Search for continuous gravitational waves from HESS J1427-608 with a hidden Markov model

Abstract

We present a search for continuous gravitational-wave signals from an unidentified pulsar potentially poweringHESS J1427-608, a spatially unresolvedTeVpoint source detected by the HighEnergy Stereoscopic System (HESS). The search uses a semicoherent algorithm, which combines the maximum likelihood F statistic with a hidden Markov model to efficiently detect and track quasimonochromatic signals that wander randomly in frequency. It uses data from the second observing run of the Advanced Laser Interferometer Gravitational-Wave Observatory. Multiwavelength observations of the HESS source are combined with the proprieties of the population of TeV-bright pulsar wind nebulae to constrain the search parameters.We find no evidence of gravitational-wave emission from this target.We set upper limits on the characteristic wave strain h95% 0 (for circularly polarized signals) at95%confidence level in sample subbands and interpolate it to estimate the sensitivity in the full band. We find h95% 0 ¼ 1.3 × 10−25 near 185 Hz. The implied constraints on the ellipticity and r-mode amplitude reach ϵ ≤ 10−5 and α ≤ 10−3 at 200 Hz, respectively.