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Astrophysics papers — page 18

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Massive gravitational waves from f(R) theories of gravity: Potential detection with LISA
This letter is a generalization of previous results on gravitational waves (GWs) from f(R) theories of gravity. In some previous papers, particular f(R) theories have been linearized for the first…
Salvatore Capozziello, Christian Corda, Maria Felicia De LaurentisDec 11, 2008
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Heating in an Extended Accretion Disk Corona along the Z-Pattern in Cyg X-2
We observed at very high spectral resolution the prototype Z-source Cyg x-2 twice along its entire X-ray spectral variation pattern. In this preliminary analysis we find an extended accretion disk…
N. S. Schulz, D. P. Huenemoerder, L. Ji et al.Dec 11, 2008
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The nonlinear probability distribution function in models with local primordial non-Gaussianity
We use the spherical evolution approximation to investigate nonlinear evolution from the non-Gaussian initial conditions characteristic of the local fnl model. We provide an analytic formula for the…
Tsz Yan Lam, Ravi K. ShethDec 11, 2008
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Modeling the X-ray emission of SN 1993J
We investigate the effects of radiative shocks on the observed X-ray emission from the Type II supernova SN 1993J. To this end, the X-ray emission is modeled as a result of the interaction between…
Tanja K. Nymark, Poonam Chandra, Claes FranssonDec 11, 2008
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Rayleigh-Taylor-Unstable Accretion and Variability of Magnetized Stars: Global Three-Dimensional Simulations
We present results of 3D simulations of MHD instabilities at the accretion disk-magnetosphere boundary. The instability is Rayleigh-Taylor, and develops for a fairly broad range of accretion rates…
Akshay K. Kulkarni, Marina M. RomanovaDec 11, 2008
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The butterfly diagram in the 18th century
Digitized images of the drawings by J.C. Staudacher were used to determine sunspot positions for the period of 1749-1796. From the entire set of drawings, 6285 sunspot positions were obtained for a…
Rainer ArltDec 11, 2008
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Improved Neutron-Capture Element Abundances in Planetary Nebulae
Spectroscopy of planetary nebulae (PNe) provides the means to investigate s-process enrichments of neutron(n)-capture elements that cannot be detected in asymptotic giant branch (AGB) stars. However,…
N. C. Sterling, H. L. Dinerstein, S. Hwang et al.Dec 11, 2008
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Evidence for the Missing Baryons in the Angular Correlation of the Diffuse X-ray Background
The amount of detected baryons in the local Universe is at least a factor of two smaller than measured at high redshift. It is believed that a significant fraction of the baryons in the current…
M. Galeazzi, A. Gupta, E. UrsinoDec 11, 2008
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Unifying the study of background dynamics and perturbations in f(R)-gravity
In this paper we show how the covariant gauge invariant equations for the evolution of scalar, vector and tensor perturbations for a generic f(R)-gravity theory can be recast in order to exploit…
Sante Carloni, Kishore N. Ananda, Peter K. S. Dunsby et al.Dec 11, 2008
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Cosmic polarimetry in magnetoactive plasmas
Polarimetry of the Cosmic Microwave Background (CMB) represents one of the possible diagnostics aimed at testing large-scale magnetism at the epoch of the photon decoupling. The propagation of…
Massimo Giovannini, Kerstin E. KunzeDec 11, 2008
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On the dark energy rest frame and the CMB
Dark energy is usually parametrized as a perfect fluid with negative pressure and a certain equation of state. Besides, it is supposed to interact very weakly with the rest of the components of the…
Jose Beltran Jimenez, Antonio L. MarotoDec 11, 2008
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Infrared Emission by Dust Around lambda Bootis Stars: Debris Disks or Thermally Emitting Nebulae?
We present a model that describes stellar infrared excesses due to heating of the interstellar (IS) dust by a hot star passing through a diffuse IS cloud. This model is applied to six lambda Bootis…
J. R. Martínez-Galarza, I. Kamp, K. Y. L. Su et al.Dec 11, 2008
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Star-forming cores embedded in a massive cold clump: Fragmentation, collapse and energetic outflows
The fate of massive cold clumps, their internal structure and collapse need to be characterised to understand the initial conditions for the formation of high-mass stars, stellar systems, and the…
Martin Hennemann, Stephan M. Birkmann, Oliver Krause et al.Dec 11, 2008
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Exploring the X-ray emission properties of the supernova remnant G67.7+1.8 and its central X-ray sources
We have studied the supernova remnant G67.7+1.8 with the Chandra X-ray observatory. The remnant's X-ray morphology correlates well with the double-arc structure seen at radio wavelength. The…
C. Y. Hui, W. BeckerDec 11, 2008
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The scientific use and productivity of the Telescopio Nazionale Galileo (TNG)
This paper reviews the scientific use of the TNG from the beginning of regular observations till the end of 2007. Statistics are given for the time request, use and productivity of the telescope and…
E. OlivaDec 11, 2008
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Radial differential rotation vs surface differential rotation: investigation based on dynamo models
Differential rotation plays a crucial role in the alpha-omega dynamo, and thus also in creation of magnetic fields in stars with convective outer envelopes. Still, measuring the radial differential…
H. Korhonen, D. ElstnerDec 11, 2008
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Constraints on a phenomenologically parameterized neutron-star equation of state
We introduce a parameterized high-density equation of state (EOS) in order to systematize the study of constraints placed by astrophysical observations on the nature of neutron-star matter. To obtain…
Jocelyn S. Read, Benjamin D. Lackey, Benjamin J. Owen et al.Dec 11, 2008
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PIERNIK mhd code - a multi-fluid, non-ideal extension of the relaxing-TVD scheme (I)
We present a new multi-fluid, grid MHD code PIERNIK, which is based on the Relaxing TVD scheme. The original scheme has been extended by an addition of dynamically independent, but interacting…
Michał Hanasz, Kacper Kowalik, Dominik Wóltański et al.Dec 11, 2008
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Can the cosmic-ray driven dynamo model explain the observations of the polarized emission of edge-on galaxies ?
In the present paper we construct maps of polarized synchrotron radio emission of a whole galaxy, based on local models of the cosmic ray (CR) driven dynamo. We perform numerical simulations of the…
Katarzyna Otmianowska-Mazur, Marian Soida, Barbara Kulesza-Żydzik et al.Dec 11, 2008
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Driving mechanism in massive B-type pulsators
After a historical introduction, I present the current status of our understanding of the mechanism responsible for pulsation in Beta Cephei and SPB stars.
W. A. DziembowskiDec 11, 2008
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Teff and logg dependence of FeH in M-dwarfs
We present synthetic FeH band spectra in the z-filter range for several M-dwarf models with logg=3.0-5.0 [cgs] and Teff=2800K -3450K. Our aim is to characterize convective velocities in M-dwarfs and…
S. Wende, A. Reiners, H. G. LudwigDec 11, 2008
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Binarity and multiperiodicity in high-amplitude delta Scuti stars
We have carried out a photometric and spectroscopic survey of bright high-amplitude delta Scuti (HADS) stars. The aim was to detect binarity and multiperiodicity (or both) in order to explore the…
A. Derekas, L. L. Kiss, T. R. Bedding et al.Dec 11, 2008
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A Relativistic Electron-Positron Outflow from a Tepid Fireball
Through detailed numerical simulations, we demonstrate that relativistic outflows (Lorentz factor Γ 7) of electron-positron pairs can be produced by radiative acceleration even when the flow…
Katsuaki Asano, Fumio TakaharaDec 11, 2008
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Distances and Stellar Population properties using the SBF method
We present some results on the study of stellar population properties and distances of galaxies using the SBF technique. The applications summarized here show that the Surface Brightness Fluctuations…
Michele Cantiello, Gabriella Raimondo, Enzo Brocato et al.Dec 11, 2008
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Performance of the First ANTARES Detector Line
In this paper we report on the data recorded with the first Antares detector line. The line was deployed on the 14th of February 2006 and was connected to the readout two weeks later. Environmental…
ANTARES collaboration, M. AgeronDec 11, 2008
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