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

TL;DR

This paper searches for continuous gravitational waves from an unidentified pulsar near HESS J1427-608 using a semi-coherent method with LIGO data, but finds no signals and sets upper limits on wave strain and neutron star properties.

Contribution

It introduces a semi-coherent search method combining the $ ext{F}$-statistic with a hidden Markov model for detecting wandering signals in gravitational wave data.

Findings

No gravitational wave signals detected from the target.

Upper limits on wave strain $h_0^{95\%}$ at $1.3\times 10^{-25}$ near 185 Hz.

Constraints on neutron star ellipticity and r-mode amplitude.

Abstract

We present a search for continuous gravitational wave signals from an unidentified pulsar potentially powering HESS~J1427-608, a spatially unresolved TeV point source detected by the High Energy Stereoscopic System (HESS). The search uses a semi-coherent algorithm, which combines the maximum likelihood $\mathcal{F}$~statistic with a hidden Markov model to efficiently detect and track quasi-monochromatic signals that wander randomly in frequency. It uses data from the second observing run of the Advanced Laser Interferometer Gravitational-Wave Observatory. Multi-wavelength 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 $h_0^{95\%}$ (for circularly polarized signals) at $95\%$ confidence level in sample sub-bands and interpolate it to estimate the sensitivity in the full band. We find $h_0^{95\%} = 1.3\times 10^{-25}$ near 185~Hz. The implied constraints on the ellipticity and \textit{r}-mode amplitude reach $\epsilon\leq 10^{-5}$ and $\alpha \leq 10^{-3}$ at 200~Hz, respectively.