A frequency resolved atlas of the sky in continuous gravitational waves

TL;DR

This paper introduces the first comprehensive sky atlas for continuous gravitational waves using LIGO O3a data, providing upper limits and analysis results across frequencies and sky positions, but finds no evidence of signals.

Contribution

It presents the first sky atlas of continuous gravitational waves with detailed upper limits, using an advanced pipeline and reanalysis to improve sensitivity over previous results.

Findings

Upper limits are 50% more constraining than previous results.

Neutron stars with ellipticity 1e-8 detectable up to 150 pc.

No signals detected in the reanalyzed top candidates.

Abstract

We present the first atlas of the continuous gravitational wave sky, produced using LIGO O3a public data. For each 0.045 Hz frequency band and every point on the sky the atlas provides gravitational wave amplitude upper limits, signal-to-noise ratios (SNR) and frequencies where the search measures the maximum SNR. The approximately top 1.5% of the atlas results are reanalyzed with a series of more sensitive searches with the purpose of finding high SNR long coherence signals from isolated neutron stars. However, these searches do not reveal the presence of such signals. The results presented in the atlas are produced with the Falcon pipeline and cover nearly monochromatic gravitational-wave signals in the 500-1000 Hz band, with up to +/- 5e-11 Hz/s frequency derivative. The Falcon pipeline computes loosely coherent power estimates to search data using a succession of coherence lengths. For this search we used 6 months of data, started with a 12 hour coherence length and progressed to 6 days. Compared to the most sensitive results previously published (also produced with the Falcon pipeline) our upper limits are 50% more constraining. Neutron stars with ellipticity of 1e-8 can be detected up to 150 pc away, while allowing for a large fraction of the stars' energy to be lost through non-gravitational channels. These results are within an order of magnitude of the _minimum_ neutron star ellipticity of 1e-9 suggested in [33].