475 research outputs found
Optomechanical sideband cooling of a thin membrane within a cavity
We present an experimental study of dynamical back-action cooling of the
fundamental vibrational mode of a thin semitransparent membrane placed within a
high-finesse optical cavity. We study how the radiation pressure interaction
modifies the mechanical response of the vibrational mode, and the experimental
results are in agreement with a Langevin equation description of the coupled
dynamics. The experiments are carried out in the resolved sideband regime, and
we have observed cooling by a factor 350 We have also observed the mechanical
frequency shift associated with the quadratic term in the expansion of the
cavity mode frequency versus the effective membrane position, which is
typically negligible in other cavity optomechanical devices.Comment: 15 pages, 7 figure
The AMBRE Project: Stellar parameterisation of the ESO:FEROS archived spectra
The AMBRE Project is a collaboration between the European Southern
Observatory (ESO) and the Observatoire de la Cote d'Azur (OCA) that has been
established in order to carry out the determination of stellar atmospheric
parameters for the archived spectra of four ESO spectrographs.
The analysis of the FEROS archived spectra for their stellar parameters
(effective temperatures, surface gravities, global metallicities, alpha element
to iron ratios and radial velocities) has been completed in the first phase of
the AMBRE Project. From the complete ESO:FEROS archive dataset that was
received, a total of 21551 scientific spectra have been identified, covering
the period 2005 to 2010. These spectra correspond to ~6285 stars.
The determination of the stellar parameters was carried out using the stellar
parameterisation algorithm, MATISSE (MATrix Inversion for Spectral SynthEsis),
which has been developed at OCA to be used in the analysis of large scale
spectroscopic studies in galactic archaeology. An analysis pipeline has been
constructed that integrates spectral reduction and radial velocity correction
procedures with MATISSE in order to automatically determine the stellar
parameters of the FEROS spectra.
Stellar atmospheric parameters (Teff, log g, [M/H] and [alpha/Fe]) were
determined for 6508 (30.2%) of the FEROS archived spectra (~3087 stars). Radial
velocities were determined for 11963 (56%) of the archived spectra. 2370 (11%)
spectra could not be analysed within the pipeline. 12673 spectra (58.8%) were
analysed in the pipeline but their parameters were discarded based on quality
criteria and error analysis determined within the automated process. The
majority of these rejected spectra were found to have broad spectral features
indicating that they may be hot and/or fast rotating stars, which are not
considered within the adopted reference synthetic spectra grid of FGKM stars.Comment: 28 pages, 28 figures, 9 table
Spectroscopic analysis of the B/Be visual binary HR 1847
We studied both components of a slightly overlooked visual binary HR 1847
spectroscopically to determine its basic physical and orbital parameters. Basic
stellar parameters were determined by comparing synthetic spectra to the
observed echelle spectra, which cover both the optical and near-IR regions. New
observations of this system used the Ond\v{r}ejov and Rozhen 2-m telescopes and
their coud\'e spectrographs. Radial velocities from individual spectra were
measured and then analysed with the code {\FOTEL} to determine orbital
parameters. The spectroscopic orbit of HR 1847A is presented for the first
time. It is a single-lined spectroscopic binary with a B-type primary, a period
of 719.79 days, and a highly eccentric orbit with e=0.7. We confirmed that HR
1847B is a Be star. Its H\alpha emission significantly decreased from 2003 to
2008. Both components have a spectral type B7-8 and luminosity class IV-V.Comment: Astronomy and Astrophysics, accepte
The age of the Galactic thin disk from Th/Eu nucleocosmochronology III. Extended sample
The first determination of the age of the Galactic thin disk from Th/Eu
nucleocosmochronology was accomplished by us in Papers I and II. The present
work aimed at reducing the age uncertainty by expanding the stellar sample with
the inclusion of seven new objects - an increase by 37%. A set of [Th/Eu]
abundance ratios was determined from spectral synthesis and merged with the
results from Paper I. Abundances for the new, extended sample were analyzed
with the aid of a Galactic disk chemical evolution (GDCE) model developed by us
is Paper II. The result was averaged with an estimate obtained in Paper II from
a conjunction of literature data and our GDCE model, providing our final,
adopted disk age T_G = (8.8 +/- 1.7) Gyr with a reduction of 0.1 Gyr (6%) in
the uncertainty. This value is compatible with the most up-to-date white dwarf
age determinations (<~ 10 Gyr). Considering that the halo is currently presumed
to be (13.5 +/- 0.7) Gyr old, our result prompts groups developing Galactic
formation models to include an hiatus of (4.7 +/- 1.8) Gyr between the
formation of halo and disk.Comment: 7 pages, 5 Postscript figures, accepted for publication in Astronomy
& Astrophysic
Search for gravitational waves associated with the InterPlanetary Network short gamma ray bursts
We outline the scientific motivation behind a search for gravitational waves
associated with short gamma ray bursts detected by the InterPlanetary Network
(IPN) during LIGO's fifth science run and Virgo's first science run. The IPN
localisation of short gamma ray bursts is limited to extended error boxes of
different shapes and sizes and a search on these error boxes poses a series of
challenges for data analysis. We will discuss these challenges and outline the
methods to optimise the search over these error boxes.Comment: Methods paper; Proceedings for Eduardo Amaldi 9 Conference on
Gravitational Waves, July 2011, Cardiff, U
Swift follow-up observations of candidate gravitational-wave transient events
We present the first multi-wavelength follow-up observations of two candidate
gravitational-wave (GW) transient events recorded by LIGO and Virgo in their
2009-2010 science run. The events were selected with low latency by the network
of GW detectors and their candidate sky locations were observed by the Swift
observatory. Image transient detection was used to analyze the collected
electromagnetic data, which were found to be consistent with background.
Off-line analysis of the GW data alone has also established that the selected
GW events show no evidence of an astrophysical origin; one of them is
consistent with background and the other one was a test, part of a "blind
injection challenge". With this work we demonstrate the feasibility of rapid
follow-ups of GW transients and establish the sensitivity improvement joint
electromagnetic and GW observations could bring. This is a first step toward an
electromagnetic follow-up program in the regime of routine detections with the
advanced GW instruments expected within this decade. In that regime
multi-wavelength observations will play a significant role in completing the
astrophysical identification of GW sources. We present the methods and results
from this first combined analysis and discuss its implications in terms of
sensitivity for the present and future instruments.Comment: Submitted for publication 2012 May 25, accepted 2012 October 25,
published 2012 November 21, in ApJS, 203, 28 (
http://stacks.iop.org/0067-0049/203/28 ); 14 pages, 3 figures, 6 tables;
LIGO-P1100038; Science summary at
http://www.ligo.org/science/Publication-S6LVSwift/index.php ; Public access
area to figures, tables at
https://dcc.ligo.org/cgi-bin/DocDB/ShowDocument?docid=p110003
Search for Gravitational Waves from Low Mass Compact Binary Coalescence in LIGO's Sixth Science Run and Virgo's Science Runs 2 and 3
We report on a search for gravitational waves from coalescing compact
binaries using LIGO and Virgo observations between July 7, 2009 and October 20,
2010. We searched for signals from binaries with total mass between 2 and 25
solar masses; this includes binary neutron stars, binary black holes, and
binaries consisting of a black hole and neutron star. The detectors were
sensitive to systems up to 40 Mpc distant for binary neutron stars, and further
for higher mass systems. No gravitational-wave signals were detected. We report
upper limits on the rate of compact binary coalescence as a function of total
mass, including the results from previous LIGO and Virgo observations. The
cumulative 90%-confidence rate upper limits of the binary coalescence of binary
neutron star, neutron star- black hole and binary black hole systems are 1.3 x
10^{-4}, 3.1 x 10^{-5} and 6.4 x 10^{-6} Mpc^{-3}yr^{-1}, respectively. These
upper limits are up to a factor 1.4 lower than previously derived limits. We
also report on results from a blind injection challenge.Comment: 11 pages, 5 figures. For a repository of data used in the
publication, go to:
. Also see the
announcement for this paper on ligo.org at:
<http://www.ligo.org/science/Publication-S6CBCLowMass/index.php
Implementation and testing of the first prompt search for gravitational wave transients with electromagnetic counterparts
Aims. A transient astrophysical event observed in both gravitational wave
(GW) and electromagnetic (EM) channels would yield rich scientific rewards. A
first program initiating EM follow-ups to possible transient GW events has been
developed and exercised by the LIGO and Virgo community in association with
several partners. In this paper, we describe and evaluate the methods used to
promptly identify and localize GW event candidates and to request images of
targeted sky locations.
Methods. During two observing periods (Dec 17 2009 to Jan 8 2010 and Sep 2 to
Oct 20 2010), a low-latency analysis pipeline was used to identify GW event
candidates and to reconstruct maps of possible sky locations. A catalog of
nearby galaxies and Milky Way globular clusters was used to select the most
promising sky positions to be imaged, and this directional information was
delivered to EM observatories with time lags of about thirty minutes. A Monte
Carlo simulation has been used to evaluate the low-latency GW pipeline's
ability to reconstruct source positions correctly.
Results. For signals near the detection threshold, our low-latency algorithms
often localized simulated GW burst signals to tens of square degrees, while
neutron star/neutron star inspirals and neutron star/black hole inspirals were
localized to a few hundred square degrees. Localization precision improves for
moderately stronger signals. The correct sky location of signals well above
threshold and originating from nearby galaxies may be observed with ~50% or
better probability with a few pointings of wide-field telescopes.Comment: 17 pages. This version (v2) includes two tables and 1 section not
included in v1. Accepted for publication in Astronomy & Astrophysic
Gravitational Waves From Known Pulsars: Results From The Initial Detector Era
We present the results of searches for gravitational waves from a large selection of pulsars using data from the most recent science runs (S6, VSR2 and VSR4) of the initial generation of interferometric gravitational wave detectors LIGO (Laser Interferometric Gravitational-wave Observatory) and Virgo. We do not see evidence for gravitational wave emission from any of the targeted sources but produce upper limits on the emission amplitude. We highlight the results from seven young pulsars with large spin-down luminosities. We reach within a factor of five of the canonical spin-down limit for all seven of these, whilst for the Crab and Vela pulsars we further surpass their spin-down limits. We present new or updated limits for 172 other pulsars (including both young and millisecond pulsars). Now that the detectors are undergoing major upgrades, and, for completeness, we bring together all of the most up-to-date results from all pulsars searched for during the operations of the first-generation LIGO, Virgo and GEO600 detectors. This gives a total of 195 pulsars including the most recent results described in this paper.United States National Science FoundationScience and Technology Facilities Council of the United KingdomMax-Planck-SocietyState of Niedersachsen/GermanyAustralian Research CouncilInternational Science Linkages program of the Commonwealth of AustraliaCouncil of Scientific and Industrial Research of IndiaIstituto Nazionale di Fisica Nucleare of ItalySpanish Ministerio de Economia y CompetitividadConselleria d'Economia Hisenda i Innovacio of the Govern de les Illes BalearsNetherlands Organisation for Scientific ResearchPolish Ministry of Science and Higher EducationFOCUS Programme of Foundation for Polish ScienceRoyal SocietyScottish Funding CouncilScottish Universities Physics AllianceNational Aeronautics and Space AdministrationOTKA of HungaryLyon Institute of Origins (LIO)National Research Foundation of KoreaIndustry CanadaProvince of Ontario through the Ministry of Economic Development and InnovationNational Science and Engineering Research Council CanadaCarnegie TrustLeverhulme TrustDavid and Lucile Packard FoundationResearch CorporationAlfred P. Sloan FoundationAstronom
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