Refine
Year of publication
Document Type
- Article (604)
- Preprint (299)
- Postprint (257)
- Conference Proceeding (160)
- Doctoral Thesis (51)
- Working Paper (48)
- Review (45)
- Monograph/Edited Volume (26)
- Part of a Book (24)
- Other (16)
Language
- English (1534) (remove)
Is part of the Bibliography
- no (1534) (remove)
Keywords
- Curriculum Framework (31)
- European values education (31)
- Europäische Werteerziehung (31)
- Familie (31)
- Family (31)
- Lehrevaluation (31)
- Studierendenaustausch (31)
- Unterrichtseinheiten (31)
- curriculum framework (31)
- lesson evaluation (31)
Institute
- Institut für Mathematik (309)
- Extern (276)
- Vereinigung für Jüdische Studien e. V. (125)
- Institut für Physik und Astronomie (119)
- Department Linguistik (91)
- Department Psychologie (86)
- Institut für Chemie (65)
- Hasso-Plattner-Institut für Digital Engineering GmbH (55)
- Historisches Institut (52)
- Institut für Umweltwissenschaften und Geographie (49)
In order to evade detection by network-traffic analysis, a growing proportion of malware uses the encrypted HTTPS protocol. We explore the problem of detecting malware on client computers based on HTTPS traffic analysis. In this setting, malware has to be detected based on the host IP address, ports, timestamp, and data volume information of TCP/IP packets that are sent and received by all the applications on the client. We develop a scalable protocol that allows us to collect network flows of known malicious and benign applications as training data and derive a malware-detection method based on a neural networks and sequence classification. We study the method's ability to detect known and new, unknown malware in a large-scale empirical study.
Well-developed phonological awareness skills are a core prerequisite for early literacy development. Although effective phonological awareness training programs exist, children at risk often do not reach similar levels of phonological awareness after the intervention as children with normally developed skills. Based on theoretical considerations and first promising results the present study explores effects of an early musical training in combination with a conventional phonological training in children with weak phonological awareness skills. Using a quasi-experimental pretest-posttest control group design and measurements across a period of 2 years, we tested the effects of two interventions: a consecutive combination of a musical and a phonological training and a phonological training alone. The design made it possible to disentangle effects of the musical training alone as well the effects of its combination with the phonological training. The outcome measures of these groups were compared with the control group with multivariate analyses, controlling for a number of background variables. The sample included N = 424 German-speaking children aged 4–5 years at the beginning of the study. We found a positive relationship between musical abilities and phonological awareness. Yet, whereas the well-established phonological training produced the expected effects, adding a musical training did not contribute significantly to phonological awareness development. Training effects were partly dependent on the initial level of phonological awareness. Possible reasons for the lack of training effects in the musical part of the combination condition as well as practical implications for early literacy education are discussed.
Tarkovsky’s legacy
(2016)
Archaeology can be understood as a tool used in the process of identity formation,
contributing to a sense of belonging and unity within a diverse set of communities.
Research was conducted with the intention of analyzing the wide range of perceptions
regarding archaeological sites in the mixed city of Lod, Israel. I explored the impact of
urban cultural heritage on shaping the identity of local Jewish and Arab children, who
were chosen as the youngest active members of society living in the city, and who
participated in the 2013 archaeological excavation season at the Khan al-Hilu. Israel is
an ideal location for such research, due to its nature as simultaneously being the focus
of extensive archaeological excavations as well as being the setting of an intractable conflict. Ancestral attachment to the land serves as a foundation for the collective
identity of both Jews and Arabs. Yet, each community and individual may relate differently
to the surrounding archaeological sites, which is further shaped by their sense of
societal hierarchy and cultural heritage.
After the mass immigration to Israel from 1948 to 1950, about 2000 Jews remained
in Yemen. These Jews lived in small communities and continued to maintain their
religious environment as it was. In the years that followed, many of them, however, moved from Yemen to Israel with the assistance of the Jewish Agency and the Joint
Distribution Committee (JDC). The community was of a small size and the fact that it
was dispersed throughout the predominantly Muslim areas, created a certain closeness
between the two groups. About ten percent of the Jews chose to convert to Islam, many
of them in groups. In about twenty cases, the husbands chose to convert to Islam while
their wives emigrated to preserve their Judaism. Some of the converts refused to grant
their wives a divorce, because, according to Muslim law, conversion is enough to sever
the marital relationship. This procedure is called ʿAgunot. Meaning, women bound in
marriage to a husband and they no longer lived together, but the husband didn’t formally
‘released’ her from marriage union. The article follows the efforts undertaken
to release the ʿAgunot, and shows that Jewish and Muslim scholars were able to find
solutions to the ʿAgunot problem and, at times, managed to bridge the gap between the
two religions.
In this article we will present a few examples of the theme of “calling for help and redemption” in Arabic and Hebrew poetry, with particular focus on eleventh and twelfth century Muslim Spain. More particularly, we will offer a glimpse into the life and oeuvre of two medieval poets (one Muslim, one Jewish); both were active in Muslim Spain in the same period and shared a similar fate of exile and wandering: on the one hand, the Sicilian Arabic poet Ibn Ḥamdīs (c. 1056–c. 1133) and on the other hand, the Spanish Jewish poet Moses ibn Ezra (1055–1138). We will take into account the impact of exile and wandering on the profusion of the theme of “calling for help and redemption” as well as the related theme of “yearning for one’s homeland” through an analysis and comparison of poetic fragments by the two aforementioned poets as well as additional Andalusian Jewish (Judah ha-Levi) and Muslim (Ibn Khafāja, al-Rundī and Ibn al-Abbār) poets.
The concept of three journeys as a way to denote spiritual development was introduced
by Dhu al-Nun, one of the founding fathers of Islamic mysticism. The use of this
concept was later refined by combining it with the Sufi technique of adding different
prepositions to a certain term, in order to differentiate between spiritual stages. By
using the words journey (Safar) and God (Allah) and inserting a preposition before the
word God, Sufi writers could map the different roads to God or the stations (Maqamat) on this road. Ibn al-'Arabi, in the beginning of the thirteenth century, speaks of three
different ways: from God, toward God and in God. Tanchum ha-Yerushalmi, the Judeo
Arabic biblical commentator from the end of this century, speaks of the three journeys
as three stations of one continuous way. A nearly identical description we can find in
the writing of the Muslim scholar Ibn Qayyim al-Jawziyya, a generation later. Later in
the fourteenth century, in the writing of the Sufi writer al-Qashani, the three travels
become four, although the scheme of three prepositions is preserved. Near the end of
the fourteenth century, in the writings of R. David ha-Nagid, we find only two journeys:
to God and in God. All this tells us that Judeo Arabic literature can help us map
with greater precision the historical development of Sufi ideas.
The figure of Moses constitutes an important link between Jewish and Muslim traditions.
Muslims consider him to be one of the five elite prophets of God, his story therefore
has a prominent place in the Qurʼan. While there are minor differences, the story
of Moses found in the Qurʼan confirms the account of the Torah; the life of Moses thus
is considered a model for all Muslims to follow. Though elements of his story are found throughout the Qurʼan, it is in chapter 7 where it is given in its greatest detail. As the
focus point of this article, chapter 7 discusses many events in Mosesʼ life, which are important for both Muslims and Jews, and reveals his great importance and Godliness. It also demonstrates how truly similar Islamʼs Moses and Judaismʼs Moses are. Therefore,
through an examination of the various elements of the story of Moses as found in
the Qurʼan, this article will show how by following him, Jews and Muslims can come
together in friendship, harmony and peace. Moses is the common ground on which
Jews and Muslims can come together in order to open up a dialogue and further their
shared commitment to the worship of the One God.
In this contribution, we provide a detailed dynamical analysis of the interfacial hydrogen migration mediated by scanning tunneling microscopy (STM). Contributions from the STM-current and from the non-adiabatic couplings are taken into account using only first principle models. The slight asymmetry of the tunnelling rates with respect to the potential bias sign inferred from experimental observations is reproduced by weighting the contributions of the metal acceptor–donor states for the propagation of the impinging electrons. The quasi-thermal inelastic collision mechanism is treated perturbatively. The influence of hydrogen pre-coverage is also investigated using new potential energy surfaces obtained from periodic density functional theory calculations. Fully quantum dynamical simulations of the system evolution are performed by solving the Pauli master equation, providing insight into the reaction mechanism of STM manipulation of subsurface hydrogens. It is observed that the hydrogen impurity favors resurfacing over occupation of the bulk and subsurface sites whenever possible. The present simulations give strong indication that the experimentally observed protuberances after STM-excitation are due to hydrogen accumulating in the vicinity of the surface.
In June 2013, widespread flooding and consequent damage and losses occurred in Central Europe, especially in Germany. This paper explores what data are available to investigate the adverse impacts of the event, what kind of information can be retrieved from these data and how well data and information fulfil requirements that were recently proposed for disaster reporting on the European and international levels. In accordance with the European Floods Directive (2007/60/EC), impacts on human health, economic activities (and assets), cultural heritage and the environment are described on the national and sub-national scale. Information from governmental reports is complemented by communications on traffic disruptions and surveys of flood-affected residents and companies.
Overall, the impacts of the flood event in 2013 were manifold. The study reveals that flood-affected residents suffered from a large range of impacts, among which mental health and supply problems were perceived more seriously than financial losses. The most frequent damage type among affected companies was business interruption. This demonstrates that the current scientific focus on direct (financial) damage is insufficient to describe the overall impacts and severity of flood events.
The case further demonstrates that procedures and standards for impact data collection in Germany are widely missing. Present impact data in Germany are fragmentary, heterogeneous, incomplete and difficult to access. In order to fulfil, for example, the monitoring and reporting requirements of the Sendai Framework for Disaster Risk Reduction 2015–2030 that was adopted in March 2015 in Sendai, Japan, more efforts on impact data collection are needed.
Beyond the Crystal-Image
(2016)
A Conjunction of Mysteries
(2016)
Singular quantified terms
(2016)
In this paper, I discuss the behavior of singular partitives, focusing on Hebrew. I show that group noun-headed singular quantified terms behave essentially different from other singular quantified terms. Specifically, the domain of quantification in the former is a discrete set (the members of the group), while in the latter the domain of quantification is a set of mass entities. I propose a preliminary analysis of singular quantified terms in Hebrew, respecting the properties peculiar to this language as well as the observations about group vs. non-group singular quantified terms. This analysis is based on a novel class of quantifiers I name ’Measure Quantifiers’, which instantiate relations between algebraic sums. Using shifts between algebraic sums, we can represent the different readings of singular and plural individual or group terms.
This paper investigates an unnoticed difference in Mandarin between the Q-adjectives and the gradable adjectives of quality and shows that this observation follows straightforwardly from a theory that differentiates gradable predication of quantity and that of quality (e.g., Rett 2008; Lin 2014; Solt 2015; a.o.).
Recent work in semantics has shown that languages can vary in whether or not they include degrees (that is, elements of type < d >) in their semantic ontology. Several authors have argued that their languages of study lack degrees, including Bochnak (2013) for Washo (isolate, USA), Pearson (2009) for Fijian (Austronesian, Fiji), and Beck, et al. (2009) for Motu (Austronesian, Papua New Guinea). In this paper, I follow the tests proposed in Beck, et al. (2009) to assess the status of degrees in Warlpiri (Pama-Nyungan, Australia).
I use Warlpiri data collected following the Beck, et al. survey to argue that Warlpiri gradable predicates do not combine with a degree argument. (Like many other Australian languages, adjectival concepts like big and small are expressed using nouns in Warlpiri (Dixon 1982, Bittner & Hale 1995, among others). I refer to these lexical items as “gradable predicates” in this paper.) This paper represents a first pass at assessing the status of degrees in an Australian language, which have otherwise been unexamined from the point of view of degree semantics.
Ever since our first research into Alexander von Humboldt's stay in Spain, the absence of an ensuing relationship between the wise Prussian and the Spanish Crown and Authorities had always surprised us. On starting new research, we found that indeed he sent his first work to Carlos IV from Rome accompanied by a letter of gratitude for the protection he had received during his American trip and submission to the Spanish Crown, which we now present. This first literary fruit of his voyage, which Alexander von Humboldt alluded to in the letter is the first instalment of his work Plantes Équinoxiales, Recueillies au Mexique, dans l’ile de Cuba, dans les provinces de Caracas, de Cumana etc., published in Paris in 1805.
The X-ray observations of the colliding wind binary WR 21a is reported. The first monitoring performed by Swift/XRT in order to reveal the phase-locked variation. Our observations cover 201 different epochs from 2013 October 1 to 2015 January 30 for a total exposure of about 306 ks. It is found for the first time that the luminosity varies roughly in inverse proportion to the separation of the two stars before the X-ray maximum but later drops rapidly toward periastron.
We an optically-thick, transonic, steady wind model for a H-free Wolf-Rayet star. A bifurcation is found across a critical mass loss rate Mb. Slower winds M < Mb extend by several hydrostatic stellar radii, reproduce features of envelope in ation from Petrovic et al. (2006) and Gräfener et al. (2012), and are energetically unbound. This work is of particular interest for extended envelopes and winds, radiative hydrodynamic instabilities (eg. wind stagnation, clumping, etc.), and NLTE atmospheric models.
We present 3D numerical simulations of the NGC6888 nebula considering the proper motion and the evolution of the star, from the red supergiant (RSG) to the Wolf-Rayet (WR) phase. Our simulations reproduce the limb-brightened morphology observed in [OIII] and X-ray emission maps. The synthetic maps computed by the numerical simulations show filamentary and clumpy structures produced by instabilities triggered in the interaction between the WR wind and the RSG shell.
We present the first physical characterization of the young open cluster VVVCL041. We spectroscopically observed the cluster main-sequence stellar population and a very-massive star candidate: WR62-2. CMFGEN modelling to our near-infrared spectra indicates that WR62-2 is a very luminous (10^6.4±0.2 L⊙)and massive (∼ 80M⊙) star.
We present results of investigation of spectral variability of one of the most interesting massive stars, Romano's star (M33/V532 or GR290), located in the M33 galaxy. Brightness of the star changes together with its spectral class, which varies from WN11 to WN8. Using CMFGEN code we estimated parameters of stellar atmosphere and found that during last ten years bolometric luminosity of the star changed synchronously with stellar magnitude. Our calculations argue in favor of the hypothesis of a post-LBV status of GR290.
We present the results of the new photometric observations of the famous hypergiant PCygni. New observations were obtained in 2014 using the 48 cm Cassegrain telescope of the Abastumani Astrophysical Observatory, Georgia. We reveal some interesting behaviors of the B,V,R,I light curves, and also report new results on the periodicity of PCygni's variation. The latter result is based on the analysis of the photometric data (U,B,V filters) collected at the Abastumani Observatory between 1937 and 1983.
Using ESPaDOnS optical spectra of WR6, we search variations on the stellar wind parameters during the different phases of the spectral variations. We use the radiative transfer code CMFGEN (Hillier & Miller 1998) to determine the wind parameters. Our work gives mean parameters for WR6, Teff = 55 kK, M = 2.7 × 10^-5 M⊙/yr and v∞ =1700 km/s. Furthermore the line profiles variations at different phases are the consequence of a variation of mass loss rate and temperature un the winds. Effective temperature reaches 59 kK at the highest intensity, whereas the mass-loss rate decreases to 2.5 × 10^-5 M⊙/yr in that case. On the other hand, effective temperature decreases to 52.5 kK and the mass-loss rate increases to 3 × 10^-5 M/⊙yr when the line profile reach its minimum intensity. Results confirm the variable nature of the stellar wind, presented in this case on two of its fundamental parameters: temperature and mass-loss; which could be used to constrain the nature of the instability at the basis of the wind.
The gas cloud G2 is currently being tidally disrupted by the Galactic Centre super-massive black hole, Sgr A*. The region around the black hole is populated by ∼ 30 Wolf-Rayet stars, which produce strong outflows. Here we explore the possibility that gas clumps like G2 originate from the collision of stellar winds via the non-linear thin shell instability.
75 WR stars and 164 RSGs are identified in a single WFC3 pointing of our M101 survey. We find that within it's large star-forming complex NGC 5462 WR stars are preferentially located in the core whilst RSGs are found in the halo, suggesting two bursts of star-formation. A review of our WR candidates reveals that only ∼30% are detected in the archival broad-band ACS imaging whilst only ∼50% are associated with HII regions.
Spectroscopy is the preferred way to study the physical and wind properties of Wolf-Rayet (WR) stars, but with decreasing brightness and increasing distance of the object spectroscopy become very expensive. However, photometry still delivers a high signal to noise ratio. Current and past astronomical surveys and space missions provide large data sets, that can be harvested to discover new WR stars and study them over a wide metallicity range with the help of state of the art stellar atmosphere and evolutionary models.
We found original observations of PCygni by E. Kharadze and N. Magalashvili in the archives of the Abastumani Observatory. These observations were carried out in the period 1951–1983. Initially they used 29 Cygni as a comparison star, and all observations of PCygni were processed using this star. On the basis of their calculations, the authors decided that PCygni may be a WUMa type binary with an orbital period of 0.500565 d, but this hypothesis was not confirmed. The only observations that have been published in the Bulletin of the Abastumani Astrophysical Observatory were those of of 1951–1955. There are whole sets of observational data not only for PCygni and 29 Cygni, but in the majority of cases also for 36 Cygni in the archives. We recalculated all data (where it was possible) using 36 Cygni as a comparison star. We are presenting UBV light curves of the variable, and also observations made by V. Nikonov in Abastumani in the period 1935–1937
Concluding Remarks
(2015)
The interaction between massive star formation and gas is a key ingredient in galaxy evolution. Given the level of observational detail currently achievable in nearby starbursts, they constitute ideal laboratories to study interaction process that contribute to global evolution in all types of galaxies. Wolf-Rayet (WR) stars, as an observational marker of high mass star formation, play a pivotal role and their winds can strongly influence the surrounding gas. Imaging spectroscopy of two nearby (<4 Mpc) starbursts, both of which show multiple regions with WR stars, are discussed. The relation between the WR content and the physical and chemical properties of the surrounding ionized gas is explored.
The feedback from massive stars is important to super star cluster (SSC) evolution and the timescales on which it occurs. SSCs form embedded in thick material, and eventually, the cluster is cleared out and revealed at optical wavelengths – however, this transition is not well understood. We are investigating this critical SSC evolutionary transition with a multi-wavelength observational campaign. Although previously thought to appear after the cluster has fully removed embedding natal material, we have found that SSCs may host large populations of Wolf-Rayet stars. These evolved stars provide ionization and mechanical feedback that we hypothesize is the tipping point in the combined feedback processes that drive a SSC to emerge. Utilizing optical spectra obtained with the 4m Mayall Telescope at Kitt Peak National Observatory and the 6.5m MMT, we have compiled a sample of embedded SSCs that are likely undergoing this short-lived evolutionary phase and in which we confirm the presence of Wolf-Rayet stars. Early results suggest that WRs may accelerate the cluster emergence.
We discuss our most recent findings on the diffuse X-ray emission within Wolf-Rayet (WR) nebulae. The best-quality X-ray observations of these objects are those performed by XMM- Newton and Chandra towards S 308, NGC 2359, and NGC 6888. Even though these three WR nebulae might have different formation scenarios, they all share similar characteristics: i) the main plasma temperatures of the X-ray-emitting gas is found to be T =[1–2]×^K, ii) the diffuse X-ray emission is confined inside the [O iii] shell, and iii) their X-ray luminosities and electron densities in the 0.3–2.0 keV energy range are LX ≈10^33–10^34 erg s-1 and ne ≈0.1–1 cm^-3 . These properties and the nebular-like abundances of the hot gas suggest mixing and/or thermal conduction is taking an important rôle reducing the temperature of the hot bubble.
Using a code that employs a self-consistent method for computing the effects of photoionization on circumstellar gas dynamics, we model the formation of wind-driven nebulae around massive Wolf-Rayet (W-R) stars. Our algorithm incorporates a simplified model of the photo-ionization source, computes the fractional ionization of hydrogen due to the photoionizing flux and recombination, and determines self-consistently the energy balance due to ionization, photo-heating and radiative cooling. We take into account changes in stellar properties and mass-loss over the star's evolution. Our multi-dimensional simulations clearly reveal the presence of strong ionization front instabilities. Using various X-ray emission models, and abundances consistent with those derived for W-R nebulae, we compute the X-ray flux and spectra from our wind bubble models. We show the evolution of the X-ray spectral features with time over the evolution of the star, taking the absorption of the X-rays by the ionized bubble into account. Our simulated X-ray spectra compare reasonably well with observed spectra of Wolf-Rayet bubbles. They suggest that X-ray nebulae around massive stars may not be easily detectable, consistent with observations.∗
Ring Nebulae
(2015)
Preliminary results are presented from spectroscopic data in the optical range of the Galactic ring nebulae NGC 6888, G2:4+1:4, RCW 58 and Sh2-308. Deep observations with long exposure times were carried out at the 6.5m Clay Telescope and at the 10.4m Gran Telescopio Canarias. In NGC 6888, recombination lines of C ii, O ii and N ii are detected with signal-to-noise ratios higher than 8. The chemical content of NGC 6888 is discussed within the chemical enrichment predicted by evolution models of massive stars. For all nebulae, a forthcoming work will content in-depth details about observations, analysis and final results (Esteban et al. 2015, in prep.).
We analyse whether a stellar atmosphere model computed with the code CMFGEN provides an optimal description of the stellar observations of WR 136 and simultaneously reproduces the nebular observations of NGC 6888, such as the ionization degree, which is modelled with the pyCloudy code. All the observational material available (far and near UV and optical spectra) were used to constrain such models. We found that the stellar temperature T∗, at τ = 20, can be in a range between 70 000 and 110 000 K, but when using the nebula as an additional restriction, we found that the stellar models with T∗ ∼ 70 000 K represent the best solution for both, the star and the nebula.
I review our current understanding of the interaction between a Wolf-Rayet star's fast wind and the surrounding medium, and discuss to what extent the predictions of numerical simulations coincide with multiwavelength observations of Wolf-Rayet nebulae. Through a series of examples, I illustrate how changing the input physics affects the results of the numerical simulations. Finally, I discuss how numerical simulations together with multiwavelength observations of these objects allow us to unpick the previous mass-loss history of massive stars.
Colliding Wolf-Rayet (WR) winds produce thermal X-ray emission widely observed by X-ray telescopes. In wide WR+O binaries, such as WR 140, the X-ray flux is tied to the orbital phase, and is a direct probe of the winds’ properties. In the Galactic center, ~30 WRs orbit the super massive black hole (SMBH) within ~10”, leading to a smorgasbord of wind-wind collisions. To model the X-ray emission of WR 140 and the Galactic center, we perform 3D hydrodynamic simulations to trace the complex gaseous flows, and then carry out 3D radiative transfer calculations to compute the variable X-ray spectra. The model WR 140 RXTE light curve matches the data well for all phases except the X-ray minimum associated with periastron, while the model spectra agree with the RXTE hardness ratio and the shape of the Suzaku observations throughout the orbit. The Galactic center model of the Chandra flux and spectral shape match well in the region r ≤ 3”, but the model flux falls off too rapidly beyond this radius.
Two of the main physical parameters that govern the massive star evolution, the mass and the mass-loss rate, are still poorly determined from the observational point of view. Only binary systems could provide well constrained masses and colliding-wind binaries could bring some constraints on the mass-loss rate. Therefore, colliding-wind binaries turn out to be very promising objects. In this framework, we present detailed studies of basic observational data obtained with the XMM-Newton facility and combined with ground-based observations and other data. We expose the results for two particularly interesting WR+O colliding-wind binaries: WR22 and WR21a.
Magnetic fields, non-thermal radiation and particle acceleration in colliding winds of WR-O stars
(2015)
Non-thermal emission has been detected in WR-stars for many years at long wavelengths spectral range, in general attributed to synchrotron emission. Two key ingredients are needed to explain such emissions, namely magnetic fields and relativistic particles. Particles can be accelerated to relativistic speeds by Fermi processes at strong shocks. Therefore, strong synchrotron emission is usually attributed to WR binarity. The magnetic field may also be amplified at shocks, however the actual picture of the magnetic field geometry, intensity, and its role on the acceleration of particles at WR binary systems is still unclear. In this work we discuss the recent developments in MHD modelling of wind-wind collision regions by means of numerical simulations, and the coupled particle acceleration processes related.
Wolf-Rayet (WR) stars lose copious amounts of mass and momentum through dense stellar winds. The interaction of these outflows with their surroundings results in highly structured and complex circumstellar environments, often featuring knots, arcs, shells and spirals. Recent improvements in computational power and techniques have led to the development of detailed, multi-dimensional simulations that have given new insight into the origin of these structures, and better understanding of the physical mechanisms driving their formation. We review three of the main mechanisms that shape the outflows of WR stars:
• interaction with the interstellar medium (ISM), i.e., wind-ISM interactions;
• interaction with a stellar wind, either from a previous phase of evolution or the wind from a companion star, i.e., wind-wind interactions;
• and interaction with a companion star that has a weak or insignificant outflow (e.g., a compact companion such as a neutron star or black hole), i.e.,wind-companion interactions.
We also highlight the broader implications and impact of these circumstellar structures for related phenomena, e.g., for X-ray binaries and Gamma-ray bursts.
We look at how the dynamics of colliding wind binaries (CWB) can be investigated in 2D, and how several parameters influence the dynamics of the small scale structures inside the colliding wind and the shocked regions, as well as in how the dynamics influence the shape of the collision region at large distances. The parameters we adopt are based on the binary system WR98a, one of the few Wolf-Rayet (WR) dusty pinwheels known.
Observations of the WC9+OB system WR65 in the infrared show variations of its dust emission consistent with a period near 4.8 yr, suggesting formation in a colliding-wind binary (CWB) having an elliptical orbit. If we adopt the IR maximum as zero phase, the times of X-ray maximum count and minimum extinction to the hard component measured by Oskinova & Hamann fall at phases 0.4–0.5, when the separation of the WC9 and OB stars is greatest. We consider WR65 in the context of other WC8–9+OB stars showing dust emission.
Carbon-rich Wolf-Rayet stars are efficient carbon dust makers. Despite the strong evidence for dust formation in these objects provided by infrared thermal emission from dust, the routes to nucleation and condensation and the physical conditions required for dust production are still poorly understood. We discuss here the potential routes to carbon dust and the possible locations conducive to dust formation in the colliding winds of WC binaries.
Two types of X-ray sources are mostly found in planetary nebulae (PNe): point sources at their central stars and diffuse emission inside hot bubbles. Here we describe these two types of sources based on the most recent observations obtained in the framework of the Chandra Planetary Nebula Survey, ChanPlaNS, an X-ray survey targeting a volume-limited sample of PNe. Diffuse X-ray emission is found preferentially in young PNe with sharp, closed inner
shells. Point sources of X-ray emission at the central stars reveal magnetically active binary companions and shock-in stellar winds.