1,180 research outputs found
Extension of Tycho catalog for low-extinction windows in the galactic bulge
We present in this work secondary catalogs up to based on
the Tycho reference frame (ESA, 1997) for 12 selected low-extinction fields
towards the galactic bulge. The observations have been performed with the
Askania-Zeiss Meridian Circle equiped with a CCD camera, located at the
Abrah\~ao de Moraes Observatory (Valinhos, Brazil) and operated by the
Institute of Astronomy and Geophysics, S\~ao Paulo University. The presented
catalog, though not complete, has been designed to help in intensive search
programmes (e.g. microlensing and variable searches) and therefore the selected
standards have a high astrometric and photometric ( band, approximately)
quality. The mean precisions obtained were in , 0.013'' in
, 0.030 for the standard deviation in magnitude and 0.0042 for the
magnitude when weighted with the error bars in each night (in the mean, 42
stars for the catalog of each window). Tables B.1 to B.12 are also available in
eletronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr
(130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html.Comment: 16 pages, 6 figures, A&A Latex style. Published in A&A
Stellar variability in low-extinction regions towards the Galactic Bulge
Intensive monitoring of low-extinction windows towards the galactic bulge has
provided in the last years valuable information for studies about the dynamics,
kinematics and formation history of this part of the galaxy, mainly by
characterizing the bulge stellar populations (Paczy\'nski, 1996). Since 1997,
we have been conducting an intensive photometric-astrometric survey of the
galactic bulge, with the monitoring of about 120000 stars in 12 windows
uniformly distributed in galactic latitude and longitude (Blanco & Terndrup,
1989 e Blanco, 1988) never before submitted to this kind of survey. For this
purpose, we have used the IAG/USP CCD Meridian Circle of the Abrah\~ao de
Moraes Observatory. The main objective of this work is the identification and
classification of variable objects. In this work we present the set up and
development of the necessary tools for a project like this and the posterior
analysis of our data. We briefly describe the construction of a program to
organize and detect variables among the observed stars, including real time
alerts (for variations greater than 0.3 magnitudes). The preliminary analysis
after the processing of 76 nights of observation yielded 479 variable stars,
from which 96.7 % of them are new. We discuss the preliminary classification of
this variables, based on: a) the observed amplitude of variation; b) the shape
of light curve; c) the expected variable classes among our data and d) the
calculated periods, whenever possible. Finally, we discuss the future
perspectives for the project and for the applications and analysis of the
discovered variable stars.Comment: 10 pages, 14 figures. Accepted by A&A
Consequences of a covariant Description of Heavy Ion Reactions at intermediate Energies
Heavy ion collisions at intermediate energies are studied by using a new RQMD
code, which is a covariant generalization of the QMD approach. We show that
this new implementation is able to produce the same results in the
nonrelativistic limit (i.e. 50MeV/nucl.) as the non-covariant QMD. Such a
comparison is not available in the literature. At higher energies (i.e. 1.5
GeV/nucl. and 2 GeV/nucl.) RQMD and QMD give different results in respect to
the time evolution of the phase space, for example for the directed transverse
flow. These differences show that consequences of a covariant description of
heavy ion reactions within the framework of RQMD are existing even at
intermediate energies.Comment: LaTex-file, 28 pages, 8 figures (available upon request), accepted
for publication in Physical Review
Microvariability in the optical polarization of 3C 279
We present results of a microvariability polarization study in the violently variable quasaer 3C279. We have resolved the polarization curves in the V band for this object down to timescales of minutes. We found two main components in the evolution of the degree of linear polarization, one consisting of a flicker with timescales of several tens of minutes and other component with far more significant variations on timescales of a few days. The linear polarization descended from ∼17%. down to ∼8% in three nights. The polarization angle underwent a sudden change of more that 10 degrees in a few hours, perhaps indicating the injection of a new shock in the jet. The amplitude of the intranight flickering in the degree of polarization is at the level of ∼1%. These are probably the best sampled polarization data ever obtained for this object. We also performed IR observations and we provide a follow-up of the evolution of this source at such energies after the main polarization outburst.Facultad de Ciencias Astronómicas y GeofísicasInstituto Argentino de Radioastronomí
Testing the performance of a blind burst statistic
In this work we estimate the performance of a method for the detection of
burst events in the data produced by interferometric gravitational wave
detectors. We compute the receiver operating characteristics in the specific
case of a simulated noise having the spectral density expected for Virgo, using
test signals taken from a library of possible waveforms emitted during the
collapse of the core of Type II Supernovae.Comment: 8 pages, 6 figures, Talk given at the GWDAW2002 worksho
Pseudo Goldstones at Future Colliders from the Extended Bess Model
We consider the production of the lightest pseudo-Goldstone bosons at future
colliders through the vector resonances predicted by the extended BESS model,
which consists of an effective lagrangian parametrization with dynamical
symmetry breaking, describing scalar, vector and axial-vector bound states in a
rather general framework. We find that the detection of pseudo-Goldstone pairs
at LHC requires a careful evaluation of backgrounds. For e+e- collisions in the
TeV range the backgrounds can be easily reduced and the detection of
pseudo-Goldstone pairs is generally easier.Comment: 17 pages and 12 figures (included as a uuencoded tar file), LaTeX
(style article), UGVA-DPT 1994/03-84
New vector bosons in the electroweak sector: a renormalizable model with decoupling
A linear realization of a model of dynamical electroweak symmetry breaking
describing additional heavy vector bosons is proposed. The model is a SU(2)_L x
U(1) x SU(2)_L' x SU(2)_R' gauge theory, breaking at some high scale u to
SU(2)_weak x U(1)_Y and breaking again in the standard way at the electroweak
scale v to U(1)_(em). The model is renormalizable and reproduces the Standard
Model in the limit u\to infinity. This decoupling property is shown to hold
also at the level of radiative corrections by computing, in particular, the
epsilon parameters.Comment: 39 pages, 16 Figures, Late
Dimensionless Coupling of Bulk Scalars at the LHC
We identify the lowest-dimension interaction which is possible between
Standard Model brane fields and bulk scalars in 6 dimensions. The
lowest-dimension interaction is unique and involves a trilinear coupling
between the Standard Model Higgs and the bulk scalar. Because this interaction
has a dimensionless coupling, it depends only logarithmically on ultraviolet
mass scales and heavy physics need not decouple from it. We compute its
influence on Higgs physics at ATLAS and identify how large a coupling can be
detected at the LHC. Besides providing a potentially interesting signal in
Higgs searches, such couplings provide a major observational constraint on 6D
large-extra-dimensional models with scalars in the bulk.Comment: 20 page
Strong tree level unitarity violations in the extra dimensional Standard Model with scalars in the bulk
We show how the tree level unitarity violations of compactified extra
dimensional extensions of the Standard Model become much stronger when the
scalar sector is included in the bulk. This effect occurs when the couplings
are not suppressed for larger Kaluza-Klein levels, and could have relevant
consequences for the phenomenology of the next generation of colliders. We also
introduce a simple and generic formalism to obtain unitarity bounds for finite
energies, taking into account coupled channels including the towers of
Kaluza-Klein excitations.Comment: Version to appear in Phys. Rev. D Typos corrected and remarks added
to clarify figure
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