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

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 $[10,2000]\text{ }\text{ }\mathrm{Hz}$ 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 $7.6\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}26}$ at $\ensuremath{\simeq}142\text{ }\text{ }\mathrm{Hz}$. 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.