Infrared Spectroscopy of GX 1+4/V2116 Oph: Evidence for a Fast Red Giant Wind?

We present infrared spectroscopy of the low-mass X-ray binary GX 1+4/V2116 Oph. This symbiotic binary consists of a 2-min accretion-powered pulsar and an M5 III red giant. A strong He I 1.083 micron emission line with a pronounced P Cygni profile was observed. From the blue edge of this feature, we infer an outflow velocity of 250(50) km/s. This is an order of magnitude faster than a typical red giant wind, and we suggest that radiation from the accretion disk or the neutron star may contribute to the acceleration of the outflow. We infer a wind mass loss rate of around 10^-6 Msun/yr. Accretion from such a strong stellar wind provides a plausible alternative to Roche lobe overflow for supplying the accretion disk which powers the X-ray source. The H I Paschen beta and He I 1.083 micron lines showed no evidence for the dramatic changes previously reported in some optical lines, and no evidence for pulsations at the 2-min pulsar period.Comment: 11 pages including 2 PS figures. To appear in ApJ Letter

Akzeptanz von Location Based Services

Die enormen Investitionen in UMTS-Lizenzen und den Aufbau einer neuen Netzinfrastruktur zwingen die Mobilfunkanbieter zur Erschließung neuer Umsatzpotenziale. Durch Entwicklung neuer mobiler Mehrwertdienste hoffen sie, die „Killerapplikation“ der 3. Mobilfunkgeneration zu finden, die ähnlich wie der Short Message Service (SMS) für GSM, zum Treiber des UMTS-Markterfolges werden kann. Nach Meinung vieler Marktbeobachter könnten Location Based Services, d.h. mobile Dienste, die sich an den aktuellen Standort des Nutzers anpassen, diese Rolle für UMTS übernehmen. Location Based Services können jedoch am Markt nur langfristig erfolgreich sein, wenn sie seitens potenzieller Nutzer akzeptiert werden. Die Konsumentenakzeptanz ortsbezogener mobiler Anwendung ist aber bisher wenig untersucht. Aus diesem Grund beschäftigt sich die vorliegende Studie mit der Identifizierung und Analyse von Determinanten der Akzeptanz von Location Based Services. Dazu wird basierend auf theoretischen Erkenntnissen und Ergebnissen bisheriger Studien ein Hypothesensystem hinsichtlich der Einflussfaktoren der konsumentenseitigen Akzeptanz von standortbezogenen Diensten konzipiert. Als Ergebnis lässt sich festhalten, dass die Einstellung zur Nutzung von LBS positiv durch die wahrgenommenen Preiswürdigkeit, die wahrgenommene Dienstqualität sowie stark durch das wahrgenommemen Vergnügen bestimmt wird. Die Zielgröße Akzeptanz wird primär durch die Einstellung zur Nutzung und die subjektive Norm direkt determiniert

On the Luminosities and Temperatures of Extended X-ray Emission from Planetary Nebulae

We examine mechanisms that may explain the luminosities and relatively low temperatures of extended X-ray emission in planetary nebulae. By building a simple flow structure for the wind from the central star during the proto, and early, planetary nebulae phase, we estimate the temperature of the X-ray emitting gas and its total X-ray luminosity. We conclude that in order to account for the X-ray temperature and luminosity, both the evolution of the wind from the central star and the adiabatic cooling of the post-shocked wind's material must be considered. The X-ray emitting gas results mainly from shocked wind segments that were expelled during the early planetary nebulae phase, when the wind speed was moderate. Alternatively, the X-ray emitting gas may result from a collimated fast wind blown by a companion to the central star. Heat conduction and mixing between hot and cool regions are likely to occur in some cases and may determine the detailed X-ray morphology of a nebula, but are not required to explain the basic properties of the X-ray emitting gas.Comment: ApJ, submitted; 16 page

Contact binaries with additional components. III. The adaptive optics detections

We present results of the CFHT adaptive optics search for companions of a homogeneous group of contact binary stars, as a contribution to our attempts to prove a hypothesis that these binaries require a third star to become so close as observed. In addition to companions directly discovered at separations of >=1", we introduced a new method of AO image analysis utilizing distortions of the AO diffraction ring pattern at separations of 0.07"-1". Very close companions, with separations in the latter range were discovered in systems HV Aqr, OO Aql, CK Boo, XY Leo, BE Scl, and RZ Tau. More distant companions were detected in V402 Aur, AO Cam, V2082 Cyg. Our results provide a contribution to the mounting evidence that the presence of close companions is a very common phenomenon for very close binaries with orbital periods <1 day.Comment: Full Figs.4 and 5 are in http://www.astro.utoronto.ca/~rucinski/Triples3

Knots in the outer shells of the planetary nebulae IC 2553 and NGC 5882

We present images and high-resolution spectra of the planetary nebulae IC 2553 and NGC 5882. Spatio-kinematic modeling of the nebulae shows that they are composed of a markedly elongated inner shell, and of a less aspherical outer shell expanding at a considerably higher velocity than the inner one. Embedded in the outer shells of both nebulae are found several low-ionization knots. In IC 2553, the knots show a point-symmetric distribution with respect to the central star: one possible explanation for their formation is that they are the survivors of pre-existing point-symmetric condensations in the AGB wind, a fact which would imply a quite peculiar mass-loss geometry from the giant progenitor. In the case of NGC 5882, the lack of symmetry in the distribution of the observed low-ionization structures makes it possible that they are the result of in situ instabilities.Comment: 20 pages including 1 table and 6 figures. ApJ accepted. Also available at http://andromeda.roque.ing.iac.es/~sanchez/ingpub/index2000.htm

A Multiplicity Census of Young Stars in Chamaeleon I

We present the results of a multiplicity survey of 126 stars spanning ~0.1-3 solar masses in the ~2-Myr-old Chamaeleon I star-forming region, based on adaptive optics imaging with the ESO Very Large Telescope. Our observations have revealed 30 binaries and 6 triples, of which 19 and 4, respectively, are new discoveries. The overall multiplicity fraction we find for Cha I (~30%) is similar to those reported for other dispersed young associations, but significantly higher than seen in denser clusters and the field, for comparable samples. Both the frequency and the maximum separation of Cha I binaries decline with decreasing mass, while the mass ratios approach unity; conversely, tighter pairs are more likely to be equal mass. We confirm that brown dwarf companions to stars are rare, even at young ages at wide separations. Based on follow-up spectroscopy of two low-mass substellar companion candidates, we conclude that both are likely background stars. The overall multiplicity fraction in Cha I is in rough agreement with numerical simulations of cloud collapse and fragmentation, but its observed mass dependence is less steep than predicted. The paucity of higher-order multiples, in particular, provides a stringent constraint on the simulations, and seems to indicate a low level of turbulence in the prestellar cores in Cha I.Comment: Accepted for publication in Ap

Isometries of infinite dimensional Hilbert geometries

In this paper we extend two classical results concerning the isometries of strictly convex Hilbert geometries, and the characterisation of the isometry groups of Hilbert geometries on finite dimensional simplices, to infinite dimensions. The proofs rely on a mix of geometric and functional analytic methods

Indirekte Selektionmethoden auf Methioninreichtum des Samenproteins bei heimischen Leguminosen

While grain legumes can be regarded as highly valuable protein sources for animal nutrition, ceratin drawbacks inhibit their use as sole foodstuff for livestock. The nutrient quality is reduced by low concentrations of tryptophan and sulfur amino acids