A Galactic Origin for HE 0437-5439, The Hypervelocity Star Near the Large Magellanic Cloud
Anderson, Jay; Livio, Mario; Bond, Howard E.; Geller, Margaret J.; Gnedin, Oleg Y.; Brown, Warren R.; Kenyon, Scott J.
United States
Abstract
We use Hubble Space Telescope imaging to measure the absolute proper motion of the hypervelocity star (HVS) HE 0437-5439, a short-lived B star located in the direction of the Large Magellanic Cloud (LMC). We observe (μα, μδ) = (+0.53 ± 0.25(stat) ± 0.33(sys), + 0.09 ± 0.21(stat) ± 0.48(sys)) mas yr-1. The velocity vector points directly away from the center of the Milky Way; an origin from the center of the LMC is ruled out at the 3σ level. The flight time of the HVS from the Milky Way exceeds its main-sequence lifetime, thus its stellar nature requires it to be a blue straggler. The large space velocity rules out a Galactic-disk ejection. Combining the HVS's observed trajectory, stellar nature, and required initial velocity, we conclude that HE 0437-5439 was most likely a compact binary ejected by the Milky Way's central black hole.
Based on observations with the NASA/ESA Hubble Space Telescope obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.