@inproceedings{Fernando2008,
  author    = {Fernando, Tim},
  title     = {Temporal propositions as regular languages},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-27194},
  year      = {2008},
  abstract  = {Temporal propositions are mapped to sets of strings that witness (in a precise sense) the propositions over discrete linear Kripke frames. The strings are collected into regular languages to ensure the decidability of entailments given by inclusions between languages. (Various notions of bounded entailment are shown to be expressible as language inclusions.) The languages unwind computations implicit in the logical (and temporal) connectives via a system of finite-state constraints adapted from finite-state morphology. Applications to Hybrid Logic and non-monotonic inertial reasoning are briefly considered.},
  language  = {en}
}
@inproceedings{IlarrazaGojenolaOronozetal.2008,
  author    = {Ilarraza, Arantza D{\´i}az de and Gojenola, Koldo and Oronoz, Maite and Otaegi, Maialen and Alegria, I{\~n}aki},
  title     = {Syntactic error detection and correction in date expressions using finite-state transducers},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-27180},
  year      = {2008},
  abstract  = {This paper presents a system for the detection and correction of syntactic errors. It combines a robust morphosyntactic analyser and two groups of finite-state transducers specified using the Xerox Finite State Tool (xfst). One of the groups is used for the description of syntactic error patterns while the second one is used for the correction of the detected errors. The system has been tested on a corpus of real texts, containing both correct and incorrect sentences, with good results.},
  language  = {en}
}
@inproceedings{Didakowski2008,
  author    = {Didakowski, J{\"o}rg},
  title     = {SynCoP : combining syntactic tagging with chunking using weighted finite state transducers},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-27172},
  year      = {2008},
  abstract  = {This paper describes the key aspects of the system SynCoP (Syntactic Constraint Parser) developed at the Berlin-Brandenburgische Akademie der Wissenschaften. The parser allows to combine syntactic tagging and chunking by means of constraint grammar using weighted finite state transducers (WFST). Chunks are interpreted as local dependency structures within syntactic tagging. The linguistic theories are formulated by criteria which are formalized by a semiring; these criteria allow structural preferences and gradual grammaticality. The parser is essentially a cascade of WFSTs. To find the most likely syntactic readings a best-path search is used.},
  language  = {en}
}
@inproceedings{Daciuk2008,
  author    = {Daciuk, Jan},
  title     = {Perfect hashing tree automata},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-27163},
  year      = {2008},
  abstract  = {We present an algorithm that computes a function that assigns consecutive integers to trees recognized by a deterministic, acyclic, finite-state, bottom-up tree automaton. Such function is called minimal perfect hashing. It can be used to identify trees recognized by the automaton. Its value may be seen as an index in some other data structures. We also present an algorithm for inverted hashing.},
  language  = {en}
}
@inproceedings{BoegelButtHautlietal.2008,
  author    = {B{\"o}gel, Tina and Butt, Miriam and Hautli, Annette and Sulger, Sebastian},
  title     = {Developing a finite-state morphological analyzer for Urdu and Hindi},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-27155},
  year      = {2008},
  abstract  = {We introduce and discuss a number of issues that arise in the process of building a finite-state morphological analyzer for Urdu, in particular issues with potential ambiguity and non-concatenative morphology. Our approach allows for an underlyingly similar treatment of both Urdu and Hindi via a cascade of finite-state transducers that transliterates the very different scripts into a common ASCII transcription system. As this transliteration system is based on the XFST tools that the Urdu/Hindi common morphological analyzer is also implemented in, no compatibility problems arise.},
  language  = {en}
}
@inproceedings{BonfanteLeRoux2008,
  author    = {Bonfante, Guillaume and Le Roux, Joseph},
  title     = {Intersection optimization is NP-complete},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-27146},
  year      = {2008},
  abstract  = {Finite state methods for natural language processing often require the construction and the intersection of several automata. In this paper, we investigate the question of determining the best order in which these intersections should be performed. We take as an example lexical disambiguation in polarity grammars. We show that there is no efficient way to minimize the state complexity of these intersections.},
  language  = {en}
}
@inproceedings{BlancConstantWatrin2008,
  author    = {Blanc, Olivier and Constant, Matthieu and Watrin, Patrick},
  title     = {Segmentation in super-chunks with a finite-state approach},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-27133},
  year      = {2008},
  abstract  = {Since Harris' parser in the late 50s, multiword units have been progressively integrated in parsers. Nevertheless, in the most part, they are still restricted to compound words, that are more stable and less numerous. Actually, language is full of semi-fixed expressions that also form basic semantic units: semi-fixed adverbial expressions (e.g. time), collocations. Like compounds, the identification of these structures limits the combinatorial complexity induced by lexical ambiguity. In this paper, we detail an experiment that largely integrates these notions in a finite-state procedure of segmentation into super-chunks, preliminary to a parser.We show that the chunker, developped for French, reaches 92.9\% precision and 98.7\% recall. Moreover, multiword units realize 36.6\% of the attachments within nominal and prepositional phrases.},
  language  = {en}
}
@inproceedings{Barthelemy2008,
  author    = {Barth{\´e}lemy, Fran{\c{c}}ois},
  title     = {Finite-state compilation of feature structures for two-level morphology},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-27120},
  year      = {2008},
  abstract  = {This paper describes a two-level formalism where feature structures are used in contextual rules. Whereas usual two-level grammars describe rational sets over symbol pairs, this new formalism uses tree structured regular expressions. They allow an explicit and precise definition of the scope of feature structures. A given surface form may be described using several feature structures. Feature unification is expressed in contextual rules using variables, like in a unification grammar. Grammars are compiled in finite state multi-tape transducers.},
  language  = {en}
}
@inproceedings{BarbaianiCanceddaDanceetal.2008,
  author    = {Barbaiani, Mădălina and Cancedda, Nicola and Dance, Chris and Fazekas, Szil{\´a}rd and Ga{\´a}l, Tam{\´a}s and Gaussier, {\´E}ric},
  title     = {Asymmetric term alignment with selective contiguity constraints by multi-tape automata},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-27115},
  year      = {2008},
  abstract  = {This article describes a HMM-based word-alignment method that can selectively enforce a contiguity constraint. This method has a direct application in the extraction of a bilingual terminological lexicon from a parallel corpus, but can also be used as a preliminary step for the extraction of phrase pairs in a Phrase-Based Statistical Machine Translation system. Contiguous source words composing terms are aligned to contiguous target language words. The HMM is transformed into a Weighted Finite State Transducer (WFST) and contiguity constraints are enforced by specific multi-tape WFSTs. The proposed method is especially suited when basic linguistic resources (morphological analyzer, part-of-speech taggers and term extractors) are available for the source language only.},
  language  = {en}
}
@inproceedings{YliJyrae2008,
  author    = {Yli-Jyr{\"a}, Anssi},
  title     = {Applications of diamonded double negation},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-27109},
  year      = {2008},
  abstract  = {Nested complementation plays an important role in expressing counter- i.e. star-free and first-order definable languages and their hierarchies. In addition, methods that compile phonological rules into finite-state networks use double-nested complementation or "double negation". This paper reviews how the double-nested complementation extends to a relatively new operation, generalized restriction (GR), coined by the author (Yli-Jyr{\"a} and Koskenniemi 2004). This operation encapsulates a double-nested complementation and elimination of a concatenation marker, diamond, whose finite occurrences align concatenations in the arguments of the operation. The paper demonstrates that the GR operation has an interesting potential in expressing regular languages, various kinds of grammars, bimorphisms and relations. This motivates a further study of optimized implementation of the operator.},
  language  = {en}
}
@inproceedings{Watson2008,
  author    = {Watson, Bruce W.},
  title     = {Advances in automata implementation techniques (Abstract)},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-27094},
  year      = {2008},
  language  = {en}
}
@inproceedings{Karttunen2008,
  author    = {Karttunen, Lauri},
  title     = {New features in PARC finite state toolkits (Abstract)},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-27085},
  year      = {2008},
  language  = {en}
}
@inproceedings{OPUS4-2516,
  title     = {Finite-state methods and natural language processing : 6th International Workshop, FSMNLP 2007 Potsdam, Germany, september 14 - 16 ; revised papers},
  editor    = {Hanneforth, Thomas and W{\"u}rzner, Kay-Michael},
  publisher = {Universit{\"a}tsverlag Potsdam},
  address   = {Potsdam},
  isbn      = {978-3-940793-57-7},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-23812},
  pages     = {225},
  year      = {2008},
  abstract  = {Proceedings with the revised papers of the FSMNLP (Finite-state Methods and Natural Language Processing) 2007 Workshop in Potsdam},
  language  = {en}
}
@inproceedings{OPUS4-1658,
  title     = {Seelisch gesund von Anfang an : Programm und Abstracts des 26. Symposiums der Fachgruppe Klinische Psychologie und Psychotherapie der Deutschen Gesellschaft f{\"u}r Psychologie, 1. - 3. Mai 2008 in Potsdam},
  editor    = {Warschburger, Petra and Ihle, Wolfgang and Esser, G{\"u}nter},
  publisher = {Universit{\"a}tsverlag Potsdam},
  address   = {Potsdam},
  isbn      = {978-3-940793-34-8},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17551},
  pages     = {302},
  year      = {2008},
  abstract  = {Der Tagungsband enth{\"a}lt das Programm und die Abstracts des 26. Symposiums der Fachgruppe Klinische Psychologie und Psychotherapie der Deutschen Gesellschaft f{\"u}r Psychologie, veranstaltet an der Universit{\"a}t Potsdam vom 1. bis 3. Mai 2008. Etwa 450 Kongressteilnehmer pr{\"a}sentieren den aktuellen Forschungs- und Wissensstand der Klinischen Psychologie und Psychotherapie in Deutschland. Grußworte halten die brandenburgische Ministerin f{\"u}r Arbeit, Soziales, Gesundheit und Familie, Dagmar Ziegler, die Pr{\"a}sidentin der Universit{\"a}t Potsdam, Prof. Dr.-Ing. Dr. Sabine Kunst, sowie Prof. Dr. Michael Linden als Vertreter der Deutschen Gesellschaft f{\"u}r Psychiatrie, Psychotherapie und Nervenheilkunde (DGPPN). Zu den Themenschwerpunkten des Kongresses geh{\"o}ren Einflussfaktoren auf die psychische Gesundheit {\"A}lterer, Impulsivit{\"a}t, Schlaf- und Traumforschung in der Klinischen Psychologie, Behandlung von Essst{\"o}rungen, Wirksamkeitsstudien psychischer St{\"o}rungen des Kindes- und Jugendalters, Angst und Depression, Behandlung von Kriegs- und Folteropfern, Risiko- und Schutzfaktoren der Kindesentwicklung sowie Adipositas im Kindes- und Jugendalter. Außer den Vortr{\"a}gen gibt es eine Pr{\"a}sentation von etwa 150 Postern. Zum Programm der Tagung geh{\"o}rt ebenso die Verleihung des Klaus-Grawe-Awards for the Advancement of Innovative Research in Clinical Psychology and Psychotherapy an Prof. Dr. Timothy J. Strauman von der Duke University (USA), die Verleihung der Nachwuchswissenschaftler- und Posterpreise sowie ein Pre-conference Workshop f{\"u}r Doktorandinnen und Doktoranden der Klinischen Psychologie zum Thema "Verhaltens- und Molekulargenetik".},
  subject      = {Konferenz},
  language  = {de}
}
@inproceedings{Reimer2007,
  author    = {Reimer, A.},
  title     = {Clumping effects on non-thermal particle spectra in massive star systems},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18246},
  year      = {2007},
  abstract  = {Observational evidence exists that winds of massive stars are clumped. Many massive star systems are known as non-thermal particle production sites, as indicated by their synchrotron emission in the radio band. As a consequence they are also considered as candidate sites for non-thermal high-energy photon production up to gamma-ray energies. The present work considers the effects of wind clumpiness expected on the emitting relativistic particle spectrum in colliding wind systems, built up from the pool of thermal wind particles through diffusive particle acceleration, and taking into account inverse Compton and synchrotron losses. In comparison to a homogeneous wind, a clumpy wind causes flux variations of the emitting particle spectrum when the clump enters the wind collision region. It is found that the spectral features associated with this variability moves temporally from low to high energy bands with the time shift between any two spectral bands being dependent on clump size, filling factor, and the energy-dependence of particle energy gains and losses.},
  language  = {en}
}
@inproceedings{Weis2007,
  author    = {Weis, K.},
  title     = {Wind relics : clumps, inhomogeneities and outflows in LBV nebulae},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18235},
  year      = {2007},
  abstract  = {The most massive stars are those with the shortest but most active life. One group of massive stars, the Luminous Blue Variables (LBVs), of which only a few objects are known, are in particular of interest concerning the stability of stars. They have a high mass loss rate and are close to being instable. This is even more likely as rotation becomes an important factor in stellar evolution of these stars. Through massive stellar winds and sometimes giant eruptions, LBV nebulae are formed. Various aspects in the evolution in the LBV phase lead, beside the large scale morphological and kinematical differences, to a diversity of small structures like clumps, rims, and outflows in these nebulae.},
  language  = {en}
}
@inproceedings{RomeroOwockiAraudoetal.2007,
  author    = {Romero, G. E. and Owocki, S. P. and Araudo, A. T. and Townsend, R. H. D. and Benaglia, P.},
  title     = {Using gamma-rays to probe the clumped structure of stellar winds},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18210},
  year      = {2007},
  abstract  = {Gamma-rays can be produced by the interaction of a relativistic jet and the matter of the stellar wind in the subclass of massive X-ray binaries known as "microquasars". The relativistic jet is ejected from the surroundings of the compact object and interacts with cold protons from the stellar wind, producing pions that then quickly decay into gamma-rays. Since the resulting gamma-ray emissivity depends on the target density, the detection of rapid variability in microquasars with GLAST and the new generation of Cherenkov imaging arrays could be used to probe the clumped structure of the stellar wind. In particular, we show here that the relative fluctuation in gamma rays may scale with the square root of the ratio of porosity length to binary separation, \$\sqrt{h/a}\$, implying for example a ca. 10\% variation in gamma ray emission for a quite moderate porosity, h/a ∼ 0.01.},
  language  = {en}
}
@inproceedings{Nielsen2007,
  author    = {Nielsen, K. E.},
  title     = {On irregular line profiles in the optical spectrum of Eta Carinae},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18227},
  year      = {2007},
  abstract  = {The optical spectrum of Eta Carinae (η Car) is prominent in H I, He i and Fe ii wind lines, all of which vary both in absorption and emission with phase. The phase dependance is a consequence of the interaction between the two objects in the η Car binary (η Car A \& B). The binary system is enshrouded by ejecta from previous mass ejection events and consequently, η Car B is not directly observable. We have traced the He i lines over η Car's spectroscopic period, using HST/STIS data obtained with medium spectral, but high angular, resolving power, and created a radial velocity curve for the system. The He I lines are formed in the core of the system, and appear to be a composite of multiple features formed in spatially separated regions. The sources of their irregular line profiles are still not fully understood, but can be attributed to emission/absorption near the wind-wind interface and/or a direct consequence of the η Car A's, massive, clumpy wind. This paper will discuss the spectral variability, the narrow emission structure of the He i lines and how clumpiness of the winds may impede the construction of the reliable radial velocity curve, necessary for characterizations of especially η Car B.},
  language  = {en}
}
@inproceedings{Gull2007,
  author    = {Gull, T. R.},
  title     = {Eta Carinae viewed from different vantages},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18200},
  year      = {2007},
  abstract  = {The spatially-resolved winds of the massive binary, Eta Carinae, extend an arcsecond on the sky, well beyond the 10 to 20 milliarcsecond binary orbital dimension. Stellar wind line profiles, observed at very different angular resolutions of VLTI/AMBER, HST/STIS and VLT/UVES, provide spatial information on the extended wind interaction structure as it changes with orbital phase. These same wind lines, observable in the starlight scattered off the foreground lobe of the dusty Homunculus, provide time-variant line profiles viewed from significantly different angles. Comparisons of direct and scattered wind profiles observed in the same epoch and at different orbital phases provide insight on the extended wind structure and promise the potential for three-dimensional imaging of the outer wind structures. Massive, long-lasting clumps, including the nebularWeigelt blobs, originated during the two historical ejection events. Wind interactions with these clumps are quite noticeable in spatially-resolved spectroscopy. As the 2009.0 minimum approaches, analysis of existing spectra and 3-D modeling are providing bases for key observations to gain further understanding of this complex massive binary.},
  language  = {en}
}
@inproceedings{Cassinelli2007,
  author    = {Cassinelli, Joseph P.},
  title     = {Discussion: Magnetic fields, variability},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18195},
  year      = {2007},
  language  = {en}
}
@inproceedings{ReimerAharonianHintonetal.2007,
  author    = {Reimer, O. and Aharonian, Felix A. and Hinton, J. and Hofmann, W. and Hoppe, S. and Raue, M. and Reimer, A.},
  title     = {VHE gamma-rays from Westerlund 2 and implications for the inferred energetics},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18172},
  year      = {2007},
  abstract  = {The H.E.S.S. collaboration recently reported the discovery of VHE γ-ray emission coincident with the young stellar cluster Westerlund 2. This system is known to host a population of hot, massive stars, and, most particularly, the WR binary WR 20a. Particle acceleration to TeV energies in Westerlund 2 can be accomplished in several alternative scenarios, therefore we only discuss energetic constraints based on the total available kinetic energy in the system, the actual mass loss rates of respective cluster members, and implied gamma-ray production from processes such as inverse Compton scattering or neutral pion decay. From the inferred gammaray luminosity of the order of 1035erg/s, implications for the efficiency of converting available kinetic energy into non-thermal radiation associated with stellar winds in the Westerlund 2 cluster are discussed under consideration of either the presence or absence of wind clumping.},
  language  = {en}
}
@inproceedings{Kholtygin2007,
  author    = {Kholtygin, A. F.},
  title     = {Modelling the induced clumping stochastic line profile variability},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18180},
  year      = {2007},
  abstract  = {We model the line profile variability (lpv) in spectra of clumped stellar atmospheres using the Stochastic Clump Model (SCM) of the winds of early-type stars. In this model the formation of dense inhomogeneities (clumps) in the line driven winds is considered as being a stochastic process. It is supposed that the emission due to clumps mainly contributes to the intensities of emission lines in the stellar spectra. It is shown that in the framework of the SCM it is possible to reproduce both the mean line profiles and a common pattern of the lpv.},
  language  = {en}
}
@inproceedings{CheneMoffatCrowther2007,
  author    = {Chen{\´e}, A.-N. and Moffat, Anthony F. J. and Crowther, P. A.},
  title     = {Rapidly accelerating clumps in the winds of the very hot WNE Stars},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18163},
  year      = {2007},
  abstract  = {We study the time variability of emission lines in three WNE stars : WR 2 (WN2), WR 3 (WN3ha) and WR152 (WN3). While WR 2 shows no variability above the noise level, the other stars do show variation, which are like other WR stars in WR 152 but very fast in WR 3. From these motions, we deduce a value of β ∼1 for WR 3 that is like that seen in O stars and β ∼2-3 for WR 152, that is intermediate between other WR stars and WR 3.},
  language  = {en}
}
@inproceedings{StLouis2007,
  author    = {St-Louis, N.},
  title     = {Discussion: Binaries, colliding winds, LBVs and high energy radiation},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18155},
  year      = {2007},
  abstract  = {Clumping in hot-star winds : proceedings of an international workshop held in Potsdam, Germany, 18. - 22. June 2007},
  language  = {en}
}
@inproceedings{Szeifert2007,
  author    = {Szeifert, T.},
  title     = {Wind variabilities and asymmetries in Luminous Blue Variables},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18146},
  year      = {2007},
  abstract  = {Luminous Blue Variables show strong changes in their stellar wind on time scales of typically years to decades when they expand and contract radially at approximately constant luminosity. Micro-variability on shorter time scales and amplitudes can be observed superimposed to the larger scale radial changes. I will show long-term time series of high resolution spectra which we have collected in the past 20 years for many of the well known LBVs together with a few time series of weekly sampling (HR Car, R40, R71, R110, R127, S Dor) covering a time windows of up to a few months. Wind variability is seen on short and intermediate time scales with the line profiles changing from P Cygni to inverse P Cygni and double peeked profiles sometimes for the same star and spectral line. On longer time scales the ionisation levels for all chemical elements change drastically due to the strong change of the temperature on the stellar surface. While on the long term the characteristic radial changes may have impact on the over all mass loss rates, the variabilities and asymmetries on short and intermediate time scales may cause false estimates of the mass loss rates when confronting models with the observed line profiles},
  language  = {en}
}
@inproceedings{MorrisonRotherKurschat2007,
  author    = {Morrison, N. D. and Rother, R. and Kurschat, N.},
  title     = {Hα line profile variability in the B8Ia-type supergiant Rigel (β Ori)},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18120},
  year      = {2007},
  abstract  = {Hα observations of Rigel obtained on 184 nights during the past ten years with the 1-m telescope and ´echelle spectrograph of Ritter Observatory are surveyed. The line profiles were classified in terms of morphology. About 1/4 of them are of P Cygni type, about 15\% inverse P Cygni, about 25\% double-peaked, about 1/3 pure absorption, and a few are single emission lines. Transformation of the profile from one type to another typically takes a few days. Although the line stays in absorption for extended intervals, only one high-velocity absorption event of the intensity reported by Kaufer et al. (1996a) was observed, in late 2006. Late in this event, Hα absorption occurred farther to the red than the red wing of a plausible photospheric absorption component, an indication of infalling material. In general, as the absorption events come to an end, the emission typically returns with an inverse P Cygni profile. The Hα profile class shows no obvious correlation with the radial velocity of C II λ6578, a photospheric absorption line.},
  language  = {en}
}
@inproceedings{OskinovaHamannFeldmeier2007,
  author    = {Oskinova, Lida and Hamann, Wolf-Rainer and Feldmeier, Achim},
  title     = {X-raying clumped stellar winds},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18133},
  year      = {2007},
  abstract  = {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.},
  language  = {en}
}
@inproceedings{CohenLeuteneggerTownsend2007,
  author    = {Cohen, David H. and Leutenegger, M. A. and Townsend, R. H. D.},
  title     = {Quantitative analysis of resolved X-ray emission line profiles of O stars},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18115},
  year      = {2007},
  abstract  = {By quantitatively fitting simple emission line profile models that include both atomic opacity and porosity to the Chandra X-ray spectrum of ζ Pup, we are able to explore the trade-offs between reduced mass-loss rates and wind porosity. We find that reducing the mass-loss rate of ζ Pup by roughly a factor of four, to 1.5 × 10-6 M⊙ yr-1, enables simple non-porous wind models to provide good fits to the data. If, on the other hand, we take the literature mass-loss rate of 6×10-6 M⊙ yr-1, then to produce X-ray line profiles that fit the data, extreme porosity lengths - of h∞ ≈ 3 R∗ - are required. Moreover, these porous models do not provide better fits to the data than the non-porous, low optical depth models. Additionally, such huge porosity lengths do not seem realistic in light of 2-D numerical simulations of the wind instability.},
  language  = {en}
}
@inproceedings{Blomme2007,
  author    = {Blomme, R.},
  title     = {Corotating Interaction Regions and clumping},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18100},
  year      = {2007},
  abstract  = {We present hydrodynamical models for Corotating Interaction Regions, which were used by Lobel (2007) to model the Discrete Absorption Components in HD 64760. We also discuss our failure to model the rotational modulations seen in the same star.},
  language  = {en}
}
@inproceedings{MassaPrinjaFullerton2007,
  author    = {Massa, D. L. and Prinja, R. K. and Fullerton, A. W.},
  title     = {The effects of clumping on wind line variability},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18095},
  year      = {2007},
  abstract  = {We review the effects of clumping on the profiles of resonance doublets. By allowing the ratio of the doublet oscillator strenghts to be a free parameter, we demonstrate that doublet profiles contain more information than is normally utilized. In clumped (or porous) winds, this ratio can lies between unity and the ratio of the f-values, and can change as a function of velocity and time, depending on the fraction of the stellar disk that is covered by material moving at a particular velocity at a given moment. Using these insights, we present the results of SEI modeling of a sample of B supergiants, ζ Pup and a time series for a star whose terminal velocity is low enough to make the components of its Si VIλλ1400 independent. These results are interpreted within the framewrok of the Oskinova et al. (2007) model, and demonstrate how the doublet profiles can be used to extract infromation about wind structure.},
  language  = {en}
}
@inproceedings{LeuteneggerCohenKahnetal.2007,
  author    = {Leutenegger, M. A. and Cohen, David H. and Kahn, S. M. and Owocki, S. P. and Paerels, F. B. S.},
  title     = {Resonance scattering in the X-ray emission lines profiles of ζ Puppis},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18085},
  year      = {2007},
  abstract  = {We present XMM-Newton Reflection Grating Spectrometer observations of pairs of X-ray emission line profiles from the O star ζ Pup that originate from the same He-like ion. The two profiles in each pair have different shapes and cannot both be consistently fit by models assuming the same wind parameters. We show that the differences in profile shape can be accounted for in a model including the effects of resonance scattering, which affects the resonance line in the pair but not the intercombination line. This implies that resonance scattering is also important in single resonance lines, where its effect is difficult to distinguish from a low effective continuum optical depth in the wind. Thus, resonance scattering may help reconcile X-ray line profile shapes with literature mass-loss rates.},
  language  = {en}
}
@inproceedings{SchnerrHenrichs2007,
  author    = {Schnerr, R. S. and Henrichs, H. F.},
  title     = {Magnetic fields and wind variability in massive stars},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18075},
  year      = {2007},
  abstract  = {This paper describes the thesis work of Schnerr (2007) entitled "Magnetic fields and mass loss in massive stars", which aimed at a better understanding of the impact of magnetic fields on the winds of massive stars.},
  language  = {en}
}
@inproceedings{IgnaceGayley2007,
  author    = {Ignace, R. and Gayley, K. G.},
  title     = {Circumstellar Magnetic Field Diagnostics from Line Polarization},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18066},
  year      = {2007},
  language  = {en}
}
@inproceedings{CassinelliIgnaceWaldronetal.2007,
  author    = {Cassinelli, Joseph P. and Ignace, R. and Waldron, W. and Cho, J. and Murphy, N. and Lazarian, A.},
  title     = {X-ray line emission produced in clump bow shocks},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18057},
  year      = {2007},
  abstract  = {We summarize Chandra observations of the emission line profiles from 17 OB stars. The lines tend to be broad and unshifted. The forbidden/intercombination line ratios arising from Helium-like ions provide radial distance information for the X-ray emission sources, while the H-like to He-like line ratios provide X-ray temperatures, and thus also source temperature versus radius distributions. OB stars usually show power law differential emission measure distributions versus temperature. In models of bow shocks, we find a power law differential emission measure, a wide range of ion stages, and the bow shock flow around the clumps provides transverse velocities comparable to HWHM values. We find that the bow shock results for the line profile properties, consistent with the observations of X-ray line emission for a broad range of OB star properties.},
  language  = {en}
}
@inproceedings{Vink2007,
  author    = {Vink, J. S.},
  title     = {Discussion: Hydrodynamic modeling},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18046},
  year      = {2007},
  language  = {en}
}
@inproceedings{Runacres2007,
  author    = {Runacres, M. C.},
  title     = {Hydrodynamical models of clumping beyond 50 R∗},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18030},
  year      = {2007},
  abstract  = {We present one-dimensional, time-dependent models of the clumps generated by the linedeshadowing instability. In order to follow the clumps out to distances of more than 1000 R∗, we use an efficient moving-box technique. We show that, within the approximations, the wind can remain clumped well into the formation region of the radio continuum.},
  language  = {en}
}
@inproceedings{WalterZuritaHerasLeyder2007,
  author    = {Walter, R. and Zurita-Heras, J. and Leyder, J.-C.},
  title     = {Probing clumpy stellar winds with a neutron star},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18024},
  year      = {2007},
  abstract  = {INTEGRAL tripled the number of super-giant high-mass X-ray binaries (sgHMXB) known in the Galaxy by revealing absorbed and fast transient (SFXT) systems. Quantitative constraints on the wind clumping of massive stars can be obtained from the study of the hard X-ray variability of SFXT. A large fraction of the hard X-ray emission is emitted in the form of flares with a typical duration of 3 ksec, frequency of 7 days and luminosity of \$10^{36}\$ erg/s. Such flares are most probably emitted by the interaction of a compact object orbiting at \$\sim10~R_*\$ with wind clumps (\$10^{22 ... 23}\$ g) representing a large fraction of the stellar mass-loss rate. The density ratio between the clumps and the inter-clump medium is \$10^{2 ... 4}\$. The parameters of the clumps and of the inter-clump medium, derived from the SFXT flaring behavior, are in good agreement with macro-clumping scenario and line-driven instability simulations. SFXT are likely to have larger orbital radius than classical sgHMXB.},
  language  = {en}
}
@inproceedings{udDoula2007,
  author    = {ud-Doula, A.},
  title     = {Large-scale wind structure due to magnetic fields},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18010},
  year      = {2007},
  abstract  = {Magnetic fields influence the dynamics of hot-star winds and create large scale structure. Based on numerical magnetohydrodynamic (MHD) simulations, we model the wind of θ¹ Ori C, and then use the SEI method to compute synthetic line profiles for a range of viewing angles as function of rotational phase. The resulting dynamic spectrum for a moderately strong line shows a distinct modulation, but with a phase that seems at odds with available observations.},
  language  = {en}
}
@inproceedings{Puls2007,
  author    = {Puls, Joachim},
  title     = {Discussion : X-rays},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18000},
  year      = {2007},
  abstract  = {Clumping in hot-star winds : proceedings of an international workshop held in Potsdam, Germany, 18. - 22. June 2007},
  language  = {en}
}
@inproceedings{Owocki2007,
  author    = {Owocki, S. P.},
  title     = {Dynamical simulation of the "velocity-porosity" reduction in observed strength of stellar wind lines},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17992},
  year      = {2007},
  abstract  = {I use dynamical simulations of the line-driven instability to examine the potential role of the resulting flow structure in reducing the observed strength of wind absorption lines. Instead of the porosity length formalism used to model effects on continuum absorption, I suggest reductions in line strength can be better characterized in terms of a velocity clumping factor that is insensitive to spatial scales. Examples of dynamic spectra computed directly from instability simulations do exhibit a net reduction in absorption, but only at a modest 10-20\% level that is well short of the ca. factor 10 required by recent analyses of PV lines.},
  language  = {en}
}
@inproceedings{Sonneborn2007,
  author    = {Sonneborn, G.},
  title     = {Imaging and spectroscopy with the James Webb Space Telescope},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17983},
  year      = {2007},
  abstract  = {The James Webb Space Telescope (JWST) is a large, infrared-optimized space telescope scheduled for launch in 2013. JWST will find the first stars and galaxies that formed in the early universe, connecting the Big Bang to our own Milky Way galaxy. JWST will peer through dusty clouds to see stars forming planetary systems, connecting the MilkyWay to our own Solar System. JWST's instruments are designed to work primarily in the infrared range of 1 - 28 μm, with some capability in the visible range. JWST will have a large mirror, 6.5 m in diameter, and will be diffraction-limited at 2 μm (0.1 arcsec resolution). JWST will be placed in an L2 orbit about 1.5 million km from the Earth. The instruments will provide imaging, coronography, and multi-object and integral-field spectroscopy across the 1 - 28 μm wavelength range. The breakthrough capabilities of JWST will enable new studies of massive star winds from the Milky Way to the early universe.},
  language  = {en}
}
@inproceedings{FeldmeierHamannRaetzeletal.2007,
  author    = {Feldmeier, Achim and Hamann, Wolf-Rainer and R{\"a}tzel, D. and Oskinova, Lida},
  title     = {Hydrodynamic simulations of clumps},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17975},
  year      = {2007},
  abstract  = {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.},
  language  = {en}
}
@inproceedings{MoffatHillierHamannetal.2007,
  author    = {Moffat, Anthony F. J. and Hillier, D. J. and Hamann, Wolf-Rainer and Owocki, S. P.},
  title     = {General Discussion},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17953},
  year      = {2007},
  abstract  = {Clumping in hot-star winds : proceedings of an international workshop held in Potsdam, Germany, 18. - 22. June 2007},
  language  = {en}
}
@inproceedings{KrtičkaPulsKubat2007,
  author    = {Krtička, Jiri and Puls, Joachim and Kub{\´a}t, Jiř{\´i}},
  title     = {The influence of clumping on predicted O star wind parameters},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17969},
  year      = {2007},
  abstract  = {We study the influence of clumping on the predicted wind structure of O-type stars. For this purpose we artificially include clumping into our stationary wind models. When the clumps are assumed to be optically thin, the radiative line force increases compared to corresponding unclumped models, with a similar effect on either the mass-loss rate or the terminal velocity (depending on the onset of clumping). Optically thick clumps, alternatively, might be able to decrease the radiative force.},
  language  = {en}
}
@inproceedings{VinkBenagliaDaviesetal.2007,
  author    = {Vink, J. S. and Benaglia, P. and Davies, B. and de Koter, A. and Oudmaijer, R. D.},
  title     = {Advances in mass-loss predictions},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17948},
  year      = {2007},
  abstract  = {We present the results of Monte Carlo mass-loss predictions for massive stars covering a wide range of stellar parameters. We critically test our predictions against a range of observed massloss rates - in light of the recent discussions on wind clumping. We also present a model to compute the clumping-induced polarimetric variability of hot stars and we compare this with observations of Luminous Blue Variables, for which polarimetric variability is larger than for O and Wolf-Rayet stars. Luminous Blue Variables comprise an ideal testbed for studies of wind clumping and wind geometry, as well as for wind strength calculations, and we propose they may be direct supernova progenitors.},
  language  = {en}
}
@inproceedings{DaviesVinkOudmaijer2007,
  author    = {Davies, B. and Vink, J. S. and Oudmaijer, R. D.},
  title     = {Modelling the polarimetric variability of hot stars},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17939},
  year      = {2007},
  abstract  = {Many hot stars exhibit stochastic polarimetric variability, thought to arise from clumping low in the wind. Here we investigate the wind properties required to reproduce this variability using analytic models, with particular emphasis on Luminous Blue Variables. We find that the winds must be highly structured, consisting of a large number of optically-thin clumps; while we find that the overall level of polarization should scale with mass-loss rate - consistent with observations of LBVs. The models also predict variability on very short timescales, which is supported by the results of a recent polarimetric monitoring campaign.},
  language  = {en}
}
@inproceedings{Graefener2007,
  author    = {Gr{\"a}fener, G.},
  title     = {Clumping in hydrodynamic atmosphere models},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17925},
  year      = {2007},
  abstract  = {We investigate the effect of wind clumping on the dynamics of Wolf-Rayet winds, by means of the Potsdam Wolf-Rayet (PoWR) hydrodynamic atmosphere models. In the limit of microclumping the radiative acceleration is generally enhanced. We examine the reasons for this effect and show that the resulting wind structure depends critically on the assumed radial dependence of the clumping factor D(r). The observed terminal wind velocities for WR stars imply that D(r) increases to very large values in the outer part of the wind, in agreement with the assumption of detached expanding shells.},
  language  = {en}
}
@inproceedings{Fullerton2007,
  author    = {Fullerton, A. W.},
  title     = {Discussion: Spectral modeling},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17917},
  year      = {2007},
  language  = {en}
}
@inproceedings{Hillier2007,
  author    = {Hillier, D. J.},
  title     = {On the influence of clumping on O and Wolf-Rayet spectra},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17903},
  year      = {2007},
  abstract  = {Overwhelming observational and theoretical evidence suggests that the winds of massive stars are highly clumped. We briefly discuss the influence of clumping on model diagnostics and the difficulties of allowing for the influence of clumping on model spectra. Because of its simplicity, and because of computational ease, most spectroscopic analyses incorporate clumping using the volume filling factor. The biases introduced by this approach are uncertain. To investigate alternative clumping models, and to help determine the validity of parameters derived using the volume filling factor method, we discuss results derived using an alternative model in which we assume that the wind is composed of optically thick shells.},
  language  = {en}
}
@inproceedings{IpingSonnebornMassaetal.2007,
  author    = {Iping, R.C. and Sonneborn, G. and Massa, D.L. and Gies, D. and Williams, Simon E.},
  title     = {Far-ultraviolet spectroscopy of O+O binaries in the Magellanic Clouds},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17896},
  year      = {2007},
  abstract  = {We report FUSE observations in 2005-2006 of three O-type, double-lined spectroscopic binaries in the Magellanic Clouds. The systems have very short periods (1.4-2.25 d), represent rare, young evolutionary stages of massive stars and binaries, and provide a unique glimpse at some of the most massive systems that form in dense clusters of massive stars. Improved orbit parameters, including revised masses, for LH54-425 are derived from new ctio spectroscopy. The systems are: LH54-425 in the LMC (O3V + O5V, P=2.25d, 62+37M⊙), J053441-693139 in the LMC (O2-3If+O6V, P=1.4 d, 41+27M⊙), and Hodge 53-47 in the SMC (O6V + O4-5IIIf, P=2.2 d, 24+14M⊙, where the O4 star appears to be less massive than the O6 star). Their short periods indicates that wind interaction and mass transfer are likely important factors in their evolution. The spectra provide quantitative and systematic studies of phase-dependent stellar wind properties, wind collision effects in O+O binaries at lower metallicities, improved radial velocity curves, and FUV spectro-photometric changes as a function of orbital phase.},
  language  = {en}
}