4,451 research outputs found
The Large- Limit of the Two-Hermitian-matrix model by the hidden BRST method
This paper discusses the large N limit of the two-Hermitian-matrix model in
zero dimensions, using the hidden BRST method. A system of integral equations
previously found is solved, showing that it contained the exact solution of the
model in leading order of large .Comment: 19 pages, Latex,CERN--TH-6531/9
A Multi-Membership Catalogue for 1876 Open Clusters using UCAC4 data
The main objective of this work is to determine the cluster members of 1876
open clusters, using positions and proper motions of the astrometric catalogue
UCAC4. For this purpose we apply three different methods, all them based on a
Bayesian approach, but with different formulations: a purely parametric method,
another completely non-parametric algorithm, and a third, recently developed by
Sampedro & Alfaro, using both formulations at different steps of the whole
process. The first and second statistical moments of the members phase-space
subspace, obtained after applying the three methods, are compared for every
cluster. Although, on average, the three methods yield similar results,
specific differences between them, as well as for some particular clusters, are
also present. The comparison with other published catalogues shows good
agreement. We have also estimated for the first time the mean proper motion for
a sample of 18 clusters. The results are organized in a single catalogue formed
by two main files, one with the most relevant information for each cluster,
partially including that in UCAC4, and the other showing the individual
membership probabilities for each star in the cluster area. The final
catalogue, with an interface design that enables an easy interaction with the
user, is available in electronic format at SSG-IAA
(http://ssg.iaa.es/en/content/sampedro-cluster-catalog) website.Comment: Accepted for publication in MNRAS. 9 pages, 3 figures, 6 table
Lucky Spectroscopy, an equivalent technique to Lucky Imaging. Spatially resolved spectroscopy of massive close visual binaries using the William Herschel Telescope
CONTEXT: Many massive stars have nearby companions whose presence hamper
their characterization through spectroscopy. AIMS: We want to obtain spatially
resolved spectroscopy of close massive visual binaries to derive their spectral
types. METHODS: We obtain a large number of short long-slit spectroscopic
exposures of five close binaries under good seeing conditions, select those
with the best characteristics, extract the spectra using multiple-profile
fitting, and combine the results to derive spatially separated spectra.
RESULTS: We demonstrate the usefulness of Lucky Spectroscopy by presenting the
spatially resolved spectra of the components of each system, in two cases with
separations of only ~0.3". Those are delta Ori Aa+Ab (resolved in the optical
for the first time) and sigma Ori AaAb+B (first time ever resolved). We also
spatially resolve 15 Mon AaAb+B, zeta Ori AaAb+B (both previously resolved with
GOSSS, the Galactic O-Star Spectroscopic Survey), and eta Ori AaAb+B, a system
with two spectroscopic B+B binaries and a fifth visual component. The systems
have in common that they are composed of an inner pair of slow rotators orbited
by one or more fast rotators, a characteristic that could have consequences for
the theories of massive star formation.Comment: Accepted for publication in A&A, 7 page
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