Hypervelocity Stars

Brown, Warren R.

doi:10.1146/annurev-astro-082214-122230

Cited by 167 publications

(105 citation statements)

References 205 publications

(303 reference statements)

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“…The figure shows how much of an outlier S5-HVS1 is, in particular because of the apparent clumping of previously known HVS at 800-1000 km s −1 , which begs the question whether S5-HVS1 was produced using the same mechanism as other HVS. Another difference between S5-HVS1 and other HVS is that it is an A-type star, and thus is somewhat cooler, lower mass and later spectral type than the classical O/B-type hyper-velocity stars (Brown 2015). It is also brighter and much more nearby than the majority of the faint, blue HVS that have been discovered in the Northern sky.…”

Section: Discussionmentioning

confidence: 95%

“…This mechanism was almost forgotten until the early 2000s, when Yu & Tremaine (2003) analysed the ejection mechanism from single and binary SMBHs and Brown et al (2005) identified a star in the Milky Way halo at a distance of 40 − 70 kpc with a total velocity of ∼ 700 km s −1 , well above the escape velocity at such a distance. This discovery spurred a renewed interest in hyper-velocity stars and lead to dedicated searches resulting in multiple new HVS and candidate HVS (see Brown 2015, for an overview and references).…”

Section: Introductionmentioning

confidence: 99%

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Discovery of a nearby 1700 km s−1 star ejected from the Milky Way by Sgr A*

Koposov

Boubert

et al. 2019

Monthly Notices of the Royal Astronomical Society

117

123

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We present the serendipitous discovery of the fastest Main Sequence hyper-velocity star (HVS) by the Southern Stellar Stream Spectroscopic Survey (S 5 ). The star S5-HVS1 is a ∼ 2.35 M A-type star located at a distance of ∼ 9 kpc from the Sun and has a heliocentric radial velocity of 1017 ± 2.7 km s −1 without any signature of velocity variability. The current 3-D velocity of the star in the Galactic frame is 1755 ± 50 km s −1 . When integrated backwards in time, the orbit of the star points unambiguously to the Galactic Centre, implying that S5-HVS1 was kicked away from Sgr A* with a velocity of ∼ 1800 km s −1 and travelled for 4.8 Myr to the current location. This is so far the only HVS confidently associated with the Galactic Centre. S5-HVS1 is also the first hyper-velocity star to provide constraints on the geometry and kinematics of the Galaxy, such as the Solar motion V y, = 246.1 ± 5.3 km s −1 or position R 0 = 8.12 ± 0.23 kpc. The ejection trajectory and transit time of S5-HVS1 coincide with the orbital plane and age of the annular disk of young stars at the Galactic centre, and thus may be linked to its formation. With the S5-HVS1 ejection velocity being almost twice the velocity of other hyper-velocity stars previously associated with the Galactic Centre, we question whether they have been generated by the same mechanism or whether the ejection velocity distribution has been constant over time.

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Section: Discussionmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

Discovery of a nearby 1700 km s−1 star ejected from the Milky Way by Sgr A*

Koposov

Boubert

et al. 2019

Monthly Notices of the Royal Astronomical Society

117

123

View full text Add to dashboard Cite

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“…The lifetime of this star is several times shorter than its flight time from the Milky Way, suggesting an LMC origin (Gualandris & Portegies Zwart 2007) or a blue straggler origin (Perets 2009). The latter channel suggest that the progenitor was likely a binary system ejected from the Milky Way at 800 km s −1 (Brown 2015). Recently, Németh et al (2016) have spotted the first binary HVS candidate ≈ 5.7 kpc far from the GC travelling at ≈ 571 km s −1 .…”

Section: Discussionmentioning

confidence: 98%

“…Other possible origins have been advanced (Brown 2015), such as the interaction of a BH binary with a single star (Yu & Tremaine 2003), the interaction of star clusters and BHs (Capuzzo-Dolcetta & Fragione 2015;Fragione & Capuzzo-Dolcetta 2016), supernova explosions (Zubovas, Wynn & Gualandris 2013;Tauris 2015), tidal disruption of a dwarf galaxy passing through the Galactic Center (GC) (Abadi et al 2009) and the dynamical evolution of a thin and eccentric disk orbiting around a massive BH ( The importance of HVSs is that they can pro-vide information on the environment where they were born (Gould & Quillen 2003). In particular, they can discriminate between a single and a binary BH in the GC (Sesana, Haardt & Madau 2007).…”

Section: Introductionmentioning

confidence: 99%

Hypervelocity stars from young stellar clusters in the Galactic Centre

Fragione

Capuzzo-Dolcetta

Kroupa

2017

Mon. Not. R. Astron. Soc.

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The enormous velocities of the so called hypervelocity stars (HVSs) derive, likely, from close interactions with massive black holes, binary stars encounters or supernova explosions. In this paper, we investigate the origin of hypervelocity stars as consequence of the close interaction between the Milky Way central massive black hole and a passing-by young stellar cluster. We found that both single and binary HVSs may be generated in a burst-like event, as the cluster passes near the orbital pericentre. High velocity stars will move close to the initial cluster orbital plane and in the direction of the cluster orbital motion at the pericentre. The binary fraction of these HVS jets depends on the primordial binary fraction in the young cluster. The level of initial mass segregation determines the value of the average mass of the ejected stars. Some binary stars will merge, continuing their travel across and out of the Galaxy as blue stragglers.

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“…We check whether the compact objects remain bound to the SMBH after the disruption or they escape the nuclear star clusters as hyper-velocity stars (HVSs; Brown 2015). We found that in 99.4% of the disrupted systems (i.e.…”

Section: Hypervelocity Starsmentioning

confidence: 99%

Intermediate-mass Black Holes’ Effects on Compact Object Binaries

Deme

Meiron

Kocsis

2020

ApJ

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Although their existence is not yet confirmed observationally, intermediate mass black holes (IMBHs) may play a key role in the dynamics of galactic nuclei. In this paper, we investigate how a small reservoir of IMBHs influences the secular dynamics of stellar-mass black hole binaries in a nuclear star cluster, using N -body simulations. We show that the IMBHs significantly enhance binary evaporation by pushing the binaries into the Hill-unstable region of parameter space, where they are separated by the SMBH's tidal field. For binaries in the S-cluster region of the Milky Way, IMBHs drive the binaries to merge in up to 1-6% of cases, assuming five IMBHs within 5 pc of mass 10 4 M each. Observations of binaries in the Galactic center may strongly constrain the population of IMBHs therein.

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Hypervelocity Stars

Cited by 167 publications

References 205 publications

Discovery of a nearby 1700 km s−1 star ejected from the Milky Way by Sgr A*

Discovery of a nearby 1700 km s−1 star ejected from the Milky Way by Sgr A*

Hypervelocity stars from young stellar clusters in the Galactic Centre

Intermediate-mass Black Holes’ Effects on Compact Object Binaries

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