Tidal Disruption Events by Relatively Compact Supermassive Black Hole Binaries (original) (raw)
Related papers
Tidal disruption events by compact supermassive black hole binaries
Monthly Notices of the Royal Astronomical Society
Stars can be tidally destroyed or swallowed by supermassive black hole binaries (SMBHBs). Using a large number of few-body simulations, we investigate the enhancement and suppression of full and partial disruption and direct capture events by hard SMBHBs with wide ranges of key parameters, i.e. the primary BH mass ($M_{\rm BH, 1}= 10^{5}{-}10^{8}\, {\rm M}_{\odot }$), the binary mass ratio (10−3–1), the ratio of the binary semimajor axis to the hardening radius (10−4–1), the binary eccentricity (0.0–0.9) and the stellar mass (0.3−3,rmModot)(0.3{-}3\, {\rm M}_{\odot})(0.3−3,rmModot). This is a significant extension of the parameter space compared to previous work. We show that the encounter probabilities of all three events are well-described by the encounter cross-section. The probability of full tidal disruption events (FTDEs) by SMBHBs can be enhanced by up to a factor of 40–50 or suppressed by up to a factor of 10, relative to that by single BHs, depending on the binary parameters. Relativistic effects can ...
Tidal disruption rate of stars by supermassive black holes obtained by direct N-body simulations
Monthly Notices of the Royal Astronomical Society, 2011
The disruption rate of stars by supermassive black holes (SMBHs) is calculated numerically with a modified version of Aarseth's NBODY6 code. Equal-mass systems without primordial binaries are treated. The initial stellar distribution around the SMBH follows a Sérsic n = 4 profile representing bulges of late type galaxies as well of early type galaxies without central light deficits, i.e. without cores. In order to infer relaxation driven effects and to increase the statistical significance, a very large set of N-body integrations with different particle numbers N, ranging from 10 3 to 0.5 · 10 6 particles, is performed. Three different black hole capture radii are taken into account, enabling us to scale these results to a broad range of astrophysical systems with relaxation times shorter than one Hubble time, i.e. for SMBHs up to M • ≈ 10 7 M ⊙ . The computed number of disrupted stars are driven by diffusion in angular momentum space into the loss cone of the black hole and the rate scales with the total number of particles as dN dt ∝ N b , where b is as large as 0.83. This is significantly steeper than the expected scaling dN dt ∝ ln(N ) derived from simplest energy relaxation arguments. Only a relatively modest dependence of the tidal disruption rate on the mass of the SMBH is found and we discuss our results in the context of the M • − σ relation. The number of disrupted stars contribute a significant part to the mass growth of black holes in the lower mass range as long as a significant part of the stellar mass becomes swallowed by the SMBH. This also bears direct consequences for the search and existence of IMBHs in globular clusters. For SMBHs similar to the galactic center black hole Sgr A ⋆ , a tidal disruption rate of 55 ± 27 events per Myr is deduced. Finally relaxation driven stellar feeding can not account for the masses of massive black holes M • ≥ 10 7 M ⊙ in complete agreement with conventional gas accretion and feedback models.
The Astrophysical Journal, 2017
Supermassive black hole binaries (SMBHBs) are productions of the hierarchical galaxy formation model. There are many close connections between central SMBH and its host galaxy because the former plays very important roles on the formation and evolution of a galaxy. For this reason, the evolution of SMBHBs in merging galaxies is an essential problem. Since there are many discussions about SMBHB evolution in gas rich environment, we focus on the quiescent galaxy, using tidal disruption as a diagnostic tool. Our study is based on a series of numerical large particle number direct N-body simulations for dry major mergers. According to the simulation results, the evolution can be divided into three phases. In phase I, the tidal disruption rate for two well separated SMBHs in merging system has similar level to single SMBH in isolate galaxy. After two SMBHs getting close enough to form a bound binary in phase II, the disruption rate can be enhanced for ∼ 2 order of magnitudes within a short time. This "boosted" disruption stage finishes after the SMBHB evolving to compact binary system in phase III, corresponding to a drop back of disruption rate to a level of a few times higher than that in Phase I. How to correctly extrapolate our N-body simulation results to reality, and implications of our results to observations, are discussed too.
Tidal Disruption of a Main-sequence Star by an Intermediate-mass Black Hole: A Bright Decade
The Astrophysical Journal, 2018
There has been suggestive evidence of intermediate-mass black holes (IMBHs; 10 3−5 M e) existing in some globular clusters (GCs) and dwarf galaxies, but IMBHs as a population remain elusive. As a main-sequence star passes too close by an IMBH it might be tidally captured and disrupted. We study the long-term accretion and observational consequence of such tidal disruption events. The disruption radius is hundreds to thousands of the BH's Schwarzschild radius, so the circularization of the falling-back debris stream is very inefficient due to weak general relativity effects. Due to this and a high mass fallback rate, the bound debris initially goes through a ∼10 yr long super-Eddington accretion phase. The photospheric emission of the outflow ejected during this phase dominates the observable radiation and peaks in the UV/optical bands with a luminosity of 10 erg s 42 1-. After the accretion rate drops below the Eddington rate, the bolometric luminosity follows the conventional t −5/3 powerlaw decay, and X-rays from the inner accretion disk start to be seen. Modeling the newly reported IMBH tidal disruption event candidate 3XMM J2150-0551, we find a general consistency between the data and predictions. The search for these luminous, long-term events in GCs and nearby dwarf galaxies could unveil the IMBH population.
Tidal disruption of asteroids by supermassive black holes
EPJ Web of Conferences, 2012
The compact radio source Sgr A * at the centre of our Galaxy harbours a super-massive black hole, and is therefore the nearest laboratory for testing the super-massive black hole astrophysics and environment. Since it is not an active galactic nucleus, it also offers the possibility of observing the capture of low-mass objects, such as comets or asteroids, that may orbit the central black hole. In this paper we discuss conditions for tidal disruption of low-mass objects and predictions of the appearance and light curve of such events, as well as their relevance for the X-ray and infra-red flares detected in Sgr A *. The modelled light curves of such tidal disruption events bear marks of the strong gravitational field: tidal squeezing and elongation of the object, gravitational lensing, aberration of light, and Doppler effects. Finally, we show that this model is able to reproduce and fit X-ray flares.
Tidal disruptions of separated binaries in galactic nuclei
Arxiv preprint arXiv: …, 2011
Several galaxies have exhibited X-ray flares that are consistent with the tidal disruption of a star by a central supermassive black hole. In theoretical treatments of this process it is usually assumed that the star was initially on a nearly parabolic orbit relative to the black hole. Such an assumption leads in the simplest approximation to a t −5/3 decay of the bolometric luminosity and this is indeed consistent with the relatively poorly sampled light curves of such flares. We point out that there is another regime in which the decay would be different: if a binary is tidally separated and the star that remains close to the hole is eventually tidally disrupted from a moderate eccentricity orbit, the decay is slower, typically ∼ t −1.2 . As a result, careful sampling of the light curves of such flares could distinguish between these processes and yield insight into the dynamics of binaries as well as single stars in galactic centres. We explore this process using three-body simulations and analytic treatments and discuss the consequences for present-day X-ray detections and future gravitational wave observations.
2022
In the cores of dense stellar clusters, close gravitational encounters between binary and single stars can frequently occur. Using the code, we computed the outcome of a large number of binary-single interactions involving two black holes (BHs) and a star to check how the inclusion of orbital energy losses due to tidal dissipation can change the outcome of these chaotic interactions. Each interaction was first simulated without any dissipative processes and then we systematically added orbital energy losses due to gravitational wave emission (using post-Newtonian (PN) corrections) and dynamical tides and recomputed the interactions. We find that the inclusion of tides increases the number of BH-star mergers by up to 75 per cent but it does not affect the number of BH-BH mergers. These results highlight the importance of including orbital energy dissipation due to dynamical tides during few-body encounters and evolution of close binary systems within stellar cluster simulations. Consistent with previous studies, we find that the inclusion of PN terms increases the number of BH-BH mergers during binary-single encounters. However, BH-star mergers are largely unaffected by the inclusion of these terms.
The Astrophysical Journal, 2012
We present numerical relativity results of tidal disruptions of white dwarfs from ultra-close encounters with a spinning, intermediate mass black hole. These encounters require a full general relativistic treatment of gravity. We show that the disruption process and prompt accretion of the debris strongly depend on the magnitude and orientation of the black hole spin. However, the late-time accretion onto the black hole follows the same decay,Ṁ ∝ t −5/3 , estimated from Newtonian gravity disruption studies. We compute the spectrum of the disk formed from the fallback material using a slim disk model. The disk spectrum peaks in the soft X-rays and sustains Eddington luminosity for 1 − 3 yrs after the disruption. For arbitrary black hole spin orientations, the disrupted material is scattered away from the orbital plane by relativistic frame dragging, which often leads to obscuration of the inner fallback disk by the outflowing debris. The disruption events also yield bursts of gravitational radiation with characteristic frequencies of ∼ 3.2 Hz and strain amplitudes of ∼ 10 −18 for galactic intermediate mass black holes. The optimistic rate of considered ultra-close disruptions is consistent with no sources found in ROSAT all-sky survey. The future missions like Wide-Field X-ray Telescope (WFXT) could observe dozens of events.
Intermediate-mass Black Holes’ Effects on Compact Object Binaries
The Astrophysical Journal
Although their existence is not yet confirmed observationally, intermediate mass black holes (IMBHs) may play a key role in the dynamics of galactic nuclei. In this paper, we neglect the effect the nuclear star cluster itself and investigate only how a small reservoir of IMBHs influences the secular dynamics of stellar-mass black hole binaries, using N-body simulations. We show that our simplifications are valid and that the IMBHs significantly enhance binary evaporation by pushing the binaries into the Hill-unstable region of parameter space, where they are separated by the SMBH's tidal field. For binaries in the S-cluster region of the Milky Way, IMBHs drive the binaries to merge in up to 1-6% of cases, assuming five IMBHs within 5 pc of mass 10 4 M each. Observations of binaries in the Galactic center may strongly constrain the population of IMBHs therein.
Tidal disruption of white dwarfs by intermediate mass black holes
EPJ Web of Conferences, 2012
Modeling ultra-close encounters between a white dwarf and a spinning, intermediate mass black hole requires a full general relativistic treatment of gravity. This paper summarizes results from such a study. Our results show that the disruption process and prompt accretion of the debris strongly depend on the magnitude and orientation of the black hole spin. On the other hand, the late-time accretion onto the black hole follows the same decay,Ṁ ∝ t −5/3 , estimated from Newtonian gravity disruption studies. The spectrum of the fallback material peaks in the soft X-rays and sustains Eddington luminosity for 1-3 yrs after the disruption. The orientation of the black hole spin has also a profound effect on how the outflowing debris obscures the central region. The disruption produces a burst of gravitational radiation with characteristic frequencies of ∼3.2 Hz and strain amplitudes of ∼10 −18 for galactic intermediate mass black holes.