Testing the presence of a dormant black hole inside HR 6819
  HR 6819 was reported in Rivinius et al. (2020) to be a triple system with a
non-accreting black hole (BH). The inner binary system was defined as a B3 III
type star and a dormant BH. The period of the inner binary was estimated to be
around 40 days with an eccentricity between 0.02 and 0.04. As the inner binary
is not resolved, the third component may actually be just spatially coinciding
with the inner binary. In this study we test whether the system inner binary
can be reconstructed using isolated binary evolution in the Galactic field or
through dynamical evolution within globular star clusters. Our goal is to
understand the formation of the HR 6819 inner binary. To simulate the inner
binary evolution we assumed that the influence of the third body on the inner
binary is negligible. We created synthetic populations of BH-MS binaries for
the Galactic disk and the Galactic globular clusters to compare to the reported
parameters of HR 6819 inner binary. We have adopted very optimistic input
physics, in terms of common envelope evolution and BH formation, for the
formation of binaries like the reported inner HR 6819 binary. Despite our
optimistic assumptions we cannot form systems like the inner HR 6819 binary in
globular clusters. Even with our extreme assumptions, the formation of HR 6819
inner binary in the Galactic field population is not expected. We argue that HR
6819 does not host a dormant BH in support of the conclusions reached by
El-Badry & Quataert (2021), Bodensteiner et al. (2020) and by Safarzadeh et al.
(2020).
