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Astrophysics, Cosmology and Extragalactic Astrophysics, astro-ph.CO, Astrophysics, Galaxy Astrophysics, astro-ph.GA, Astrophysics, High Energy Astrophysical Phenomena, astro-ph.HE
Abstract:
Several galaxies have exhibited X-ray flares that are consistent with the
tidal disruption of a star by a central supermassive black hole. In theoretical
treatments of this process it is usually assumed that the star was initially on
a nearly parabolic orbit relative to the black hole. Such an assumption leads
in the simplest approximation to a $t^{-5/3}$ decay of the bolometric
luminosity and this is indeed consistent with the relatively poorly sampled
light curves of such flares. We point out that there is another regime in which
the decay would be different: if a binary is tidally separated and the star
that remains close to the hole is eventually tidally disrupted from a moderate
eccentricity orbit, the decay is slower, typically $\sim t^{-1.2}$. As a
result, careful sampling of the light curves of such flares could distinguish
between these processes and yield insight into the dynamics of binaries as well
as single stars in galactic centres. We explore this process using three-body
simulations and analytic treatments and discuss the consequences for
present-day X-ray detections and future gravitational wave observations.
