Tidal disruption event

TDEs were first theorized by J.G. Hills in 1975[7]. A consequence of a star getting sufficiently close to a SMBH that the tidal forces between the star will overcome the star's self-gravity. The seminal paper on the topic by Martin G. Rees described how approximately half of the disrupted stellar material will remain bound, eventually accreting onto the black hole and forming a luminous accretion disk[8].

TDEs were first observed in the early 1990s in the X-ray regime by the ROSAT All-Sky Survey [citation needed].

As of May 2024, roughly 100 TDEs are known[9][10][11], and have been discovered through several astronomical methods. such as optical transient surveys including Zwicky Transient Facility (ZTF)[11] and All Sky Automated Survey for SuperNovae (ASASS-SN) [12]. Other TDEs have been discovered in X-rays, using the ROSAT, XMM-Newton, and eROSITA[13].

In September 2019, scientists using the TESS satellite announced they had witnessed a tidal disruption event called ASASSN-19bt, 375 million light-years away, which was first discovered by ASASS-SN.[14][15]

A star gets tidally disrupted when the tidal force exerted by a black hole ${\displaystyle f_{tidal}\approx {\frac {GM_{BH}R^{*}}{R^{3}}}}$ exceeds the self-gravity of the star ${\displaystyle f_{sg}\approx {\frac {GM^{*}}{R^{*2}}}}$ . The distance below which ${\displaystyle f_{tidal}>f_{sg}}$ is called the tidal radius and is given approximately by:[18][19]

${\displaystyle R_{T}\approx R^{*}({\frac {M_{BH}}{M^{*}}})^{\frac {1}{3}}}$

This is identical to the Roche limit for disruptions of planetary bodies.

Usually, the tidal-disruption radius of a black hole is bigger than its Schwarzschild radius, ${\displaystyle R_{S}={\frac {2GM}{c^{2}}}}$, but considering the radius and mass of the star fixed there is a mass for the black hole where both radii become equal meaning that at this point the star would simply disappear before being torn apart.[20][21]

• Swift J1644+57 [22]
• ASASSN-14li [23][24]
• AT2022cmc [25]
• ASASSN-20hx, located near the nucleus of galaxy NGC 6297, was discovered in July 2020 and noted that the observation represented one of the "very few tidal disruption events with hard powerlaw X-ray spectra".[26][27]

• Gamma-ray burst#Tidal disruption events
• Super soft X-ray source#Large amplitude outbursts
• RX J1242-11

• Parsons, Jeff (23 October 2015). "Watch what happens when a black hole rips apart a star". mirror. Retrieved 26 November 2016.
• "Scientists get first glimpse of black hole eating star, ejecting high-speed flare". Retrieved 26 November 2016.
• "Supermassive black hole ASSASSN 14LI destroying a Sun-like star". ABC News. 27 November 2015. Retrieved 26 November 2016.
• Parsons, Jeff (6 October 2016). "A gigantic 'wandering' supermassive black hole is ripping through the galaxy". mirror. Retrieved 26 November 2016.

• The Open TDE catalog, a catalog of claimed tidal disruption events.