Constraints from LIGO O3 data on gravitational-wave emission due to r-modes in the glitching pulsar PSR J0537-6910

TL;DR

This paper searches for gravitational waves from r-modes in the pulsar PSR J0537-6910 using LIGO O3 data, setting upper limits that challenge existing theoretical models and improve previous constraints.

Contribution

It provides the first direct search for r-mode gravitational waves in PSR J0537-6910 with LIGO O3 data and establishes more stringent upper limits on their amplitude.

Findings

No detection of r-mode signals in the 86-97 Hz band.

Upper limits improve previous bounds by up to a factor of 3.

Constraints challenge certain theoretical models of r-mode emission.

Abstract

We present a search for continuous gravitational-wave emission due to r-modes in the pulsar PSR J0537-6910 using data from the LIGO-Virgo Collaboration observing run O3. PSR J0537-6910 is a young energetic X-ray pulsar and is the most frequent glitcher known. The inter-glitch braking index of the pulsar suggests that gravitational-wave emission due to r-mode oscillations may play an important role in the spin evolution of this pulsar. Theoretical models confirm this possibility and predict emission at a level that can be probed by ground-based detectors. In order to explore this scenario, we search for r-mode emission in the epochs between glitches by using a contemporaneous timing ephemeris obtained from NICER data. We do not detect any signals in the theoretically expected band of 86-97 Hz, and report upper limits on the amplitude of the gravitational waves. Our results improve on previous amplitude upper limits from r-modes in J0537-6910 by a factor of up to 3 and place stringent constraints on theoretical models for r-mode driven spin-down in PSR J0537-6910, especially for higher frequencies at which our results reach below the spin-down limit defined by energy conservation.