Where intermediate-mass black holes could hide in the Galactic Centre: A full parameter study with the S2 orbit
Creators: name: The GRAVITY Collaboration
name: Straub, O.
name: Bauböck, M.
name: Abuter, R.
name: Aimar, N.
name: Seoane, P. Amaro
name: Amorim, A.
name: Berger, J. P.
name: Bonnet, H.
name: Bourdarot, G.
name: Brandner, W.
name: Cardoso, V.
name: Clénet, Y.
name: Dallilar, Y.
name: Davies, R.
name: de Zeeuw, P. T.
name: Dexter, J.
name: Drescher, A.
name: Eisenhauer, F.
name: Schreiber, N. M. Förster
name: Foschi, A.
name: Garcia, P.
name: Gao, F.
name: Gendron, E.
name: Genzel, R.
name: Gillessen, S.
name: Habibi, M.
name: Haubois, X.
name: Heißel, G.
name: Henning, T.
name: Hippler, S.
name: Horrobin, M.
name: Jochum, L.
name: Jocou, L.
name: Kaufer, A.
name: Kervella, P.
name: Lacour, S.
name: Lapeyrère, V.
name: Bouquin, J. -B. Le
name: Léna, P.
name: Lutz, D.
name: Ott, T.
name: Paumard, T.
name: Perraut, K.
name: Perrin, G.
name: Pfuhl, O.
name: Rabien, S.
name: Ribeiro, D. C.
name: Bordoni, M. Sadun
name: Scheithauer, S.
name: Shangguan, J.
name: Shimizu, T.
name: Stadler, J.
name: Straubmeier, C.
name: Sturm, E.
name: Tacconi, L. J.
name: Vincent, F.
name: von Fellenberg, S.
name: Widmann, F.
name: Wieprecht, E.
name: Wiezorrek, E.
name: Woillez, J.
Publisher: name: arXiv
Year: 2023
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: In the Milky Way the central massive black hole, SgrA*, coexists with a compact nuclear star cluster that contains a sub-parsec concentration of fast-moving young stars called S-stars. Their location and age are not easily explained by current star formation models, and in several scenarios the presence of an intermediate-mass black hole (IMBH) has been invoked. We use GRAVITY astrometric and SINFONI, KECK, and GNIRS spectroscopic data of S2 to investigate whether a second massive object could be present deep in the Galactic Centre (GC) in the form of an IMBH binary companion to SgrA*. To solve the three-body problem, we used a post-Newtonian framework and consider two types of settings: (i) a hierarchical set-up where the star S2 orbits the SgrA* - IMBH binary and (ii) a non-hierarchical set-up where the IMBH trajectory lies outside the S2 orbit. In both cases we explore the full 20-dimensional parameter space by employing a Bayesian dynamic nested sampling method. For the hierarchical case we find: IMBH masses &gt; 2000 Msun on orbits with smaller semi-major axes than S2 are largely excluded. For the non-hierarchical case the parameter space contains several pockets of valid IMBH solutions. However, a closer analysis of their impact on the resident stars reveals that IMBHs on semi-major axes larger than S2 tend to disrupt the S-star cluster in less than a million years. This makes the existence of an IMBH among the S-stars highly unlikely. The current S2 data do not formally require the presence of an IMBH. If an IMBH hides in the GC, it has to be either a low-mass IMBH inside the S2 orbit that moves on a short and significantly inclined trajectory or an IMBH with a semi-major axis &gt;1". We provide the parameter maps of valid IMBH solutions in the GC and discuss the general structure of our results. (abridged)
description: 11 pages, 6 figures, published in A $\&amp;$ A