Run-away IMBH formation in dense star clusters

2004-01-01
Freitag, M
Gürkan, Mehmet Atakan
Rasio, FA
We have established under which conditions core collapse of a spherical cluster occurs before massive stars have time to evolve off the main sequence (MS). We consider cluster central velocity dispersions of 100 km s(-1) and higher, appropriate for galactic nuclei. At such high velocities, binary stars play little dynamical role and are therefore neglected. On the other hand whether collisions allow the growth of very massive stars (VMS, with M-* >> 100 M-circle dot) or, on the contrary, grind them down is a central unknown addressed in this work. We find that, in spite of the high relative velocities, run-away growth of a VMS, a likely progenitor for an intermediate-mass BH (IMBH), occurs in all clusters with short enough a core collapse time.

Suggestions

Pre-Main-Sequence evolution of rotating low-mass stars
Kızıloğlu, Nilgün (Springer Science and Business Media LLC, 1989-4)
The evolutionary behaviour of rotating low-mass stars in the mass range 0.2 and 0.9M ⊙ has been investigated during the pre-Main-Sequence phase. The angular momentum is conserved locally in radiative regions and totally in convective regions, according to a predetermined angular velocity distribution depending on the structure of the star. As the stars contract toward the zero-age Main Sequence, they spin up under the assumption that the angular momentum is conserved during the evolution of the stars. When ...
Early phases of different types of isolated neutron star
Ankay, A; Sahin, S; Karanfil, G; Yazgan, E (World Scientific Pub Co Pte Lt, 2005-06-01)
Two Galactic isolated strong X-ray pulsars seem to be in the densest environments compared to other types of Galactic pulsar. X-ray pulsar J1846-0258 can be in an early phase of anomalous X-ray pulsars and soft gamma repeaters if its average braking index is similar to 1.8-2.0. X-ray pulsar J1811-1925 must have a very large average braking index (similar to 11) if this pulsar was formed by SN 386AD. This X-ray pulsar can be in an early phase of the evolution of the radio pulsars located in the region P simi...
Modelling the oscillating star V1162 Ori
Civelek, R; Kiziloglu, N; Kirbiyik, H (EDP Sciences, 2003-12-01)
Evolutionary stellar models of V1162 Ori, with the latest observations of a multiperiodic delta Scuti star, have been calculated theoretically and compared with the observations. Theoretical models representative of the star indicate that it is at an advanced stage of its main-sequence evolution. Calculations have been made for two different masses, 1.80 and 1.82 M-., at different rotational speeds. Rotation was treated as a perturbation and only the first-order effect was considered. The evolutionary model...
Pulsar spin-down by a fallback disk and the P-P diagram
Alpar, MA; Ankay, A; Yazgan, E (American Astronomical Society, 2001-08-10)
Neutron stars may be surrounded by fallback disks formed from supernova core collapse. If the disk circumscribes the light cylinder, the neutron star will be an active radio pulsar spinning down under the propeller spin-down torque applied by the disk as well as the usual magnetic dipole radiation torque. Evolution across the P-P diagram is very rapid when pulsar spin-down is dominated by the propeller torque. This explains the distribution of pulsars in the P-P diagram.
Age determination of the open cluster NGC 2287 (M41)
Küçük, İbrahim; Eryurtezer, Dilan (Springer Science and Business Media LLC, 1988)
We have estimated the age of the open cluster NGC 2287 (M41) by taking into account the rotation of the member stars. TheUBV photoelectric measurement values were taken from Eggen (1974). Besides the Main-Sequence stars this cluster has seven red giants, all of them above the turn-off point. Having obtained the theoretical Hertzsprung-Russell diagram from observed colour-magnitude diagram, we have discussed two methods, given in the literature, to estimate the age of the cluster under consideration. The f...
Citation Formats
M. Freitag, M. A. Gürkan, and F. Rasio, “Run-away IMBH formation in dense star clusters,” 2004, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/68884.