The NANOGrav 12.5-year Data Set: Search for Non-Einsteinian Polarization Modes in the Gravitational-wave Background

Abstract We search NANOGrav’s 12.5 yr data set for evidence of a gravitational-wave background (GWB) with all the spatial correlations allowed by general metric theories of gravity. We find no substantial evidence in favor of the existence of such correlations in our data. We find that scalar-transverse (ST) correlations yield signal-to-noise ratios and Bayes factors that are higher than quadrupolar (tensor-transverse, TT) correlations. Specifically, we find ST correlations with a signal-to-noise ratio of 2.8 that are preferred over TT correlations (Hellings and Downs correlations) with Bayesian odds of about 20:1. However, the significance of ST correlations is reduced dramatically when we include modeling of the solar system ephemeris systematics and/or remove pulsar J0030+0451 entirely from consideration. Even taking the nominal signal-to-noise ratios at face value, analyses of simulated data sets show that such values are not extremely unlikely to be observed in cases where only the usual TT modes are present in the GWB. In the absence of a detection of any polarization mode of gravity, we place upper limits on their amplitudes for a spectral index of γ = 5 and a reference frequency of f yr = 1 yr−1. Among the upper limits for eight general families of metric theories of gravity, we find the values of A TT 95 % = ( 9.7 ± 0.4 ) × 10 − 16 and A ST 95 % = ( 1.4 ± 0.03 ) × 10 − 15 for the family of metric spacetime theories that contain both TT and ST modes.

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Measuring the eccentricity of binary black holes in GWTC-1 by using the inspiral-only waveform

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa1176 ◽

2020 ◽

Vol 495 (1) ◽

pp. 466-478 ◽

Cited By ~ 1

Author(s):

Shichao Wu ◽

Zhoujian Cao ◽

Zong-Hong Zhu

Keyword(s):

Black Holes ◽

Gravitational Wave ◽

Signal To Noise Ratio ◽

Credible Interval ◽

Reference Frequency ◽

Binary Black Holes ◽

Upper Limits ◽

Large Eccentricity ◽

Near Future

ABSTRACT In this article, we estimate the eccentricity of 10 binary black holes (BBHs) in the Gravitational-Wave Transient Catalog GWTC-1 by using the inspiral-only BBH waveform template EccentricFD. First, we test our method with simulated eccentric BBHs. Afterwards we apply the method to real BBH gravitational-wave data. We find that the BBHs in GWTC-1, with the exception of GW151226, GW170608 and GW170729, show very small eccentricity. Their upper limits on eccentricity range from 0.033–0.084 with 90 per cent credible interval at a reference frequency of 10 Hz. For GW151226, GW170608 and GW170729, the upper limits are higher than 0.1. The relatively large eccentricity of GW151226 and GW170729 is probably due to ignoring χeff and the low signal-to-noise ratio, and GW170608 is worthy of follow-up research. We also point out the limitations of the inspiral-only non-spinning waveform template in eccentricity measurement. Measurement of BBH eccentricity helps us to understand its formation mechanism. With an increase in the number of BBH gravitational-wave events and a more complete eccentric BBH waveform template, this will become a viable method in the near future.

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Geometric Approach to Analytic Marginalisation of the Likelihood Ratio for Continuous Gravitational Wave Searches

Universe ◽

10.3390/universe7060174 ◽

2021 ◽

Vol 7 (6) ◽

pp. 174

Author(s):

Karl Wette

Keyword(s):

Gravitational Wave ◽

Likelihood Ratio ◽

Signal To Noise Ratio ◽

Geometric Approach ◽

The Other ◽

Efficient Computation ◽

Likelihood Ratios ◽

Signal To Noise ◽

Noise Ratio ◽

Optimal Signal

The likelihood ratio for a continuous gravitational wave signal is viewed geometrically as a function of the orientation of two vectors; one representing the optimal signal-to-noise ratio, and the other representing the maximised likelihood ratio or F-statistic. Analytic marginalisation over the angle between the vectors yields a marginalised likelihood ratio, which is a function of the F-statistic. Further analytic marginalisation over the optimal signal-to-noise ratio is explored using different choices of prior. Monte-Carlo simulations show that the marginalised likelihood ratios had identical detection power to the F-statistic. This approach demonstrates a route to viewing the F-statistic in a Bayesian context, while retaining the advantages of its efficient computation.

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Multilag Correlation Estimators for Polarimetric Radar Measurements in the Presence of Noise

Journal of Atmospheric and Oceanic Technology ◽

10.1175/jtech-d-11-00010.1 ◽

2012 ◽

Vol 29 (6) ◽

pp. 772-795 ◽

Cited By ~ 24

Author(s):

Lei Lei ◽

Guifu Zhang ◽

Richard J. Doviak ◽

Robert Palmer ◽

Boon Leng Cheong ◽

...

Keyword(s):

Theoretical Analysis ◽

Data Quality ◽

Signal To Noise Ratio ◽

Simulated Data ◽

Radar Data ◽

Polarimetric Radar ◽

Signal To Noise ◽

Spectral Moments ◽

Radar Measurements

Abstract The quality of polarimetric radar data degrades as the signal-to-noise ratio (SNR) decreases. This substantially limits the usage of collected polarimetric radar data to high SNR regions. To improve data quality at low SNRs, multilag correlation estimators are introduced. The performance of the multilag estimators for spectral moments and polarimetric parameters is examined through a theoretical analysis and by the use of simulated data. The biases and standard deviations of the estimates are calculated and compared with those estimates obtained using the conventional method.

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A high signal-to-noise HST spectrum towards J1009+0713: precise absorption measurements in the CGM of two galaxies

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2108 ◽

2019 ◽

Vol 489 (1) ◽

pp. 78-98 ◽

Cited By ~ 2

Author(s):

Cassandra Lochhaas ◽

Smita Mathur ◽

Stephan Frank ◽

Debopam Som ◽

Yair Krongold ◽

...

Keyword(s):

Galactic Halo ◽

Hubble Space Telescope ◽

Signal To Noise Ratio ◽

Noise Spectrum ◽

High Signal ◽

Signal To Noise ◽

Additional Absorption ◽

Upper Limits ◽

Collisional Ionization ◽

Density Ratios

ABSTRACT High signal-to-noise spectra towards background quasars are crucial for uncovering weak absorption in the circumgalactic medium (CGM) of intervening galaxies, such as the diagnostic lines of N v that provide insight to the ionization process of warm gas but typically have low equivalent widths. We present a new spectrum from the Hubble Space Telescope with a signal-to-noise ratio of ∼20–35 towards the quasar SDSS J1009+0713 and analyse absorption systems in the CGM of two L⋆ galaxies close to the line of sight. We identify additional absorption in the CGM of these galaxies that was not reported by the previous lower signal-to-noise spectrum, as well as Milky Way absorbers and quasar outflows from J1009+0713. We measure log (NN v/NO vi) ∼ −1.1 for two CGM absorbers, inconsistent with gas in collisional ionization equilibrium and consistent with a radiatively cooling bulk flow of ∼50–150 km s−1, which could be produced by galactic winds. These column density ratios are also consistent with those found for other L⋆ galaxies and for some gas in the Milky Way’s halo. We place upper limits of log (NN v/NO vi) < −1.8 to −1.2 for other O vi absorbers in the same haloes, which suggests that O vi is produced by different processes in different parts of the CGM, even within the same galactic halo. Together with the kinematically different structure of high- and low-ionization lines, these results indicate there are many components to a single galaxy’s gaseous halo. We find the redshift number density of Ly α forest absorbers and broad Ly α absorbers are consistent with expectations at this redshift.

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Stochastic Gravitational Wave Background: Upper Limits in the 10−6to 10−3Hz Band

The Astrophysical Journal ◽

10.1086/379505 ◽

2003 ◽

Vol 599 (2) ◽

pp. 806-813 ◽

Cited By ~ 74

Author(s):

J. W. Armstrong ◽

L. Iess ◽

P. Tortora ◽

B. Bertotti

Keyword(s):

Gravitational Wave ◽

Upper Limits ◽

Gravitational Wave Background

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Using Spatial Correlations of SPDC Sources for Increasing the Signal to Noise Ratio in Images

Journal of Physics Conference Series ◽

10.1088/1742-6596/839/1/012025 ◽

2017 ◽

Vol 839 ◽

pp. 012025

Author(s):

A I Ruíz ◽

R Caudillo ◽

V M Velázquez ◽

E Barrios

Keyword(s):

Signal To Noise Ratio ◽

Spatial Correlations ◽

Signal To Noise ◽

Noise Ratio

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The Eccentric and Accelerating Stellar Binary Black Hole Mergers in Galactic Nuclei: Observing in Ground and Space Gravitational-wave Observatories

The Astrophysical Journal ◽

10.3847/1538-4357/ac2c07 ◽

2021 ◽

Vol 923 (2) ◽

pp. 139

Author(s):

Fupeng Zhang ◽

Xian Chen ◽

Lijing Shao ◽

Kohei Inayoshi

Keyword(s):

Black Hole ◽

Gravitational Wave ◽

Signal To Noise Ratio ◽

Galactic Nuclei ◽

Signal To Noise ◽

High Eccentricity ◽

Massive Black Hole ◽

Binary Black Holes ◽

Binary Black Hole ◽

Space Observatories

Abstract We study the stellar binary black holes (BBHs) inspiraling/merging in galactic nuclei based on our numerical method GNC. We find that 3%–40% of all newborn BBHs will finally merge due to various dynamical effects. In a five-year mission, up to 104, 105, and ∼100 of BBHs inspiraling/merging in galactic nuclei can be detected with signal-to-noise ration >8 in Advanced LIGO (aLIGO), Einstein/DECIGO, and TianQin/LISA/TaiJi, respectively. Roughly tens are detectable in both LISA/TaiJi/TianQin and aLIGO. These BBHs have two unique characteristics. (1) Significant eccentricities: 1%–3%, 2%–7%, or 30%–90% of them have e i > 0.1 when they enter into aLIGO, Einstein, or space observatories, respectively. Such high eccentricities provide a possible explanation for that of GW190521. Most highly eccentric BBHs are not detectable in LISA/Tianqin/TaiJi before entering into aLIGO/Einstein, as their strain becomes significant only at f GW ≳ 0.1 Hz. DECIGO becomes an ideal observatory to detect those events, as it can fully cover the rising phase. (2) Up to 2% of BBHs can inspiral/merge at distances ≲103 r SW from the massive black hole, with significant accelerations, such that the Doppler phase drift of ∼10–105 of them can be detected with signal-to-noise ratio >8 in space observatories. The energy density of the gravitational-wave backgrounds (GWBs) contributed by these BBHs deviates from the power-law slope of 2/3 at f GW ≲ 1 mHz. The high eccentricity, significant accelerations, and the different profile of the GWB of these sources make them distinguishable, and thus interesting for future gravitational-wave detections and tests of relativities.

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Improved deconvolution of very weak confocal signals

F1000Research ◽

10.12688/f1000research.11773.1 ◽

2017 ◽

Vol 6 ◽

pp. 787 ◽

Cited By ~ 6

Author(s):

Kasey J. Day ◽

Patrick J. La Rivière ◽

Talon Chandler ◽

Vytas P. Bindokas ◽

Nicola J. Ferrier ◽

...

Keyword(s):

Background Noise ◽

Signal To Noise Ratio ◽

Simulated Data ◽

Time Lapse ◽

Confocal Image ◽

Signal To Noise ◽

4D Imaging ◽

Fluorescence Images ◽

Gaussian Blur ◽

Imaging Conditions

Deconvolution is typically used to sharpen fluorescence images, but when the signal-to-noise ratio is low, the primary benefit is reduced noise and a smoother appearance of the fluorescent structures. 3D time-lapse (4D) confocal image sets can be improved by deconvolution. However, when the confocal signals are very weak, the popular Huygens deconvolution software erases fluorescent structures that are clearly visible in the raw data. We find that this problem can be avoided by prefiltering the optical sections with a Gaussian blur. Analysis of real and simulated data indicates that the Gaussian blur prefilter preserves meaningful signals while enabling removal of background noise. This approach is very simple, and it allows Huygens to be used with 4D imaging conditions that minimize photodamage.

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