Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Does the HR 6819 triple system contain a dormant black hole? Not
  necessarily   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.

20
The categories of this paper are: acc-phys
26
The categories of this paper are: bayes-an
5
The categories of this paper are: gr-qc
23
The categories of this paper are: solv-int
1
The categories of this paper are: cs
15
The categories of this paper are: nucl-ex
24
The categories of this paper are: dg-ga
32
The categories of this paper are: atom-ph
18
The categories of this paper are: econ
10
The categories of this paper are: q-bio
4
The categories of this paper are: cond-mat
0
The categories of this paper are: hep-ph
12
The categories of this paper are: nucl-th
13
The categories of this paper are: quant-ph
7
The categories of this paper are: hep-th
34
The categories of this paper are: chem-ph