Directed search for continuous gravitational-wave signals from the Galactic Center in the Advanced LIGO second observing run

TL;DR

This study conducted a sensitive directed search for continuous gravitational waves from isolated neutron stars near the Galactic Center using LIGO O2 data, setting upper limits but detecting no signals.

Contribution

First LIGO O2 directed search for continuous gravitational waves from the Galactic Center, utilizing a semi-coherent pipeline and FrequencyHough transform for robustness.

Findings

No continuous gravitational wave signals detected.

Set the most stringent upper limits to date on gravitational wave amplitude from this region.

Achieved a sensitivity of approximately 1.4 x 10^{-25} at 160 Hz.

Abstract

In this work we present the results of a search for continuous gravitational waves from the Galactic Center using LIGO O2 data. The search uses the Band-Sampled-Data directed search pipeline, which performs a semi-coherent wide-parameter-space search, exploiting the robustness of the FrequencyHough transform algorithm. The search targets signals emitted by isolated asymmetric spinning neutron stars, located within 25-150 parsecs from the Galactic Center. The frequencies covered in this search range between 10 and 710 Hz with a spin-down range from $-1.8\times10^{-9}$ to $3.7\times10^{-11}$ Hz/s. No continuous wave signal has been detected and upper limits on the gravitational wave amplitude are presented. The most stringent upper limit at $95\%$ confidence level, for the Livingston detector, is $\sim 1.4 \times 10^{-25}$ at frequencies near 160 Hz. To date, this is the most sensitive directed search for continuous gravitational-wave signals from the Galactic Center and the first search of this kind using the LIGO second observing run.