Observing gravitational-wave transient GW150914 with minimal assumptions (1602.03843v2)

Abstract: The gravitational-wave signal GW150914 was first identified on Sept 14 2015 by searches for short-duration gravitational-wave transients. These searches identify time-correlated transients in multiple detectors with minimal assumptions aboutthe signal morphology, allowing them to be sensitive to gravitational waves emitted by a wide range of sources including binary black-hole mergers. Over the observational period from September 12th to October 20th 2015, these transient searches were sensitive to binary black-hole mergers similar to GW150914 to an average distance of $\sim 600$ Mpc. In this paper, we describe the analyses that first detected GW150914 as well as the parameter estimation and waveform reconstruction techniques that initially identified GW150914 as the merger of two black holes. We find that the reconstructed waveform is consistent with the signal from a binary black-hole merger with a chirp mass of $\sim 30 \, M_\odot$ and a total mass before merger of $\sim 70 \, M_\odot$ in the detector frame.

Observing Gravitational-Wave Transient GW150914 with Minimal Assumptions

The paper examines the detection and analysis of the gravitational-wave signal GW150914, characterized by using minimal assumptions concerning the signal morphology. This approach enables detecting gravitational waves from diverse sources, notably binary black-hole mergers. The detection was achieved primarily through unmodelled searches that capitalize on time-correlated transients in multiple detectors. Such methodical detection ensures sensitivity to gravitational waves from a myriad of astrophysical sources over an observational period extending from September 12th to October 20th, 2015, reaching up to an average distance of approximately 600 megaparsecs (Mpc).

Analysis and Methodology

The research utilizes several analytical techniques to uncover GW150914, including coherent Waveburst (cWB), omicron-LALInference bursts, and BayesWave. These methodologies, though distinct in their operational principles, provide converging evidence on the nature of the gravitational-wave transient observed. The initial identification relies on coherent Waveburst, which rapidly ascertains the event, indicating a binary black-hole merger with a chirp mass around 30 solar masses and a total pre-merger mass approximating 70 solar masses in the detector frame.

Data Quality and Background Estimation

To ensure robust detection, the paper delineates the methods of maintaining data quality and estimating background noise levels. Time-shift methodologies were employed to estimate the false alarm rate by introducing artificial time delays between data from different detectors, effectively calculating coincident noise events arising from chance glitches. This comprehensive analysis using tremendous amounts of simulated background data achieves unparalleled precision in estimating the false alarm rate.

Gravitational-Wave Burst Searches

The paper elucidates a spectrum of burst search algorithms, targeting gravitational-wave signals without stringent assumptions regarding their origins, directions, or temporal characteristics. These searches operate both online (with swift feedback for electromagnetic follow-up) and offline, offering refined insights on gravitational-wave candidates. The coherence and wave characteristics are meticulously analyzed to segregate genuine signals from noise transients, strengthening detection confidence across varied parameter spaces.

Source Characterization

The analyses extend towards source characterization, offering estimates on sky position, waveform reconstruction, and mass parameters of the binary black holes implicated in the GW signal. Remarkably, the source characterization stretches further to include waveform reconstructions compared against numerical relativity simulations, ensuring consistency with general relativity expectations.

Conclusion and Implications

Through its methodological rigor, the paper establishes the newfound capability to detect and interpret gravitational-wave signals with minimal assumptions, opening avenues to explore a vast array of astrophysical phenomena, prominently binary black-hole mergers. The techniques demonstrated promise widespread application in future gravitational-wave astronomy ventures, facilitating multi-messenger observations and robust astrophysical source parameter estimations with high confidence. The practicability of these methods, as showcased, categorically draws us closer to understanding the multifaceted universe characterized by transient astrological phenomena.