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Discovery of an Unbound Hyper-Velocity Star in the Milky Way Halo | | Warren R. Brown
; Margaret J. Geller
; Scott J. Kenyon
; Michael J. Kurtz
; | | Date: |
11 Dec 2004 | | Journal: | Astrophys.J. 622 (2005) L33 | | Subject: | astro-ph | | Affiliation: | SAO | | Abstract: | We have discovered a star, SDSS J090745.0+024507, leaving the Galaxy with a heliocentric radial velocity of +853+-12 km/s, the largest velocity ever observed in the Milky Way halo. The star is either a hot blue horizontal branch star or a B9 main sequence star with a heliocentric distance ~55 kpc. Corrected for the solar reflex motion and to the local standard of rest, the Galactic rest-frame velocity is +709 km/s. Because its radial velocity vector points 173.8 deg from the Galactic center, we suggest that this star is the first example of a hyper-velocity star ejected from the Galactic center as predicted by Hills and later discussed by Yu & Tremaine. The star has [Fe/H]~0, consistent with a Galactic center origin, and a travel time of <80 Myr from the Galactic center, consistent with its stellar lifetime. If the star is indeed traveling from the Galactic center, it should have a proper motion of 0.3 mas/yr observable with GAIA. Identifying additional hyper-velocity stars throughout the halo will constrain the production rate history of hyper-velocity stars at the Galactic center. | | Source: | arXiv, astro-ph/0501177 | | Services: | Forum | Review | PDF | Favorites | |
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