2007MNRAS.376L..29G

We study the acceleration of the star HE0437-5439to hypervelocity and discuss its possible origin in the Large Magellanic Cloud (LMC). The star has a radial velocity of 723km/s and is located at a distance of 61 kpc from the Sun. With a mass of about 8M_☉, the traveltime from the Galactic Centre is about 100 Myr, much longer than its main-sequence lifetime. Given the relatively small distance to the LMC (18 kpc), we consider it likely that HE0437-5439originated in the Cloud rather than in the Galactic Centre like the other hypervelocity stars. The minimum ejection velocity required to travel from the LMC to its current location within its lifetime is about 500km/s. Such a high velocity can only be obtained in a dynamical encounter with a massive black hole. We perform three-body scattering simulations in which a stellar binary encounters a massive black hole, and find that a black hole more massive than 10³M_☉ is necessary to explain the high velocity of HE0437-5439. We look for possible parent clusters for HE0437-5439, and find that NGC2100 and 2004 are young enough to host stars coeval to HE0437-5439and dense enough to produce an intermediate-mass black hole able to eject an 8-M_☉ star with hypervelocity.