A bright year for tidal disruptions

By B. Metzger, Nicholas C. Stone. 2015

220 citations recorded by the source corpus.

When a star is tidally disrupted by a supermassive black hole (BH), roughly half of its mass falls back to the BH at super-Eddington rates. Being tenuously gravitationally bound and unable to cool radiatively, only a small fraction f_in few 1e4 K, converting the emission to optical/near-UV wavelengths where photons more readily escape due to the lower opacity. This can explain the unexpectedly low and temporally constant effective temperatures of optically-discovered TDE flares. For BHs with relatively high masses M_BH > 1e7 M_sun the ejecta can become ionized at an earlier stage, or for a wider range of viewing angles, producing a TDE flare which is instead dominated by thermal X-ray emission. We predict total radiated energies consistent with those of observed TDE flares, and ejecta velocities that agree with the measured emission line widths. The peak optical luminosity for M_BH < 1e6 M_sun is suppressed due to adiabatic losses in the inner disk wind, possibly contributing to the unexpected dearth of optical TDEs in galaxies with low mass BHs. In the classical picture, where f_in ~ 1, TDEs de-spin supermassive BHs and cap their maximum spins well below theoretical accretion physics limits. This cap is greatly relaxed in our model, and existing Fe K-alpha spin measurements provide suggestive preliminary evidence that f_in < 1.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/e4a826812de72ca4991163c22e5fa745e6293102

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In Astronomy and Astrophysics

1. B. Metzger
2. E. Berger
3. Bing Zhang
4. E. Ramirez-Ruiz
5. Masaomi Tanaka
6. J. Guillochon
7. D. Kasen
8. B. Mockler

Citations in the corpus

• A Unified Model for Tidal Disruption Events (2018, methodology): “In particular, Metzger & Stone (2016) and Roth et al. (2016) suggested that there could be a viewing angle dependence for emission, though they still used a spherically symmetric envelope with ad-hoc profile for calculations.”
• Revisiting Optical Tidal Disruption Events with iPTF16axa (2017, background): “For example, the production of an optically thick envelope that radiates at the Eddington limit (Loeb & Ulmer 1997), or a strong disk wind or outflow that regulates the accretion rate (Strubbe & Quataert 2009; Miller 2015; Metzger & Stone 2016).”
• The Final Season Reimagined: 30 Tidal Disruption Events from the ZTF-I Survey (2022, background): “Outflows and winds have been proposed as the origin of this emission (Metzger & Stone 2016; Dai et al. 2018), as have shocks from the intersecting debris streams (Piran et al. 2015; Jiang et al. 2016).”
• Weighing Black Holes Using Tidal Disruption Events (2018, background): “A reprocessing layer, either static or outflowing (Miller 2015; Metzger & Stone 2016), can help explain the observed emission by reprocessing the luminosity generated by the various dissipation processes at play (Loeb & Ulmer 1997; Ulmer et al. 1998; Bogdanović et al. 2004; Guillochon et al. 2014;…”
• The fast, luminous ultraviolet transient AT2018cow: extreme supernova, or disruption of a star by an intermediate-mass black hole? (2018, background): “This could be associated with matter blown to larger radii during an early wind phase (Jiang et al. 2016; Metzger & Stone 2016).”