arXiv subjects

Sebastian von Hausegger

Publications and source records attributed to Sebastian von Hausegger.

25 records · Page 2Linked to original sources

arXiv2018

Degeneracy of gravitational waveforms in the context of GW150914

We study the degeneracy of theoretical gravitational waveforms for binary black hole mergers using an aligned-spin effective-one-body model. After appropriate truncation, bandpassing, and matching, we identify regions in the mass--spin parameter space containing waveforms similar to the template proposed for GW150914, with masses $m_1 = 36^{+5}_{-4} M_\odot$ and $m_2 = 29^{+4}_{-4} M_\odot$, using the cross-correlation coefficient as a measure of the similarity between waveforms. Remarkably high cross-correlations are found across broad regions of parameter space. The associated uncertanties exceed these from LIGO's Bayesian analysis considerably. We have shown that waveforms with greatly increased masses, such as $m_1 = 70 M_\odot$ and $m_2 = 35 M_\odot$, and strong anti-aligned spins ($χ_1=0.95$ and $χ_2=-0.95$) yield almost the same signal-to-noise ratio in the strain data for GW150914.

gr-qc↗

arXiv2018

A blind search for a common signal in gravitational wave detectors

We propose a blind, template-free method for the extraction of a common signal between the Hanford and Livingston detectors and apply it especially to the GW150914 event. We construct a log-likelihood method that maximizes the cross-correlation between each detector and the common signal and minimizes the cross-correlation between the residuals. The reliability of this method is tested using simulations with an injected common signal. Finally, our method is used to assess the quality of theoretical gravitational wave templates for GW150914.

astro-ph.IM↗

arXiv2017

On the time lags of the LIGO signals

To date, the LIGO collaboration has detected three gravitational wave (GW) events appearing in both its Hanford and Livingston detectors. In this article we reexamine the LIGO data with regard to correlations between the two detectors. With special focus on GW150914, we report correlations in the detector noise which, at the time of the event, happen to be maximized for the same time lag as that found for the event itself. Specifically, we analyze correlations in the calibration lines in the vicinity of 35\,Hz as well as the residual noise in the data after subtraction of the best-fit theoretical templates. The residual noise for the other two events, GW151226 and GW170104, exhibits similar behavior. A clear distinction between signal and noise therefore remains to be established in order to determine the contribution of gravitational waves to the detected signals.

astro-ph.IM↗

arXiv2017

Towards understanding the Planck thermal dust models

Understanding the properties of dust emission in the microwave domain is an important premise for the next generation of cosmic microwave background (CMB) experiments, devoted to the measurement of the primordial $B$-modes of polarization. In this paper, we compare three solutions to thermal dust emission by the Planck Collaboration \cite{PlanckDust03,planck_16,planck_com} to point out significant differences between their respective parameters (the spectral index $β$, the optical depth $τ$ and the dust temperature $T_d$). These differences originate from e.g. the priors on the parameters or the contribution of the Cosmic infrared background (CIB).

astro-ph.CO↗

arXiv2016

Footprints of Loop I on Cosmic Microwave Background Maps

Cosmology has made enormous progress through studies of the cosmic microwave background, however the subtle signals being now sought such as B-mode polarisation due to primordial gravitational waves are increasingly hard to disentangle from residual Galactic foregrounds in the derived CMB maps. We revisit our finding that on large angular scales there are traces of the nearby old supernova remnant Loop I in the WMAP 9-year map of the CMB and confirm this with the new SMICA map from the Planck satellite.

astro-ph.CO↗

arXiv2015

Skewness and Kurtosis as Indicators of Non-Gaussianity in Galactic Foreground Maps

Observational cosmology is entering an era in which high precision will be required in both measurement and data analysis. Accuracy, however, can only be achieved with a thorough understanding of potential sources of contamination from foreground effects. Our primary focus will be on non- Gaussian effects in foregrounds. This issue will be crucial for coming experiments to determine B-mode polarization. We propose a novel method for investigating a data set in terms of skewness and kurtosis in locally defined regions that collectively cover the entire sky. The method is demonstrated on two sky maps: (i) the SMICA map of Cosmic Microwave Background fluctuations provided by the Planck Collaboration and (ii) a version of the Haslam map at 408 MHz that describes synchrotron radiation. We find that skewness and kurtosis can be evaluated in combination to reveal local physical information. In the present case, we demonstrate that the local properties of both maps are predominantly Gaussian. This result was expected for the SMICA map; that it also applies for the Haslam map is surprising. The approach described here has a generality and flexibility that should make it useful in a variety of astrophysical and cosmological contexts.

astro-ph.CO↗

arXiv2015

The Morphology of the Anomalous Microwave Emission in the Planck 2015 data release

We calculate weighted mosaic correlations between the recently published Planck 2015 foreground maps - both anomalous microwave emission (AME) maps, free-free emission, synchrotron radiation and thermal dust emission. The weighting coefficients are constructed taking account of the signal-to-error ratio given by the data product. Positive correlation is found for AME compared with thermal dust emission as well as synchrotron radiation. We find AME and free-free emission tending to be anti-correlated, however, when investigating different scales, their relationship appears to be more complex. We argue that dust particles responsible for AME are pushed out of hot zones in the interstellar medium (ISM).

astro-ph.CO↗