Binaries are key objects in Globular Clusters and they influence their structure and dynamics. Especially interesting are pairs of stellar remnants as potential sources of gravitational wave events. Spectroscopic observations of binary stars in Globular Clusters allow to shed light on the poorly constrained period, eccentricity and mass ratio distributions, to develop an understanding of the...
We investigate the impact of massive black holes (MBHs) in merging star clusters of $M_{\star} = 5.3 \cdot 10^4 M_{\odot}$ on the escaping population of high-velocity stars and compact objects (COs) incorporating relativistic effects (up to 3.5PN order) , utilizing the GPU-accelerated N-Body code BIFROST. If the merging clusters host central MBHs of $M_{\bullet} = 10^3 M_{\odot}$ , a fraction...
In dense star clusters close encounters between stars and stellar mass black holes can have a wide variety of outcomes ranging from disruption of stars to the formation of bound quiescent binary systems as those recently discovered thanks to Gaia. The former are transients addressed as โmicro-Tidal Disruption Eventsโ (TDEs). To date, micro-TDEs have not yet been observed but they are promising...
Close binary systems are the progenitors to a variety of compact object mergers producing Type Ia supernovae and gravitational waves. While most short-period binaries are believed to have evolved through at least one common envelope (CE) phase, our understanding of CE evolution is limited due to the lack of observational benchmarks that connect the post-CE parameters with the pre-CE initial...
We explore three-body binary formation (3BBF), the formation of a bound system via gravitational scattering of three initially unbound bodies (3UB), using direct numerical integrations. For the first time, we consider systems with unequal masses, as well as finite-size and post-Newtonian effects. Our analytically derived encounter rates and numerical scattering results reproduce the 3BBF rate...
Blue straggler stars (BSS) are anomalous core hydrogen-burning stars that have undergone a rejuvenation by acquiring mass either in a direct stellar collision or through mass transfer in binaries or mergers. We have been surveying the BSS of open clusters and Galactic fields using the Ultraviolet Imaging Telescope onboard the AstroSat telescope. Together in five open clusters (NGC 7789, NGC...
Millisecond pulsars (MSPs) are neutron stars with rotational periods as low as a few milliseconds. They are formed via angular momentum transfer from accreted materials from a companion star. In the high density environment of globular clusters (GCs), MSPs are likely to form through dynamically formed interacting binaries. In fact, over 300 MSPs are detected in GCs, more than half of the known...
This study examines how the dynamical interactions in globular clusters (GCs) influence the formation and evolution of binary sources like cataclysmic variables (CVs), focusing on their X-ray luminosity distributions. Using the MOCCA simulation tool, we classify simulated GCs into three evolutionary stages (Classes I, II, and III) and observe significant differences in CV X-ray luminosities...
In the talk I would like to show the results of MOCCA simulations of globular star clusters, which show clear signs of excess of number of blue stragglers stars (BSSs) due to core collapse. The excess of BSSs happens for the core collapses happening for different times (starting from 1-2 Gyr, and up to Hubble time) and for star clusters with different parameters. This feature seems to be...
Runaway stars are thought to have been ejected from star clusters with high velocities relative to the cluster centre-of-mass motion. There are two competing mechanisms for their production: supernova-based ejections in binaries, where one companion explodes leaving no remnant and launching the other companion at the instantaneous orbital velocity, and the disintegration of triples (or...
Gaia mission offers opportunities to search for compact binaries not involved in binary interactions (hereafter inert compact binaries), and results in the discoveries of binaries containing one black hole (BH) or one neutron star (NS), called "Gaia BHs" and "Gaia NSs", respectively. Tanikawa et al. (2024, MNRAS, 527, 4031) have first pointed out that Gaia BHs can be formed much more...
In dense stellar environments, stars can collide physically. Stellar collisions are known to play a key role in shaping the stellar population in the center of stellar clusters and galactic nuclei, as well as in creating exotic stars, such as blue stragglers, and electromagnetic transients. Previous studies on stellar collisions have mostly focused on the hydrodynamical effects on the...
The exceptionally high stellar densities in the cores of globular clusters (GCs) makes them remarkable hosts for an exotic pulsar population. In this talk, I will discuss the results from the radio timing analysis of a couple of massive binary pulsars in the dense globular cluster NGC 1851, observed with the MeerKAT as a part of the TRAPUM (TRAnsients and Pulsars with MeerKAT) GC Survey. Both...
It is well-established that young stellar clusters in Magellanic Clouds (MCs) host stellar populations that are not simple. Features such as the split main sequence (MS) and the extended main sequence turn-off (eMSTO) are characteristics easily visible in all clusters younger than 2 Gyrs. Initially, these features were explained with prolonged or multiple star formation episodes, suggesting...
Despite the potential of GAIA DR3 to reveal a large population of black holes (BHs), only a few BHs have been discovered to date in orbit with luminous stars without an X-ray counterpart. It has recently been shown that black holes in orbit with main sequence companions seldom form accretion disks, from where observable X-ray flux is conventionally thought to be produced. Yet, even without...
For decades, it has been believed that globular clusters (GCs) are efficient environments for producing cataclysmic variables (CVs) due to the significant number of stellar interactions among their members. However, models in the last years have cast doubt on the validity of this scenario. In this study, I present the results of the first analysis of detectable CVs in core-collapsed and...
In collisional system simulations such as globular clusters, stable criteria for hierarchical triple systems are essential. SDAR (Wang et al. 2020) is a method capable of rapidly computing binaries, particularly hierarchical triple systems, but its efficiency depends on the accuracy of the stability criteria for these systems. Traditional criterion is expressed by the parameter $Q =...
Ultra-Luminous X-ray Sources (ULXs), which emit more X-rays than typical accreting black holes, remain enigmatic objects in astrophysics. With only around 20 ULXs potentially residing in Globular Clusters (GCs), they pose challenging targets for study. Previous research predominantly focused on ULXs in the field, yet in the dense environment of GCs, where stars are densely packed, dynamics...
Stars do not form in isolation but together with other stars, often in a clustered environment. During the dynamical evolution of these environments, stars will interact with each other. These encounters will affect any planetary systems that are in the process of forming around them. Many typical fly-by simulations focus on a single fly-by event's effect on a planetary system. However, during...
Discoveries of Milky Way stars with velocities in excess of the Galactic escape speed (~500 km/s at the Solar position) have been reported with increasing frequency in the era of large Galactic surveys. These 'hyper-velocity stars' serve as a fascinating probe of the extreme dynamical and astrophysical phenomena which produce them, such dynamical interactions with Sgr A* or supernovae within...
Over a third of all observed millisecond pulsars appear in Galactic globular clusters, which collectively account for less than 0.05% of the total number of stars in the Milky Way. Recently, there have been radio observations (with MeerKAT) of a possible millisecond pulsar-black hole (mass gap) eccentric binary in the globular cluster NGC 1851. On the other hand, the current generation of...
