41,048 research outputs found
Disc atmospheres and winds in X-ray binaries
We review the current status of studies of disc atmospheres and winds in low
mass X-ray binaries. We discuss the possible wind launching mechanisms and
compare the predictions of the models with the existent observations. We
conclude that a combination of thermal and radiative pressure (the latter being
relevant at high luminosities) can explain the current observations of
atmospheres and winds in both neutron star and black hole binaries. Moreover,
these winds and atmospheres could contribute significantly to the broad iron
emission line observed in these systems.Comment: Accepted for publication in Acta Polytechnica. Invited review talk at
the Vulcano Workshop 2012: "Frontier Objects in Astrophysics and Particle
Physics
A search for brown-dwarf like secondaries in cataclysmic variables
We present VTL/ISAAC infrared spectroscopy of a sample of short orbital
period cataclysmic variables which are candidates for harboring substellar
companions. We have detected the KI and NaI absorption lines of the companion
star in VY Aqr. The overall spectral distribution in this system is best fit
with a M9.5 type dwarf spectra, implying a distance of pc. VY Aqr
seems to fall far from the theoretical distribution of secondary star
temperatures around the orbital period minimum. Fitting of the IR spectral
energy distribution (SED) was performed by comparing the observed spectrum with
late-type templates. The application of such a spectral fitting procedure
suggests that the continuum shape in the 1.1-2.5 m spectral region in
short orbital period cataclysmic variables may be an useful indicator of the
companion spectral type. The SED fitting for RZ Leo and CU Vel suggests M5 type
dwarf companions, and distances of 340 110 and 150 50 pc,
respectively. These systems may be placed in the upper evolution branch for
short period cataclysmic variables.Comment: accepted for publication in MNRAS, 6 pages, 7 figure
Prototype Graphs for radiative Corrections to Polarized Chargino or Neutralino Production in Electron-Positron Annihilation
We present the contributions from all types of one-loop corrections to the
scattering amplitude for the pair production of polarized charginos or
neutralinos from polarized electron-positron annihilation. The contributions
are classified in terms of ``prototypes'' distinguished by the number of
particles inside the loops and their spins. The results are quoted in terms of
the Veltman-Passarino functions in terms of general couplings and internal
masses. The results can therefore be applied to any supersymmetric extension of
the Standard Model or indeed to any polarized fermion pair production process
in electron-positron annihilation.Comment: LATEX 38 pages, 26 figure
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