From Pericenter and Back: Full Debris Stream Evolution in Tidal Disruption Events. (arXiv:2112.08384v2 [astro-ph.HE] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Bonnerot_C/0/1/0/all/0/1">Clément Bonnerot</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pessah_M/0/1/0/all/0/1">Martin E. Pessah</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lu_W/0/1/0/all/0/1">Wenbin Lu</a>
When a star passes too close to a supermassive black hole, it gets disrupted
by strong tidal forces. The stellar debris then evolves into an elongated
stream of gas that partly falls back towards the black hole. We present an
analytical model describing for the first time the full stream evolution during
such a tidal disruption event (TDE). Our framework consists in dividing the
stream into different sections of elliptical geometry, whose properties are
independently evolved in their co-moving frame under the tidal, pressure, and
self-gravity forces. Through an explicit treatment of the tidal force and the
inclusion of the gas angular momentum, we can accurately follow the stream
evolution near pericenter. Our model evolves the longitudinal stream stretching
and both transverse widths simultaneously. For the latter, we identify two
regimes depending on whether the dynamics is entirely dominated by the tidal
force (ballistic regime) or additionally influenced by pressure and
self-gravity (hydrostatic regime). We find that the stream undergoes transverse
collapses both shortly after the stellar disruption and upon its return near
the black hole, at specific locations determined by the regime of evolution
considered. The stream evolution predicted by our model can be used to
determine the subsequent interactions experienced by this gas that are at the
origin of most of the electromagnetic emission from TDEs. Our results suggest
that the accretion disk may be fed at a rate that differs from the standard
fallback rate, which would provide novel observational signatures dependent on
black hole spin.
When a star passes too close to a supermassive black hole, it gets disrupted
by strong tidal forces. The stellar debris then evolves into an elongated
stream of gas that partly falls back towards the black hole. We present an
analytical model describing for the first time the full stream evolution during
such a tidal disruption event (TDE). Our framework consists in dividing the
stream into different sections of elliptical geometry, whose properties are
independently evolved in their co-moving frame under the tidal, pressure, and
self-gravity forces. Through an explicit treatment of the tidal force and the
inclusion of the gas angular momentum, we can accurately follow the stream
evolution near pericenter. Our model evolves the longitudinal stream stretching
and both transverse widths simultaneously. For the latter, we identify two
regimes depending on whether the dynamics is entirely dominated by the tidal
force (ballistic regime) or additionally influenced by pressure and
self-gravity (hydrostatic regime). We find that the stream undergoes transverse
collapses both shortly after the stellar disruption and upon its return near
the black hole, at specific locations determined by the regime of evolution
considered. The stream evolution predicted by our model can be used to
determine the subsequent interactions experienced by this gas that are at the
origin of most of the electromagnetic emission from TDEs. Our results suggest
that the accretion disk may be fed at a rate that differs from the standard
fallback rate, which would provide novel observational signatures dependent on
black hole spin.
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