6th FERO meeting

ASTRONOMICAL INSTITUTE
ACADEMY OF SCIENCES, PRAGUE
Boční II 1401, 141 00 Praha 4
Czech Republic

30th – 31st of August 2012



Euro in Czech Crowns: 1€ = Kč
Metro-Tram scheme
Map of centre (more detailed)
    Participants

August



Ladislav Šubr

Catch me if you can: is there a 'runaway-mass' black hole in the Orion Nebula Cluster?

[presentation]

We investigate the dynamical evolution of the Orion Nebula Cluster (ONC) by means of direct N-body integrations. A large fraction of residual gas was probably expelled when the ONC formed, so we assume that the ONC was much more compact when it formed compared to its current size. Hence, we assume that few-body relaxation played an important role during the initial phase of evolution of the ONC. In particular, three body interactions among OB stars likely led to their ejection from the cluster and, at the same time, to the formation of a massive object via 'runaway' physical stellar collisions. The resulting depletion of the high mass end of the stellar mass function in the cluster is one of the important points where our models fit the observational data. We speculate that the runaway-mass star may have collapsed directly into a massive black hole (more than 100 solar masses). Such a dark object could explain the large velocity dispersion of the four Trapezium stars observed in the ONC core. We further show that the putative massive black hole is likely to be a member of a binary system with ~70% probability. In such a case, it could be detected either due to short periods of enhanced accretion of stellar winds from the secondary star during pericentre passages, or through a measurement of the motion of the secondary whose velocity would exceed 10km/s along the whole orbit.