Hypervelocity Stars Ejected from the Galactic Center

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Hypervelocity StarsEjected from the Galactic
Center
MMT Symposium June 14, 2006 Warren R.
Brown Harvard-Smithsonian CfA Collaborators
Margaret Geller, Scott Kenyon, Michael Kurtz
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The Milky Way
30 kpc
8 kpc
r100 kpc
Kaufmann
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The Galactic Center
http//www.mpe.mpg.de/ir/GC/prop.html
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Eisenhauer et al. 2005
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Three-body exchange
Bromley 2005
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Radial Velocities from the MMT
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(No Transcript)
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An Unexpected Star
Brown et al. (2005)

• VRF 709 km/s
• B9 main sequence star.
• Fe/H 0.
• Distance 110 kpc.
• Travel time 160 Myr to 110 kpc.

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A Hypervelocity Star
Brown et al. (2005)

• VRF 709 km/s
• B9 main sequence star.
• Fe/H 0.
• Distance 110 kpc.
• Travel time 160 Myr to 110 kpc.

NY Times
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Our Search for more Hypervelocity Stars
O
B
F
A
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K
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Fukugita et al (1996)
Brown et al. (2005)
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Our Search for more Hypervelocity Stars
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B
F
A
G
K
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Fukugita et al (1996)
Brown et al. (2006a)
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Our Search for more Hypervelocity Stars
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B
F
A
G
K
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Fukugita et al (1996)
Brown et al. (2006b)
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New Discoveries
Brown et al. (2006b)
astro-ph/0604111
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The Big Picture
Brown et al. (2006b)
-300 0
300 km/s
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Mass Function of Stars
We Observe 4 HVS in 4000 deg2
40 3-4 Msun HVSs
U. Heber
Salpeter
16 3-4 Msun stars
Predicted 2000 HVSs (Yu Tremaine)
Arches
460 3-4 Msun stars
NASA HST
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Applications Galactic

• Yu Tremaine (2003) HVS rates
• Gualandris et al (2005) velocities
• Ginsburg Loeb (2005) orbits
• Levin (2005) in-spiral signature
• Gnedin et al (2005) dark matter

Ginsburg Loeb (2006)
LISA
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Applications Extra-Galactic
M87

• Holley-Bockelmann et al. (2006)
• M87 planetary nebulae?
• Demarque Virani (2006)
• center of M31?

D. Malin
M31
J. Ware
Bender et al (2005)
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Coming Attractions

• Discovery surveys MMT, 1.5m.
• Spectroscopic identifications
• HET, VLT (Edelmann, Heber).
• Space velocities HST (Gnedin).
• Variability MDM (Stanek).
• N-body simulations (Bromley).
• Other unusual objects (Kewley).

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Conclusions

• MBH a hypervelocity stars.
• First HVS B star 709 km/s
• Now seven known HVSs.
• Provide constraints on mass function of stars
• and infall history of MBH.

NY Times
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The Hypervelocity Stars
Brown et al. (2006b)