Were recently reported MHz events planet mass primordial black hole mergers?

November 2021

Abstract

A bulk acoustic wave cavity as high frequency gravitational wave antenna has recently detected two rare events at $5.5$ MHz. Assuming that the detected events are due to gravitational waves, their characteristic strain amplitude lies at about $hc\approx 2.5 \times 10^{-16} $. W h i l e a c o s m o l o g i c a l s i g n a l i s o u t o f t h e p i c t u r e d u e t o t h e l a r g e e n e r g y c a r r i e d b y t h e h i g h f r e q u e n c y w a v e s, t h e s i g n a l c o u l d b e d u e t o t h e m e r g i n g o f t w o p l a n e t m a s s p r i m o r d i a l b l a c k h o l e s ($ \approx 4\times 10^{-4} M\odot $) i n s i d e t h e O o r t c l o u d a t r o u g h l y$ 0.025 $p c ($ 5300 $A U) a w a y . I n t h i s s h o r t n o t e, w e s h o w t h a t t h e p r o b a b i l i t y o f o n e s u c h e v e n t t o o c c u r w i t h i n t h i s v o l u m e p e r y e a r i s a r o u n d$ 1:10^{24} $, i f s u c h S a t u r n - l i k e m a s s p r i m o r d i a l b l a c k h o l e s a r e$ 1\%$ of the dark matter. Thus, the detected signal is very unlikely to be due the merger of planet mass primordial black holes. Nevertheless, the stochastic background of saturn mass primordial black holes binaries might be seen by next generation gravitational wave detectors, such as DECIGO and BBO.

Type

Journal article

Publication

Eur. Phys. J. C

Guillem Domènech

Researcher in gravity and cosmology

I am an Emmy Noether Research Group Leader at the Insitute for Theoretical Physics at the Leibniz University Hannover. My research focuses in various aspects of cosmology, gravity and particle physics.