3 years ago

A New Type of Extreme-mass-ratio Inspirals Produced by Tidal Capture of Binary Black Holes.

Xian Chen, Wen-Biao Han

Extreme-mass-ratio inspiral (EMRI) is an important gravitational-wave (GW) source and it normally consists of one stellar-mass black hole (BH) whirling closely around a supermassive black hole (SMBH). In this Letter, we demonstrate that the small body, in fact, could be a BH binary (BHB). Previous numerical scatting experiments have shown that SMBHs can tidally capture BHBs to bound orbits. Here we investigate the subsequent long-term evolution. We find that those BHBs with a semi-major axis of $a\lesssim5\times10^{-3}$ AU can be captured to tightly-bound orbits such that they will successfully inspiral towards the central SMBHs without being scattered away by stellar relaxation processes. We estimate that these binary-EMRIs (b-EMRIs) could constitute at most $10\%$ percent of the EMRI population. Moreover, we show that when the eccentricity of a b-EMRI drops to about $0.85$, the two stellar BHs will quickly merge due to the tidal perturbation by the SMBH. The high-frequency ($\sim10^2$ Hz) GWs generated during the coalescence coincide with the low-frequency ($\sim10^{-3}$ Hz) waves from the b-EMRI, making this system an ideal target for future multi-band GW observations.

Publisher URL: http://arxiv.org/abs/1801.05780

DOI: arXiv:1801.05780v2

You might also like
Discover & Discuss Important Research

Keeping up-to-date with research can feel impossible, with papers being published faster than you'll ever be able to read them. That's where Researcher comes in: we're simplifying discovery and making important discussions happen. With over 19,000 sources, including peer-reviewed journals, preprints, blogs, universities, podcasts and Live events across 10 research areas, you'll never miss what's important to you. It's like social media, but better. Oh, and we should mention - it's free.

  • Download from Google Play
  • Download from App Store
  • Download from AppInChina

Researcher displays publicly available abstracts and doesn’t host any full article content. If the content is open access, we will direct clicks from the abstracts to the publisher website and display the PDF copy on our platform. Clicks to view the full text will be directed to the publisher website, where only users with subscriptions or access through their institution are able to view the full article.