Probing the string axiverse by gravitational waves from Cygnus X-1

H Yoshino,H Kodama

doi:10.1093/ptep/ptv067

Abstract

In the axiverse scenario, a massive scalar field (string axion) forms a cloud around a rotating black hole (BH) by superradiant instability and emits continuous gravitational waves (GWs). We examine constraints on the string axion parameters that can be obtained from GW observations. If no signal is detected in a targeted search for GWs from Cygnus X-1 in the LIGO data, the decay constant $f_a$ must be smaller than the GUT scale in the mass range $1.1\times 10^{-12}\mathrm{eV}<\mu<2.5\times 10^{-12}\mathrm{eV}$. Constraints from invisible isolated BHs are also discussed.

Highlights

The second-generation ground-based gravitational wave (GW) detectors will begin operations within a few years and provide us with a new eye to discover various new phenomena, which include those caused by fundamental fields in hidden sector
The expected constraints from Cygnus X-1 are shown in Fig. 2 for the LIGO and Advanced LIGO (aLIGO) detectors
A targeted search for continuous waves from Cygnus X-1 is required in order to detect the signal or derive the upper bound on the GW amplitude in the condition (10)

Summary

Introduction

The second-generation ground-based gravitational wave (GW) detectors will begin operations within a few years and provide us with a new eye to discover various new phenomena, which include those caused by fundamental fields in hidden sector. Promising candidates for such hidden sector objects are string axions with tiny masses [1,2,3]. The axion masses are naturally expected to be uniformly distributed in the logarithmic scale in the range −33 log10(μ[eV]) −10. When their Compton wavelengths are astrophysical scales, they may cause new astrophysical phenomena that can be observed by GWs

Objectives

Methods

Findings

Conclusion