Sambaran Banerjee

A Perfect Starburst Cluster made in One Go: The NGC 3603 Young Cluster

Understanding how distinct, near-spherical gas-free clusters of very young, massive stars shape out of vast, complex clouds of molecular hydrogen is one of the biggest challenges in astrophysics. A popular thought dictates that a single gas cloud fragments into many newborn stars which, in turn, energize and rapidly expel the residual gas to form a gas-free cluster. This study demonstrates that the above classical paradigm remarkably reproduces the well-observed central, young cluster (HD 97950) of the Galactic NGC 3603 star-forming region, in particular, its shape, internal motion, and mass distribution of stars naturally and consistently follow from a single model calculation. Remarkably, the same parameters (star formation efficiency, gas expulsion timescale, and delay) reproduce HD 97950, as were found to reproduce the Orion Nebula Cluster, Pleiades, and R136. The present results therefore provide intriguing evidence of formation of star clusters through single-starburst events followed by significant residual gas expulsion.

Very Massive Stars in the local Universe

Recent studies suggest the existence of very massive stars (VMS) up to 300 solar masses in the local Universe. As this finding may represent a paradigm shift for the canonical stellar upper-mass limit of 150 solar masses, it is timely to evaluate the physics specific to VMS, which is currently missing. For this reason, we decided to construct a book entailing both a discussion of the accuracy of VMS masses (Martins), as well as the physics of VMS formation (Krumholz), mass loss (Vink), instabilities (Owocki), evolution (Hirschi), and fate (theory -- Woosley & Heger; observations -- Smith).

How can young massive clusters reach their present-day sizes?

The classic question that how young massive star clusters attain their shapes and sizes, as we find them today, remains to be a challenge. Both observational and computational studies of star-forming massive molecular gas clouds infer that massive cluster formation is primarily triggered along the small-scale (

The bound fraction of young star clusters

\lesssim0.3

Collisional hardening of compact binaries in globular clusters

pc) filamentary substructures within the clouds. The present study is intended to investigate the possible ways in which a filament-like-compact, massive star cluster (effective radius 0.1-0.3 pc) can expand

Possible smoking-gun evidence for initial mass segregation in re-virialized post-gas expulsion globular clusters

\gtrsim10

R144: a very massive binary likely ejected from R136 through a binary–binary encounter

times, still remaining massive enough (

Very Massive Stars (VMS) in the Local Universe

\gtrsim10^4 M_\odot

Evolution of Compact Binary Populations in Globular Clusters: A Boltzmann Study. I. The Continuous Limit

), to become a young massive star cluster, as we observe today. To that end, model massive clusters (of initially

Neutron stars and millisecond pulsars in star clusters: implications for the diffuse γ-radiation from the Galactic Centre

10^4 M_\odot-10^5 M_\odot