The Tidal Disruption of Sun-like Stars by Massive Black Holes. (arXiv:1907.04859v1 [astro-ph.HE])

The Tidal Disruption of Sun-like Stars by Massive Black Holes. (arXiv:1907.04859v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Law_Smith_J/0/1/0/all/0/1">Jamie Law-Smith</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Guillochon_J/0/1/0/all/0/1">James Guillochon</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ramirez_Ruiz_E/0/1/0/all/0/1">Enrico Ramirez-Ruiz</a>

We present the first simulations of the tidal disruption of stars with
realistic structures and compositions by massive black holes (BHs). We build
stars in the stellar evolution code MESA and simulate their disruption in the
3D adaptive-mesh hydrodynamics code FLASH, using an extended Helmholtz equation
of state and tracking 49 elements. We study the disruption of a $1 M_odot$
star and $3 M_odot$ star at zero-age main sequence (ZAMS), middle-age, and
terminal-age main sequence (TAMS). The maximum BH mass for tidal disruption
increases by a factor of $sim$2 from stellar radius changes due to main
sequence evolution; this is equivalent to the change in maximum BH mass from
varying BH spin from 0 to 0.75. The shape of the resulting mass fallback rate
curves is different from the results for polytropes of Guillochon &
Ramirez-Ruiz (2013). The peak timescale $t_{rm peak}$ increases with stellar
age, while the peak fallback rate $dot M_{rm peak}$ decreases with age, and
these effects diminish with increasing impact parameter $beta$. For a
$beta=1$ disruption of a $1 M_odot$ star by a $10^6 M_odot$ BH, from ZAMS to
TAMS, $t_{rm peak}$ increases from 30 days to 54 days, while $dot M_{rm
peak}$ decreases from $0.66~M_odot$/yr to $0.14~M_odot$/yr. We find that
compositional anomalies in nitrogen, helium, and carbon can occur before the
peak of the mass fallback rate for disruptions of main sequence stars, which is
in contrast to predictions from the “frozen-in” model. More massive stars can
show stronger abundance anomalies at earlier times, meaning that compositional
constraints can be key in determining the mass of the disrupted star. The
abundance anomalies predicted by these simulations provide a natural
explanation for the spectral features and varying line strengths observed in
tidal disruption events.

We present the first simulations of the tidal disruption of stars with
realistic structures and compositions by massive black holes (BHs). We build
stars in the stellar evolution code MESA and simulate their disruption in the
3D adaptive-mesh hydrodynamics code FLASH, using an extended Helmholtz equation
of state and tracking 49 elements. We study the disruption of a $1 M_odot$
star and $3 M_odot$ star at zero-age main sequence (ZAMS), middle-age, and
terminal-age main sequence (TAMS). The maximum BH mass for tidal disruption
increases by a factor of $sim$2 from stellar radius changes due to main
sequence evolution; this is equivalent to the change in maximum BH mass from
varying BH spin from 0 to 0.75. The shape of the resulting mass fallback rate
curves is different from the results for polytropes of Guillochon &
Ramirez-Ruiz (2013). The peak timescale $t_{rm peak}$ increases with stellar
age, while the peak fallback rate $dot M_{rm peak}$ decreases with age, and
these effects diminish with increasing impact parameter $beta$. For a
$beta=1$ disruption of a $1 M_odot$ star by a $10^6 M_odot$ BH, from ZAMS to
TAMS, $t_{rm peak}$ increases from 30 days to 54 days, while $dot M_{rm
peak}$ decreases from $0.66~M_odot$/yr to $0.14~M_odot$/yr. We find that
compositional anomalies in nitrogen, helium, and carbon can occur before the
peak of the mass fallback rate for disruptions of main sequence stars, which is
in contrast to predictions from the “frozen-in” model. More massive stars can
show stronger abundance anomalies at earlier times, meaning that compositional
constraints can be key in determining the mass of the disrupted star. The
abundance anomalies predicted by these simulations provide a natural
explanation for the spectral features and varying line strengths observed in
tidal disruption events.

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