MMT hypervelocity star survey. III. The complete survey

Journal Article · Tue May 20 04:00:00 EDT 2014 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/787/1/89· OSTI ID:22356820

Brown, Warren R.; Geller, Margaret J.

We describe our completed spectroscopic survey for unbound hypervelocity stars (HVSs) ejected from the Milky Way. Three new discoveries bring the total number of unbound late B-type stars to 21. We place new constraints on the nature of the stars and on their distances using moderate resolution MMT spectroscopy. Half of the stars are fast rotators; they are certain 2.5-4 M {sub ☉} main sequence stars at 50-120 kpc distances. Correcting for stellar lifetime, our survey implies that unbound 2.5-4 M {sub ☉} stars are ejected from the Milky Way at a rate of 1.5 × 10{sup –6} yr{sup –1}. These unbound HVSs are likely ejected continuously over the past 200 Myr and do not share a common flight time. The anisotropic spatial distribution of HVSs on the sky remains puzzling. Southern hemisphere surveys like SkyMapper will soon allow us to map the all-sky distribution of HVSs. Future proper motion measurements with Hubble Space Telescope and Gaia will provide strong constraints on origin. Existing observations are all consistent with HVS ejections from encounters with the massive black hole in the Galactic center.

• OSTI ID: 22356820
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 787; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ANISOTROPY
BLACK HOLES
DISTANCE
GALAXY NUCLEI
LIFETIME
LIMITING VALUES
MAIN SEQUENCE STARS
MAPS
MILKY WAY
PROPER MOTION
RESOLUTION
SOUTHERN HEMISPHERE
SPACE
SPATIAL DISTRIBUTION
SPECTROSCOPY
TELESCOPES