Search for continuous gravitational waves from ten H.E.S.S. sources using a hidden Markov model

Abstract

Isolated neutron stars are prime targets for continuous−wave (CW) searches by ground−based gravitational−wave interferometers. Results are presented from a CW search targeting ten pulsars. The search uses a semi−coherent algorithm, which combines the maximum−likelihood F−statistic with a hidden Markov model (HMM) to efficiently detect and track quasi−monochromatic signals which wander randomly in frequency. The targets, which are associated with TeV sources detected by the High Energy Stereoscopic System (H.E.S.S.), are chosen to test for gravitational radiation from young, energetic pulsars with strong γ−ray emission, and take maximum advantage of the frequency tracking capabilities of HMM compared to other CW search algorithms. The search uses data from the second observing run of the Advanced Laser Interferometer Gravitational−Wave Observatory (aLIGO). It scans 1−Hz sub−bands around f * , 4f * /3, and 2f * , where f * denotes the star's rotation frequency, in order to accommodate a physically plausible frequency mismatch between the electromagnetic and gravitational−wave emission. The 24 sub−bands searched in this study return 5,256 candidates above the Gaussian threshold with a false alarm probability of 1% per sub−band per target. Only 12 candidates survive the three data quality vetoes which are applied to separate non−Gaussian artifacts from true astrophysical signals. CW searches using the data from subsequent observing runs will clarify the status of the remaining candidates.

Application of a hierarchical MCMC follow-up to Advanced LIGO continuous gravitational-wave candidates

“…We have introduced the first complete framework to analyze outliers from arbitrary CW searches using a multistage MCMC-based follow-up. After demonstrating its general behavior on Gaussian noise, we applied it to a set of 30 outliers obtained by different CW search pipelines on O2 Advanced LIGO data [64,[78][79][80][81].…”

“…Another implementation of the Viterbi pipeline, similar in scope and assumptions to that mentioned above, was used to perform a search on a set of ten pulsars observed by very high-energy γ-ray surveys in [81].…”

“…12. The original search [81] ascribed them to instrumental artifacts in the L1 detector. We confirm that to be the case for the outlier J1831-0952@19.9991 Hz: the loudest fully coherent F -statistic recovered by our follow-up is located at f 0 ≃ 20.0011 Hz, crossing a well-known instrumental comb at both LIGO detectors [110].…”

Searches for Continuous Gravitational Waves from Young Supernova Remnants in the Early Third Observing Run of Advanced LIGO and Virgo

“…The most likely sources of CWs detectable by ground-based interferometers are nonaxisymmetric, rapidly rotating neutron stars. Searches for CWs have been carried out targeting various isolated sources, including known pulsars with electromagnetic ephemerides (Abbott et al 2019c(Abbott et al , 2021b, neutron stars without ephemerides in the galactic center or in globular clusters (Aasi et al 2013;Abbott et al 2017;Dergachev et al 2019;Piccinni et al 2020), neutron stars in binary systems (Abbott et al 2019d;Middleton et al 2020;Zhang et al 2021), and young supernova remnants (SNRs; Aasi et al 2015b;Sun et al 2016;Ming et al 2019;Abbott et al 2019e;Lindblom & Owen 2020;Millhouse et al 2020;Papa et al 2020;Beniwal et al 2021). Searches have also been conducted over the whole sky for CWs instead of targeting at a particular direction (Abbott et al 2019f;Covas & Sintes 2020;Dergachev & Papa 2020;Abbott et al 2021c;Steltner et al 2021;Wette et al 2021).…”

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

“…Continuous gravitational waves are, at best, weak signals relative to the sensitivity of current-generation interferometric detectors [1][2][3]. Searches of data from the LIGO and Virgo observatories, most recently from their second [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] and third observing runs [21,22], have yet to make a first detection. Theoretical modelling of rapidly-rotating, non-axisymmetric neutron stars-the most likely source of continuous waves-predict a wide range of possible signal strengths [23][24][25][26][27][28][29][30].…”