Search for gravitational waves from a long-lived remnant of the binary neutron star merger GW170817

TL;DR

This study searches for long-duration gravitational waves from a neutron star remnant after GW170817, finding no signals but establishing sensitivity limits and providing a framework for future, more sensitive searches.

Contribution

It extends previous searches by focusing on longer signal durations up to 8.5 days and compares multiple algorithms for detecting post-merger gravitational waves.

Findings

No significant post-merger signals detected.

Sensitivity limited to within 1 Mpc with current detectors.

Framework established for future higher-sensitivity searches.

Abstract

One unanswered question about the binary neutron star coalescence GW170817 is the nature of its post-merger remnant. A previous search for post-merger gravitational waves targeted high-frequency signals from a possible neutron star remnant with a maximum signal duration of 500 s. Here we revisit the neutron star remnant scenario with a focus on longer signal durations up until the end of the Second Advanced LIGO-Virgo Observing run, 8.5 days after the coalescence of GW170817. The main physical scenario for such emission is the power-law spindown of a massive magnetar-like remnant. We use four independent search algorithms with varying degrees of restrictiveness on the signal waveformand different ways of dealing with noise artefacts. In agreement with theoretical estimates, we find no significant signal candidates. Through simulated signals, we quantify that with the current detector sensitivity, nowhere in the studied parameter space are we sensitive to a signal from more than 1 Mpc away, compared to the actual distance of 40 Mpc. This study however serves as a prototype for post-merger analyses in future observing runs with expected higher sensitivity.