The Tidal Disruption of Stars by Supermassive Black Holes

A tidal disruption event (TDE) ensues when a star passes too close to the supermassive black hole (SMBH) in a galactic center and is ripped apart by the tidal field of the SMBH. The gaseous debris produced in a TDE can power a bright electromagnetic flare as it is accreted by the SMBH; so far, several dozen TDE candidates have been observed. For SMBHs with masses above ∼ 10 7 M , the tidal disruption of solar-type stars occurs within ten gravitational radii of the SMBH, implying that general relativity (GR) is needed to describe gravity. Three promising signatures of GR in TDEs are: (1) a super-exponential cutoff in the volumetric TDE rate for SMBH masses above ∼ 10 8 M due to direct capture of tidal debris by the event horizon, (2) delays in accretion disk formation (and a consequent alteration of the early-time light curve) caused by the effects of relativistic precession on stream circularization, and (3) quasi-periodic modulation of X-ray emission due to global precession of misaligned accretion disks and the jets they launch. We review theoretical models and simulations of TDEs in Newtonian gravity, then describe how relativistic modifications give rise to these proposed observational signatures, as well as more speculative effects of GR. We conclude with a brief summary of TDE observations and the extent to which they show indications of these predicted relativistic signatures.

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“…The large Hills masses M H of these stars permit disruptions by almost any known SMBH. Adapted from Ref [34]…”

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confidence: 99%

Stellar tidal disruption events in general relativity

et al. 2019

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“…TDEs and different flavours of the process affecting the plunging stars was examined, first mainly theoretically and later on also observationally (Komossa, 2015;Stone, 2015;Stone, Kesden, Cheng, & van Velzen, 2019). Furthermore, it has been argued and the evidence confirms that TDEs can provide new constraints of dormant supermassive black holes in normal galaxies (Komossa et al, 2004;Saxton et al, 2012).…”

Section: Introductionmentioning

confidence: 98%

“…It has been soon recognized that the mechanism of circularization and the onset of accretion play an important role in the way how TDEs can be revealed observationally (Evans & Kochanek ). Since then, over almost three decades, the understanding of the mechanism of TDEs and different flavors of the process affecting the plunging stars was examined, first mainly theoretically and later on also observationally (Komossa ; Stone ; Stone et al ). Furthermore, it has been argued and the evidence confirms that TDEs can provide new constraints of dormant SMBHs in normal galaxies (Komossa et al ; Saxton et al ).…”

Section: Introductionmentioning

confidence: 99%

“…The newly emerging gaseous trail initially has low angular momentum, and only later, it circularizes into a fluid ring that spreads by the viscous forces (see Section 2). Given the scaling relations for the characteristic masses,

R_{tidal} \propto M_{SMBH}^{1 / 3}

for tidal radius and R g ∝ M SMBH for the gravitational radius, respectively, there is an upper limit constraining the SMBH capable of tidally damaging the star: Hills' critical mass is determined by the relation (Stone )

M_{Hills} ≃ 1.1 \times 10^{8} M_{⊙} {((), \frac{R_{*}}{R_{⊙}})}^{\frac{3}{2}} {((), \frac{M_{*}}{M_{⊙}})}^{- \frac{1}{2}},

where M ⊙ and R ⊙ are the mass and the radius of sun, respectively.…”

Section: Introductionmentioning

confidence: 99%

“…2). Given the scaling relations for the characteristic masses, tidal ∝ 1∕3 SMBH for tidal radius and g ∝ SMBH for the gravitational radius, respectively, there is an upper limit constraining the SMBH capable of tidally damaging the star: Hills' critical mass is determined by the relation (Stone, 2015)…”

Section: Introductionmentioning

confidence: 99%

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Tidal disruption events as a site of an evolving relativistic spectral line

Štolc

Karas

2019

Astron Nachr

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In nuclei of galaxies, strong tidal forces can destroy stars passing within a critical distance from the central supermassive black hole (SMBH). Observational signatures of tidal disruption events (TDEs) depend on the environment around the SBMH horizon and the level of its accretion activity. Evidence for optical and ultraviolet spectral features has been reported in TDE flares; nevertheless, to test the effects of general relativity in the immediate vicinity of SMBH, the relativistically broadened and skewed X-ray line would tell us significantly more useful information. This will require to proceed beyond inactive nuclei. To this end, we consider a system where the material from a disrupted star forms a gaseous ring that circularizes near the tidal radius around SMBH, it gradually spreads in radius by viscous processes and resides embedded within a hot corona. In our test calculation, the remnant trail is assumed to be fully circularized and embedded in a hot environment and illuminated by X-rays from a surrounding corona or a jet base of (mild) active galactic nucleus activity. We show the expected effects on the observed profile and the centroid energy. In the future, the evolving spectral features can enhance the diagnostic capability and provide a novel way to reveal the parameters of TDEs in such sources; the distance of the remnant gas from the SMBH, the radial extent of the gaseous trail, and the spin of the SMBH could be measured.

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Probing boson stars with extreme mass ratio inspirals

Guo

Sinha

Sun

2019

J. Cosmol. Astropart. Phys.

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We propose to use gravitational waves from extreme mass ratio inspirals (EMRI), composed of a boson star and a supermassive black hole in the center of galaxies, as a new method to search for boson stars. Gravitational waves from EMRI have the advantage of being long-lasting within the frequency band of future space-based interferometer gravitational wave detectors and can accumulate large signal-to-noise ratio (SNR) for very sub-solar mass boson stars. Compared to gravitational waves from boson star binaries, which fall within the LIGO band, we find that much larger ranges of the mass and compactness of boson stars, as well as the underlying particle physics parameter space, can be probed by EMRI. We take tidal disruption of the boson stars into account and distinguish those which dissolve before the inner-most-stable-circular-orbit (ISCO) and those which dissolve after it. Due to the large number of cycles recorded, EMRIs can lead to a very precise mass determination of the boson star and distinguish it from standard astrophysical compact objects in the event of a signal. Tidal effects in inspiralling binary systems, as well as possible correlated electromagnetic signals, can also serve as potential discriminants.

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The Tidal Disruption of Stars by Supermassive Black Holes

Cited by 5 publications

References 278 publications

Stellar tidal disruption events in general relativity

Stellar tidal disruption events in general relativity

Tidal disruption events as a site of an evolving relativistic spectral line

Probing boson stars with extreme mass ratio inspirals

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