1 research outputs found
Short gamma-ray bursts from dynamically-assembled compact binaries in globular clusters: pathways, rates, hydrodynamics and cosmological setting
We present a detailed assessment of the dynamical pathways leading to the
coalescence of compact objects in Globular Clusters (GCs) and Short Gamma-Ray
Burst (SGRB) production. We consider primordial binaries, dynamically formed
binaries (through tidal two-body and three-body exchange interactions) and
direct impacts of compact objects (WD/NS/BH). We show that if the primordial
binary fraction is small, close encounters dominate the production rate of
coalescing compact systems. We find that the two dominant channels are the
interaction of field NSs with dynamically formed binaries, and two-body
encounters. We then estimate the redshift distribution and host galaxy
demographics of SGRB progenitors, and find that GCs can provide a significant
contribution to the overall observed rate.
We have carried out hydrodynamical modeling of evolution of close stellar
encounters with WD/NS/BH, and show that there is no problem in accounting for
the energy budget of a typical SGRB. The particulars of each encounter are
variable and lead to interesting diversity: the encounter characteristics are
dependent on the impact parameter, in contrast to the merger scenario; the
nature of the compact star itself can produce very different outcomes; the
presence of tidal tails in which material falls back onto the central object at
later times is a robust feature of these calculations, with the mass involved
being larger than for binary mergers. It is thus possible to account
generically in this scenario for a prompt episode of energy release, as well as
for activity many dynamical time scales later (abridged).Comment: Accepted for publication in ApJ (24 pages, 19 figures