Does the HR 6819 triple system contain a dormant black hole? Not necessarily. (arXiv:2007.08522v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Mazeh_T/0/1/0/all/0/1">Tsevi Mazeh</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Faigler_S/0/1/0/all/0/1">Simchon Faigler</a>

A recent paper by Rivinius et al. proposed that HR 6819 is a triple system,
with a distant Be star and a binary of 40-day orbit, composed of a B3 III giant
and a dormant black hole (BH). We suggest that the evidence for this model is
not conclusive. In an alternative model, the companion of the giant is by
itself a short-period binary in, say, a $sim$$4$-day orbit, consisting, for
example, of two A0 stars. Each of the two A0 stars should contribute
$sim$$4%$ of the total brightness of the system in the $V$ band, and their
spectral lines are moving due to their assumed orbital motion with an unknown
period. Therefore, only a careful analysis of the observed spectra can exclude
such a model. Before such an analysis is presented and upper limits for the
depths of the hypothetical A0 star absorption lines are derived, the model of a
hidden close pair is more probable than the BH model.

A recent paper by Rivinius et al. proposed that HR 6819 is a triple system,
with a distant Be star and a binary of 40-day orbit, composed of a B3 III giant
and a dormant black hole (BH). We suggest that the evidence for this model is
not conclusive. In an alternative model, the companion of the giant is by
itself a short-period binary in, say, a $sim$$4$-day orbit, consisting, for
example, of two A0 stars. Each of the two A0 stars should contribute
$sim$$4%$ of the total brightness of the system in the $V$ band, and their
spectral lines are moving due to their assumed orbital motion with an unknown
period. Therefore, only a careful analysis of the observed spectra can exclude
such a model. Before such an analysis is presented and upper limits for the
depths of the hypothetical A0 star absorption lines are derived, the model of a
hidden close pair is more probable than the BH model.

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