity with a spatial resolution of 6 mas (similar to 14 au). The radius of the faintest outer wind regions is similar to 26 mas (similar to 60 au). At several negative LOS velocities, the primary stellar wind is less extended to the northwest than in other directions. This asymmetry is most likely caused by the WWC. Therefore, we see both the velocity field of the undisturbed primary wind and the WWC cavity. In continuum spectral channels, the primary star wind is more compact than in line channels. A fit of the observed continuum visibilities with the visibilities of a stellar wind CMFGEN model (CMFGEN is an atmosphere code developed to model the spectra of a variety of objects) provides a full width at half maximum fit diameter of the primary stellar wind of 2.84 +/- 0.06 mas (6.54 +/- 0.14 au). We comparethe derived intensity distributions with the CMFGEN stellar wind model and hydrodynamic WWC models.
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| 2. |
- Kattge, Jens, et al.
(author)
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TRY plant trait database - enhanced coverage and open access
- 2020
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In: Global Change Biology. - : Wiley-Blackwell. - 1354-1013 .- 1365-2486. ; 26:1, s. 119-188
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Journal article (peer-reviewed)abstract
- Plant traits-the morphological, anatomical, physiological, biochemical and phenological characteristics of plants-determine how plants respond to environmental factors, affect other trophic levels, and influence ecosystem properties and their benefits and detriments to people. Plant trait data thus represent the basis for a vast area of research spanning from evolutionary biology, community and functional ecology, to biodiversity conservation, ecosystem and landscape management, restoration, biogeography and earth system modelling. Since its foundation in 2007, the TRY database of plant traits has grown continuously. It now provides unprecedented data coverage under an open access data policy and is the main plant trait database used by the research community worldwide. Increasingly, the TRY database also supports new frontiers of trait-based plant research, including the identification of data gaps and the subsequent mobilization or measurement of new data. To support this development, in this article we evaluate the extent of the trait data compiled in TRY and analyse emerging patterns of data coverage and representativeness. Best species coverage is achieved for categorical traits-almost complete coverage for 'plant growth form'. However, most traits relevant for ecology and vegetation modelling are characterized by continuous intraspecific variation and trait-environmental relationships. These traits have to be measured on individual plants in their respective environment. Despite unprecedented data coverage, we observe a humbling lack of completeness and representativeness of these continuous traits in many aspects. We, therefore, conclude that reducing data gaps and biases in the TRY database remains a key challenge and requires a coordinated approach to data mobilization and trait measurements. This can only be achieved in collaboration with other initiatives.
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| 3. |
- Chiavassa, A., et al.
(author)
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The extended atmosphere and circumstellar environment of the cool evolved star VX Sagittarii as seen by MATISSE star
- 2022
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 658
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Journal article (peer-reviewed)abstract
- Context. VX Sgr is a cool, evolved, and luminous red star whose stellar parameters are difficult to determine, which affects its classification.Aims. We aim to spatially resolve the photospheric extent as well as the circumstellar environment.Methods. We used interferometric observations obtained with the MATISSE instrument in the L (3-4 mu m), M (4.5-5 mu m), and N (8-13 mu m) bands. We reconstructed monochromatic images using the MIRA software. We used 3D radiation-hydrodynamics simulations carried out with (COBOLD)-B-5 and a uniform disc model to estimate the apparent diameter and interpret the stellar surface structures. Moreover, we employed the radiative transfer codes OPTIM3D and RADMC3D to compute the spectral energy distribution for the L, M, and N bands, respectively.Results. MATISSE observations unveil, for the first time, the morphology of VX Sgr across the L, M, and N bands. The reconstructed images show a complex morphology with brighter areas whose characteristics depend on the wavelength probed. We measured the angular diameter as a function of the wavelength and showed that the photospheric extent in the L and M bands depends on the opacity through the atmosphere. In addition to this, we also concluded that the observed photospheric inhomogeneities can be interpreted as convection-related surface structures. The comparison in the N band yielded a qualitative agreement between the N-band spectrum and simple dust radiative transfer simulations. However, it is not possible to firmly conclude on the interpretation of the current data because of the difficulty in constraing the model parameters using the limited accuracy of our absolute flux calibration.Conclusions. MATISSE observations and the derived reconstructed images unveil the appearance of VX Sgr's stellar surface and circumstellar environment across a very large spectral domain for the first time.
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| 4. |
- Damineli, Augusto, et al.
(author)
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The Long-term Spectral Changes of Eta Carinae : Are they Caused by a Dissipating Occulter as Indicated by CMFGEN Models?
- 2023
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In: Astrophysical Journal. - : Institute of Physics Publishing (IOPP). - 0004-637X .- 1538-4357. ; 954
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Journal article (peer-reviewed)abstract
- Eta Carinae (η Car) exhibits a unique set of P Cygni profiles with both broad and narrow components. Over many decades, the spectrum has changed-there has been an increase in observed continuum fluxes and a decrease in Fe II and H I emission-line equivalent widths. The spectrum is evolving toward that of a P Cygni star such as P Cygni itself and HDE 316285. The spectral evolution has been attributed to intrinsic variations such as a decrease in the mass-loss rate of the primary star or differential evolution in a latitudinal-dependent stellar wind. However, intrinsic wind changes conflict with three observational results: the steady long-term bolometric luminosity; the repeating X-ray light curve over the binary period; and the constancy of the dust-scattered spectrum from the Homunculus. We extend previous work that showed a secular strengthening of P Cygni absorptions by adding more orbital cycles to overcome temporary instabilities and by examining more atomic transitions. CMFGEN modeling of the primary wind shows that a time-decreasing mass-loss rate is not the best explanation for the observations. However, models with a small dissipating absorber in our line of sight can explain both the increase in brightness and changes in the emission and P Cygni absorption profiles. If the spectral evolution is caused by the dissipating circumstellar medium, and not by intrinsic changes in the binary, the dynamical timescale to recover from the Great Eruption is much less than a century, different from previous suggestions.
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| 5. |
- Beecken, Jörg, 1982, et al.
(author)
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Performance assessment of state-of-the-art and novel methods for remote compliance monitoring of sulfur emissions from shipping
- 2023
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In: Atmospheric Measurement Techniques. - 1867-1381 .- 1867-8548. ; 16:23, s. 5883-5895
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Journal article (peer-reviewed)abstract
- The fuel sulfur content (FSC) of ocean-going and inland vessels was measured simultaneously by eight different state-of-the-art and novel monitoring systems during a 6-week campaign at the Elbe River, at a distance of about 10 km to the port of Hamburg, Germany. Both stationary and airborne systems on unoccupied aerial vehicles (UAVs) were operated by four participating partners in a side-by-side measurement setup to measure the emission factors of the same emission sources. A novel laser spectrometer, with significantly better-precision specifications as compared with the other instruments, was used for the first time for emission monitoring regarding the International Convention for the Prevention of Pollution from Ships (MARPOL) Annex VI regulations. The comparison took place in the North Sea sulfur emission control area (SECA), where the allowed FSC is limited to 0.10 %Sm/m. The unit %Sm/m relates to the percentage of mass sulfur per mass combusted fuel. In total, 966 plumes that originated from 436 different vessels were analysed in this study. At the same time, fuel samples obtained from 34 different vessels and bunker delivery notes (BDNs) from five frequently monitored vessels were used as a reference to assess the uncertainties of the different systems. Seven of the eight measurement systems tended to underestimate the FSC found from fuel samples and BDNs. A possible relation between underestimation and high relative humidities (above 80 %) was observed. The lowest systematic deviations were observed for the airborne systems and the novel laser spectrometer. The two UAV-borne systems showed total uncertainties of 0.07 %Sm/m and 0.09 %Sm/m (confidence level: 95 %). The novel laser spectrometer showed the lowest total uncertainty of 0.05 %Sm/m compared with other stationary sniffer systems, whose total uncertainties range from 0.08 %Sm/m to 0.09 %Sm/m. It was concluded that non-compliant vessels, with an actual FSC of the combusted fuel above 0.15 %Sm/m to 0.19 %Sm/m, can be detected by the compared systems with 95 % confidence.
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| 6. |
- Bennett, Jennifer A., et al.
(author)
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A Distinctive Adnexal (Usually Paratubal) Neoplasm Often Associated with Peutz-Jeghers Syndrome and Characterized by STK11 Alterations (STK11 Adnexal Tumor) : A Report of 22 Cases
- 2021
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In: American Journal of Surgical Pathology. - 0147-5185. ; 45:8, s. 1061-1074
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Journal article (peer-reviewed)abstract
- We describe 22 examples of a novel, usually paratubal, adnexal tumor associated with Peutz-Jeghers syndrome in nearly 50% of cases that harbored STK11 alterations in all tested (n=21). The patients ranged from 17 to 66 years (median=39 y) and the tumors from 4.5 to 25.5 cm (median=11 cm). Most (n=18) were paratubal, with metastases noted in 11/22 (50%) and recurrences in 12/15 (80%). Morphologically, they were characterized by interanastomosing cords and trabeculae of predominantly epithelioid cells, set in a variably prominent myxoid to focally edematous stroma, that often merged to form tubular, cystic, cribriform, and microacinar formations, reminiscent of salivary gland-type tumors. The tumor cells were uniformly atypical, often with prominent nucleoli and a variable mitotic index (median=9/10 HPFs). The tumors were usually positive to a variable extent for epithelial (CAM5.2, AE1/AE3, cytokeratin 7), sex cord (calretinin, inhibin, WT1), and mesothelial (calretinin, D2-40) markers, as well as hormone receptors. PAX8, SF1, and GATA-3 were rarely positive, while claudin-4, FOXL2, and TTF-1 were consistently negative. All sequenced tumors (n=21) harbored alterations in STK11, often with a loss of heterozygosity event. There were no other recurrently mutated genes. Recurrent copy number alterations included loss of 1p and 11q, and gain of 1q, 15q, and 15p. Despite an extensive morphologic, immunohistochemical, and molecular evaluation, we are unable to determine with certainty the histogenesis of this unique tumor. Wolffian, sex cord stromal, epithelial, and mesothelial origins were considered. We propose the term STK11 adnexal tumor to describe this novel entity and emphasize the importance of genetic counseling in these patients as a significant number of neoplasms occur in association with Peutz-Jeghers syndrome.
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| 7. |
- Gallou, Arnaud, et al.
(author)
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Diurnal temperature range as a key predictor of plants' elevation ranges globally
- 2023
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In: Nature Communications. - 2041-1723. ; 14:1
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Journal article (peer-reviewed)abstract
- A prominent hypothesis in ecology is that larger species ranges are found in more variable climates because species develop broader environmental tolerances, predicting a positive range size-temperature variability relationship. However, this overlooks the extreme temperatures that variable climates impose on species, with upper or lower thermal limits more likely to be exceeded. Accordingly, we propose the 'temperature range squeeze' hypothesis, predicting a negative range size-temperature variability relationship. We test these contrasting predictions by relating 88,000 elevation range sizes of vascular plants in 44 mountains to short- and long-term temperature variation. Consistent with our hypothesis, we find that species' range size is negatively correlated with diurnal temperature range. Accurate predictions of short-term temperature variation will become increasingly important for extinction risk assessment in the future. This study relates 88,000 elevation range sizes of vascular plants in 44 mountains to short-term and long-term temperature variation. The authors finding of decreasing elevation range sizes with greater diurnal temperature range supports a novel biodiversity hypothesis and indicates increased extinction risk of continental species.
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| 8. |
- Gull, Theodore R., et al.
(author)
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Eta Carinae : A Tale of Two Periastron Passages
- 2021
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In: Astrophysical Journal. - : Institute of Physics (IOP). - 0004-637X .- 1538-4357. ; 923:1, s. 102-102
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Journal article (peer-reviewed)abstract
- Since 2002, the far-ultraviolet (FUV) flux (1150–1680 Å) of Eta Carinae, monitored by the Hubble Space Telescope/Space Telescope Imaging Spectrograph, has increased by an order of magnitude. This increase is attributed to partial dissipation of a line-of-sight (LOS) occulter that blocks the central core of the system. Across the 2020 February periastron passage, changes in the FUV emission show a stronger wavelength dependence than occurred across the 2003 July periastron passage. Across both periastron passages, most of the FUV spectrum dropped in flux then recovered a few months later. The 2020 periastron passage included enhancements of FUV flux in narrow spectral intervals near periastron followed by a transient absorption and recovery to pre-periastron flux levels. The drop in flux is due to increased absorption by singly ionized species as the secondary star plunges deep into the wind of the primary star, which blocks the companion's ionizing radiation. The enhanced FUV emission is caused by the companion's wind-blown cavity briefly opening a window to deeper layers of the primary star. This is the first time transient brightening has been seen in the FUV comparable to transients previously seen at longer wavelengths. Changes in resonance line-velocity profiles hint that the dissipating occulter is associated with material in LOS moving at −100 to −300 km s−1, similar in velocity of structures previously associated with the 1890s lesser eruption
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| 9. |
- Gull, Theodore R., et al.
(author)
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Eta Carinae : An Evolving View of the Central Binary, Its Interacting Winds and Its Foreground Ejecta
- 2022
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In: Astrophysical Journal. - : IOP Publishing Ltd. - 0004-637X .- 1538-4357. ; 933:2, s. 1-28
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Journal article (peer-reviewed)abstract
- FUV spectra of eta Car, recorded across two decades with HST/STIS, document multiple changes in resonant lines caused by dissipating extinction in our line of sight. The FUV flux has increased nearly tenfold, which has led to increased ionization of the multiple shells within the Homunculus and photodestruction of H-2. Comparison of observed resonant line profiles with CMFGEN model profiles allows separation of wind-wind collision and shell absorptions from the primary wind P Cygni profiles. The dissipating occulter preferentially obscured the central binary and interacting winds relative to the very extended primary wind. We are now able to monitor changes in the colliding winds with orbital phase. High-velocity transient absorptions occurred across the most recent periastron passage, indicating acceleration of the primary wind by the secondary wind, which leads to a downstream, high-velocity bow shock that is newly generated every orbital period. There is no evidence of changes in the properties of the binary winds.
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| 10. |
- Gull, Theodore R., et al.
(author)
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Eta Carinae - The Dissipating Occulter Is an Extended Structure
- 2023
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In: Astrophysical Journal. - : Institute of Physics Publishing (IOPP). - 0004-637X .- 1538-4357. ; 954:1
-
Journal article (peer-reviewed)abstract
- Previous Hubble Space Telescope (HST)/Space Telescope Imaging Spectrograph (STIS) longslit observations of Eta Carinae (η Car) identified numerous absorption features in both the stellar spectrum, and in the adjacent nebular spectra, along our line of sight (LOS). The absorption features became temporarily stronger when the ionizing far-ultraviolet radiation field was reduced by the periastron passage of the secondary star. Subsequently, dissipation of a dusty structure in our LOS has led to a long-term increase in the apparent brightness of η Car, an increase in the ionizing ultraviolet (UV) radiation, and the disappearance of absorption from multiple velocity-separated shells extending across the foreground Homunculus lobe. We use HST/STIS spectro-images, coupled with published infrared and radio observations, to locate this intervening dusty structure. The velocity and spatial information indicate the occulter is ≈1000 au in front of η Car. The Homunculus is a transient structure composed of dusty, partially ionized ejecta that eventually will disappear due to the relentless rain of ionizing radiation and wind from the current binary system along with dissipation and mixing with the interstellar medium. This evolving complex continues to provide an astrophysical laboratory that changes on human timescales.
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