Pulsar timing limits on very low frequency stochastic gravitational radiation

1996 ◽  
Vol 53 (6) ◽  
pp. 3468-3471 ◽  
Author(s):  
S. E. Thorsett ◽  
R. J. Dewey
Keyword(s):  
Gravitational Radiation ◽  
Low Frequency ◽  
Very Low Frequency ◽  
Pulsar Timing

scholarly journals PULSAR TIMING ARRAYS

2013 ◽  
Vol 22 (01) ◽  
pp. 1341008 ◽  
Author(s):  
BHAL CHANDRA JOSHI
Keyword(s):  
Gravitational Wave ◽  
Gravitational Waves ◽  
Low Frequency ◽  
Radio Pulsars ◽  
Very Low Frequency ◽  
Pulsar Timing ◽  
Gravitational Wave Background ◽  
Pulsar Timing Array ◽  
Current Operating

In the last decade, the use of an ensemble of radio pulsars to constrain the characteristic strain caused by a stochastic gravitational wave background has advanced the cause of detection of very low frequency gravitational waves (GWs) significantly. This electromagnetic means of GW detection, called Pulsar Timing Array (PTA), is reviewed in this paper. The principle of operation of PTA, the current operating PTAs and their status are presented along with a discussion of the main challenges in the detection of GWs using PTA.

scholarly journals Path length variations due to changes in tropospheric refraction

1979 ◽  
Vol 89 ◽  
pp. 157-162 ◽  
Author(s):  
Allen Joel Anderson
Keyword(s):  
Spectral Analysis ◽  
Gravitational Radiation ◽  
Path Length ◽  
Low Frequency ◽  
Length Variation ◽  
Deep Space ◽  
Very Low Frequency ◽  
Tropospheric Refraction ◽  
Detection Capabilities

An experiment is described in which microwave Doppler is used to determine very small changes in path length to spacecraft tracked by the Deep Space Tracking Network (DSN). The experiment was carried out to test the detection capabilities of the DSN system to gravitational radiation of very low frequency (10−2–10−4 Hz). In this work spectral analysis of Doppler variations were performed for periods over 4 hours and more.These results indicated that one of major sources of noise was due to rapid variations in tropospheric refraction. The results obtained a differential path length variation, ΔL/L, of 1 part in 1014 for periods between 100 and 1 000 seconds.Doppler spectra are shown and a general discussion of the experiment is given.

scholarly journals Pulsar Timing Limits on Very Low Frequency Stochastic Gravitational Radiation

1996 ◽  
Vol 160 ◽  
pp. 132
Author(s):  
Rachel J. Dewey ◽  
Stephen E. Thorsett
Keyword(s):  
Galaxy Formation ◽  
Gravitational Radiation ◽  
Low Frequency ◽  
Radiation Background ◽  
Arrival Times ◽  
Statistical Framework ◽  
Pulsar Timing ◽  
Orbital Decay ◽  
Timing Data ◽  
Gravitational Wave Background

AbstractA low-frequency, stochastic gravitational radiation background can be detected through the irregularities it induces in pulsar arrival times. In this poster we re-examine pulsar timing data presented in Kaspi, Taylor and Ryba (1994) [Ap.J.,428, p. 713] and present an optimal statistical framework for using timing data from a single pulsar to constrain the energy density in a gravitational wave background. Observations of PSRB1855+09 yield an upper limit (95% confidence) 1.0 × 10−8or (90% confidence) 4.8 × 10−9of the closure density at frequency 4.4 × 10−9Hz. This result probably rules out cosmological models that use cosmic strings as seeds for galaxy formation. Using combined observations of the orbital decay of four binary pulsars we also derive weaker limits at frequencies as low as 10−12Hz.

The Attenuation of Very Low Frequency Brain Oscillations in Transitions from a Rest State to Active Attention

2009 ◽  
Vol 23 (4) ◽  
pp. 191-198 ◽  
Author(s):  
Suzannah K. Helps ◽  
Samantha J. Broyd ◽  
Christopher J. James ◽  
Anke Karl ◽  
Edmund J. S. Sonuga-Barke
Keyword(s):  
Brain Activity ◽  
Sampling Rate ◽  
Low Frequency ◽  
Future Research ◽  
Adhd Symptoms ◽  
Default Mode ◽  
Very Low Frequency ◽  
Wide Range ◽  
Interference Hypothesis ◽  
Mode Interference

Background: The default mode interference hypothesis ( Sonuga-Barke & Castellanos, 2007 ) predicts (1) the attenuation of very low frequency oscillations (VLFO; e.g., .05 Hz) in brain activity within the default mode network during the transition from rest to task, and (2) that failures to attenuate in this way will lead to an increased likelihood of periodic attention lapses that are synchronized to the VLFO pattern. Here, we tested these predictions using DC-EEG recordings within and outside of a previously identified network of electrode locations hypothesized to reflect DMN activity (i.e., S3 network; Helps et al., 2008 ). Method: 24 young adults (mean age 22.3 years; 8 male), sampled to include a wide range of ADHD symptoms, took part in a study of rest to task transitions. Two conditions were compared: 5 min of rest (eyes open) and a 10-min simple 2-choice RT task with a relatively high sampling rate (ISI 1 s). DC-EEG was recorded during both conditions, and the low-frequency spectrum was decomposed and measures of the power within specific bands extracted. Results: Shift from rest to task led to an attenuation of VLFO activity within the S3 network which was inversely associated with ADHD symptoms. RT during task also showed a VLFO signature. During task there was a small but significant degree of synchronization between EEG and RT in the VLFO band. Attenuators showed a lower degree of synchrony than nonattenuators. Discussion: The results provide some initial EEG-based support for the default mode interference hypothesis and suggest that failure to attenuate VLFO in the S3 network is associated with higher synchrony between low-frequency brain activity and RT fluctuations during a simple RT task. Although significant, the effects were small and future research should employ tasks with a higher sampling rate to increase the possibility of extracting robust and stable signals.

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