scholarly journals Search for ultra-long gravitational waves in pulsars' rotational parameters

2009 ◽  
Vol 5 (H15) ◽  
pp. 231-231
Author(s):  
Maxim S. Pshirkov
Keyword(s):  
Time Series ◽  
Energy Density ◽  
Gravitational Waves ◽  
Low Frequency ◽  
Rotational Frequency ◽  
Second Derivative ◽  
Frequency Range ◽  
Residuals Analysis ◽  
Gravitational Wave Background ◽  
Derivatives Of

AbstractA method is suggested to explore the gravitational wave background (GWB) in the frequency range from 10−12 to 10−8 Hz. That method is based on the precise measurements of pulsars' rotational parameters: the influence of the gravitational waves (GW) in the range will affect them and therefore some conclusions about energy density of the GWB can be made using analysis of the derivatives of pulsars' rotational frequency. The calculated values of the second derivative from a number of pulsars limit the density of GWB Ωgw as follows: Ωgwh2 < 10−6. Also, the time series of the frequency ν of different pulsars in pulsar array can be cross-correlated pairwise in the same manner as in anomalous residuals analysis thus providing the possibility of GWB detection in ultra-low frequency range.

scholarly journals Constraints on ultra-low-frequency gravitational waves with statistics of pulsar spin-down rates

2019 ◽  
Vol 489 (3) ◽  
pp. 3547-3552
Author(s):  
Hiroki Kumamoto ◽  
Yuya Imasato ◽  
Naoyuki Yonemaru ◽  
Sachiko Kuroyanagi ◽  
Keitaro Takahashi
Keyword(s):  
Black Hole ◽  
Gravitational Waves ◽  
Time Derivative ◽  
Low Frequency ◽  
Upper Bounds ◽  
Galactic Centre ◽  
Frequency Range ◽  
Rate Distribution ◽  
Black Hole Binaries ◽  
Supermassive Black Hole

Abstract We probe ultra-low-frequency gravitational waves (GWs) with statistics of spin-down rates of millisecond pulsars (thereafter MSPs) by a method proposed in our previous work. The considered frequency range is 10−12 Hz ≲ fGW ≲ 10−10  Hz . The effect of such low-frequency GWs appears as a bias to spin-down rates that has a quadrupole pattern in the sky. We use the skewness of the spin-down rate distribution and the number of MSPs with negative spin-down rates to search for the bias induced by GWs. Applying this method to 149 MSPs selected from the ATNF pulsar catalogue, we derive upper bounds on the time derivative of the GW amplitudes of $\dot{h} \lt 6.2 \times 10^{-18}~{\rm s}^{-1}$ and $\dot{h} \lt 8.1 \times 10^{-18}~{\rm s}^{-1}$ in the directions of the Galactic Centre and M87, respectively. Approximating the GW amplitude as $\dot{h} \sim 2 \pi f_{\rm GW} h$, the bounds translate into h < 3 × 10−8 and h < 4 × 10−8, respectively, for fGW = 1/(1000 yr). Finally, we give the implications to possible supermassive black hole binaries at these sites.

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.

Analysis of Engine Vibration and Noise Induced by a Valve Train Element Combined With the Dynamic Behaviors

2016 ◽  
Vol 138 (9) ◽  
Author(s):  
Jie Guo ◽  
Yipeng Cao ◽  
Wenping Zhang ◽  
Xinyu Zhang
Keyword(s):  
Low Frequency ◽  
Rotational Frequency ◽  
Valve Train ◽  
Acoustic Model ◽  
Frequency Range ◽  
Combined Model ◽  
Engine Vibration ◽  
Vibration Responses ◽  
Combined Structure ◽  
Cam Profile

The engine vibration and noise induced by a valve train element are analyzed through the modeling and experiment method. The valve train dynamics are first studied to make clear the sources of the valve train noise. The component flexibility and inertia of mass are all taken into consideration as well as the contact or impact behaviors. The contact or impact forces are applied on the combined model of a combined structure. The resulting vibration responses at the outer surfaces are considered to be the boundary conditions of the acoustic model. The acoustic model is built by the boundary element method. The analysis results show that the noise induced by the valve train element is mainly in the 500–800 Hz 1/3 octave bands. The noise in this frequency range is related to not only the resonance of oil pan and valve cover but also the overall combined structure stiffness. And moreover, the resonance of the valve train element excited by the harmonic of the camshaft rotational frequency has heightened the noise radiation in this frequency range. The noise in the low-frequency range is determined by the exciting components of the cam profile, and that in the high-frequency range are produced mainly by the valve–seat impact and by the cam–tappet impact. The analysis results are proved well by comparison with the experimental results. Thus, the results are very useful for understanding the source characteristics of valve train noise.

scholarly journals Principles of Gravitational-Wave Detection with Pulsar Timing Arrays

Symmetry ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 2418
Author(s):  
Michele Maiorano ◽  
Francesco De Paolis ◽  
Achille A. Nucita
Keyword(s):  
Gravitational Wave ◽  
Gravitational Waves ◽  
Low Frequency ◽  
Black Hole Binaries ◽  
Pulsar Timing ◽  
Time Correlations ◽  
Array Detection ◽  
Square Kilometer Array ◽  
Gravitational Wave Background ◽  
Pulsar Timing Array

Pulsar timing uses the highly stable pulsar spin period to investigate many astrophysical topics. In particular, pulsar timing arrays make use of a set of extremely well-timed pulsars and their time correlations as a challenging detector of gravitational waves. It turns out that pulsar timing arrays are particularly sensitive to ultra-low-frequency gravitational waves, which makes them complementary to other gravitational-wave detectors. Here, we summarize the basics, focusing especially on supermassive black-hole binaries and cosmic strings, which have the potential to form a stochastic gravitational-wave background in the pulsar timing array detection band, and the scientific goals on this challenging topic. We also briefly outline the recent interesting results of the main pulsar timing array collaborations, which have found strong evidence of a common-spectrum process compatible with a stochastic gravitational-wave background and mention some new perspectives that are particularly interesting in view of the forthcoming radio observatories such as the Five hundred-meter Aperture Spherical Telescope, the MeerKAT telescope, and the Square Kilometer Array.

scholarly journals Solar gravity modes from ACRIM/SMM irradiance data

1988 ◽  
Vol 123 ◽  
pp. 83-86
Author(s):  
Claus Fröhlich
Keyword(s):  
Time Series ◽  
Solar Maximum ◽  
Power Spectra ◽  
Rotational Frequency ◽  
Weakly Interacting Massive Particles ◽  
Frequency Range ◽  
Solar Constant ◽  
Irradiance Data ◽  
Solar Gravity

Solar irradiance data from the ACRIM solar constant experiment on board the Solar Maximum Mission satellite (SMM) have been used to search for solar gravity modes. The power spectra of the time series of 270 days in 1980 and of 240 days in 1984 are analysed using a statistical method for the determination of the basic g-mode period separation To and the rotational frequency vR. In the view of the proposal of weakly interacting massive particles (WIMP) in the solar core and their impact on To the search has been extended down to 25 minutes. The results of the analysis of both time series in the frequency range from 10 to 40 μHz are best fitted by a To of 29.85 minutes. This is close to the expected value for the WIMP model. The angular velocity in the center of the Sun inferred from the rotational splitting of the g-modes amounts to 6.6·10−6 per sec, which is 2.3 times the photospheric rate.

Empirical and theoretical analysis of the extremely low frequency arterial blood pressure power spectrum in unanesthetized rat

2006 ◽  
Vol 291 (6) ◽  
pp. H2816-H2824 ◽  
Author(s):  
David R. Brown ◽  
Lisa A. Cassis ◽  
Dennis L. Silcox ◽  
Laura V. Brown ◽  
David C. Randall
Keyword(s):  
Blood Pressure ◽  
Time Series ◽  
Power Spectrum ◽  
Arterial Blood Pressure ◽  
Low Frequency ◽  
Absolute Difference ◽  
Frequency Range ◽  
Low Frequencies ◽  
Extremely Low Frequency ◽  
Arterial Blood

The slope of the log of power versus the log of frequency in the arterial blood pressure (BP) power spectrum is classically considered constant over the low-frequency range (i.e., “fractal” behavior), and is quantified by β in the relationship “1/ fβ.” In practice, the fractal range cannot extend to indefinitely low frequencies, but factor(s) that terminate this behavior, and determine β, are unclear. We present 1) data in rats ( n = 8) that reveal an extremely low frequency spectral region (0.083–1 cycle/h), where β approaches 0 (i.e., the “shoulder”); and 2) a model that 1) predicts realistic values of β within that range of the spectrum that conforms to fractal dynamics (∼1–60 cycles/h), 2) offers an explanation for the shoulder, and 3) predicts that the “successive difference” in mean BP (mBP) is an important parameter of circulatory function. We recorded BP for up to 16 days. The absolute difference between successive mBP samples at 0.1 Hz (the successive difference, or Δ) was 1.87 ± 0.21 mmHg (means ± SD). We calculated β for three frequency ranges: 1) 0.083–1; 2) 1–6; and 3) 6–60 cycles/h. The β for all three regions differed ( P < 0.01). For the two higher frequency ranges, β indicated a fractal relationship (β6–60/h = 1.27 ± 0.01; β1–6/h = 1.80 ± 0.16). Conversely, the slope of the lowest frequency region (i.e., the shoulder) was nearly flat (β0.083–1 /h = 0.32 ± 0.28). We simulated the BP time series as a random walk about 100 mmHg with ranges above and below of 10, 30, and 50 mmHg and with Δ from 0.5 to 2.5. The spectrum for the conditions mimicking actual BP time series (i.e., range, 85–115 mmHg; Δ, 2.00) resembled the observed spectra, with β in the lowest frequency range = 0.207 and fractal-like behavior in the two higher frequency ranges (β = 1.707 and 2.057). We suggest that the combined actions of mechanisms limiting the excursion of arterial BP produce the shoulder in the spectrum and that Δ contributes to determining β.

scholarly journals Suppression of the Primordial Gravitational Waves

2016 ◽  
Vol 43 ◽  
pp. 1660204 ◽  
Author(s):  
Gansukh Tumurtushaa ◽  
Seoktae Koh ◽  
Bum-Hoon Lee
Keyword(s):  
Phase Transition ◽  
Energy Spectrum ◽  
Gravitational Waves ◽  
Low Frequency ◽  
Frequency Range ◽  
Model Parameter ◽  
Evolution Of The Universe ◽  
Inflation Model ◽  
Primordial Gravitational Waves ◽  
The Universe

We study the primordial gravitational waves induced by space-space condensate inflation model. For modes that cross the comoving horizon during matter dominated era, we calculate the energy spectrum of gravitational waves. The energy spectrum of gravitational waves for our model has significantly suppressed in the low frequency range. The suppression occurs due to the phase transition during the early evolution of the Universe and depends on model parameter.

Two ranges in blood pressure power spectrum with different 1/f characteristics

1994 ◽  
Vol 267 (2) ◽  
pp. H449-H454 ◽  
Author(s):  
C. D. Wagner ◽  
P. B. Persson
Keyword(s):  
Blood Pressure ◽  
Time Series ◽  
Power Spectrum ◽  
Low Frequency ◽  
Frequency Range ◽  
F Region ◽  
Autonomic Blockade ◽  
Beta Receptor Blockade ◽  
The Difference ◽  
Fast Fourier Analysis

Most time series of biological systems contain a considerable amount of 1/f noise. This form of noise is characterized by fluctuations in which power steadily increases at lower frequencies. To determine the origin of 1/f noise, blood pressure (BP) was measured over 4 h in conscious foxhounds. The power spectrum of BP was obtained by fast Fourier analysis. After log-log transformation, the power spectrum (log power vs. log frequency) characteristically revealed a linear regression. Surprisingly, there were two 1/f ranges. The first 1/f region was located within a low-frequency range (< 10(-1.7) Hz; slope -0.9; r = -0.9). The second 1/f range was identified at 10(-1.4) to 10(-1) Hz (slope -1.2; r = -0.7). After baroreceptor denervation (n = 7), the steepness of both slopes increased significantly (P < 0.05 for lower 1/f range, P < 0.001 for higher 1/f range), and the difference in slopes was clearly greater (slope in lower range -1.2; r = 0.96 vs. -3.1, r = -0.92 in the higher range; P < 0.001). Neither alpha-receptor (n = 6) nor beta-receptor blockade (n = 4) considerably changed the slopes after denervation. However, autonomic blockade (n = 5) restored the slope in the low-frequency range (-0.9; r = -0.9). In conclusion, there are two independently modulated 1/f frequency ranges in BP time series. Baroreceptors especially attenuate 1/f noise in the higher frequency range.

PRELIMINARY TEST OF NEW ALGORITHM FOR SEARCHING GRAVITATIONAL-WAVE PERTURBATION IN EARTH CRUST NOISES

1995 ◽  
Vol 04 (01) ◽  
pp. 63-67 ◽  
Author(s):  
V.K. KRAVCHUK ◽  
A.V. GUSEV ◽  
V.N. RUDENKO
Keyword(s):  
Gravitational Wave ◽  
Low Frequency ◽  
Preliminary Test ◽  
Wave Perturbation ◽  
Frequency Range ◽  
Seismic Stations ◽  
Upper Limit ◽  
Optimal Filtration ◽  
Seismic Detection ◽  
Gravitational Wave Background

A new algorithm for optimal filtration of gravitational wave signals in Earth crust noises is described. Digital synchronous data recorded from two pairs of European seismic stations—Moxa (Germany)-Membach (Belgium) and Obninsk (Russia)-Moskva (Russia)—are used. New upper limit of gravitational wave background for a seismic detection of GW bursts in low-frequency range ν=(0.01–0.1) Hz is obtained.

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