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ANDREW D. JACKSON et al

ANDREW D. JACKSON et al On the time lags of the LIGO signals James Creswell, Sebastian von Hausegger, Andrew D. Jackson, Hao Liu, Pavel Naselsky (Submitted on 13 Jun 2017 (v1), last revised 9 Aug 2017 (this version, v2)) 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. Comments: Subjects: The body of the current version is essentially identical to the previous one submitted to arxiv and JCAP. In order to meet the various suggestions of the referees, we have included an extended and detailed Appendix. This Appendix also contains significant new results that provide additional support for our conclusions. This version of our manuscript has been accepted for publication by JCAP Instrumentation and Methods for Astrophysics (astro-ph.IM); General Relativity and Quantum Cosmology (gr-qc) DOI: 10.1088/1475-7516/2017/08/013 Cite as: arXiv:1706.04191 [astro-ph.IM] (or arXiv:1706.04191v2 [astro-ph.IM] for this version) 124

AKHILA RAMAN On the Signal Processing Operations in LIGO signals Akhila Raman (Submitted on 20 Nov 2017 (v1), last revised 21 Nov 2017 (this version, v2)) This article analyzes the data for the five gravitational wave (GW) events detected in Hanford(H1), Livingston(L1) and Virgo(V1) detectors by the LIGO collaboration. It is shown that GW170814, GW170817, GW151226 and GW170104 are very weak signals whose amplitude does not rise significantly during the GW event, and they are indistinguishable from nonstationary detector noise. LIGO software implements cross-correlation funcion(CCF) of H1/L1 signals with the template reference signal, in frequency domain, in a matched filter, using 32 second windows. It is shown that this matched filter misfires with high SNR/CCF peaks, even for very low-amplitude, short bursts of sine wave signals and additive white gaussian noise(AWGN), all the time. It is shown that this erratic behaviour of the matched filter, is due to the error in signal processing operations, such as lack of cyclic prefix necessary to account for circular convolution. It is also shown that normalized CCF method implemented in time domain using short windows, does not have false CCF peaks for sine wave and noise bursts. It is shown that the normalized CCF for GW151226 and GW170104, when correlating H1/L1 and template, is indistinguishable from correlating detector noise and the template. It is also shown that the normalized CCF for GW151226 and GW170104, when correlating H1/L1 and template, is indistinguishable from correlating H1/L1 and bogus chirp templates which are frequency modulated(FM) waveforms which differ significantly from ideal templates. Similar results are shown with LIGO matched filter, which misfires with high Signal to Noise Ratio (SNR) for bogus chirp templates. Comments: Subjects: Cite as: Corrected typographical errors, updated names, references and acknowledgement section Signal Processing (eess.SP); Instrumentation and Methods for Astrophysics (astro-ph.IM) arXiv:1711.07421 [eess.SP] (or arXiv:1711.07421v2 [eess.SP] for this version) 125

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