• DOI:10.1093/mnras/stt1787
• Corpus ID: 119258211

Accretion into the central cavity of a circumbinary disc

@article{DOrazio2013AccretionIT,
  title={Accretion into the central cavity of a circumbinary disc},
  author={Daniel J. D’Orazio and Zolt{\'a}n Haiman and Andrew MacFadyen},
  journal={Monthly Notices of the Royal Astronomical Society},
  year={2013},
  volume={436},
  pages={2997-3020}
}

• D. D’Orazio, Z. Haiman, A. MacFadyen
• Published 1 October 2012
• Physics
• Monthly Notices of the Royal Astronomical Society

A near-equal mass binary black hole can clear a central cavity in a circumbinary accretion disk; however, previous works have revealed accretion streams entering this cavity. Here we use 2D hydrodynamical simulations to study the accretion streams and their periodic behavior. In particular, we perform a suite of simulations, covering different binary mass ratios $q=M_2/M_1$ in the range $0.01 \leq q \leq 1$. In each case, we follow the system for several thousand binary orbits, until it relaxes to a stable accretion pattern. We find the following results: (i) while the binary is efficient in maintaining a low-density cavity, the time-averaged mass accretion rate into the cavity, through narrow coherent accretion streams, is suppressed by at most a factor of $\sim 5$, compared to a disk with a single BH with the same mass; (ii) the largest suppression occurs for $q\approx 0.05$; binaries whose mass ratios are either lower or higher both suppress accretion less significantly; (iii) for $q \gtrsim 0.05$, the accretion rate is strongly modulated by the binary, and depending on the precise value of $q$, the power spectrum of the accretion rate shows either one, two, or three distinct periods; and (v) for $q \lesssim 0.05$, the accretion rate becomes steady, with no time-variations. Most binaries produced in galactic mergers are expected to have $q\gtrsim 0.05$. If the luminosity of these binaries tracks their accretion rate, then a periodogram of their light-curve could help in their identification, and to constrain their mass ratio and disk properties.