Search for continuous gravitational wave emission from the Milky Way center in O3 LIGO--Virgo data

TL;DR

This paper reports a search for continuous gravitational waves from neutron stars in the Galactic Center using LIGO-Virgo O3 data, setting new upper limits and constraining neutron star properties and hypothetical boson clouds.

Contribution

First directed search for CW signals from Galactic Center neutron stars using full O3 data, providing more stringent upper limits and astrophysical constraints.

Findings

No significant CW signals detected.

Deepest strain upper limit of about 7.6×10⁻²⁶ at 142 Hz.

Constraints on neutron star ellipticity, r-mode amplitude, and boson cloud parameters.

Abstract

We present a directed search for continuous gravitational wave (CW) signals emitted by spinning neutron stars located in the inner parsecs of the Galactic Center (GC). Compelling evidence for the presence of a numerous population of neutron stars has been reported in the literature, turning this region into a very interesting place to look for CWs. In this search, data from the full O3 LIGO--Virgo run in the detector frequency band $[10,2000]\rm~Hz$ have been used. No significant detection was found and 95$\%$ confidence level upper limits on the signal strain amplitude were computed, over the full search band, with the deepest limit of about $7.6\times 10^{-26}$ at $\simeq 142\rm~Hz$. These results are significantly more constraining than those reported in previous searches. We use these limits to put constraints on the fiducial neutron star ellipticity and r-mode amplitude. These limits can be also translated into constraints in the black hole mass -- boson mass plane for a hypothetical population of boson clouds around spinning black holes located in the GC.