148 research outputs found
Global and Local Three-dimensional Studies of The Residual Vector Field from 2MASS and Hipparcos-2 Catalog
[EN] The Gaia mission will provide a six-parameter solution for millions of stars, including a tridimensional map of our Galaxy. The estimation of distances has been made for the Tycho-Gaia Astrometric Solution (TGAS), while to contrast the proper motions it is interesting to consider positions from the different Gaia Data Release with older ones given in ground-based massive catalogs. This process has been followed to build, for example, the PMA catalog using the 2MASS. Our aim is to improve the positions of this catalog (although the process is applicable to any other). The first stage, presented here, consists of carrying out a three-dimensional study using vector spherical harmonics (VSH) development of the systematisms in position for the stars common with Hipparcos-2; we take into account the distances, magnitudes, and spectral types. To this aim, we use linear polynomial regression of first order that fits vector fields and the derivatives of their components. We verify that the coefficients of the developments of first order have different behavior according to the characteristics of stars and distances. To deepen the study, we focus on the conservative component of the field, applying the Helmholtz theorem. Each potential function is obtained solving a Poisson equation on the sphere, after finding the divergence of the corresponding vector field. Both vector and potential fields present patterns, at certain points, that depend on the three considered parameters (distance, magnitude, and spectral type); their sources and shrinks correspond to maxima and minima. In this sense, we observe that these critical points are also critical points of the surface that represents the VT magnitude of Tycho-2, which makes sense because this catalog was used in the reduction of 2MASS positions. Finally, we selected some stars near the critical points of the vector fields and apply the adjustments obtained in the previous sections. The difference with the positions in DR1 allows us to compare the proper motions: those from the PMA and those induced after our corrections.This paper was partially supported by the UJI-B2016-18, 16I356 project.Marco Castillo, FJ.; Martínez Uso, MJ.; Lopez, J. (2019). Global and Local Three-dimensional Studies of The Residual Vector Field from 2MASS and Hipparcos-2 Catalog. Publications of the Astronomical Society of the Pacific. 131(998):1-22. https://doi.org/10.1088/1538-3873/aaed5dS122131998Akhmetov, V. S., Fedorov, P. N., Velichko, A. B., & Shulga, V. M. (2017). The PMA Catalogue: 420 million positions and absolute proper motions. Monthly Notices of the Royal Astronomical Society, 469(1), 763-773. doi:10.1093/mnras/stx812Arenou, F., Luri, X., Babusiaux, C., Fabricius, C., Helmi, A., Robin, A. C., … Bragaglia, A. (2017). Gaia Data Release 1. Astronomy & Astrophysics, 599, A50. doi:10.1051/0004-6361/201629895Astraatmadja, T. L., & Bailer-Jones, C. A. L. (2016). 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Acoustic and optical variations during rapid downward motion episodes in the deep north-western Mediterranean Sea
An Acoustic Doppler Current Profiler (ADCP) was moored at the deep-sea site
of the ANTARES neutrino telescope near Toulon, France, thus providing a unique
opportunity to compare high-resolution acoustic and optical observations
between 70 and 170 m above the sea bed at 2475 m. The ADCP measured downward
vertical currents of magnitudes up to 0.03 m s-1 in late winter and early
spring 2006. In the same period, observations were made of enhanced levels of
acoustic reflection, interpreted as suspended particles including zooplankton,
by a factor of about 10 and of horizontal currents reaching 0.35 m s-1. These
observations coincided with high light levels detected by the telescope,
interpreted as increased bioluminescence. During winter 2006 deep dense-water
formation occurred in the Ligurian subbasin, thus providing a possible
explanation for these observations. However, the 10-20 days quasi-periodic
episodes of high levels of acoustic reflection, light and large vertical
currents continuing into the summer are not direct evidence of this process. It
is hypothesized that the main process allowing for suspended material to be
moved vertically later in the year is local advection, linked with topographic
boundary current instabilities along the rim of the 'Northern Current'.Comment: 30 pages, 7 figure
A First Search for coincident Gravitational Waves and High Energy Neutrinos using LIGO, Virgo and ANTARES data from 2007
We present the results of the first search for gravitational wave bursts
associated with high energy neutrinos. Together, these messengers could reveal
new, hidden sources that are not observed by conventional photon astronomy,
particularly at high energy. Our search uses neutrinos detected by the
underwater neutrino telescope ANTARES in its 5 line configuration during the
period January - September 2007, which coincided with the fifth and first
science runs of LIGO and Virgo, respectively. The LIGO-Virgo data were analysed
for candidate gravitational-wave signals coincident in time and direction with
the neutrino events. No significant coincident events were observed. We place
limits on the density of joint high energy neutrino - gravitational wave
emission events in the local universe, and compare them with densities of
merger and core-collapse events.Comment: 19 pages, 8 figures, science summary page at
http://www.ligo.org/science/Publication-S5LV_ANTARES/index.php. Public access
area to figures, tables at
https://dcc.ligo.org/cgi-bin/DocDB/ShowDocument?docid=p120000
Status and Recent Results of the Acoustic Neutrino Detection Test System AMADEUS
The AMADEUS system is an integral part of the ANTARES neutrino telescope in
the Mediterranean Sea. The project aims at the investigation of techniques for
acoustic neutrino detection in the deep sea. Installed at a depth of more than
2000m, the acoustic sensors of AMADEUS are based on piezo-ceramics elements for
the broad-band recording of signals with frequencies ranging up to 125kHz.
AMADEUS was completed in May 2008 and comprises six "acoustic clusters", each
one holding six acoustic sensors that are arranged at distances of roughly 1m
from each other. The clusters are installed with inter-spacings ranging from
15m to 340m. Acoustic data are continuously acquired and processed at a
computer cluster where online filter algorithms are applied to select a
high-purity sample of neutrino-like signals. 1.6 TB of data were recorded in
2008 and 3.2 TB in 2009. In order to assess the background of neutrino-like
signals in the deep sea, the characteristics of ambient noise and transient
signals have been investigated. In this article, the AMADEUS system will be
described and recent results will be presented.Comment: 7 pages, 8 figures. Proceedings of ARENA 2010, the 4th International
Workshop on Acoustic and Radio EeV Neutrino Detection Activitie
<i>Gaia</i> Data Release 1. Summary of the astrometric, photometric, and survey properties
Context. At about 1000 days after the launch of Gaia we present the first Gaia data release, Gaia DR1, consisting of astrometry and photometry for over 1 billion sources brighter than magnitude 20.7.
Aims. A summary of Gaia DR1 is presented along with illustrations of the scientific quality of the data, followed by a discussion of the limitations due to the preliminary nature of this release.
Methods. The raw data collected by Gaia during the first 14 months of the mission have been processed by the Gaia Data Processing and Analysis Consortium (DPAC) and turned into an astrometric and photometric catalogue.
Results. Gaia DR1 consists of three components: a primary astrometric data set which contains the positions, parallaxes, and mean proper motions for about 2 million of the brightest stars in common with the HIPPARCOS and Tycho-2 catalogues – a realisation of the Tycho-Gaia Astrometric Solution (TGAS) – and a secondary astrometric data set containing the positions for an additional 1.1 billion sources. The second component is the photometric data set, consisting of mean G-band magnitudes for all sources. The G-band light curves and the characteristics of ∼3000 Cepheid and RR-Lyrae stars, observed at high cadence around the south ecliptic pole, form the third component. For the primary astrometric data set the typical uncertainty is about 0.3 mas for the positions and parallaxes, and about 1 mas yr−1 for the proper motions. A systematic component of ∼0.3 mas should be added to the parallax uncertainties. For the subset of ∼94 000 HIPPARCOS stars in the primary data set, the proper motions are much more precise at about 0.06 mas yr−1. For the secondary astrometric data set, the typical uncertainty of the positions is ∼10 mas. The median uncertainties on the mean G-band magnitudes range from the mmag level to ∼0.03 mag over the magnitude range 5 to 20.7.
Conclusions. Gaia DR1 is an important milestone ahead of the next Gaia data release, which will feature five-parameter astrometry for all sources. Extensive validation shows that Gaia DR1 represents a major advance in the mapping of the heavens and the availability of basic stellar data that underpin observational astrophysics. Nevertheless, the very preliminary nature of this first Gaia data release does lead to a number of important limitations to the data quality which should be carefully considered before drawing conclusions from the data
Measurement of Atmospheric Neutrino Oscillations with the ANTARES Neutrino Telescope
The data taken with the ANTARES neutrino telescope from 2007 to 2010, a total
live time of 863 days, are used to measure the oscillation parameters of
atmospheric neutrinos. Muon tracks are reconstructed with energies as low as 20
GeV. Neutrino oscillations will cause a suppression of vertical upgoing muon
neutrinos of such energies crossing the Earth. The parameters determining the
oscillation of atmospheric neutrinos are extracted by fitting the event rate as
a function of the ratio of the estimated neutrino energy and reconstructed
flight path through the Earth. Measurement contours of the oscillation
parameters in a two-flavour approximation are derived. Assuming maximum mixing,
a mass difference of eV is
obtained, in good agreement with the world average value.Comment: 9 pages, 5 figure
The ANTARES Telescope Neutrino Alert System
The ANTARES telescope has the capability to detect neutrinos produced in
astrophysical transient sources. Potential sources include gamma-ray bursts,
core collapse supernovae, and flaring active galactic nuclei. To enhance the
sensitivity of ANTARES to such sources, a new detection method based on
coincident observations of neutrinos and optical signals has been developed. A
fast online muon track reconstruction is used to trigger a network of small
automatic optical telescopes. Such alerts are generated for special events,
such as two or more neutrinos, coincident in time and direction, or single
neutrinos of very high energy.Comment: 17 pages, 9 figures submitted to Astroparticle Physic
A First Search for Coincident Gravitational Waves and High Energy Neutrinos Using LIGO, Virgo and ANTARES Data from 2007
We present the results of the first search for gravitational wave bursts associated with high energy neutrinos. Together, these messengers could reveal new, hidden sources that are not observed by conventional photon astronomy, particularly at high energy. Our search uses neutrinos detected by the underwater neutrino telescope ANTARES in its 5 line configuration during the period January - September 2007, which coincided with the fifth and first science runs of LIGO and Virgo, respectively. The LIGO-Virgo data were analysed for candidate gravitational-wave signals coincident in time and direction with the neutrino events. No significant coincident events were observed. We place limits on the density of joint high energy neutrino - gravitational wave emission events in the local universe, and compare them with densities of merger and core-collapse events
A first search for coincident gravitational waves and high energy neutrinos using LIGO, Virgo and ANTARES data from 2007
We present the results of the first search for gravitational wave bursts associated with high energy neutrinos. Together, these messengers could reveal new, hidden sources that are not observed by conventional photon astronomy, particularly at high energy. Our search uses neutrinos detected by the underwater neutrino telescope ANTARES in its 5 line configuration during the period January - September 2007, which coincided with the fifth and first science runs of LIGO and Virgo, respectively. The LIGO-Virgo data were analysed for candidate gravitational-wave signals coincident in time and direction with the neutrino events. No significant coincident events were observed. We place limits on the density of joint high energy neutrino - gravitational wave emission events in the local universe, and compare them with densities of merger and core-collapse events. © 2013 IOP Publishing Ltd and Sissa Medialab srl
On the detection of TeV gamma-rays from GRB with km-cube neutrino telescopes --- I. Muon event rate from single GRBs
This is a preliminary study to examine the prospect of detecting TeV photons
from -ray bursts (GRB) using km-size neutrino telescopes, specifically
for the ANTARES neutrino telescope. Although optimized to detect upgoing
neutrino-induced muons, neutrino telescopes nevertheless have a potential to
detect high-energy photons by detecting downgoing muons from the
electromagnetic cascade induced by the interaction of TeV photons with the
Earth's atmosphere. The photon energy spectrum of a GRB is modeled by a simple
power law and is normalized by simple energy considerations. Taking into
account the absorption of TeV photons by cosmic infrared backgrounds, an
optical depth table calculated from a model by \cite{fin10} is used and the
arriving number of photons on top of the Earth atmosphere is determined. Muon
production in the atmosphere is determined by considering two main channels of
muon production: Pion photoproduction and direct muon pair production. The muon
energy loss during their traverse from the surface to the bottom of the sea is
determined using the standard muon energy loss formula. Assuming different
detector sizes, the number of detectable muons from single GRB events located
at different redshifts and zenith distances is determined. The background is
calculated assuming it consists primarily of cosmic ray-induced downgoing
muons. The detection significance is calculated and it can be concluded that to
obtain at least detection significance, a typical GRB has to be
located at redshift if the detector's muon effective area is
, or redshift ,
if the muon effective area is .Comment: Thirteen pages, 14 figures. Accepted for publication in MNRA
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