Idan Ginsburg

The fate of former companions to hypervelocity stars originating at the Galactic Centre

The hypervelocity star SDSS J090745.0+024507 in the halo of the Milky Way galaxy most likely originated from the breakup of a binary star system by the central black hole, SgrA*. We examine the fate of former binary companions to similar hypervelocity stars (HVSs) by simulating 600 different binary orbits around SgrA* with a direct N-body integration code. For some orbital parameters, the binary breakup process leads to HVSs with ejection velocities that are almost an order of magnitude larger than the velocity observed for SDSS J090745.0+024507. The former companion stars populate highly eccentric orbits which resemble the observed orbits for some of the stars nearest to SgrA*.

Hypervelocity collisions of binary stars at the Galactic Centre

Recent surveys have identified seven hypervelocity stars (HVSs) in the halo of the Milky Way. Most of these stars may have originated from the breakup of binary star systems by the nuclear black hole SgrA*. In some instances, the breakup of the binary may lead to a collision between its member stars. We examine the dynamical properties of these collisions by simulating thousands of different binary orbits around SgrA* with a direct N-body integration code. For some orbital parameters, the two stars collide with an impact velocity lower than their escape velocity and may therefore coalesce. It is possible for a coalescing binary to have sufficient velocity to escape the galaxy. Furthermore, some of the massive S-stars near Sgr A* might be the merger remnants of binary systems, however this production method can not account for most of the S-stars.

Gravitational Waves and Intermediate Massive Black Hole Retention in Globular Clusters

The recent discovery of gravitational waves has opened new horizons for physics. Current and upcoming missions, such as LIGO, VIRGO, KAGRA, and LISA, promise to shed light on black holes of every size from stellar mass (SBH) sizes up to supermassive black holes which reside in galactic nuclei. The intermediate mass black hole (IMBH) family has not been detected beyond any reasonable doubt neither directly nor indirectly. Recent analyses suggest observational evidence for the presence of IMBHs in the centers of two Galactic globular clusters. In this paper, we investigate the possibility that globular clusters were born with a central IMBH, which undergo repeated merger events with SBHs in the cluster core. By means of a semi-analytical method, we follow the evolution of the primordial cluster population in the galactic potential and the Gravitational Wave (GW) mergers of the binary IMBH-SBH systems. Our models predict

Revisiting hypervelocity stars after Gaia DR2

\approx 1000

Transit probabilities around hypervelocity and runaway stars

IMBHs within

Detecting stars at the galactic centre via synchrotron emission

1

Eclipsing Stellar Binaries in the Galactic Center

kpc from the Galactic Center. Our results show that the IMBH-SBH merger rate density changes from

Dating the Tidal Disruption of Globular Clusters with GAIA Data on Their Stellar Streams

\mathcal{R}\approx 1000

A dynamical origin for planets in triple star systems

Gpc

Galactic Panspermia.

^{-3}