695 research outputs found

    Why IT is not being used for financial advisory

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    Swiss banks have returned to their roots and pay an increasing amount of attention to differentiating themselves from others through good financial advisory services. This has led to a loudly publicized standardization of IT-advisory processes, but not to an increasing use of supporting IT tools. This paper uses interviews with Swiss advisors, sales managers and IT managers, as well as focus groups of users and a survey with users to identify reasons for non-usage. The analysis is based on a framework combining principal-agent theory, IT-business alignment, technology acceptance and information behaviour. We provide evidence that the key problem explanation is the incentive system of the advisors and that poor usability of the software and lack of engagement by sales managers also contribute to the non-usage of most tools

    Modeling RR Tel through the Evolution of the Spectra

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    We investigate the evolution of RR Tel after the outburst by fitting the emission spectra in two epochs. The first one (1978) is characterized by large fluctuations in the light curve and the second one (1993) by the slow fading trend. In the frame of a colliding wind model two shocks are present: the reverse shock propagates in the direction of the white dwarf and the other one expands towards or beyond the giant. The results of our modeling show that in 1993 the expanding shock has overcome the system and is propagating in the nearby ISM. The large fluctuations observed in the 1978 light curve result from line intensity rather than from continuum variation. These variations are explained by fragmentation of matter at the time of head-on collision of the winds from the two stars. A high velocity (500 km/s) wind component is revealed from the fit of the SED of the continuum in the X-ray range in 1978, but is quite unobservable in the line profiles. The geometrical thickness of the emitting clumps is the critical parameter which can explain the short time scale variabilities of the spectrum and the trend of slow line intensity decrease.Comment: 26 pages, LaTeX (including 5 Tables) + 6 PostScript figures. To appear in "The Astrophysical Journal

    Optical and near infrared observations of SN 1998bu

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    Infrared and optical spectra of SN 1998bu at an age of one year after explosion are presented. The data show evidence for the radioactive decay of 56Co to 56Fe, long assumed to be the powering source for the supernova light curve past maximum light. The spectra provide direct evidence for at least 0.4 solar masses of iron being present in the ejecta of the supernova. The fits to the data also show that the widths of the emission lines increase with time. Photometric measurements in the H-band show that the supernova is not fading during the observation period. This is consistent with theoretical expectations.Comment: accepted A&A, 7 pages, 9 figure

    Illumination in symbiotic binary stars: Non-LTE photoionization models. II. Wind case

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    We describe a non-LTE photoionization code to calculate the wind structure and emergent spectrum of a red giant wind illuminated by the hot component of a symbiotic binary system. We consider spherically symmetric winds with several different velocity and temperature laws and derive predicted line fluxes as a function of the red giant mass loss rate, \mdot. Our models generally match observations of the symbiotic stars EG And and AG Peg for \mdot about 10^{-8} \msunyr to 10^{-7} \msunyr. The optically thick cross- section of the red giant wind as viewed from the hot component is a crucial parameter in these models. Winds with cross-sections of 2--3 red giant radii reproduce the observed fluxes, because the wind density is then high, about 10^9 cm^{-3}. Our models favor winds with acceleration regions that either lie far from the red giant photosphere or extend for 2--3 red giant radii.Comment: 51 pages, LaTeX including three tables, requires 15 Encapsulated Postscript figures, to appear in Ap

    The Unusual Object IC 2144/MWC 778

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    IC 2144 is a small reflection nebula located in the zone of avoidance near the Galactic anticenter. It has been investigated here largely on the basis of Keck/HIRES optical spectroscopy (R ~ 48,000) and a SpeX spectrogram in the near-IR (R = 2000) obtained at the NASA IRTF. The only star in the nebula that is obvious in the optical or near-IR is the peculiar emission-line object MWC 778 (V = 12.8), which resembles a T Tauri star in some respects. What appear to be F- or G-type absorption features are detectable in its optical region under the very complex emission line spectrum; their radial velocity agrees with the CO velocity of the larger cloud in which IC 2144 is embedded. There are significant differences between the spectrum of the brightest area of the nebula and of MWC 778, the presumed illuminator, an issue discussed in some detail. The distance of IC 2144 is inferred to be about 1.0 kpc by reference to other star-forming regions in the vicinity. The extinction is large, as demonstrated by [Fe II] emission line ratios in the near-IR and by the strength of the diffuse interstellar band spectrum; a provisional value of A_V of 3.0 mag was assumed. The SED of MWC 778 rises steeply beyond about 1 ÎĽ\mum, with a slope characteristic of a Class I source. Integration of the flux distribution leads to an IR luminosity of about 510 L_solar. If MWC 778 is indeed a F- or G-type pre--main-sequence star several magnitudes above the ZAMS, a population of faint emission Halpha stars would be expected in the vicinity. Such a search, like other investigations that are recommended in this paper, has yet to be carried out.Comment: 36 pages, 13 figures, accepted by A

    Silicates in D-type symbiotic stars: an ISO overview

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    We investigate the IR spectral features of a sample of D-type symbiotic stars. Analyzing unexploited ISO-SWS data, deriving the basic observational parameters of dust bands and comparing them with respect to those observed in other astronomical sources, we try to highlight the effect of environment on grain chemistry and physic. We find strong amorphous silicate emission bands at 10 micron and 18 micron in a large fraction of the sample. The analysis of the 10 micron band, along with a direct comparison with several astronomical sources, reveals that silicate dust in symbiotic stars shows features between the characteristic circumstellar environments and the interstellar medium. This indicates an increasing reprocessing of grains in relation to specific symbiotic behavior of the objects. A correlation between the central wavelength of the 10 and 18 micron dust bands is found. By the modeling of IR spectral lines we investigate also dust grains conditions within the shocked nebulae. Both the unusual depletion values and the high sputtering efficiency might be explained by the formation of SiO moleculae, which are known to be a very reliable shock tracer. We conclude that the signature of dust chemical disturbance due to symbiotic activity should be looked for in the outer, circumbinary, expanding shells where the environmental conditions for grain processing might be achieved. Symbiotic stars are thus attractive targets for new mid-infrared and mm observations.Comment: 24 pages, 6 figures, 5 tables - to be published in A

    The Effects of Dark Matter Decay and Annihilation on the High-Redshift 21 cm Background

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    The radiation background produced by the 21 cm spin-flip transition of neutral hydrogen at high redshifts can be a pristine probe of fundamental physics and cosmology. At z~30-300, the intergalactic medium (IGM) is visible in 21 cm absorption against the cosmic microwave background (CMB), with a strength that depends on the thermal (and ionization) history of the IGM. Here we examine the constraints this background can place on dark matter decay and annihilation, which could heat and ionize the IGM through the production of high-energy particles. Using a simple model for dark matter decay, we show that, if the decay energy is immediately injected into the IGM, the 21 cm background can detect energy injection rates >10^{-24} eV cm^{-3} sec^{-1}. If all the dark matter is subject to decay, this allows us to constrain dark matter lifetimes <10^{27} sec. Such energy injection rates are much smaller than those typically probed by the CMB power spectra. The expected brightness temperature fluctuations at z~50 are a fraction of a mK and can vary from the standard calculation by up to an order of magnitude, although the difference can be significantly smaller if some of the decay products free stream to lower redshifts. For self-annihilating dark matter, the fluctuation amplitude can differ by a factor <2 from the standard calculation at z~50. Note also that, in contrast to the CMB, the 21 cm probe is sensitive to both the ionization fraction and the IGM temperature, in principle allowing better constraints on the decay process and heating history. We also show that strong IGM heating and ionization can lead to an enhanced H_2 abundance, which may affect the earliest generations of stars and galaxies.Comment: submitted to Phys Rev D, 14 pages, 8 figure

    Fluorescent Excitation of Spectral Lines in Planetary Nebulae

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    Fluorescent excitation of spectral lines is demonstrated as a function of temperature-luminosity and the distance of the emitting region from the central stars of planetary nebulae. The electron densities and temperatures are determined, and the method is exemplified through a detailed analysis of spectral observations of a high excitation PN, NGC 6741, observed by Hyung and Aller(1997). Fluorescence should also be important in the determination of element abundances. It is suggested that the method could be generally applied to determine or constrain the luminosity and the region of spectral emission in other intensively radiative sources such as novae, supernovae, and active galactic nuclei.Comment: 5 pages, 4 figures (fig.4 in color), ApJ (in press

    Star Formation in M51 Triggered by Galaxy Interaction

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    We have mapped the inner 360'' regions of M51 in the 158micron [CII] line at 55'' spatial resolution using the Far-infrared Imaging Fabry-Perot Interferometer (FIFI) on the Kuiper Airborne Observatory (KAO). The emission is peaked at the nucleus, but is detectable over the entire region mapped, which covers much of the optical disk of the galaxy. There are also two strong secondary peaks at ~43% to 70% of the nuclear value located roughly 120'' to the north-east, and south-west of the nucleus. These secondary peaks are at the same distance from the nucleus as the corotation radius of the density wave pattern. The density wave also terminates at this location, and the outlying spiral structure is attributed to material clumping due to the interaction between M51 and NGC5195. This orbit crowding results in cloud-cloud collisions, stimulating star formation, that we see as enhanced [CII] line emission. The [CII] emission at the peaks originates mainly from photodissociation regions (PDRs) formed on the surfaces of molecular clouds that are exposed to OB starlight, so that these [CII] peaks trace star formation peaks in M51. The total mass of [CII] emitting photodissociated gas is ~2.6x10^{8} M_{sun}, or about 2% of the molecular gas as estimated from its CO(1-0) line emission. At the peak [CII] positions, the PDR gas mass to total gas mass fraction is somewhat higher, 3-17%, and at the secondary peaks the mass fraction of the [CII] emitting photodissociated gas can be as high as 72% of the molecular mass.... (continued)Comment: 14 pages, 6 figures, Accepted in ApJ (for higher resolution figures contact the author
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