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We report the discovery of two new Galactic candidate luminous blue variable (LBV) stars via detection of circular shells (typical of confirmed and candidate LBVs) and follow-up spectroscopy of their central stars. The shells were detected at 22 mu m in the archival data of the Mid-Infrared All Sky Survey carried out with the Wide-field Infrared Survey Explorer (WISE). Follow-up optical spectroscopy of the central stars of the shells conducted with the renewed Southern African Large Telescope (SALT) showed that their spectra are very similar to those of the well-known LBVs P Cygni and AG Car, and the recently discovered candidate LBV MN112, which implies the LBV classification for these stars as well. The LBV classification of both stars is supported by detection of their significant photometric variability: one of them brightened in the R and I bands by 0.68 +/- 0.10 and 0.61 +/- 0.04 mag, respectively, during the last 1318 years, while the second one (known as Hen 3-1383) varies its B, V, R, I and Ks brightnesses by similar or equal to 0.50.9 mag on time-scales from 10 d to decades. We also found significant changes in the spectrum of Hen 3-1383 on a time-scale of similar or equal to 3 months, which provides additional support for the LBV classification of this star. Further spectrophotometric monitoring of both stars is required to firmly prove their LBV status. We discuss a connection between the location of massive stars in the field and their fast rotation, and suggest that the LBV activity of the newly discovered candidate LBVs might be directly related to their possible runaway status.
To identify genetic variants associated with head circumference in infancy, we performed a meta-analysis of seven genome-wide association studies (GWAS) (N = 10,768 individuals of European ancestry enrolled in pregnancy and/or birth cohorts) and followed up three lead signals in six replication studies (combined N = 19,089). rs7980687 on chromosome 12q24 (P = 8.1 x 10(-9)) and rs1042725 on chromosome 12q15 (P = 2.8 x 10(-10)) were robustly associated with head circumference in infancy. Although these loci have previously been associated with adult height(1), their effects on infant head circumference were largely independent of height (P = 3.8 x 10(-7) for rs7980687 and P = 1.3 x 10(-7) for rs1042725 after adjustment for infant height). A third signal, rs11655470 on chromosome 17q21, showed suggestive evidence of association with head circumference (P = 3.9 x 10(-6)). SNPs correlated to the 17q21 signal have shown genome-wide association with adult intracranial volume(2), Parkinson's disease and other neurodegenerative diseases(3-5), indicating that a common genetic variant in this region might link early brain growth with neurological disease in later life.
A catalog of genetic loci associated with kidney function from analyses of a million individuals
(2019)
Chronic kidney disease (CKD) is responsible for a public health burden with multi-systemic complications. Through transancestry meta-analysis of genome-wide association studies of estimated glomerular filtration rate (eGFR) and independent replication (n = 1,046,070), we identified 264 associated loci (166 new). Of these,147 were likely to be relevant for kidney function on the basis of associations with the alternative kidney function marker blood urea nitrogen (n = 416,178). Pathway and enrichment analyses, including mouse models with renal phenotypes, support the kidney as the main target organ. A genetic risk score for lower eGFR was associated with clinically diagnosed CKD in 452,264 independent individuals. Colocalization analyses of associations with eGFR among 783,978 European-ancestry individuals and gene expression across 46 human tissues, including tubulo-interstitial and glomerular kidney compartments, identified 17 genes differentially expressed in kidney. Fine-mapping highlighted missense driver variants in 11 genes and kidney-specific regulatory variants. These results provide a comprehensive priority list of molecular targets for translational research.
Reproducibility is a defining feature of science, but the extent to which it characterizes current research is unknown. We conducted replications of 100 experimental and correlational studies published in three psychology journals using high-powered designs and original materials when available. Replication effects were half the magnitude of original effects, representing a substantial decline. Ninety-seven percent of original studies had statistically significant results. Thirty-six percent of replications had statistically significant results; 47% of original effect sizes were in the 95% confidence interval of the replication effect size; 39% of effects were subjectively rated to have replicated the original result; and if no bias in original results is assumed, combining original and replication results left 68% with statistically significant effects. Correlational tests suggest that replication success was better predicted by the strength of original evidence than by characteristics of the original and replication teams.
Rapid decline of glomerular filtration rate estimated from creatinine (eGFRcrea) is associated with severe clinical endpoints. In contrast to cross-sectionally assessed eGFRcrea, the genetic basis for rapid eGFRcrea decline is largely unknown. To help define this, we meta-analyzed 42 genome-wide association studies from the Chronic Kidney Diseases Genetics Consortium and United Kingdom Biobank to identify genetic loci for rapid eGFRcrea decline. Two definitions of eGFRcrea decline were used: 3 mL/min/1.73m(2)/year or more ("Rapid3"; encompassing 34,874 cases, 107,090 controls) and eGFRcrea decline 25% or more and eGFRcrea under 60 mL/min/1.73m(2) at follow-up among those with eGFRcrea 60 mL/min/1.73m(2) or more at baseline ("CKDi25"; encompassing 19,901 cases, 175,244 controls). Seven independent variants were identified across six loci for Rapid3 and/or CKDi25: consisting of five variants at four loci with genome-wide significance (near UMOD-PDILT (2), PRKAG2, WDR72, OR2S2) and two variants among 265 known eGFRcrea variants (near GATM, LARP4B). All these loci were novel for Rapid3 and/or CKDi25 and our bioinformatic follow-up prioritized variants and genes underneath these loci. The OR2S2 locus is novel for any eGFRcrea trait including interesting candidates. For the five genome-wide significant lead variants, we found supporting effects for annual change in blood urea nitrogen or cystatin-based eGFR, but not for GATM or (LARP4B). Individuals at high compared to those at low genetic risk (8-14 vs. 0-5 adverse alleles) had a 1.20-fold increased risk of acute kidney injury (95% confidence interval 1.08-1.33). Thus, our identified loci for rapid kidney function decline may help prioritize therapeutic targets and identify mechanisms and individuals at risk for sustained deterioration of kidney function.
Rapid decline of glomerular filtration rate estimated from creatinine (eGFRcrea) is associated with severe clinical endpoints. In contrast to cross-sectionally assessed eGFRcrea, the genetic basis for rapid eGFRcrea decline is largely unknown. To help define this, we meta-analyzed 42 genome-wide association studies from the Chronic Kidney Diseases Genetics Consortium and United Kingdom Biobank to identify genetic loci for rapid eGFRcrea decline. Two definitions of eGFRcrea decline were used: 3 mL/min/1.73m(2)/year or more ("Rapid3"; encompassing 34,874 cases, 107,090 controls) and eGFRcrea decline 25% or more and eGFRcrea under 60 mL/min/1.73m(2) at follow-up among those with eGFRcrea 60 mL/min/1.73m(2) or more at baseline ("CKDi25"; encompassing 19,901 cases, 175,244 controls). Seven independent variants were identified across six loci for Rapid3 and/or CKDi25: consisting of five variants at four loci with genome-wide significance (near UMOD-PDILT (2), PRKAG2, WDR72, OR2S2) and two variants among 265 known eGFRcrea variants (near GATM, LARP4B). All these loci were novel for Rapid3 and/or CKDi25 and our bioinformatic follow-up prioritized variants and genes underneath these loci. The OR2S2 locus is novel for any eGFRcrea trait including interesting candidates. For the five genome-wide significant lead variants, we found supporting effects for annual change in blood urea nitrogen or cystatin-based eGFR, but not for GATM or (LARP4B). Individuals at high compared to those at low genetic risk (8-14 vs. 0-5 adverse alleles) had a 1.20-fold increased risk of acute kidney injury (95% confidence interval 1.08-1.33). Thus, our identified loci for rapid kidney function decline may help prioritize therapeutic targets and identify mechanisms and individuals at risk for sustained deterioration of kidney function.
A considerable fraction of the central stars of planetary nebulae (CSPNe) are hydrogen-deficient. Almost all of these H-deficient central stars (CSs) display spectra with strong carbon and helium lines. Most of them exhibit emission-line spectra resembling those of massive WC stars. Therefore these stars are classed as CSPNe of spectral type [WC]. Recently, quantitative spectral analysis of two emission-line CSs, PB 8 and IC 4663, revealed that these stars do not belong to the [WC] class. Instead PB 8 has been classified as [WN/WC] type and IC 4663 as [WN] type. In this work we report the spectroscopic identification of another rare [WN] star, the CS of Abell 48. We performed a spectral analysis of Abell 48 with the Potsdam Wolf-Rayet (PoWR) models for expanding atmospheres. We find that the expanding atmosphere of Abell 48 is mainly composed of helium (85 per cent by mass), hydrogen (10 per cent) and nitrogen (5 per cent). The residual hydrogen and the enhanced nitrogen abundance make this object different from the other [WN] star IC 4663. We discuss the possible origin of this atmospheric composition.
During aging, intracranial volume remains unchanged and represents maximally attained brain size, while various interacting biological phenomena lead to brain volume loss. Consequently, intracranial volume and brain volume in late life reflect different genetic influences. Our genome-wide association study (GWAS) in 8,175 community-dwelling elderly persons did not reveal any associations at genome-wide significance (P < 5 x 10(-8)) for brain volume. In contrast, intracranial volume was significantly associated with two loci: rs4273712 (P = 3.4 x 10(-11)), a known height-associated locus on chromosome 6q22, and rs9915547 (P = 1.5 x 10(-12)), localized to the inversion on chromosome 17q21. We replicated the associations of these loci with intracranial volume in a separate sample of 1,752 elderly persons (P = 1.1 x 10(-3) for 6q22 and 1.2 x 10(-3) for 17q21). Furthermore, we also found suggestive associations of the 17q21 locus with head circumference in 10,768 children (mean age of 14.5 months). Our data identify two loci associated with head size, with the inversion at 17q21 also likely to be involved in attaining maximal brain size.
We introduce a new survey of massive stars in the Galaxy and the Magellanic Clouds using the Fibre Large Array Multi- Element Spectrograph ( FLAMES) instrument at the Very Large Telescope ( VLT). Here we present observations of 269 Galactic stars with the FLAMES- Giraffe Spectrograph ( R similar or equal to 25 000), in fields centered on the open clusters NGC3293, NGC4755 and NGC6611. These data are supplemented by a further 50 targets observed with the Fibre- Fed Extended Range Optical Spectrograph ( FEROS, R = 48 000). Following a description of our scientific motivations and target selection criteria, the data reduction methods are described; of critical importance the FLAMES reduction pipeline is found to yield spectra that are in excellent agreement with less automated methods. Spectral classifications and radial velocity measurements are presented for each star, with particular attention paid to morphological peculiarities and evidence of binarity. These observations represent a significant increase in the known spectral content of NGC3293 and NGC4755, and will serve as standards against which our subsequent FLAMES observations in the Magellanic Clouds will be compared
Gilbert et al. conclude that evidence from the Open Science Collaboration’s Reproducibility Project: Psychology indicates high reproducibility, given the study methodology. Their very optimistic assessment is limited by statistical misconceptions and by causal inferences from selectively interpreted, correlational data. Using the Reproducibility Project: Psychology data, both optimistic and pessimistic conclusions about reproducibility are possible, and neither are yet warranted.
The photochemical ring-opening of 1,3-cyclohexadiene imaged by ultrafast electron diffraction
(2019)
The ultrafast photoinduced ring-opening of 1,3-cyclohexadiene constitutes a textbook example of electrocyclic reactions in organic chemistry and a model for photobiological reactions in vitamin D synthesis. Although the relaxation from the photoexcited electronic state during the ring-opening has been investigated in numerous studies, the accompanying changes in atomic distance have not been resolved. Here we present a direct and unambiguous observation of the ring-opening reaction path on the femtosecond timescale and subangstrom length scale using megaelectronvolt ultrafast electron diffraction. We followed the carbon-carbon bond dissociation and the structural opening of the 1,3-cyclohexadiene ring by the direct measurement of time-dependent changes in the distribution of interatomic distances. We observed a substantial acceleration of the ring-opening motion after internal conversion to the ground state due to a steepening of the electronic potential gradient towards the product minima. The ring-opening motion transforms into rotation of the terminal ethylene groups in the photoproduct 1,3,5-hexatriene on the subpicosecond timescale.
Femtosecond x-ray laser pulses are used to probe the carbon monoxide (CO) oxidation reaction on ruthenium (Ru) initiated by an optical laser pulse. On a time scale of a few hundred femtoseconds, the optical laser pulse excites motions of CO and oxygen (O) on the surface, allowing the reactants to collide, and, with a transient close to a picosecond (ps), new electronic states appear in the OK-edge x-ray absorption spectrum. Density functional theory calculations indicate that these result from changes in the adsorption site and bond formation between CO and O with a distribution of OC-O bond lengths close to the transition state (TS). After 1 ps, 10% of the CO populate the TS region, which is consistent with predictions based on a quantum oscillator model.
The planetary nebula N66 in the Large Magellanic Cloud is an extraordinary object, as it is the only confirmed PN where the central star is a Wolf-Rayet star of the nitrogen sequence, i.e. of type [WN]. Moreover, the star showed a dramatic brightness outburst in 1993-1994. In a previous paper (Hamann et al. 2003) we analyzed the changing stellar spectra and found evidence that the central star is most likely a binary system where a white dwarf presently accretes matter from a non-degenerate companion at a high rate. Thus the object is a candidate for a future type Ia supernova in our cosmic neighborhood. In the present paper we analyze the morphology and kinematics of the nebula, using images and high-resolution spectra obtained with the Hubble Space Telescope (HST) and the Very Large Telescope (ESO-VLT). The object presents a complex multipolar structure, dominated by very bright lobes located at both sides of the central star and separated by a narrow waist. In addition there is a pair of very extended and twisted loops, also pointing in opposite directions; their symmetry axis and collimation angle differs from those of the bright lobes. High resolution spectroscopy reveals two main velocity components, "approaching" material at an average heliocentric radial velocity Of V-rad = 248 30 km s(-1) and similarly bright "receding" material at V-rad = 331 +/- 25 km s(-1). A systemic velocity of about 300 km s(-1) is derived. Opposite lobes and loops possess opposite velocities. Furthermore there are knots and filaments of complex structure and kinematics. Close to the central star, nebular gas is found, receding at very high velocity (125 km s(-1) relative to the system). The morphology and kinematics of LMC-N66 can be explained as the result of episodic bipolar ejections with changing axis. The bipolar structures could have been produced by collimated streams ejected from a precessing central source. We suggest that the precession could have been produced by an external torque, possibly due to a binary companion. Young, fast-moving nebular knots close to the star appear slightly He- and N-richer than the main body of the nebula, but are still hydrogen-rich in contrast to the helium-dominated atmosphere of the [WN]- type central star. In the binary scenario, this nebular matter must have been accreted from the non-degenerate companion and re-ejected before it was fully burnt
Simulation models that describe autonomous individual organisms (individual based models, IBM) or agents (agent-based models, ABM) have become a widely used tool, not only in ecology, but also in many other disciplines dealing with complex systems made up of autonomous entities. However, there is no standard protocol for describing such simulation models, which can make them difficult to understand and to duplicate. This paper presents a proposed standard protocol, ODD, for describing IBMs and ABMs, developed and tested by 28 modellers who cover a wide range of fields within ecology. This protocol consists of three blocks (Overview, Design concepts, and Details), which are subdivided into seven elements: Purpose, State variables and scales, Process overview and scheduling, Design concepts, Initialization, Input, and Submodels. We explain which aspects of a model should be described in each element, and we present an example to illustrate the protocol in use. In addition, 19 examples are available in an Online Appendix. We consider ODD as a first step for establishing a more detailed common format of the description of IBMs and ABMs. Once initiated, the protocol will hopefully evolve as it becomes used by a sufficiently large proportion of modellers. (c) 2006 Elsevier B.V. All rights reserved.
We used the Linac Coherent Light Source free-electron x-ray laser to probe the electronic structure of CO molecules as their chemisorption state on Ru(0001) changes upon exciting the substrate by using a femtosecond optical laser pulse. We observed electronic structure changes that are consistent with a weakening of the CO interaction with the substrate but without notable desorption. A large fraction of the molecules (30%) was trapped in a transient precursor state that would precede desorption. We calculated the free energy of the molecule as a function of the desorption reaction coordinate using density functional theory, including van der Waals interactions. Two distinct adsorption wells-chemisorbed and precursor state separated by an entropy barrier-explain the anomalously high prefactors often observed in desorption of molecules from metals.
We present an overview of four deep phase-constrained Chandra HETGS X-ray observations of delta Ori A. Delta Ori A is actually a triple system that includes the nearest massive eclipsing spectroscopic binary, delta Ori Aa, the only such object that can be observed with little phase-smearing with the Chandra gratings. Since the fainter star, delta Ori Aa2, has a much lower X-ray luminosity than the brighter primary (delta Ori Aa1), delta Ori Aa provides a unique system with which to test the spatial distribution of the X-ray emitting gas around delta Ori Aa1 via occultation by the photosphere of, and wind cavity around, the X-ray dark secondary. Here we discuss the X-ray spectrum and X-ray line profiles for the combined observation, having an exposure time of nearly 500 ks and covering nearly the entire binary orbit. The companion papers discuss the X-ray variability seen in the Chandra spectra, present new space-based photometry and ground-based radial velocities obtained simultaneously with the X-ray data to better constrain the system parameters, and model the effects of X-rays on the optical and UV spectra. We find that the X-ray emission is dominated by embedded wind shock emission from star Aa1, with little contribution from the tertiary star Ab or the shocked gas produced by the collision of the wind of Aa1 against the surface of Aa2. We find a similar temperature distribution to previous X-ray spectrum analyses. We also show that the line half-widths are about 0.3-0.5 times the terminal velocity of the wind of star Aa1. We find a strong anti-correlation between line widths and the line excitation energy, which suggests that longer-wavelength, lower-temperature lines form farther out in the wind. Our analysis also indicates that the ratio of the intensities of the strong and weak lines of Fe XVII and Ne X are inconsistent with model predictions, which may be an effect of resonance scattering.
We present time-resolved and phase-resolved variability studies of an extensive X-ray high-resolution spectral data set of the delta Ori Aa binary system. The four observations, obtained with Chandra ACIS HETGS, have a total exposure time of approximate to 479 ks and provide nearly complete binary phase coverage. Variability of the total X-ray flux in the range of 5-25 is is confirmed, with a maximum amplitude of about +/- 15% within a single approximate to 125 ks observation. Periods of 4.76 and 2.04 days are found in the total X-ray flux, as well as an apparent overall increase in the flux level throughout the nine-day observational campaign. Using 40 ks contiguous spectra derived from the original observations, we investigate the variability of emission line parameters and ratios. Several emission lines are shown to be variable, including S XV, Si XIII, and Ne IX. For the first time, variations of the X-ray emission line widths as a function of the binary phase are found in a binary system, with the smallest widths at phi = 0.0 when the secondary delta Ori Aa2 is at the inferior conjunction. Using 3D hydrodynamic modeling of the interacting winds, we relate the emission line width variability to the presence of a wind cavity created by a wind-wind collision, which is effectively void of embedded wind shocks and is carved out of the X-ray-producing primary wind, thus producing phase-locked X-ray variability.
Morphology of the planetary nebula LMC-N66 (ionized by a [WN] star) indicates that the nebula is a multipolar object with a very narrow waist. It shows several jets, knots and filaments in opposite directions from the central star. A couple of twisted long filaments could be interpreted as due to point-symmetric type ejection. If such is the case, the progenitor would be a binary precessing system. High resolution spectroscopy shows that most of the material is approaching or receding from the star. However the line profiles are very complex, showing several components at different velocities. Our high resolution spectroscopic data show that the different structures (knots, filaments, ...) present different radial velocities spreading from 240 to more than 400 km/s. The system velocity is 300 km/s. There are high velocity knots located to the north of the central star, moving at more than 100 km/s relative to the system velocity.
We address the question of the multiplicativity of the maximal p-norm output purities of bosonic Gaussian channels under Gaussian inputs. We focus on general Gaussian channels resulting from the reduction of unitary dynamics in larger Hilbert spaces. It is shown that the maximal output purity of tensor products of single-mode channels under Gaussian inputs is multiplicative for any p is an element of (1, infinity) for products of arbitrary identical channels as well as for a large class of products of different channels. In the case of p=2, multiplicativity is shown to be true for arbitrary products of generic channels acting on any number of modes
We consider the additivity of the minimal output entropy and the classical information capacity of a class of quantum channels. For this class of channels, the norm of the output is maximized for the output being a normalized projection. We prove the additivity of the minimal output Renyi entropies with entropic parameters alpha is an element of [ 0, 2], generalizing an argument by Alicki and Fannes, and present a number of examples in detail. In order to relate these results to the classical information capacity, we introduce a weak form of covariance of a channel. We then identify various instances of weakly covariant channels for which we can infer the additivity of the classical information capacity. Both additivity results apply to the case of an arbitrary number of different channels. Finally, we relate the obtained results to instances of bi-partite quantum states for which the entanglement cost can be calculated
Serving many at once: How a database approach can create unity in dynamical ecosystem modelling
(2014)
Simulation modelling in ecology is a field that is becoming increasingly compartmentalized. Here we propose a Database Approach To Modelling (DATM) to create unity in dynamical ecosystem modelling with differential equations. In this approach the storage of ecological knowledge is independent of the language and platform in which the model will be run. To create an instance of the model, the information in the database is translated and augmented with the language and platform specifics. This process is automated so that a new instance can be created each time the database is updated. We describe the approach using the simple Lotka-Volterra model and the complex ecosystem model for shallow lakes PCLake, which we automatically implement in the frameworks OSIRIS, GRIND for MATLAB, ACSL, R, DUFLOW and DELWAQ. A clear advantage of working in a database is the overview it provides. The simplicity of the approach only adds to its elegance. (C) 2014 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-SA license (http://creativecommons.org/licenses/by-nc-sa/3.0/).
In the light of ongoing land use changes, it is important to understand how multitrophic communities perform at different land use intensities. The paradox of enrichment predicts that fertilization leads to destabilization and extinction of predator-prey systems. We tested this prediction for a land use intensity gradient from natural to highly fertilized agricultural ecosystems. We included multiple aboveground and belowground trophic levels and land use-dependent searching efficiencies of insects. To overcome logistic constraints of field experiments, we used a successfully validated simulation model to investigate plant responses to removal of herbivores and their enemies. Consistent with our predictions, instability measured by herbivore-induced plant mortality increased with increasing land use intensity. Simultaneously, the balance between herbivores and natural enemies turned increasingly towards herbivore dominance and natural enemy failure. Under natural conditions, there were more frequently significant effects of belowground herbivores and their natural enemies on plant performance, whereas there were more aboveground effects in agroecosystems. This result was partly due to the "boom-bust'' behavior of the shoot herbivore population. Plant responses to herbivore or natural enemy removal were much more abrupt than the imposed smooth land use intensity gradient. This may be due to the presence of multiple trophic levels aboveground and belowground. Our model suggests that destabilization and extinction are more likely to occur in agroecosystems than in natural communities, but the shape of the relationship is nonlinear under the influence of multiple trophic interactions. Citation: Meyer KM, Vos M, Mooij WM, Hol WHG, Termorshuizen AJ, et al. (2012) Testing the Paradox of Enrichment along a Land Use Gradient in a Multitrophic Aboveground and Belowground Community.
Water quality modelling deals with multidisciplinary questions ranging from fundamental to applied. Addressing this broad range of questions requires multiple analysis techniques and therefore multiple frameworks. Through the recently developed database approach to modelling (DATM), it has become possible to run a model in multiple software frameworks without much overhead. Here we apply DATM to the ecosystem model for ditches PCDitch and its twin model for shallow lakes PCLake. Using DATM, we run these models in six frameworks (ACSL, DELWAQ, DUFLOW, GRIND for MATLAB, OSIRIS and R), and report on the possible model analyses with tools provided by each framework. We conclude that the dynamic link between frameworks and models resulting from DATM has the following main advantages: it allows one to use the framework one is familiar with for most model analyses and eases switching between frameworks for complementary model analyses, including the switch between a 0-D and 1-D to 3-D setting. Moreover, the strength of each framework - including runtime performance - can now be easily exploited. We envision that a community-based further development of the concept can contribute to the future development of water quality modelling, not only by addressing multidisciplinary questions but also by facilitating the exchange of models and process formulations within the community of water quality modellers.
Context. It is not yet clear whether magnetic fields play an essential role in shaping planetary nebulae (PNe), or whether stellar rotation alone and/or a close binary companion, stellar or substellar, can account for the variety of the observed nebular morphologies.
Aims. In a quest for empirical evidence verifying or disproving the role of magnetic fields in shaping planetary nebulae, we follow up on previous attempts to measure the magnetic field in a representative sample of PN central stars.
Methods. We obtained low-resolution polarimetric spectra with FORS2 installed on the Antu telescope of the VLT for a sample of 12 bright central stars of PNe with different morphologies, including two round nebulae, seven elliptical nebulae, and three bipolar nebulae. Two targets are Wolf-Rayet type central stars.
Results. For the majority of the observed central stars, we do not find any significant evidence for the existence of surface magnetic fields. However, our measurements may indicate the presence of weak mean longitudinal magnetic fields of the order of 100 Gauss in the central star of the young elliptical planetary nebula IC 418 as well as in the Wolf-Rayet type central star of the bipolar nebula Hen 2-113 and the weak emission line central star of the elliptical nebula Hen 2-131. A clear detection of a 250 G mean longitudinal field is achieved for the A-type companion of the central star of NGC 1514. Some of the central stars show a moderate night-to-night spectrum variability, which may be the signature of a variable stellar wind and/or rotational modulation due to magnetic features.
Conclusions. Since our analysis indicates only weak fields, if any, in a few targets of our sample, we conclude that strong magnetic fields of the order of kG are not widespread among PNe central stars. Nevertheless, simple estimates based on a theoretical model of magnetized wind bubbles suggest that even weak magnetic fields below the current detection limit of the order of 100 G may well be sufficient to contribute to the shaping of the surrounding nebulae throughout their evolution. Our current sample is too small to draw conclusions about a correlation between nebular morphology and the presence of stellar magnetic fields.
Recent experiments using time- and angle-resolved two-photon photoemission (2PPE) spectroscopy at metal/polar adsorbate interfaces succeeded in time-dependent analysis of the process of electron solvation. A fully quantum mechanical, two-dimensional simulation of this process, which explicitly includes laser excitation, is presented here, confirming the origin of characteristic features, such as the experimental observation of an apparently negative dispersion. The inference of the spatial extent of the localized electron states from the angular dependence of the 2PPE spectra has been found to be non-trivial and system-dependent. (C) 2005 American Institute of Physics
Selective ultrafast probing of transient hot chemisorbed and precursor States of CO on Ru(0001)
(2013)
We have studied the femtosecond dynamics following optical laser excitation of CO adsorbed on a Ru surface by monitoring changes in the occupied and unoccupied electronic structure using ultrafast soft x-ray absorption and emission. We recently reported [M. Dell'Angela et al. Science 339, 1302 (2013)] a phonon-mediated transition into a weakly adsorbed precursor state occurring on a time scale of >2 ps prior to desorption. Here we focus on processes within the first picosecond after laser excitation and show that the metal-adsorbate coordination is initially increased due to hot-electron-driven vibrational excitations. This process is faster than, but occurs in parallel with, the transition into the precursor state. With resonant x-ray emission spectroscopy, we probe each of these states selectively and determine the respective transient populations depending on optical laser fluence. Ab initio molecular dynamics simulations of CO adsorbed on Ru(0001) were performed at 1500 and 3000 K providing insight into the desorption process.
Eclipsing post-common-envelope binaries are highly important for resolving the poorly understood, very short-lived common-envelope phase of stellar evolution. Most hot subdwarfs (sdO/Bs) are the bare helium-burning cores of red giants that have lost almost all of their hydrogen envelope. This mass loss is often triggered by common-envelope interactions with close stellar or even substellar companions. Cool companions to hot subdwarf stars such as late-type stars and brown dwarfs are detectable from characteristic light-curve variations - reflection effects and often eclipses. In the recently published catalog of eclipsing binaries in the Galactic Bulge and in the Asteroid Terrestrial-impact Last Alert System (ATLAS) survey, we discovered 125 new eclipsing systems showing a reflection effect seen by visual inspection of the light curves and using a machine-learning algorithm, in addition to the 36 systems previously discovered by the Optical Gravitational Lesing Experiment (OGLE) team. The Eclipsing Reflection Effect Binaries from Optical Surveys (EREBOS) project aims at analyzing all newly discovered eclipsing binaries of the HW Vir type (hot subdwarf + close, cool companion) based on a spectroscopic and photometric follow up to derive the mass distribution of the companions, constrain the fraction of substellar companions, and determine the minimum mass needed to strip off the red-giant envelope. To constrain the nature of the primary we derived the absolute magnitude and the reduced proper motion of all our targets with the help of the parallaxes and proper motions measured by the Gaia mission and compared those to the Gaia white-dwarf candidate catalog. It was possible to derive the nature of a subset of our targets, for which observed spectra are available, by measuring the atmospheric parameter of the primary, confirming that less than 10% of our systems are not sdO/Bs with cool companions but are white dwarfs or central stars of planetary nebula. This large sample of eclipsing hot subdwarfs with cool companions allowed us to derive a significant period distribution for hot subdwarfs with cool companions for the first time showing that the period distribution is much broader than previously thought and is ideally suited to finding the lowest-mass companions to hot subdwarf stars. The comparison with related binary populations shows that the period distribution of HW Vir systems is very similar to WD+dM systems and central stars of planetary nebula with cool companions. In the future, several new photometric surveys will be carried out, which will further increase the sample of this project, providing the potential to test many aspects of common-envelope theory and binary evolution.
The carbon-rich WC5 star WR 114 was not detected during a 15.9 ksec XMM-Newton observation, implying an upper limit to the X-ray luminosity of Lx < 2.5 x 1030 ergs-1 and to the X-ray to bolometric luminosity ratio of Lx/Lbol < 4 x 10-9. This confirms indications from earlier less sensitive measurements that there has been no convincing X-ray detection of any single WC star. This lack of detections is reinforced by XMM-Newton and CHANDRA observations of WC stars. Thus the conclusion has to be drawn that the stars with radiatively-driven stellar winds of this particular class are insignificant X-ray sources. We attribute this to photoelectronic absorption by the stellar wind. The high opacity of the metal-rich and dense winds from WC stars puts the radius of optical depth unity at hundreds or thousands of stellar radii for much of the X-ray band. We believe that the essential absence of hot plasma so far out in the wind exacerbated by the large distances and correspondingly high ISM column densities makes the WC stars too faint to be detectable with current technology. The result also applies to many WC stars in binary systems, of which only about 20 % are identified X-ray sources, presumably due to colliding winds.
We report the serendipitous discovery of a ring nebula around a candidate Wolf-Rayet (WR) star, HBHA 4202-22, in Cygnus using the Spitzer Space Telescope archival data. Our spectroscopic follow-up observations confirmed the WR nature of this star (we named it WR 138a) and showed that it belongs to the WN8-9h subtype. We thereby add a new example to the known sample of late WN stars with circumstellar nebulae. We analysed the spectrum of WR 138a by using the Potsdam Wolf-Rayet (PoWR) model atmospheres, obtaining a stellar temperature of 40 kK. The stellar wind composition is dominated by helium with 20 per cent of hydrogen. The stellar spectrum is highly reddened and absorbed (EB- V = 2.4 mag, A(V) = 7.4 mag). Adopting a stellar luminosity of log L/L-circle dot = 5.3, the star has a mass-loss rate of 10-4.7 M- circle dot yr-1, and resides in a distance of 4.2 kpc. We measured the proper motion for WR 138a and found that it is a runaway star with a peculiar velocity of similar or equal to 50 km s-1. Implications of the runaway nature of WR 138a for constraining the mass of its progenitor star and understanding the origin of its ring nebula are discussed.
Context. SMC AB6 is the shortest-period (P = 6.5 d) Wolf-Rayet (WR) binary in the Small Magellanic Cloud. This binary is therefore a key system in the study of binary interaction and formation of WR stars at low metallicity. The WR component in AB6 was previously found to be very luminous (log L = 6.3 [L-circle dot]) compared to its reported orbital mass (approximate to 8 M-circle dot), placing it significantly above the Eddington limit. Aims. Through spectroscopy and orbital analysis of newly acquired optical data taken with the Ultraviolet and Visual Echelle Spectrograph (UVES), we aim to understand the peculiar results reported for this system and explore its evolutionary history. Methods. We measured radial velocities via cross-correlation and performed a spectral analysis using the Potsdam Wolf-Rayet model atmosphere code. The evolution of the system was analyzed using the Binary Population and Spectral Synthesis evolution code. Results. AB6 contains at least four stars. The 6.5 d period WR binary comprises the WR primary (WN3:h, star A) and a rather rapidly rotating (v(eq) = 265 km s(-1)) early O-type companion (O5.5 V, star B). Static N III and N IV emission lines and absorption signatures in He lines suggest the presence of an early-type emission line star (O5.5 I(f), star C). Finally, narrow absorption lines portraying a long-term radial velocity variation show the existence of a fourth star (O7.5 V, star D). Star D appears to form a second 140 d period binary together with a fifth stellar member, which is a B-type dwarf or a black hole. It is not clear that these additional components are bound to the WR binary. We derive a mass ratio of M-O/M-WR = 2.2 +/- 0.1. The WR star is found to be less luminous than previously thought (log L = 5.9 [L-circle dot]) and, adopting M-O = 41 M-circle dot for star B, more massive (M-WR = 18 M-circle dot). Correspondingly, the WR star does not exceed the Eddington limit. We derive the initial masses of M-i,M-WR = 60 M-circle dot and M-i,M-O = 40 M-circle dot and an age of 3.9 Myr for the system. The WR binary likely experienced nonconservative mass transfer in the past supported by the relatively rapid rotation of star B. Conclusions. Our study shows that AB6 is a multiple - probably quintuple - system. This finding resolves the previously reported puzzle of the WR primary exceeding the Eddington limit and suggests that the WR star exchanged mass with its companion in the past.
As WR 6 is a putatively single WN4 star, and is relatively bright (V = 6.9), it is an ideal case for studying the wind mechanisms in these extremely luminous stars. To obtain higher resolution spectra at higher energy (above 1 keV) than previously obtained with the XMM/Newton RGS, we have observed WR 6 with the Chandra High Energy Transmission Grating Spectrometer for 450 ks. We have resolved emission lines of S, Si, Mg, Ne, and Fe, which all show a “fin"-shaped prole, characteristic of a self-absorbed uniformly expanding shell. Steep blue edges gives robust maximal expansion velocities of about 2000 km/s, somewhat larger than the 1700km/s derived from UV lines. The He-like lines all indicate that X-ray emitting plasmas are far from the photosphere – even at the higher energies where opacity is lowest { as was also the case for the longer wavelength lines observed with XMM-Newton/RGS. Abundances determined from X-ray spectral modeling indicate enhancements consistent with nucleosynthesis. The star was also variable in X-rays and in simultaneous optical photometry obtained with Chandra aspect camera, but not coherently with the optically known period of 3.765 days.
Stars that start their lives with spectral types O and early B are the progenitors of core-collapse supernovae, long gamma-ray bursts, neutron stars, and black holes. These massive stars are the primary sources of stellar feedback in star-forming galaxies. At low metallicities, the properties of massive stars and their evolution are not yet fully explored. Here we report a spectroscopic study of 320 massive stars of spectral types O (23 stars) and B (297 stars) in the Wing of the Small Magellanic Cloud (SMC). The spectra, which we obtained with the ESO Very Large Telescope, were analyzed using state-of-the-art stellar atmosphere models, and the stellar parameters were determined. We find that the stellar winds of our sample stars are generally much weaker than theoretically expected. The stellar rotation rates show broad, tentatively bimodal distributions. The upper Hertzsprung-Russell diagram (HRD) is well populated by the stars of our sample from a specific field in the SMC Wing. A few very luminous O stars are found close to the main sequence, while all other, slightly evolved stars obey a strict luminosity limit. Considering additional massive stars in evolved stages, with published parameters and located all over the SMC, essentially confirms this picture. The comparison with single-star evolutionary tracks suggests a dichotomy in the fate of massive stars in the SMC. Only stars with an initial mass below similar to 30 M-circle dot seem to evolve from the main sequence to the cool side of the HRD to become a red supergiant and to explode as type II-P supernova. In contrast, stars with initially more than similar to 30 M-circle dot appear to stay always hot and might evolve quasi chemically homogeneously, finally collapsing to relatively massive black holes. However, we find no indication that chemical mixing is correlated with rapid rotation. We measured the key parameters of stellar feedback and established the links between the rates of star formation and supernovae. Our study demonstrates that in metal-poor environments stellar feedback is dominated by core-collapse supernovae in combination with winds and ionizing radiation supplied by a few of the most massive stars. We found indications of the stochastic mode of massive star formation, where the resulting stellar population is fully capable of producing large-scale structures such as the supergiant shell SMC-SGS 1 in the Wing. The low level of feedback in metal-poor stellar populations allows star formation episodes to persist over long timescales.
While the majority of very massive stars is clearly found in clusters, there are also very massive objects not associated with any cluster, suggesting they may have been born in isolation. In order to gain more insights, we studied the regions around two WR stars in the Galactic Center region. To understand the nature of the potential cluster around massive stars, photometry alone is not sufficient. We therefore used the ESO VLT/SINFONI integral field spectrograph to obtain photometry and spectra for the whole region around our two candidate stars. In total, more than 60 stars have been found and assigned a spectral type.
We obtained four pointings of over 100 ks each of the well-studied Wolf-Rayet star WR 6 with the XMM-Newton satellite. With a first paper emphasizing the results of spectral analysis, this follow-up highlights the X-ray variability clearly detected in all four pointings. However, phased light curves fail to confirm obvious cyclic behavior on the well-established 3.766 day period widely found at longer wavelengths. The data are of such quality that we were able to conduct a search for event clustering in the arrival times of X-ray photons. However, we fail to detect any such clustering. One possibility is that X-rays are generated in a stationary shock structure. In this context we favor a corotating interaction region (CIR) and present a phenomenological model for X-rays from a CIR structure. We show that a CIR has the potential to account simultaneously for the X-ray variability and constraints provided by the spectral analysis. Ultimately, the viability of the CIR model will require both intermittent long-term X-ray monitoring of WR 6 and better physical models of CIR X-ray production at large radii in stellar winds.
Very massive stars, 100 times heavier than the sun, are rare. It is not yet known whether such stars can form in isolation or only in star clusters. The answer to this question is of fundamental importance. The central region of our Galaxy is ideal for investigating very massive stars and clusters located in the same environment. We used archival infrared images to investigate the surroundings of apparently isolated massive stars presently known in the Galactic Centre (GC). We find that two such isolated massive stars display bow shocks and hence may be 'runaways' from their birthplace. Thus, some isolated massive stars in the GC region might have been born in star clusters known in this region. However, no bow shock is detected around the isolated star WR 102ka (Peony nebula star), which is one of the most massive and luminous stars in the Galaxy. This star is located at the centre of an associated circumstellar nebula. To study whether a star cluster may be 'hidden' in the surroundings of WR 102ka, to obtain new and better spectra of this star, and to measure its radial velocity, we obtained observations with the integral-field spectrograph SINFONI at the ESO's Very Large Telescope. Our observations confirm that WR 102ka is one of the most massive stars in the Galaxy and reveal that this star is not associated with a star cluster. We suggest that WR 102ka has been born in relative isolation, outside of any massive star cluster.
The planetary nebula A30 is believed to have undergone a very late thermal pulse resulting in the ejection of knots of hydrogen-poor material. Using multi-epoch Hubble Space Telescope images, we have detected the angular expansion of these knots and derived an age of 850(-150)(+280) yr. To investigate the spectral and spatial properties of the soft X-ray emission detected by ROSAT, we have obtained Chandra and XMM-Newton deep observations of A30. The X-ray emission from A30 can be separated into two components: a point source at the central star and diffuse emission associated with the hydrogen-poor knots and the cloverleaf structure inside the nebular shell. To help us assess the role of the current stellar wind in powering this X-ray emission, we have determined the stellar parameters and wind properties of the central star of A30 using a non-LTE model fit to its optical and UV spectra. The spatial distribution and spectral properties of the diffuse X-ray emission are highly suggestive that it is generated by the post-born-again and present fast stellar winds interacting with the hydrogen-poor ejecta of the born-again event. This emission can be attributed to shock-heated plasma, as the hydrogen-poor knots are ablated by the stellar winds, under which circumstances the efficient mass loading of the present fast stellar wind raises its density and damps its velocity to produce the observed diffuse soft X-rays. Charge transfer reactions between the ions of the stellar winds and material of the born-again ejecta have also been considered as a possible mechanism for the production of diffuse X-ray emission, and upper limits on the expected X-ray production by this mechanism have been derived. The origin of the X-ray emission from the central star of A30 is puzzling: shocks in the present fast stellar wind and photospheric emission can be ruled out, while the development of a new, compact hot bubble confining the fast stellar wind seems implausible.
We present the first high-resolutionX-ray spectrum of a putatively singleWolf-Rayet (WR) star. 400 ks observations of WR 6 by the XMM-Newton telescope resulted in a superb quality high-resolution X-ray spectrum. Spectral analysis reveals that the X-rays originate far out in the stellar wind, more than 30 stellar radii from the photosphere, and thus outside the wind acceleration zone where the line-driving instability (LDI) could create shocks. The X-ray emitting plasma reaches temperatures up to 50 MK and is embedded within the unshocked, "cool" stellar wind as revealed by characteristic spectral signatures. We detect a fluorescent Fe line at approximate to 6.4 keV. The presence of fluorescence is consistent with a two-component medium, where the cool wind is permeated with the hot X-ray emitting plasma. The wind must have a very porous structure to allow the observed amount of X-rays to escape. We find that neither the LDI nor any alternative binary scenario can explain the data. We suggest a scenario where X-rays are produced when the fast wind rams into slow "sticky clumps" that resist acceleration. Our new data show that the X-rays in single WR star are generated by some special mechanism different from the one operating in the O-star winds.
With a deep Chandra/HETGS exposure of WR 6, we have resolved emission lines whose profiles show that the X-rays originate from a uniformly expanding spherical wind of high X-ray-continuum optical depth. The presence of strong helium-like forbidden lines places the source of X-ray emission at tens to hundreds of stellar radii from the photosphere. Variability was present in X-rays and simultaneous optical photometry, but neither were correlated with the known period of the system or with each other. An enhanced abundance of sodium revealed nuclear-processed material, a quantity related to the evolutionary state of the star. The characterization of the extent and nature of the hot plasma in WR 6 will help to pave the way to a more fundamental theoretical understanding of the winds and evolution of massive stars.
We report on both high-precision photometry from the Microvariability and Oscillations of Stars (MOST) space telescope and ground-based spectroscopy of the triple system delta Ori A, consisting of a binary O9.5II+early-B (Aa1 and Aa2) with P = 5.7 days, and a more distant tertiary (O9 IV P > 400 years). This data was collected in concert with X-ray spectroscopy from the Chandra X-ray Observatory. Thanks to continuous coverage for three weeks, the MOST light curve reveals clear eclipses between Aa1 and Aa2 for the first time in non-phased data. From the spectroscopy, we have a well-constrained radial velocity (RV) curve of Aa1. While we are unable to recover RV variations of the secondary star, we are able to constrain several fundamental parameters of this system and determine an approximate mass of the primary using apsidal motion. We also detected second order modulations at 12 separate frequencies with spacings indicative of tidally influenced oscillations. These spacings have never been seen in a massive binary, making this system one of only a handful of such binaries that show evidence for tidally induced pulsations.
Eclipsing systems of massive stars allow one to explore the properties of their components in great detail. We perform a multi-wavelength, non-LTE analysis of the three components of the massive multiple system delta Ori A, focusing on the fundamental stellar properties, stellar winds, and X-ray characteristics of the system. The primary's distance-independent parameters turn out to be characteristic for its spectral type (O9.5 II), but usage of the Hipparcos parallax yields surprisingly low values for the mass, radius, and luminosity. Consistent values follow only if delta Ori lies at about twice the Hipparcos distance, in the vicinity of the sigma-Orionis cluster. The primary and tertiary dominate the spectrum and leave the secondary only marginally detectable. We estimate the V-band magnitude difference between primary and secondary to be Delta V approximate to 2.(m)8. The inferred parameters suggest that the secondary is an early B-type dwarf (approximate to B1 V), while the tertiary is an early B-type subgiant (approximate to B0 IV). We find evidence for rapid turbulent velocities (similar to 200 km s(-1)) and wind inhomogeneities, partially optically thick, in the primary's wind. The bulk of the X-ray emission likely emerges from the primary's stellar wind (logL(X)/L-Bol approximate to -6.85), initiating close to the stellar surface at R-0 similar to 1.1 R-*. Accounting for clumping, the mass-loss rate of the primary is found to be log (M) over dot approximate to -6.4 (M-circle dot yr(-1))., which agrees with hydrodynamic predictions, and provides a consistent picture along the X-ray, UV, optical, and radio spectral domains.
Recent studies have claimed the existence of very massive stars (VMS) up to 300 M⊙ in the local Universe. As this finding may represent a paradigm shift for the canonical stellar upper-mass limit of 150 M⊙, it is timely to discuss the status of the data, as well as the far-reaching implications of such objects. We held a Joint Discussion at the General Assembly in Beijing to discuss (i) the determination of the current masses of the most massive stars, (ii) the formation of VMS, (iii) their mass loss, and (iv) their evolution and final fate. The prime aim was to reach broad consensus between observers and theorists on how to identify and quantify the dominant physical processes.
Aims. To close this gap, we perform a comparative analysis of the optical companion in two important systems: IGR J175442619 (SFXT) and Vela X-1 (SGXB). We analyze the spectra of each star in detail and derive their stellar and wind properties. As a next step, we compare the wind parameters, giving us an excellent chance of recognizing key differences between donor winds in SFXTs and SGXBs. Methods. We use archival infrared, optical and ultraviolet observations, and analyze them with the non-local thermodynamic equilibrium (NLTE) Potsdam Wolf-Rayet model atmosphere code. We derive the physical properties of the stars and their stellar winds, accounting for the influence of X-rays on the stellar winds. Results. We find that the stellar parameters derived from the analysis generally agree well with the spectral types of the two donors: O9I (IGR J17544-2619) and B0.5Iae (Vela X-1). The distance to the sources have been revised and also agree well with the estimations already available in the literature. In IGR J17544-2619 we are able to narrow the uncertainty to d = 3.0 +/- 0.2 kpc. From the stellar radius of the donor and its X-ray behavior, the eccentricity of IGR J17544-2619 is constrained to e < 0.25. The derived chemical abundances point to certain mixing during the lifetime of the donors. An important difference between the stellar winds of the two stars is their terminal velocities (v(infinity) = 1500 km s(-1) in IGR J17544-2619 and v(infinity) = 700 km s(-1) in Vela X-1), which have important consequences on the X-ray luminosity of these sources. Conclusions. The donors of IGR J17544-2619 and Vela X-1 have similar spectral types as well as similar parameters that physically characterize them and their spectra. In addition, the orbital parameters of the systems are similar too, with a nearly circular orbit and short orbital period. However, they show moderate differences in their stellar wind velocity and the spin period of their neutron star which has a strong impact on the X-ray luminosity of the sources. This specific combination of wind speed and pulsar spin favors an accretion regime with a persistently high luminosity in Vela X-1, while it favors an inhibiting accretion mechanism in IGR J17544-2619. Our study demonstrates that the relative wind velocity is critical in class determination for the HMXBs hosting a supergiant donor, given that it may shift the accretion mechanism from direct accretion to propeller regimes when combined with other parameters.
To investigate if magnetic fields are present in Wolf-Rayet stars, we selected a few stars in the Galaxy and one in the Large Magellanic Cloud (LMC). We acquired low-resolution spectropolarimetric observations with the European Southern Observatory FORS 2 (FOcal Reducer low dispersion Spectrograph) instrument during two different observing runs. During the first run in visitor mode, we observed the LMC Wolf-Rayet star BAT99 7 and the stars WR 6, WR 7, WR 18, and WR 23 in our Galaxy. The second run in service mode was focused on monitoring the star WR 6. Linear polarization was recorded immediately after the observations of circular polarization. During our visitor observing run, the magnetic field for the cyclically variable star WR 6 was measured at a significance level of 3.3 sigma (< B-z > = 258 +/- 78 G). Among the other targets, the highest value for the longitudinal magnetic field, < B-z > = 327 +/- 141 G, was measured in the LMC star BAT99 7. Spectropolarimetric monitoring of the star WR 6 revealed a sinusoidal nature of the < B-z > variations with the known rotation period of 3.77 d, significantly adding to the confidence in the detection. The presence of the rotation-modulated magnetic variability is also indicated in our frequency periodogram. The reported field magnitude suffers from significant systematic uncertainties at the factor of 2 level, in addition to the quoted statistical uncertainties, owing to the theoretical approach used to characterize it. Linear polarization measurements showed no line effect in the stars, apart from WR 6. BAT99 7, WR 7, and WR 23 do not show variability of the linear polarization over two nights.
Prenatal stress (PS) has been related to altered hypothalamic-pituitary-adrenal (HPA) axis activity later in life. So far, studies in children assessing HPA axis functioning have focused on salivary cortisol, reflecting daytime activity. The present work is part of a prospective study and aims to extend knowledge about the association between PS and HPA axis regulation in children. To do so, we investigated cortisol, cortisone, and the ratio cortisone/(cortisone + cortisol) in the first morning urine of 45-month-old children in relation to several measures of maternal stress during pregnancy. Urinary cortisol and cortisone were measured by online turbulent flow chromatography coupled with high performance liquid chromatography-tandem mass spectrometry. PS was defined as: perceived stress for aim 1 (Perceived Stress Scale; n = 280); presence of self-reported (n = 371) and expert-rated psychopathology for aim 2 (Mini International Neuropsychiatric Interview; n = 281); continuous measures of anxiety and depression for exploratory aim 3 (State-Trait Anxiety Inventory and Edinburgh Postnatal Depression Scale; n = 280). The ratio cortisone/(cortisone + cortisol) as a global marker for the balance between the enzymes metabolizing cortisol to cortisone and vice versa (11 beta-hydroxysteroid dehydrogenases type 1 and 2; 11 beta-HSD1 and 2) was not associated with any measure of maternal PS (aims 1-3). The present study provides insight into possible programming effects of PS on nocturnal HPA axis activity and a proxy of 11 beta-HSD in a large sample. The results suggest that the nocturnal rate of cortisol production is lower in children exposed to PS, but do not support the hypothesis of divergent 11 beta-HSD activity.
The selaginella genome identifies genetic changes associated with the evolution of vascular plants
(2011)
Vascular plants appeared similar to 410 million years ago, then diverged into several lineages of which only two survive: the euphyllophytes (ferns and seed plants) and the lycophytes. We report here the genome sequence of the lycophyte Selaginella moellendorffii (Selaginella), the first nonseed vascular plant genome reported. By comparing gene content in evolutionarily diverse taxa, we found that the transition from a gametophyte- to a sporophyte-dominated life cycle required far fewer new genes than the transition from a nonseed vascular to a flowering plant, whereas secondary metabolic genes expanded extensively and in parallel in the lycophyte and angiosperm lineages. Selaginella differs in posttranscriptional gene regulation, including small RNA regulation of repetitive elements, an absence of the trans-acting small interfering RNA pathway, and extensive RNA editing of organellar genes.
The B fields in OB stars (BOB) survey is an ESO large programme collecting spectropolarimetric observations for a large number of early-type stars in order to study the occurrence rate, properties, and ultimately the origin of magnetic fields in massive stars. As of July 2014, a total of 98 objects were observed over 20 nights with FORS2 and HARPSpol. Our preliminary results indicate that the fraction of magnetic OB stars with an organised, detectable field is low. This conclusion, now independently reached by two different surveys, has profound implications for any theoretical model attempting to explain the field formation in these objects. We discuss in this contribution some important issues addressed by our observations (e.g., the lower bound of the field strength) and the discovery of some remarkable objects.
We have investigated the structural dynamics in photoexcited 1,2-diiodotetrafluoroethane molecules (C2F4I2) in the gas phase experimentally using ultrafast electron diffraction and theoretically using FOMO-CASCI excited-state dynamics simulations. The molecules are excited by an ultraviolet femtosecond laser pulse to a state characterized by a transition from the iodine 5p perpendicular to orbital to a mixed 5p parallel to sigma hole and CF2 center dot antibonding orbital, which results in the cleavage of one of the carbon-iodine bonds. We have observed, with sub-Angstrom resolution, the motion of the nuclear wave packet of the dissociating iodine atom followed by coherent vibrations in the electronic ground state of the C2F4I radical. The radical reaches a stable classical (nonbridged) structure in less than 200 fs.
We studied the photoinduced ultrafast relaxation dynamics of the nucleobase thymine using gas-phase time-resolved photoelectron spectroscopy. By employing extreme ultraviolet pulses from high harmonic generation for photoionization, we substantially extend our spectral observation window with respect to previous studies. This enables us to follow relaxation of the excited state population all the way to low-lying electronic states including the ground state. In thymine, we observe relaxation from the optically bright (1)pi pi* state of thymine to a dark (1)n pi* state within 80 +/- 30 fs. The (1)n pi* state relaxes further within 3.5 +/- 0.3 ps to a low-lying electronic state. By comparison with quantum chemical simulations, we can unambiguously assign its spectroscopic signature to the (3)pi pi* state. Hence, our study draws a comprehensive picture of the relaxation mechanism of thymine including ultrafast intersystem crossing to the triplet manifold.
This study examined changes in sweet cherry buds of ‘Summit’ cultivar in four seasons (2011/12–2014/15) with respect to the nitrogen (N) content and the profile of eight free amino acids (asparagine (Asn), aspartic acid (Asp), isoleucine (Ile), glutamine (Gln), glutamic acid (Glu), arginine (Arg), alanine (Ala), histidine (His)). The presented results are to our knowledge the first under natural conditions in fruit tree orchards with a high temporal resolution from the dormant stage until cluster development. The N content in the buds from October, during endo- and ecodormancy until the beginning of ontogenetic development was a relatively stable parameter in each of the four seasons. The N accumulation into the buds began after ‘swollen bud’ and significant differences were visible at ‘green tip’ with an N content of 3.24, 3.12, 3.08, 2.40 which increased markedly to the mean of ‘tight’ and ‘open cluster’ by 3.77%, 3.78%, 3.44% and 3.10% in 2012–2015, respectively. In the buds, levels of asparagine were higher (up to 44 mg g−1 DW−1) than aspartic acid (up to 2 mg g−1 DW−1) and aspartic acid higher than isoleucine (up to 0.83 mg g−1 DW−1). Levels of glutamine were higher (up to 25 mg g−1 DW−1) than glutamic acid (up to 20 mg g−1 DW−1). The course of the arginine content was higher in 2011/12 compared to 2012/13, 2013/14 and 2014/15 which showed only slight differences. The alanine content in the buds was denoted in the four seasons only by relatively minor changes. The histidine content was higher in 2011/12 and 2012/13 compared to 2013/14 and 2014/15 which showed a comparable pattern. For 6 amino acids (Asn, Asp, Ile, Glu, Arg, Ala), the highest content was observed in 2012/13, the warmest period between swollen bud and open cluster. However in 2014/15, the season with the lowest mean temperature of 8.8 °C, only the content of Gln was the lowest. It was not possible to explain any seasonal differences in the amino acid content by environmental factors (air temperature) on the basis of few seasons. From none of the measured free amino acids could a clear determination of the date of endodormancy release (t1) or the beginning of the ontogenetic development (t1*) be derived. Therefore, these amino acids are no suitable markers to improve phenological models for the beginning of cherry blossom.
Background: Cigarette smoking has severe adverse health consequences in adults and in the offspring of mothers who smoke during pregnancy. One of the most widely reported effects of smoking during pregnancy is reduced birth weight which is in turn associated with chronic disease in adulthood. Epigenome-wide association studies have revealed that smokers show a characteristic "smoking methylation pattern", and recent authors have proposed that DNA methylation mediates the impact of maternal smoking on birth weight. The aims of the present study were to replicate previous reports that methylation mediates the effect of maternal smoking on birth weight, and for the first time to investigate whether the observed mediation effects are sex-specific in order to account for known sex-specific differences in methylation levels. Methods: Methylation levels in the cord blood of 313 newborns were determined using the Illumina HumanMethylation450K Beadchip. A total of 5,527 CpG sites selected on the basis of evidence from the literature were tested. To determine whether the observed association between maternal smoking and birth weight was attributable to methylation, mediation analyses were performed for significant CpG sites. Separate analyses were then performed in males and females. Results: Following quality control, 282 newborns eventually remained in the analysis. A total of 25 mothers had smoked consistently throughout the pregnancy. The birthweigt of newborns whose mothers had smoked throughout pregnancy was reduced by >200g. After correction for multiple testing, 30 CpGs showed differential methylation in the maternal smoking subgroup including top "smoking methylation pattern" genes AHRR, MYO1G, GFI1, CYP1A1, and CNTNAP2. The effect of maternal smoking on birth weight was partly mediated by the methylation of cg25325512 (PIM1); cg25949550 (CNTNAP2); and cg08699196 (ITGB7). Sex-specific analyses revealed a mediating effect for cg25949550 (CNTNAP2) in male newborns. Conclusion: The present data replicate previous findings that methylation can mediate the effect of maternal smoking on birth weight. The analysis of sex-dependent mediation effects suggests that the sex of the newborn may have an influence. Larger studies are warranted to investigate the role of both the identified differentially methylated loci and the sex of the newborn in mediating the association between maternal smoking during pregnancy and birth weight.
We present a comprehensive study of the Magellanic Cloud planetary nebula SMP 61 and of its nucleus, a Wolf- Rayet type star classified [WC 5-6]. The observational material consists of HST STIS spectroscopy and imaging, together with optical and UV spectroscopic data collected from the literature and infrared fluxes measured by IRAS. We have performed a detailed spectral analysis of the central star, using the Potsdam code for expanding atmospheres in non-LTE. For the central star we determine the following parameters: L-star = 10(3.96) L-., R-star = 0.42 R-., T-star = 87.5 kK, (M) over dot = 10(-6.12) M-. yr(-1), v(infinity) = 1400 km s(-1), and a clumping factor of D = 4. The elemental abundances by mass are X-He = 0.45, X-C = 0.52, X-N < 5 x 10(-5), X-O = 0.03, and X-Fe < 1 x 10(-4). The fluxes from the model stellar atmosphere were used to compute photoionization models of the nebula. All the available observations, within their error bars, were used to constrain these models. We find that the ionizing fluxes predicted by the stellar model are consistent with the fluxes needed by the photoionization model to reproduce the nebular emission, within the error margins. However, there are indications that the stellar model overestimates the number and hardness of Lyman continuum photons. The photoionization models imply a clumped density structure of the nebular material. The observed C III] lambda1909/C II lambda4267 line ratio implies the existence of carbon-rich clumps in the nebula. Such clumps are likely produced by stellar wind ejecta, possibly mixed with the nebular material. We discuss our results with regard to the stellar and nebular post-AGB evolution. The observed Fe-deficiency for the central star indicates that the material which is now visible on the stellar surface has been exposed to s-process nucleosynthesis during previous thermal pulses. The absence of nitrogen allows us to set an upper limit to the remaining H-envelope mass after a possible AGB final thermal pulse. Finally, we infer from the total amount of carbon detected in the nebula that the strong [WC] mass- loss may have been active only for a limited period during the post-AGB evolution
We present a determination of the optical/UV AGN luminosity function and its evolution, based on a large sample of faint (R < 24) QSOs identified in the COMBO-17 survey. Using multi-band photometry in 17 filters within 350 nm <~ lambdaobs <~ 930 nm, we could simultaneously determine photometric redshifts with an accuracy of sigmaz <0.03 and obtain spectral energy distributions. The redshift range covered by the sample is 1.2 < z < 4.8, which implies that even at z =~ 3, the sample reaches below luminosities corresponding to MB = -23, conventionally employed to distinguish between Seyfert galaxies and quasars. We clearly detect a broad plateau-like maximum of quasar activity around z =~ 2 and map out the smooth turnover between z =~ 1 and z =~ 4. The shape of the LF is characterised by some mild curvature, but no sharp ``break'' is present within the range of luminosities covered. Using only the COMBO-17 data, the evolving LF can be adequately described by either a pure density evolution (PDE) or a pure luminosity evolution (PLE) model. However, the absence of a strong L*-like feature in the shape of the LF inhibits a robust distinction between these modes. We present a robust estimate for the integrated UV luminosity generation by AGN as a function of redshift. We find that the LF continues to rise even at the lowest luminosities probed by our survey, but that the slope is sufficiently shallow that the contribution of low-luminosity AGN to the UV luminosity density is negligible. Although our sample reaches much fainter flux levels than previous data sets, our results on space densities and LF slopes are completely consistent with extrapolations from recent major surveys such as SDSS and 2QZ.
The central star of the PN LMC-N66 showed an impressive outburst in 1993 - 1994, returning to its initial conditions about 8 years later. Its spectrum resembles that of a WN4.5 star, being the only confirmed central star of planetary nebulae showing such a spectral type. Recent analysis for the central star parameters, performed by Hamann et al. (2003) is presented. They have found that the bolometric luminosity increased by a factor larger than 6, during the outburst. We discuss the possible scenarios which have been proposed to explain the exceptional stellar parameters and the outburst mechanism. The stellar characteristics and the morphology and kinematics of the planetary nebula suggest the presence of binary system (massive star with a less massive companion or, a white dwarf accreting matter in a close- binary system). These cases pose the least severe contradictions with observational constraints.
A large number and wide variety of lake ecosystem models have been developed and published during the past four decades. We identify two challenges for making further progress in this field. One such challenge is to avoid developing more models largely following the concept of others ('reinventing the wheel'). The other challenge is to avoid focusing on only one type of model, while ignoring new and diverse approaches that have become available ('having tunnel vision'). In this paper, we aim at improving the awareness of existing models and knowledge of concurrent approaches in lake ecosystem modelling, without covering all possible model tools and avenues. First, we present a broad variety of modelling approaches. To illustrate these approaches, we give brief descriptions of rather arbitrarily selected sets of specific models. We deal with static models (steady state and regression models), complex dynamic models (CAEDYM, CE-QUAL-W2, Delft 3D-ECO, LakeMab, LakeWeb, MyLake, PCLake, PROTECH, SALMO), structurally dynamic models and minimal dynamic models. We also discuss a group of approaches that could all be classified as individual based: super-individual models (Piscator, Charisma), physiologically structured models, stage-structured models and traitbased models. We briefly mention genetic algorithms, neural networks, Kalman filters and fuzzy logic. Thereafter, we zoom in, as an in-depth example, on the multi-decadal development and application of the lake ecosystem model PCLake and related models (PCLake Metamodel, Lake Shira Model, IPH-TRIM3D-PCLake). In the discussion, we argue that while the historical development of each approach and model is understandable given its 'leading principle', there are many opportunities for combining approaches. We take the point of view that a single 'right' approach does not exist and should not be strived for. Instead, multiple modelling approaches, applied concurrently to a given problem, can help develop an integrative view on the functioning of lake ecosystems. We end with a set of specific recommendations that may be of help in the further development of lake ecosystem models.
A large number and wide variety of lake ecosystem models have been developed and published during the past four decades. We identify two challenges for making further progress in this field. One such challenge is to avoid developing more models largely following the concept of others ('reinventing the wheel'). The other challenge is to avoid focusing on only one type of model, while ignoring new and diverse approaches that have become available ('having tunnel vision'). In this paper, we aim at improving the awareness of existing models and knowledge of concurrent approaches in lake ecosystem modelling, without covering all possible model tools and avenues. First, we present a broad variety of modelling approaches. To illustrate these approaches, we give brief descriptions of rather arbitrarily selected sets of specific models. We deal with static models (steady state and regression models), complex dynamic models (CAEDYM, CE-QUAL-W2, Delft 3D-ECO, LakeMab, LakeWeb, MyLake, PCLake, PROTECH, SALMO), structurally dynamic models and minimal dynamic models. We also discuss a group of approaches that could all be classified as individual based: super-individual models (Piscator, Charisma), physiologically structured models, stage-structured models and traitbased models. We briefly mention genetic algorithms, neural networks, Kalman filters and fuzzy logic. Thereafter, we zoom in, as an in-depth example, on the multi-decadal development and application of the lake ecosystem model PCLake and related models (PCLake Metamodel, Lake Shira Model, IPH-TRIM3D-PCLake). In the discussion, we argue that while the historical development of each approach and model is understandable given its 'leading principle', there are many opportunities for combining approaches. We take the point of view that a single 'right' approach does not exist and should not be strived for. Instead, multiple modelling approaches, applied concurrently to a given problem, can help develop an integrative view on the functioning of lake ecosystems. We end with a set of specific recommendations that may be of help in the further development of lake ecosystem models.
The concept of bonding and antibonding orbitals is fundamental in chemistry. The population of those orbitals and the energetic difference between the two reflect the strength of the bonding interaction. Weakening the bond is expected to reduce this energetic splitting, but the transient character of bond-activation has so far prohibited direct experimental access. Here we apply time-resolved soft X-ray spectroscopy at a free electron laser to directly observe the decreased bonding antibonding splitting following bond-activation using an ultrashort optical laser pulse.
Completely positive, trace preserving (CPT) maps and Lindblad master equations are both widely used to describe the dynamics of open quantum systems. The connection between these two descriptions is a classic topic in mathematical physics. One direction was solved by the now famous result due to Lindblad, Kossakowski, Gorini and Sudarshan, who gave a complete characterisation of the master equations that generate completely positive semi-groups. However, the other direction has remained open: given a CPT map, is there a Lindblad master equation that generates it (and if so, can we find its form)? This is sometimes known as the Markovianity problem. Physically, it is asking how one can deduce underlying physical processes from experimental observations.
We give a complexity theoretic answer to this problem: it is NP-hard. We also give an explicit algorithm that reduces the problem to integer semi-definite programming, a well-known NP problem. Together, these results imply that resolving the question of which CPT maps can be generated by master equations is tantamount to solving P = NP: any efficiently computable criterion for Markovianity would imply P = NP; whereas a proof that P = NP would imply that our algorithm already gives an efficiently computable criterion. Thus, unless P does equal NP, there cannot exist any simple criterion for determining when a CPT map has a master equation description.
However, we also show that if the system dimension is fixed (relevant for current quantum process tomography experiments), then our algorithm scales efficiently in the required precision, allowing an underlying Lindblad master equation to be determined efficiently from even a single snapshot in this case.
Our work also leads to similar complexity-theoretic answers to a related long-standing open problem in probability theory.
Accumulating evidence suggests a role of FKBP5, a co-chaperone regulating the glucocorticoid receptor sensitivity, in the etiology of depression and anxiety disorders. Based on recent findings of altered amygdala activity following childhood adversity, the present study aimed at clarifying the impact of genetic variation in FKBP5 on threat-related neural activity and coupling as well as morphometric alterations in stress-sensitive brain systems. Functional magnetic resonance imaging during an emotional face-matching task was performed in 153 healthy young adults (66 males) from a high-risk community sample followed since birth. Voxel-based morphometry was applied to study structural alterations and DNA was genotyped for FKBP5 rs1360780. Childhood adversity was measured using retrospective self-report (Childhood Trauma Questionnaire) and by a standardized parent interview assessing childhood family adversity. Depression was assessed by the Beck Depression Inventory. There was a main effect of FKBP5 on the left amygdala, with T homozygotes showing the highest activity, largest volume and increased coupling with the left hippocampus and the orbitofrontal cortex (OFC). Moreover, amygdala-OFC coupling proved to be associated with depression in this genotype. In addition, our results support previous evidence of a gene-environment interaction on right amygdala activity with respect to retrospective assessment of childhood adversity, but clarify that this does not generalize to the prospective assessment. These findings indicated that activity in T homozygotes increased with the level of adversity, whereas the opposite pattern emerged in C homozygotes, with CT individuals being intermediate. The present results point to a functional involvement of FKBP5 in intermediate phenotypes associated with emotional processing, suggesting a possible mechanism for this gene in conferring susceptibility to stress-related disorders.
We show that coadsorbed oxygen atoms have a dramatic influence on the CO desorption dynamics from Ru(0001). In contrast to the precursor-mediated desorption mechanism on Ru(0001), the presence of surface oxygen modifies the electronic structure of Ru atoms such that CO desorption occurs predominantly via the direct pathway. This phenomenon is directly observed in an ultrafast pump-probe experiment using a soft x-ray free-electron laser to monitor the dynamic evolution of the valence electronic structure of the surface species. This is supported with the potential of mean force along the CO desorption path obtained from density-functional theory calculations. Charge density distribution and frozen-orbital analysis suggest that the oxygen-induced reduction of the Pauli repulsion, and consequent increase of the dative interaction between the CO 5 sigma and the charged Ru atom, is the electronic origin of the distinct desorption dynamics. Ab initio molecular dynamics simulations of CO desorption from Ru(0001) and oxygen-coadsorbed Ru(0001) provide further insights into the surface bond-breaking process.
Submerged macrophytes can stabilise clear water conditions in shallow lakes. However, many existing models for deep lakes neglect their impact. Here, we tested the hypothesis that submerged macrophytes can affect the water clarity in deep lakes. A one-dimensional, vertically resolved macrophyte model was developed based on PCLake and coupled to SALMO-1D and GOTM hydrophysics and validated against field data. Validation showed good coherence in dynamic growth patterns and colonisation depths. In our simulations the presence of submerged macrophytes resulted in up to 50% less phytoplankton biomass in the shallowest simulated lake (11 m) and still 15% less phytoplankton was predicted in 100 m deep oligotrophic lakes. Nutrient loading, lake depth, and lake shape had a strong influence on macrophyte effects. Nutrient competition was found to be the strongest biological interaction. Despite a number of limitations, the derived dynamic lake model suggests significant effects of submerged macrophytes on deep lake water quality. (C) 2014 Elsevier Ltd. All rights reserved.
IMPORTANCE: There is accumulating evidence relating maternal smoking during pregnancy to attention-deficit/hyperactivity disorder (ADHD) without elucidating specific mechanisms. Research investigating the neurobiological underpinnings of this disorder has implicated deficits during response inhibition. Attempts to uncover the effect of prenatal exposure to nicotine on inhibitory control may thus be of high clinical importance.
MAIN OUTCOMES AND MEASURES: Functional magnetic resonance imaging response, morphometric data, lifetime ADHD symptoms, and novelty seeking.
RESULTS: Participants prenatally exposed to nicotine exhibited a weaker response in the anterior cingulate cortex (t(168) = 4.46; peak Montreal Neurological Institute [MNI] coordinates x = -2, y = 20, z = 30; familywise error [FWE]-corrected P = .003), the right inferior frontal gyrus (t(168) = 3.65; peak MNI coordinates x = 44, y = 38, z = 12; FWE-corrected P = .04), the left inferior frontal gyrus (t(168) = 4.09; peak MNI coordinates x = -38, y = 36, z = 8; FWE-corrected P = .009), and the supramarginal gyrus (t(168) = 5.03; peak MNI coordinates x = 64, y = -28, z = 22; FWE-corrected P = .02) during the processing of the NoGo compared to neutral stimuli, while presenting a decreased volume in the right inferior frontal gyrus. These findings were obtained irrespective of the adjustment of confounders, ADHD symptoms, and novelty seeking. There was an inverse relationship between inferior frontal gyrus activity and ADHD symptoms and between anterior cingulate cortex activity and novelty seeking.
CONCLUSIONS AND RELEVANCE: These findings point to a functional involvement of prenatal exposure to tobacco smoke in neural alterations similar to ADHD, which underlines the importance of smoking prevention treatments.
The seasonal succession of plankton is an annually repeated process of community assembly during which all major external factors and internal interactions shaping communities can be studied. A quarter of a century ago, the state of this understanding was described by the verbal plankton ecology group (PEG) model. It emphasized the role of physical factors, grazing and nutrient limitation for phytoplankton, and the role of food limitation and fish predation for zooplankton. Although originally targeted at lake ecosystems, it was also adopted by marine plankton ecologists. Since then, a suite of ecological interactions previously underestimated in importance have become research foci: overwintering of key organisms, the microbial food web, parasitism, and food quality as a limiting factor and an extended role of higher order predators. A review of the impact of these novel interactions on plankton seasonal succession reveals limited effects on gross seasonal biomass patterns, but strong effects on species replacements.
The amount of terrestrial particulate organic matter (t-POM) entering lakes is predicted to increase as a result of climate change. This may especially alter the structure and functioning of ecosystems in small, shallow lakes which can rapidly shift from a clear-water, macrophyte-dominated into a turbid, phytoplankton-dominated state. We used the integrative ecosystem model PCLake to predict how rising t-POM inputs affect the resilience of the clear-water state. PCLake links a pelagic and benthic food chain with abiotic components by a number of direct and indirect effects. We focused on three pathways (zoobenthos, zooplankton, light availability) by which elevated t-POM inputs (with and without additional nutrients) may modify the critical nutrient loading thresholds at which a clear-water lake becomes turbid and vice versa. Our model results show that (1) increased zoobenthos biomass due to the enhanced food availability results in more benthivorous fish which reduce light availability due to bioturbation, (2) zooplankton biomass does not change, but suspended t-POM reduces the consumption of autochthonous particulate organic matter which increases the turbidity, and (3) the suspended t-POM reduces the light availability for submerged macrophytes. Therefore, light availability is the key process that is indirectly or directly changed by t-POM input. This strikingly resembles the deteriorating effect of terrestrial dissolved organic matter on the light climate of lakes. In all scenarios, the resilience of the clear-water state is reduced thus making the turbid state more likely at a given nutrient loading. Therefore, our study suggests that rising t-POM input can add to the effects of climate warming making reductions in nutrient loadings even more urgent.
Exploring, exploiting and evolving diversity of aquatic ecosystem models: a community perspective
(2015)
Here, we present a community perspective on how to explore, exploit and evolve the diversity in aquatic ecosystem models. These models play an important role in understanding the functioning of aquatic ecosystems, filling in observation gaps and developing effective strategies for water quality management. In this spirit, numerous models have been developed since the 1970s. We set off to explore model diversity by making an inventory among 42 aquatic ecosystem modellers, by categorizing the resulting set of models and by analysing them for diversity. We then focus on how to exploit model diversity by comparing and combining different aspects of existing models. Finally, we discuss how model diversity came about in the past and could evolve in the future. Throughout our study, we use analogies from biodiversity research to analyse and interpret model diversity. We recommend to make models publicly available through open-source policies, to standardize documentation and technical implementation of models, and to compare models through ensemble modelling and interdisciplinary approaches. We end with our perspective on how the field of aquatic ecosystem modelling might develop in the next 5-10 years. To strive for clarity and to improve readability for non-modellers, we include a glossary.
Several lines of evidence have implicated the mesolimbic dopamine reward pathway in altered brain function resulting from exposure to early adversity. The present study examined the impact of early life adversity on different stages of neuronal reward processing later in life and their association with a related behavioral phenotype, i.e. attention deficit/hyperactivity disorder (ADHD). 162 healthy young adults (mean age = 24.4 years; 58% female) from an epidemiological cohort study followed since birth participated in a simultaneous EEG-fMRI study using a monetary incentive delay task. Early life adversity according to an early family adversity index (EFA) and lifetime ADHD symptoms were assessed using standardized parent interviews conducted at the offspring's age of 3 months and between 2 and 15 years, respectively. fMRI region-of-interest analysis revealed a significant effect of EFA during reward anticipation in reward-related areas (i.e. ventral striatum, putamen, thalamus), indicating decreased activation when EFA increased. EEG analysis demonstrated a similar effect for the contingent negative variation (CNV), with the CNV decreasing with the level of EFA. In contrast, during reward delivery, activation of the bilateral insula, right pallidum and bilateral putamen increased with EFA. There was a significant association of lifetime ADHD symptoms with lower activation in the left ventral striatum during reward anticipation and higher activation in the right insula during reward delivery. The present findings indicate a differential long-term impact of early life adversity on reward processing, implicating hyporesponsiveness during reward anticipation and hyperresponsiveness when receiving a reward. Moreover, a similar activation pattern related to lifetime ADHD suggests that the impact of early life stress on ADHD may possibly be mediated by a dysfunctional reward pathway.
The development of infrared observational facilities has revealed a number of massive stars in obscured environments throughout the Milky Way and beyond. The determination of their stellar and wind properties from infrared diagnostics is thus required to take full advantage of the wealth of observations available in the near and mid infrared. However, the task is challenging. This session addressed some of the problems encountered and showed the limitations and successes of infrared studies of massive stars.
Converging evidence emphasizes the role of an interaction between monoamine oxidase A (MAOA) genotype, environmental adversity, and sex in the pathophysiology of aggression. The present study aimed to clarify the impact of this interaction on neural activity in aggression-related brain systems. Functional magnetic resonance imaging was performed in 125 healthy adults from a high-risk community sample followed since birth. DNA was genotyped for the MAOA-VNTR (variable number of tandem repeats). Exposure to childhood life stress (CLS) between the ages of 4 and 11 years was assessed using a standardized parent interview, aggression by the Youth/Young Adult Self-Report between the ages of 15 and 25 years, and the VIRA-R (Vragenlijst Instrumentele En Reactieve Agressie) at the age of 15 years. Significant interactions were obtained between MAOA genotype, CLS, and sex relating to amygdala, hippocampus, and anterior cingulate cortex (ACC) response, respectively. Activity in the amygdala and hippocampus during emotional face-matching increased with the level of CLS in male MAOA-L, while decreasing in male MAOA-H, with the reverse pattern present in females. Findings in the opposite direction in the ACC during a flanker NoGo task suggested that increased emotional activity coincided with decreased inhibitory control. Moreover, increasing amygdala activity was associated with higher Y(A)SR aggression in male MAOA-L and female MAOA-H carriers. Likewise, a significant association between amygdala activity and reactive aggression was detected in female MAOA-H carriers. The results point to a moderating role of sex in the MAOAx CLS interaction for intermediate phenotypes of emotional and inhibitory processing, suggesting a possible mechanism in conferring susceptibility to violence-related disorders.
Background: Accumulating evidence suggests that altered dopamine transmission may increase the risk of mental disorders such as ADHD, schizophrenia or depression, possibly mediated by reward system dysfunction. This study aimed to clarify the impact of the COMT Val(158)Met polymorphism in interaction with environmental variation (G x E) on neuronal activity during reward processing. Methods: 168 healthy young adults from a prospective study conducted over 25 years participated in amonetary incentive delay task measured with simultaneous EEG-fMRI. DNA was genotyped for COMT, and childhood family adversity (CFA) up to age 11 was assessed by a standardized parent interview. Results: At reward delivery, a G x E revealed that fMRI activation for win vs. no-win trials in reward-related regions increased with the level of CFA in Met homozygotes as compared to Val/Met heterozygotes and Val homozygotes, who showed no significant effect. During the anticipation of monetary vs. verbal rewards, activation decreased with the level of CFA, which was also observed for EEG, in which the CNV declined with the level of CFA. Conclusions: These results identify convergent genetic and environmental effects on reward processing in a prospective study. Moreover, G x E effects during reward delivery suggest that stress during childhood is associated with higher reward sensitivity and reduced efficiency in processing rewarding stimuli in genetically at-risk individuals. Together with previous evidence, these results begin to define a specific system mediating interacting effects of early environmental and genetic risk factors, which may be targeted by early intervention and prevention. (C) 2016 Elsevier Inc. All rights reserved.
Converging evidence has highlighted the association between poverty and conduct disorder (CD) without specifying neurobiological pathways. Neuroimaging research has emphasized structural and functional alterations in the orbitofrontal cortex (OFC) as one key mechanism underlying this disorder. The present study aimed to clarify the long-term influence of early poverty on OFC volume and its association with CD symptoms in healthy participants of an epidemiological cohort study followed since birth. At age 25 years, voxel-based morphometry was applied to study brain volume differences. Poverty (0 = non-exposed (N = 134), I = exposed (N = 33)) and smoking during pregnancy were determined using a standardized parent interview, and information on maternal responsiveness was derived from videotaped mother infant interactions at the age of 3 months. CD symptoms were assessed by diagnostic interview from 8 to 19 years of age. Information on life stress was acquired at each assessment and childhood maltreatment was measured using retrospective self-report at the age of 23 years. Analyses were adjusted for sex, parental psychopathology and delinquency, obstetric adversity, parental education, and current poverty. Individuals exposed to early life poverty exhibited a lower OFC volume. Moreover, we replicated previous findings of increased CD symptoms as a consequence of childhood poverty. This effect proved statistically mediated by OFC volume and exposure to life stress and smoking during pregnancy, but not by childhood maltreatment and maternal responsiveness. These findings underline the importance of studying the impact of early life adversity on brain alterations and highlight the need for programs to decrease income-related disparities.
We report on deep multi-color imaging (R5sigma = 26) of the Chandra Deep Field South, obtained with the Wide Field Imager (WFI) at the MPG/ESO 2.2 m telescope on La Silla as part of the multi-color survey COMBO-17. As a result we present a catalogue of 63 501 objects in a field measuring 31farcm5 x 30arcmin with astrometry and BVR photometry. A sample of 37 variable objects is selected from two-epoch photometry. We try to give interpretations based on color and variation amplitude.
Agent-based complex systems are dynamic networks of many interacting agents; examples include ecosystems, financial markets, and cities. The search for general principles underlying the internal organization of such systems often uses bottom-up simulation models such as cellular automata and agent-based models. No general framework for designing, testing, and analyzing bottom-up models has yet been established, but recent advances in ecological modeling have come together in a general strategy we call pattern-oriented modeling. This strategy provides a unifying framework for decoding the internal organization of agent-based complex systems and may lead toward unifying algorithmic theories of the relation between adaptive behavior and system complexity
SwSt 1 (PN G001.5-06.7) is a bright and compact planetary nebula containing a late [WC]-type central star. Previous studies suggested that the nebular and stellar lines are slowly changing with time. We studied new and archival optical and ultraviolet spectra of the object. The [O III] 4959 and 5007 angstrom to H beta line flux ratios decreased between about 1976 and 1997/2015. The stellar spectrum also shows changes between these epochs. We modelled the stellar and nebular spectra observed at different epochs. The analyses indicate a drop of the stellar temperature from about 42 kK to 40.5 kK between 1976 and 1993. We do not detect significant changes between 1993 and 2015. The observations show that the star performed a loop in the H-R diagram. This is possible when a shell source is activated during its post-AGB evolution. We infer that a late thermal pulse (LTP) experienced by a massive post-AGB star can explain the evolution of the central star. Such a star does not expand significantly as the result of the LTP and does not became a born-again red giant. However, the released energy can remove the tiny H envelope of the star.
Macroclumping in WR 136
(2015)
Macroclumping proved to resolve the discordance between different mass-loss rate diagnostics for O-type stars, in particular between Hα and the P v resonance lines. In this paper, we report first results from a corresponding investigation for WR stars. We apply our detailed 3-D Monte Carlo (MC) line formation code to the P v resonance doublet and show, for the Galactic WNL star WR136, that macroclumping is require to bring this line in accordance with the mass-loss rate derived from the emission-line spectrum.
Context. SAO 244567, the exciting star of the Stingray nebula, is rapidly evolving. Previous analyses suggested that it has heated up from an effective temperature of about 21 kK in 1971 to over 50 kK in the 1990s. Canonical post-asymptotic giant branch evolution suggests a relatively high mass while previous analyses indicate a low-mass star.
Aims. A comprehensive model-atmosphere analysis of UV and optical spectra taken during 1988-2006 should reveal the detailed temporal evolution of its atmospheric parameters and provide explanations for the unusually fast evolution.
Methods. Fitting line profiles from static and expanding non-LTE model atmospheres to the observed spectra allowed us to study the temporal change of effective temperature, surface gravity, mass-loss rate, and terminal wind velocity. In addition, we determined the chemical composition of the atmosphere.
Results. We find that the central star has steadily increased its effective temperature from 38 kK in 1988 to a peak value of 60 kK in 2002. During the same time, the star was contracting, as concluded from an increase in surface gravity from log g = 4.8 to 6.0 and a drop in luminosity. Simultaneously, the mass-loss rate declined from log(M/M-circle dot yr(-1)) = -9.0 to -11.6 and the terminal wind velocity increased from v(infinity) = 1800 km s(-1) to 2800 km s(-1). Since around 2002, the star stopped heating and has cooled down again to 55 kK by 2006. It has a largely solar surface composition with the exception of slightly subsolar carbon, phosphorus, and sulfur. The results are discussed by considering different evolutionary scenarios.
Conclusions. The position of SAO 244567 in the log T-eff-log g plane places the star in the region of sdO stars. By comparison with stellar-evolution calculations, we confirm that SAO 244567 must be a low-mass star (M < 0.55 M-circle dot). However, the slow evolution of the respective stellar evolutionary models is in strong contrast to the observed fast evolution and the young planetary nebula with a kinematical age of only about 1000 years. We speculate that the star could be a late He-shell flash object. Alternatively, it could be the outcome of close-binary evolution. Then SAD 244567 would be a low-mass (0.354 M-circle dot) helium pre-white dwarf after the common-envelope phase, during which the planetary nebula was ejected.
Context. HD 93129A was classified as the earliest O-type star in the Galaxy (O2 If*) and is considered as the prototype of its spectral class. However, interferometry shows that this object is a binary system, while recent observations even suggest a triple configuration. None of the previous spectral analyses of this object accounted for its multiplicity. With new high-resolution UV and optical spectra, we have the possibility to reanalyze this key object, taking its binary nature into account for the first time. Aims. We aim to derive the fundamental parameters and the evolutionary status of HD 93129A, identifying the contributions of both components to the composite spectrum Results. Despite the similar spectral types of the two components, we are able to find signatures from each of the components in the combined spectrum, which allows us to estimate the parameters of both stars. We derive log(L/L-circle dot) = 6.15, T-eff = 52 kK, and log (M)over dot = -4.7[M-circle dot yr(-1)] for the primary Aa, and log(L/L-circle dot) = 5.58, T-eff = 45 kK, and log (M)over dot = -5.8 [M(circle dot)yr(-1)] for the secondary Ab. Conclusions. Even when accounting for the binary nature, the primary of HD 93129A is found to be one of the hottest and most luminous O stars in our Galaxy. Based on the theoretical decomposition of the spectra, we assign spectral types O2 If* and O3 III(f*) to components Aa and Ab, respectively. While we achieve a good fit for a wide spectral range, specific spectral features are not fully reproduced. The data are not sufficient to identify contributions from a hypothetical third component in the system.
Tula virus (TULV) is a vole-associated hantavirus with low or no pathogenicity to humans. In the present study, 686 common voles (Microtus arvalis), 249 field voles (Microtus agrestis) and 30 water voles (Arvicola spec.) were collected at 79 sites in Germany, Luxembourg and France and screened by RT-PCR and TULV-IgG ELISA. TULV-specific RNA and/or antibodies were detected at 43 of the sites, demonstrating a geographically widespread distribution of the virus in the studied area. The TULV prevalence in common voles (16.7 %) was higher than that in field voles (9.2 %) and water voles (10.0 %). Time series data at ten trapping sites showed evidence of a lasting presence of TULV RNA within common vole populations for up to 34 months, although usually at low prevalence. Phylogenetic analysis demonstrated a strong genetic structuring of TULV sequences according to geography and independent of the rodent species, confirming the common vole as the preferential host, with spillover infections to co-occurring field and water voles. TULV phylogenetic clades showed a general association with evolutionary lineages in the common vole as assessed by mitochondrial DNA sequences on a large geographical scale, but with local-scale discrepancies in the contact areas.
Context.
The supergiant ionized shell SMC-SGS 1 (DEM 167), which is located in the outer Wing of the Small Magellanic Cloud (SMC), resembles structures that originate from an energetic star-formation event and later stimulate star formation as they expand into the ambient medium. However, stellar populations within and surrounding SMC-SGS 1 tell a different story. Aims. We present a photometric study of the stellar population encompassed by SMC-SGS 1 in order to trace the history of such a large structure and its potential influence on star formation within the low-density, low-metallicity environment of the SMC.
Methods.
For a stellar population that is physically associated with SMC-SGS 1, we combined near-ultraviolet (NUV) photometry from the Galaxy Evolution Explorer with archival optical (V-band) photometry from the ESO Danish 1.54 m Telescope. Given their colors and luminosities, we estimated stellar ages and masses by matching observed photometry to theoretical stellar isochrone models. Results. We find that the investigated region supports an active, extended star-formation event spanning similar to 25-40 Myr ago, as well as continued star formation into the present. Using a standard initial mass function, we infer a lower bound on the stellar mass from this period of similar to 3 x 10(4) M-circle dot, corresponding to a star-formation intensity of similar to 6 x 10(-3) M-circle dot kpc(-2) yr(-1).
Conclusions.
The spatial and temporal distributions of young stars encompassed by SMC-SGS 1 imply a slow, consistent progression of star formation over millions of years. Ongoing star formation, both along the edge and interior to SMC-SGS 1, suggests a combined stimulated and stochastic mode of star formation within the SMC Wing. We note that a slow expansion of the shell within this low-density environment may preserve molecular clouds within the volume of the shell, leaving them to form stars even after nearby stellar feedback expels local gas and dust.
An original set of experimental and modeling tools is used to quantify the yield of each of the physical processes leading to photocurrent generation in organic bulk heterojunction solar cells, enabling evaluation of materials and processing condition beyond the trivial comparison of device performances. Transient absorption spectroscopy, “the” technique to monitor all intermediate states over the entire relevant timescale, is combined with time-delayed collection field experiments, transfer matrix simulations, spectral deconvolution, and parametrization of the charge carrier recombination by a two-pool model, allowing quantification of densities of excitons and charges and extrapolation of their kinetics to device-relevant conditions. Photon absorption, charge transfer, charge separation, and charge extraction are all quantified for two recently developed wide-bandgap donor polymers: poly(4,8-bis((2-ethylhexyl)oxy)benzo[1,2-b:4,5-b′]dithiophene-3,4-difluorothiophene) (PBDT[2F]T) and its nonfluorinated counterpart poly(4,8-bis((2-ethylhexyl)oxy)benzo[1,2-b:4,5-b′]dithiophene-3,4-thiophene) (PBDT[2H]T) combined with PC71BM in bulk heterojunctions. The product of these yields is shown to agree well with the devices' external quantum efficiency. This methodology elucidates in the specific case studied here the origin of improved photocurrents obtained when using PBDT[2F]T instead of PBDT[2H]T as well as upon using solvent additives. Furthermore, a higher charge transfer (CT)-state energy is shown to lead to significantly lower energy losses (resulting in higher VOC) during charge generation compared to P3HT:PCBM.
We present density functional theory modeling of time-resolved optical pump/X-ray spectroscopic probe data of CO desorption from Ru(0001). The BEEF van der Waals functional predicts a weakly bound state as a precursor to desorption. The optical pump leads to a near-instantaneous (<100 fs) increase of the electronic temperature to nearly 7000 K. The temperature evolution and energy transfer between electrons, substrate phonons and adsorbate is described by the two-temperature model and found to equilibrate on a timescale of a few picoseconds to an elevated local temperature of similar to 2000K. Estimating the free energy based on the computed potential of mean force along the desorption path, we find an entropic barrier to desorption (and by time-reversal also to adsorption). This entropic barrier separates the chemisorbed and precursor states, and becomes significant at the elevated temperature of the experiment (similar to 1.4 eV at 2000 K). Experimental pump-probe X-ray absorption/X-ray emission spectroscopy indicates population of a precursor state to desorption upon laser-excitation of the system (Dell'Angela et al., 2013). Computing spectra along the desorption path confirms the picture of a weakly bound transient state arising from ultrafast heating of the metal substrate. (C) 2015 Elsevier B.V. All rights reserved.
The interplay between nanomorphology and efficiency of polymer-fullerene bulk-heterojunction (BHJ) solar cells has been the subject of intense research, but the generality of these concepts for small-molecule (SM) BHJs remains unclear. Here, the relation between performance; charge generation, recombination, and extraction dynamics; and nanomorphology achievable with two SM donors benzo[1,2-b:4,5-b]dithiophene-pyrido[3,4-b]-pyrazine BDT(PPTh2)(2), namely SM1 and SM2, differing by their side-chains, are examined as a function of solution additive composition. The results show that the additive 1,8-diiodooctane acts as a plasticizer in the blends, increases domain size, and promotes ordering/crystallinity. Surprisingly, the system with high domain purity (SM1) exhibits both poor exciton harvesting and severe charge trapping, alleviated only slightly with increased crystallinity. In contrast, the system consisting of mixed domains and lower crystallinity (SM2) shows both excellent exciton harvesting and low charge recombination losses. Importantly, the onset of large, pure crystallites in the latter (SM2) system reduces efficiency, pointing to possible differences in the ideal morphologies for SM-based BHJ solar cells compared with polymer-fullerene devices. In polymer-based systems, tie chains between pure polymer crystals establish a continuous charge transport network, whereas SM-based active layers may in some cases require mixed domains that enable both aggregation and charge percolation to the electrodes.
Global change has complex eco-evolutionary consequences for organisms and ecosystems, but related concepts (e.g., novel ecosystems) do not cover their full range. Here we propose an umbrella concept of "ecological novelty" comprising (1) a site-specific and (2) an organism-centered, eco-evolutionary perspective. Under this umbrella, complementary options for studying and communicating effects of global change on organisms, ecosystems, and landscapes can be included in a toolbox. This allows researchers to address ecological novelty from different perspectives, e.g., by defining it based on (a) categorical or continuous measures, (b) reference conditions related to sites or organisms, and (c) types of human activities. We suggest striving for a descriptive, non-normative usage of the term "ecological novelty" in science. Normative evaluations and decisions about conservation policies or management are important, but require additional societal processes and engagement with multiple stakeholders.
X-ray spectroscopy is a sensitive probe of stellar winds. X-rays originate from optically thin shock-heated plasma deep inside the wind and propagate outwards throughout absorbing cool material. Recent analyses of the line ratios from He-like ions in the X-ray spectra of O-stars highlighted problems with this general paradigm: the measured line ratios of highest ions are consistent with the location of the hottest X-ray emitting plasma very close to the base of the wind, perhaps indicating the presence of a corona, while measurements from lower ions conform with the wind-embedded shock model. Generally, to correctly model the emerging Xray spectra, a detailed knowledge of the cool wind opacities based on stellar atmosphere models is prerequisite. A nearly grey stellar wind opacity for the X-rays is deduced from the analyses of high-resolution X-ray spectra. This indicates that the stellar winds are strongly clumped. Furthermore, the nearly symmetric shape of X-ray emission line profiles can be explained if the wind clumps are radially compressed. In massive binaries the orbital variations of X-ray emission allow to probe the opacity of the stellar wind; results support the picture of strong wind clumping. In high-mass X-ray binaries, the stochastic X-ray variability and the extend of the stellar-wind part photoionized by X-rays provide further strong evidence that stellar winds consist of dense clumps.
It is commonly adopted that X-rays from O stars are produced deep inside the stellar wind, and transported outwards through the bulk of the expanding matter which attenuates the radiation and affects the shape of emission line profiles. The ability of the X-ray observatories Chandra and XMM-Newton to resolve these lines spectroscopically provided a stringent test for the theory of the X-ray production. It turned out that none of the existing models was able to fit the observations consistently. The possible caveat of these models was the underlying assumption of a smooth stellar wind. Motivated by the evidence that the stellar winds are in fact structured, we present a 2-D numerical model of a stochastic, inhomogeneous wind. Small parcels of hot, X-ray emitting gas are permeated by cool, absorbing wind material which is compressed into thin shell fragments. Wind fragmentation alters the radiative transfer drastically, compared to homogeneous models of the same mass-loss rate. X-rays produced deep inside the wind, which would be totally absorbed in a homogeneous flow, can effectively escape from a fragmented wind. The wind absorption becomes wavelength independent if the individual fragments are optically thick. The X-ray line profiles are flat-topped in the blue part and decline steeply in the red part for the winds with a short acceleration zone. For the winds where the acceleration extends over significant distances, the lines can appear nearly symmetric and only slightly blueshifted, in contrast to the skewed, triangular line profiles typically obtained from homogeneous wind models of high optical depth. We show that profiles from a fragmented wind model can reproduce the observed line profiles from zeta Orionis. The present numerical modeling confirms the results from a previous study, where we derived analytical formulae from a statistical treatment
Spectral lines formed in stellar winds from OB stars are observed to exhibit profile variations. Discrete Absorption Components (DACs) show a remarkably slow wavelength drift with time. In a straightforward interpretation, this is in sharp contradiction to the steep velocity law predicted by the radiation-driven wind theory, and by semi- empirical profile fitting. In the present paper we re-discuss the interpretation of the drift rate. We show that the Co- rotating Interaction Region (CIR) model for the formation of DACs does not explain their slow drift rate as a consequence of rotation. On the contrary, the apparent acceleration of a spectral CIR feature is even higher than for the corresponding kinematical model without rotation. However, the observations can be understood by distinguishing between the velocity field of the matter flow, and the velocity law for the motion of the patterns in which the DAC features are formed. If the latter propagate upstream against the matter flow, the resulting wavelength drift mimics a much slower acceleration although the matter is moving fast. Additional to the DACs, a second type of recurrent structures is present in observed OB star spectra, the so-called modulations. In contrast to the DACs, these structures show a steep acceleration compatible with the theoretically predicted velocity law. We see only two possible consistent scenarios. Either, the wind is accelerated fast, and the modulations are formed in advected structures, while the DACs come from structures which are propagating upstream. Or, alternatively, steep and shallow velocity laws may co-exist at the same time in different spatial regions or directions of the wind.
We discuss the connection between wind overloading and discrete absorption components in P Cygni line profiles from O stars. Overloading can create horizontal plateaus in the radial wind speed that cause the extra absorption in the line profile. The upstream propagation speed of these velocity plateaus is analyzed. The second part of the paper deals with X-ray emission from O stars. X-ray line profiles observed with Chandra and XMM are often symmetric, contrary to what is expected for lines from a homogeneous wind. We discuss the influence on line symmetry of photon escape channels in a strongly clumped wind.
We discuss X-ray line formation in dense O star winds. A random distribution of wind shocks is assumed to emit X-rays that are partially absorbed by cooler wind gas. The cool gas resides in highly compressed fragments oriented perpendicular to the radial flow direction. For fully opaque fragments, we find that the blueshifted part of X-ray line profiles remains flat-topped even after severe wind attenuation, whereas the red part shows a steep decline. These box- type, blueshifted profiles resemble recent Chandra observations of the O3 star zeta Pup. For partially transparent fragments, the emission lines become similar to those from a homogeneous wind.
Clumps in hot star winds can originate from shock compression due to the line driven instability. One-dimensional hydrodynamic simulations reveal a radial wind structure consisting of highly compressed shells separated by voids, and colliding with fast clouds. Two-dimensional simulations are still largely missing, despite first attempts. Clumpiness dramatically affects the radiative transfer and thus all wind diagnostics in the UV, optical, and in X-rays. The microturbulence approximation applied hitherto is currently superseded by a more sophisticated radiative transfer in stochastic media. Besides clumps, i.e. jumps in the density stratification, so-called kinks in the velocity law, i.e. jumps in dv/dr, play an eminent role in hot star winds. Kinks are a new type of radiative-acoustic shock, and propagate at super-Abbottic speed.
Modeling expanding atmospheres is a difficult task because of the extreme non-LTE situation, the need to account for complex model atoms, especially for the iron-group elements with their millions of lines, and because of the supersonic expansion. Adequate codes have been developed e.g. by Hillier (CMFGEN), the Munich group (Puls, Pauldrach), and in Potsdam (PoWR code, Hamann et al.). While early work was based on the assumption of a smooth and homogeneous spherical stellar wind, the need to account for clumping became obvious about ten years ago. A relatively simple first-order clumping correction was readily implemented into the model codes. However, its simplifying assumptions are severe. Most importantly, the clumps are taken to be optically thin at all frequencies (”microclumping”). We discuss the consequences of this approximation and describe an approach to account for optically thick clumps (“macroclumping”). First results demonstrate that macroclumping can generally reduce the strength of spectral features, depending on their optical thickness. The recently reported discrepancy between the Hα diagnostic and the Pv resonance lines in O star spectra can be resolved without decreasing the mass-loss rates, when macroclumping is taken into account.