9,473 research outputs found
Stellar Population Challenge: analysis of M67 with the VO
In this poster we present the analysis of the CMD of M67 (proposed in the
Stellar Population Challenge) performed with VO applications. We found that,
although the VO environment is still not ready to perform a complete analysis,
its use provides highly useful additional information for the analysis. Thanks
to the current VO framework, we are able to identify stars in the provided CMD
that are not suitable for isochrone fitting. Additionally, we can complete our
knowledge of this cluster extending the analysis to IR colors, which were not
provided in the original data but that are available thanks to the VO. On the
negative side, we find it difficult to access theoretical data from VO
applications, so, currently, it is not possible to perform completely the
analysis of the cluster inside the VO framework. However it is expected that
the situation will improve in a near future.Comment: Stellar Populations as Building Blocks of Galaxies, Proceedings of
IAU Symposium #241. Edited by A. Vazdekis and R. F. Peletier. Cambridge:
Cambridge University Press, 2007, pp. 173-17
Precovery of near-Earth asteroids by a citizen-science project of the Spanish Virtual Observatory
This article describes a citizen-science project conducted by the Spanish
Virtual Observatory (SVO) to improve the orbits of near-Earth asteroids (NEAs)
using data from astronomical archives. The list of NEAs maintained at the Minor
Planet Center (MPC) is checked daily to identify new objects or changes in the
orbital parameters of already catalogued objects. Using NEODyS we compute the
position and magnitude of these objects at the observing epochs of the 938 046
images comprising the Eigth Data Release of the Sloan Digitised Sky Survey
(SDSS). If the object lies within the image boundaries and the magnitude is
brighter than the limiting magnitude, then the associated image is visually
inspected by the project's collaborators (the citizens) to confirm or discard
the presence of the NEA. If confirmed, accurate coordinates and, sometimes,
magnitudes are submitted to the MPC. Using this methodology, 3,226 registered
users have made during the first fifteen months of the project more than
167,000 measurements which have improved the orbital elements of 551 NEAs (6%
of the total number of this type of asteroids). Even more remarkable is the
fact that these results have been obtained at zero cost to telescope time as
NEAs were serendipitously observed while the survey was being carried out. This
demonstrates the enormous scientific potential hidden in astronomical archives.
The great reception of the project as well as the results obtained makes it a
valuable and reliable tool for improving the orbital parameters of near-Earth
asteroids.Comment: 9 pages, 5 figures. Accepted in Astron. Nach
Entangled coherent states and squeezing in N trapped ions
We consider a resonant bichromatic excitation of N trapped ions that
generates displacement and squeezing in their collective motion conditioned to
their ionic internal state, producing eventually Scrhodinger cat states and
entangled squeezing. Furthermore, we study the case of tetrachromatic
illumination or producing the so called entangled coherent states in two
motional normal modes.Comment: 4 Revtex pages, no figures. To appear in Proceedings of "Mysteries,
Puzzles and Paradoxes in Quantum Mechanics", Garda Lake, Italy (2001
Field squeeze operators in optical cavities with atomic ensembles
We propose a method of generating unitarily single and two-mode field
squeezing in an optical cavity with an atomic cloud. Through a suitable laser
system, we are able to engineer a squeeze field operator decoupled from the
atomic degrees of freedom, yielding a large squeeze parameter that is scaled up
by the number of atoms, and realizing degenerate and non-degenerate parametric
amplification. By means of the input-output theory we show that ideal squeezed
states and perfect squeezing could be approached at the output. The scheme is
robust to decoherence processes.Comment: Four pages and one figure. Accepted in Physical Review Letter
Quantum Simulations of Relativistic Quantum Physics in Circuit QED
We present a scheme for simulating relativistic quantum physics in circuit
quantum electrodynamics. By using three classical microwave drives, we show
that a superconducting qubit strongly-coupled to a resonator field mode can be
used to simulate the dynamics of the Dirac equation and Klein paradox in all
regimes. Using the same setup we also propose the implementation of the
Foldy-Wouthuysen canonical transformation, after which the time derivative of
the position operator becomes a constant of the motion.Comment: 13 pages, 3 figure
A search for new hot subdwarf stars by means of Virtual Observatory tools
Hot subdwarf stars are faint, blue objects, and are the main contributors to
the far-UV excess observed in elliptical galaxies. They offer an excellent
laboratory to study close and wide binary systems, and to scrutinize their
interiors through asteroseismology, as some of them undergo stellar
oscillations. However, their origins are still uncertain, and increasing the
number of detections is crucial to undertake statistical studies. In this work,
we aim at defining a strategy to find new, uncatalogued hot subdwarfs. Making
use of Virtual Observatory tools we thoroughly search stellar catalogues to
retrieve multi-colour photometry and astrometric information of a known sample
of blue objects, including hot subdwarfs, white dwarfs, cataclysmic variables
and main sequence OB stars. We define a procedure to discriminate among these
spectral classes, particularly designed to obtain a hot subdwarf sample with a
low contamination factor. In order to check the validity of the method, this
procedure is then applied to two test sky regions: the Kepler FoV and to a test
region of around (RA:225, DEC:5) deg. As a result, we obtained 38 hot subdwarf
candidates, 23 of which had already a spectral classification. We have acquired
spectroscopy for three other targets, and four additional ones have an
available SDSS spectrum, which we used to determine their spectral type. A
temperature estimate is provided for the candidates based on their spectral
energy distribution, considering two-atmospheres fit for objects with clear
infrared excess. Eventually, out of 30 candidates with spectral classification,
26 objects were confirmed to be hot subdwarfs, yielding a contamination factor
of only 13%. The high rate of success demonstrates the validity of the proposed
strategy to find new uncatalogued hot subdwarfs. An application of this method
to the entire sky will be presented in a forthcoming work.Comment: 13 pages, 7 figure
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