800 research outputs found
Conjugate photoelectron impact ionization
Exchange of photoelectrons between magnetically conjugate parts of ionospher
Feasibility of Measuring the Shapiro Time Delay over Meter-Scale Distances
The time delay of light as it passes by a massive object, first calculated by Shapiro in 1964, is a hallmark of the curvature of space-time. To date, all measurements of the Shapiro time delay have been made over solar-system distance scales. We show that the new generation of kilometer-scale laser interferometers being constructed as gravitational wave detectors, in particular Advanced LIGO, will in principle be sensitive enough to measure variations in the Shapiro time delay produced by a suitably designed rotating object placed near the laser beam. We show that such an apparatus is feasible (though not easy) to construct, present an example design, and calculate the signal that would be detectable by Advanced LIGO. This offers the first opportunity to measure space-time curvature effects on a laboratory distance scale
Feasibility of measuring the Shapiro time delay over meter-scale distances
The time delay of light as it passes by a massive object, first calculated by
Shapiro in 1964, is a hallmark of the curvature of space-time. To date, all
measurements of the Shapiro time delay have been made over solar-system
distance scales. We show that the new generation of kilometer-scale laser
interferometers being constructed as gravitational wave detectors, in
particular Advanced LIGO, will in principle be sensitive enough to measure
variations in the Shapiro time delay produced by a suitably designed rotating
object placed near the laser beam. We show that such an apparatus is feasible
(though not easy) to construct, present an example design, and calculate the
signal that would be detectable by Advanced LIGO. This offers the first
opportunity to measure space-time curvature effects on a laboratory distance
scale.Comment: 13 pages, 6 figures; v3 has updated instrumental noise curves plus a
few text edits; resubmitted to Classical and Quantum Gravit
Searching for Gravitational Waves from Binary Inspirals with LIGO
We describe the current status of the search for gravitational waves from
inspiralling compact binary systems in LIGO data. We review the result from the
first scientific run of LIGO (S1). We present the goals of the search of data
taken in the second scientific run (S2) and describe the differences between
the methods used in S1 and S2.Comment: 9 pages, 2 figures. Published in proceedings of the 8th Gravitational
Wave Data Analysis Workshop, Milwaukee, WI, USA, 17-20 December 200
Reduced basis catalogs for gravitational wave templates
We introduce a reduced basis approach as a new paradigm for modeling,
representing and searching for gravitational waves. We construct waveform
catalogs for non-spinning compact binary coalescences, and we find that for
accuracies of 99% and 99.999% the method generates a factor of about
fewer templates than standard placement methods. The continuum of gravitational
waves can be represented by a finite and comparatively compact basis. The
method is robust under variations in the noise of detectors, implying that only
a single catalog needs to be generated.Comment: Minor changes in some of the phrasing to match the version as
published in PR
Prospects for joint radio telescope and gravitational wave searches for astrophysical transients
The radio skies remain mostly unobserved when it comes to transient
phenomena. The direct detection of gravitational waves will mark a major
milestone of modern astronomy, as an entirely new window will open on the
universe. Two apparently independent phenomena can be brought together in a
coincident effort that has the potential to boost both searches. In this paper
we will outline the scientific case that stands behind these future joint
observations and will describe the methods that might be used to conduct the
searches and analyze the data. The targeted sources are binary systems of
compact objects, known to be strong candidate sources for gravitational waves.
Detection of transients coincident in these two channels would be a significant
smoking gun for first direct detection of gravitational waves, and would open
up a new field for characterization of astrophysical transients involving
massive compact objects.Comment: 12 pages, Amaldi 8 Conference (New York, 2009) proceedings pape
LOOC UP: Locating and observing optical counterparts to gravitational wave bursts
Gravitational wave (GW) bursts (short duration signals) are expected to be
associated with highly energetic astrophysical processes. With such high
energies present, it is likely these astrophysical events will have signatures
in the EM spectrum as well as in gravitational radiation. We have initiated a
program, "Locating and Observing Optical Counterparts to Unmodeled Pulses in
Gravitational Waves" (LOOC UP) to promptly search for counterparts to GW burst
candidates. The proposed method analyzes near real-time data from the
LIGO-Virgo network, and then uses a telescope network to seek optical-transient
counterparts to candidate GW signals. We carried out a pilot study using
S5/VSR1 data from the LIGO-Virgo network to develop methods and software tools
for such a search. We will present the method, with an emphasis on the
potential for such a search to be carried out during the next science run of
LIGO and Virgo, expected to begin in 2009.Comment: 11 pages, 2 figures; v2) added acknowledgments, additional
references, and minor text changes v3) added 1 figure, additional references,
and minor text changes. v4) Updated references and acknowledgments. To be
published in the GWDAW 12 Conf. Proc. by Classical and Quantum Gravit
Methods for Reducing False Alarms in Searches for Compact Binary Coalescences in LIGO Data
The LIGO detectors are sensitive to a variety of noise transients of
non-astrophysical origin. Instrumental glitches and environmental disturbances
increase the false alarm rate in the searches for gravitational waves. Using
times already identified when the interferometers produced data of questionable
quality, or when the channels that monitor the interferometer indicated
non-stationarity, we have developed techniques to safely and effectively veto
false triggers from the compact binary coalescences (CBCs) search pipeline
Upper Limits on a Stochastic Background of Gravitational Waves
The Laser Interferometer Gravitational-Wave Observatory has performed a third science run with much improved sensitivities of all three interferometers. We present an analysis of approximately 200 hours of data acquired during this run, used to search for a stochastic background of gravitational radiation. We place upper bounds on the energy density stored as gravitational radiation for three different spectral power laws. For the flat spectrum, our limit of Ω_0<8.4×10^(-4) in the 69–156 Hz band is ~10^5 times lower than the previous result in this frequency range
Limits on Gravitational-Wave Emission from Selected Pulsars Using LIGO Data
We place direct upper limits on the amplitude of gravitational waves from 28 isolated radio pulsars by a coherent multidetector analysis of the data collected during the second science run of the LIGO interferometric detectors. These are the first direct upper limits for 26 of the 28 pulsars. We use coordinated radio observations for the first time to build radio-guided phase templates for the expected gravitational-wave signals. The unprecedented sensitivity of the detectors allows us to set strain upper limits as low as a few times 10^(-24). These strain limits translate into limits on the equatorial ellipticities of the pulsars, which are smaller than 10^(-5) for the four closest pulsars
- …