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SUMMARY:The origin of OB runaways and the Astronomical Multipurpose Softwa
 re Environment - Simon Portegies Zwart (Leiden)
DTSTART:20120315T163000Z
DTEND:20120315T173000Z
UID:TALK34615@talks.cam.ac.uk
CONTACT:Mark Gieles
DESCRIPTION:More than 20\\% of all massive stars in the Milky-way Galaxy h
 ave an\nunusual high velocity of $>30$\\\,km/s.  The origin of this popula
 tion\nof runaway OB stars has been puzzling astronomers for more than half
  a\ncentury.  In one of the favorite explanations a star is launched from\
 na binary system when its companion explodes in a core-collapse\nsupernova
 .  This mechanism fails to explain the high proportion of\nrunaway stars t
 hat ware ejected from clusters\, because the ejection\noccurred well befor
 e any star experienced a supernova explosion.  We\ndemonstrate that the ob
 served runaways are explained by stellar\nejections mediated by strong thr
 ee-body interactions with a binary\nstar. Such a binary forms during the c
 ore collapse of a young ($\\aplt\n1$\\\,Myr) and rather low mass ($ 5000-1
 0000$\\\,\\Msun) star cluster.\nThis model reproduces the key characterist
 ics of OB runaways in the\nMilky-way Galaxy and it explains the $\\apgt 10
 0$\\\,\\Msun\\\, runaway\nstars around young star clusters\, e.g. R136 and
  Westerlund 2.  The\nhigh proportion and the distribution in mass of OB ru
 naway stars in\nthe Milky-way Galaxy can be explained if the vast majority
  of massive stars are born in dense and relatively low mass clusters.\n
LOCATION:Sackler Lecture Theatre\, IoA (tea at 4:00 pm)
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