63,588 research outputs found
Gemini/GMOS search of massive binaries in the ionizing cluster of 30 Dor
If binaries are common among massive stars, it will have important
consequences for the derivation of fundamental properties like the cluster age,
IMF and dynamical mass. Making use of the multiplexing facilities of Gemini
Multi Object Spectrograph (GMOS) we were able to investigate the presence of
binary stars within the ionising cluster of 30 Doradus. From a seven epochs
observing campaign at Gemini South we detect a binary candidate rate of about
50%, which is consistent with an intrinsic 100% binary rate among massive
stars. We find that single epoch determinations of the velocity dispersion give
values around 30 km/s . After correcting the global velocity dispersion for the
binary orbital motions, the true cluster velocity dispersion is 8.3 km/s. This
value implies a virial mass of about 4.5E5 Msun or 8 percent of the mass
calculated using the single epoch value. The binary corrected virial mass
estimate is consistent with photometric mass determinations thus suggesting
that NGC 2070 is a firm candidate for a future globular cluster.Comment: 9 pages, accepted at Astronomical Journa
Factorization and Sudakov Resummation in B -> gamma l nu
We apply Soft-Collinear Effective Theory to prove at leading power in
Lambda_QCD/m_b a factorization formula for the radiative leptonic decay B ->
gamma l nu. Large logarithms entering the hard-scattering kernel are
systematically resummed by a two-step perturbative matching procedure.Comment: 3 pages, 1 figure; contribution to proceedings of "International
Europhysics Conference on High Energy Physics" EPS (July 17th-23rd 2003) in
Aachen; to appear in European Physical Journal C direc
Compatibility and stability of hyoscine n-butyl bromide and furosemide admixtures for use in palliative care
In order to avoid separate injections, admixtures of drugs are frequently used in palliative care settings. There are different factors that can influence the compatibility and stability of the mixture: drug type, concentration, solvent, container, temperature and light. There are some mixtures of drugs with proven stability, but there is lack of evidence about the stability and compatibility of the combination of hyoscine N-butyl bromide and furosemide.Universidad de Málaga,Campus de Excelencia Internacional AndalucÃa Tec
Non-thermal emission from standing relativistic shocks: an application to red giant winds interacting with AGN jets
Galactic and extragalactic relativistic jets have rich environments that are
full of moving objects, such as stars and dense clumps. These objects can enter
into the jets and generate shocks and non-thermal emission. We characterize the
emitting properties of the downstream region of a standing shock formed due to
the interaction of a relativistic jet with an obstacle. We focus on the case of
red giants interacting with an extragalactic jet. We perform relativistic
axisymmetric hydrodynamical simulations of a relativistic jet meeting an
obstacle of very large inertia. The results are interpreted in the framework of
a red giant whose dense and slow wind interacts with the jet of an active
galactic nucleus. Assuming that particles are accelerated in the standing shock
generated in the jet as it impacts the red giant wind, we compute the
non-thermal particle distribution, the Doppler boosting enhancement, and the
non-thermal luminosity in gamma rays. The available non-thermal energy from
jet-obstacle interactions is potentially enhanced by a factor of
when accounting for the whole surface of the shock induced by the obstacle,
instead of just the obstacle section. The observer gamma-ray luminosity,
including the flow velocity and Doppler boosting effects, can be ~300(g/10)^2
times higher than when the emitting flow is assumed at rest and only the
obstacle section is considered, where g is the jet Lorentz factor. For a whole
population of red giants inside the jet of an AGN, the predicted persistent
gamma-ray luminosities may be potentially detectable for a jet pointing to the
observer. Obstacles interacting with relativistic outflows, for instance clouds
and populations of stars for extragalactic jets, or stellar wind
inhomogeneities in microquasar jets and in winds of pulsars in binaries, should
be taken into account when investigating the non-thermal emission from these
sources.Comment: 7 pages, 6 figures, version after proofs to appear in Astronomy &
Astrophysic
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