The compact and, with ∼ 4.3 ± 0.3 * 10^ 6∼ 4.3±0.3× 10 6 M _ ⊙⊙, very massive object
located at the center of the Milky Way is currently the very best candidate for a supermassive …

The star S2 orbiting the compact radio source Sgr A* is a precision probe of the gravitational
field around the closest massive black hole (candidate). Over the last 2.7 decades we have …

Abstract The Galactic Center (GC) of the Milky Way, thanks to its proximity, allows to perform
astronomical observations that investigate physical phenomena at the edge of astrophysics …

We present a review of the influence of cosmic repulsion and external magnetic fields on
accretion disks rotating around rotating black holes and on jets associated with these …

While singularities are inevitable in the classical theory of general relativity, it is commonly
believed that they will not be present when quantum gravity effects are taken into account in …

The highly elliptical, 16-year-period orbit of the star S2 around the massive black hole
candidate Sgr A✻ is a sensitive probe of the gravitational field in the Galactic centre. Near …

We present high-pass filtered NACO and SINFONI images of the newly discovered stars
S4711–S4715 between 2004 and 2016. Our deep H+K-band (SINFONI) and K-band …

The Galactic centre supermassive black hole (SMBH), in sharp contrast with its complex
environment, is characterized by only three classical parameters–mass, spin, and electric …

The production and acceleration mechanisms of ultrahigh-energy cosmic rays (UHECRs) of
energy> 10 20 eV, clearly beyond the GZK cutoff limit, remain unclear, which points to the …

We present a review of the Penrose process and its modifications in relation to the Kerr
black holes and naked singularities (superspinars). We introduce the standard variant of this …