17,941 research outputs found
Haro15: Is it actually a low metallicity galaxy?
We present a detailed study of the physical properties of the nebular
material in multiple knots of the blue compact dwarf galaxy Haro 15. Using long
slit and echelle spectroscopy, obtained at Las Campanas Observatory, we study
the physical conditions (electron density and temperature), ionic and total
chemical abundances of several atoms, reddening and ionization structure. The
latter was derived by comparing the oxygen and sulphur ionic ratios to their
corresponding observed emission line ratios (the eta and eta' plots) in
different regions of the galaxy. Applying direct and empirical methods for
abundance determination, we perform a comparative analysis between these
regions.Comment: (Poster paper) 2 pages, 2 figure
The IACOB project: A grid-based automatic tool for the quantitative spectroscopic analysis of O-stars
We present the IACOB grid-based automatic tool for the quantitative
spectroscopic analysis of O-stars. The tool consists of an extensive grid of
FASTWIND models, and a variety of programs implemented in IDL to handle the
observations, perform the automatic analysis, and visualize the results. The
tool provides a fast and objective way to determine the stellar parameters and
the associated uncertainties of large samples of O-type stars within a
reasonable computational time.Comment: 8 pages, 2 figures, 1 table. Proceedings of the "GREAT-ESF Stellar
Atmospheres in the Gaia Era Workshop
Fundamental parameters of massive stars in multiple systems: The cases of HD17505A and HD206267A
Many massive stars are part of binary or higher multiplicity systems. The
present work focusses on two higher multiplicity systems: HD17505A and
HD206267A. Determining the fundamental parameters of the components of the
inner binary of these systems is mandatory to quantify the impact of binary or
triple interactions on their evolution. We analysed high-resolution optical
spectra to determine new orbital solutions of the inner binary systems. After
subtracting the spectrum of the tertiary component, a spectral disentangling
code was applied to reconstruct the individual spectra of the primary and
secondary. We then analysed these spectra with the non-LTE model atmosphere
code CMFGEN to establish the stellar parameters and the CNO abundances of these
stars. The inner binaries of these systems have eccentric orbits with e ~ 0.13
despite their relatively short orbital periods of 8.6 and 3.7 days for
HD17505Aa and HD206267Aa, respectively. Slight modifications of the CNO
abundances are found in both components of each system. The components of
HD17505Aa are both well inside their Roche lobe, whilst the primary of
HD206267Aa nearly fills its Roche lobe around periastron passage. Whilst the
rotation of the primary of HD206267Aa is in pseudo-synchronization with the
orbital motion, the secondary displays a rotation rate that is higher. The CNO
abundances and properties of HD17505Aa can be explained by single star
evolutionary models accounting for the effects of rotation, suggesting that
this system has not yet experienced binary interaction. The properties of
HD206267Aa suggest that some intermittent binary interaction might have taken
place during periastron passages, but is apparently not operating anymore.Comment: Accepted for publication in A&
The chemical composition of the Orion star forming region: stars, gas and dust
We present a summary of main results from the studies performed in the series
of papers "The chemical composition of the Orion star forming region". We
reinvestigate the chemical composition of B-type stars in the Orion OB1
association by means of state-of-the-art stellar atmosphere codes, atomic
models and techniques, and compare the resulting abundances with those obtained
from the emission line spectra of the Orion nebula (M42), and recent
determinations of the Solar chemical composition.Comment: 5 pages, 4 figures, 2 tables. Poster contribution to the proceedings
of the LIAC2010 conference "The multi-wavelength view of hot, massive stars
Gravity Effects on Neutrino Masses in Split Supersymmetry
The mass differences and mixing angles of neutrinos can neither be explained
by R-Parity violating split supersymmetry nor by flavor blind quantum gravity
alone. It is shown that combining both effects leads, within the allowed
parameter range, to good agreement with the experimental results. The
atmospheric mass is generated by supersymmetry through mixing between neutrinos
and neutralinos, while the solar mass is generated by gravity through flavor
blind dimension five operators. Maximal atmospheric mixing forces the tangent
squared of the solar angle to be equal to 1/2. The scale of the quantum gravity
operator is predicted within a 5% error, implying that the reduced Planck scale
should lie around the GUT scale. In this way, the model is very predictive and
can be tested at future experiments.Comment: 12 pages, 9 figures; In section 3 we extend our discussion about the
definition of flavor basis in order to clarify in which basis the Gravity
contributions are flavor blind. In the section 4 we add some words to explain
why the Gravity contributions will not affect the charged lepton mass matrix;
Finally we also fixed some minor typos regarding units or plot label
Feynman-Jackson integrals
We introduce perturbative Feynman integrals in the context of q-calculus
generalizing the Gaussian q-integrals introduced by Diaz and Teruel. We provide
analytic as well as combinatorial interpretations for the Feynman-Jackson
integrals.Comment: Final versio
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