Two regimes of tidal-stream circularization by supermassive black holes

Rossi, Joseph; Servin, Juan; Kesden, Michael

doi:10.1103/physrevd.104.103019

Cited by 6 publications

(3 citation statements)

References 35 publications

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“…A similar conclusion is also reached by Bogdanović et al (2014) in the case of the pTDE of a red giant envelope (which is likely relevant for GSN 069), showing that the luminosity due to circularisation can exceed the fallback luminosity at early times. Precursor X-ray flares are also found in kinematic simulations by Rossi et al (2021) if the circularisation timescale is significantly shorter than the characteristic fallback timescale at which the accretion phase peaks.…”

Section: The Precursor X-ray Flarementioning

confidence: 96%

Repeating tidal disruptions in GSN 069: Long-term evolution and constraints on quasi-periodic eruptions’ models

Miniutti¹,

Giustini²,

Arcodia³

et al. 2023

A&A

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Context. GSN 069 is the first galactic nucleus where quasi-periodic eruptions (QPEs) have been identified in December 2018. These are high-amplitude, soft X-ray bursts recurring every ∼ 9 hr, lasting ∼ 1 hr, and during which the X-ray count rate increases by up to two orders of magnitude with respect to an otherwise stable quiescent level. The X-ray spectral properties and the long-term evolution of GSN 069 in the first few years since its first X-ray detection in 2010 are consistent with a long-lived tidal disruption event (TDE). Aims. We aim to derive the properties of QPEs and of the long-term X-ray evolution in GSN 069 over the past 12 yr. Methods. We analyse timing and spectral X-ray data from 11 XMM-Newton, one Chandra, and 34 Swift observations of GSN 069 on timescales ranging from minutes to years. Results. QPEs in GSN 069 are a transient phenomenon with a lifetime of 1.05 yr. The QPE intensity and recurrence time oscillate and allow for alternating strong-weak QPEs and long-short recurrence times to be defined. In observations with QPEs, the quiescent level exhibits a quasi-periodic oscillation with a period equal to the average separation between consecutive QPEs. The QPE spectral evolution is consistent with thermal emission from a very compact region that heats up quickly and subsequently cools down via X-ray emission while expanding by a factor of ∼ 3 in radius. The long-term evolution of the quiescent level is characterised by two repeating TDEs ∼ 9 yr apart. We detect a precursor X-ray flare prior to the second TDE that may be associated with the circularisation phase during disc formation. A similar precursor flare is tentatively detected just before the first TDE. Conclusions. We provide a comprehensive summary of observational results that can be used to inform further theoretical and numerical studies on the origin of QPEs in GSN 069 and we discuss our results in terms of currently proposed QPE models. Future X-ray observations of GSN 069 promise that the QPE origin and the relation between QPEs and repeating TDEs in this galactic nucleus will be constrained, with consequences for the other sources where QPEs have been identified.

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Section: The Precursor X-ray Flarementioning

confidence: 96%

Repeating tidal disruptions in GSN 069: Long-term evolution and constraints on quasi-periodic eruptions’ models

Miniutti¹,

Giustini²,

Arcodia³

et al. 2023

A&A

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“…We assume that 'circularization' of fallback debris is efficient. However, the efficiency of 'circularization' of the fallback debris is still under debate (Kochanek (1994);Hayasaki et al (2016); Bonnerot et al (2016); Bonnerot et al (2017); ; Rossi et al (2021)). For less bound or less circularized gas, the mechanical energy (gravitational energy plus kinetic energy) is higher than that of well-circularized Keplerian flow.…”

Section: Summary and Discussionmentioning

confidence: 99%

Radiative hydrodynamical simulations of super-Eddington accretion flow in tidal disruption event: the origin of optical/UV emission

Qiao

Yang

et al. 2022

Monthly Notices of the Royal Astronomical Society

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One of the most prominent problems of optical/ultraviolet (UV) tidal disruption events (TDEs) is the origin of their optical/UV emission. It has been proposed that the soft X-rays produced by the stellar debris accretion disk can be reprocessed into optical/UV photons by a surrounding optically thick envelope or outflow. However, there is still no detailed models for this mechanism. In this paper, by performing hydrodynamic simulations with radiative transfer, we calculate the optical/UV emission of the circularized stellar debris accretion flow/outflow system. We find that the optical/UV photons can be generated by reprocessing the emission of the accretion flow in the optically thick outflows. The model can well interpret the observed emission properties of optical/UV TDEs, including the emission radius, the radiation temperature and the blackbody luminosity, as well as the evolution of these quantities with time, providing a strong theoretical basis for understanding the origin of optical/UV TDEs.

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“…Previous studies of the stream self-intersection process have relied on post-Newtonian approximations (e.g. Dai et al 2015;Rossi et al 2021;Wong et al 2021), or resorted to numerical evaluation of the geodesic equations to determine the stream properties at self-intersection while retaining a fully relativistic treatment (e.g. Batra et al 2021).…”

Section: Introductionmentioning

confidence: 99%

An Analytic, Fully Relativistic Framework for Tidal Disruption Event Streams in Schwarzschild Geometry

Dittmann

2021

Preprint

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We present an analytic and fully relativistic framework for studying the self-intersection of tidal disruption event (TDE) streams, restricting ourselves to the Schwarzschild spacetime. By taking advantage of the closed-form solution to the geodesic equations in the Schwarzschild metric, we calculate properties of the self-intersection without numerically evaluating the geodesic equations or making any post-Newtonian approximations. Our analytic treatment also facilitates geometric definitions of the orbital semi-major axis and eccentricity, as opposed to Newtonian formulas which lead to unphysical results for highly-relativistic orbits. Combined with assumptions about energy dissipation during the self-intersection shock, our framework enables the calculation of quantities such as the fraction of material unbound during the selfintersection shock, and the characteristic semi-major axes and eccentricities of the material which remains in orbit after the collision. As an example, we calculate grids of post-intersection properties in stellar and supermassive black hole (SMBH) masses for disruptions of main sequence stars, identifying regions where no material is ejected during self intersection (e.g. SMBH mass 5 × 10 6 M for 1 M stars disrupted at the tidal radius), potentially explaining the TDEs observed by SGR/eROSITA which are visible in X-rays but not optical wavelengths. We also identify parameters for which the post-intersection accretion flow has low eccentricity (𝑒 0.6), and find that the luminosity generated by self-intersection shocks only agrees with observed trends in the relationship between light curve decay timescales and peak luminosities over a narrow range of SMBH masses.

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Two regimes of tidal-stream circularization by supermassive black holes

Cited by 6 publications

References 35 publications

Repeating tidal disruptions in GSN 069: Long-term evolution and constraints on quasi-periodic eruptions’ models

Repeating tidal disruptions in GSN 069: Long-term evolution and constraints on quasi-periodic eruptions’ models

Radiative hydrodynamical simulations of super-Eddington accretion flow in tidal disruption event: the origin of optical/UV emission

An Analytic, Fully Relativistic Framework for Tidal Disruption Event Streams in Schwarzschild Geometry

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