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A self-lensing binary massive black hole interpretation of quasi-periodic eruptions

Abstract:
Binary supermassive black hole (SMBH) systems result from galaxy mergers, and will eventually coalesce due to gravitational wave (GW) emission if the binary separation can be reduced to . 0.1 pc by other mechanisms. Here, we explore a gravitational self-lensing binary SMBH model for the sharp (duration ⇠ 1 hr), quasi-regular X-ray flares – dubbed quasiperiodic eruptions – recently observed from two low mass active galactic nuclei: GSN 069 and RX J1301.9+2747. In our model, the binary is observed ⇠edge-on, such that each SMBH gravitationally lenses light from the accretion disc surrounding the other SMBH twice per orbital period. The model can reproduce the flare spacings if the current eccentricity of RX J1301.9+2747 is n0 & 0.16, implying a merger within ⇠ 1000 yrs. However, we cannot reproduce the observed flare profiles with our current calculations. Model flares with the correct amplitude are ⇠ 2/5 the observed duration, and model flares with the correct duration are ⇠ 2/5 the observed amplitude. Our modelling yields three distinct behaviours of self-lensing binary systems that can be searched for in current and future X-ray and optical time-domain surveys: i) periodic lensing flares, ii) partial eclipses (caused by occultation of the background mini-disc by the foreground mini-disc), and iii) partial eclipses with a very sharp in-eclipse lensing flare. Discovery of such features would constitute very strong evidence for the presence of a supermassive binary, and monitoring of the flare spacings will provide a measurement of periastron precession.
Publication status:
Published
Peer review status:
Peer reviewed

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Publisher copy:
10.1093/mnras/stab609

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More by this author
Institution:
University of Oxford
Department:
PHYSICS
Sub department:
Astrophysics
Role:
Author
More by this author
Institution:
University of Oxford
Division:
MPLS
Department:
Physics
Sub department:
Astrophysics
Role:
Author
ORCID:
0000-0002-6154-5843
More by this author
Institution:
University of Oxford
Division:
MPLS
Department:
Physics
Sub department:
Astrophysics
Role:
Author
More by this author
Institution:
University of Oxford
Division:
MPLS
Department:
Physics
Sub department:
Astrophysics
Role:
Author
ORCID:
0000-0002-1434-9786


Publisher:
Oxford University Press
Journal:
Monthly Notices of the Royal Astronomical Society More from this journal
Volume:
503
Issue:
2
Pages:
1703–1716
Publication date:
2021-03-03
Acceptance date:
2021-02-26
DOI:
EISSN:
1365-2966
ISSN:
0035-8711


Language:
English
Keywords:
Pubs id:
1164147
Local pid:
pubs:1164147
Deposit date:
2021-03-01

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