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Following a dynamical encounter with Sgr A*, binaries in the Galactic Centre (GC) can be tidally separated and one member star ejected as a hyper-velocity star (HVS) with a velocity beyond the escape speed of the Milky Way. As GC-born…

Astrophysics of Galaxies · Physics 2022-03-09 F. A. Evans , T. Marchetti , E. M. Rossi

Hypervelocity stars (HVSs) are amongst the fastest objects in our Milky Way. These stars are predicted to come from the Galactic center (GC) and travel along unbound orbits across the Galaxy. In the coming years, the ESA satellite Gaia will…

Astrophysics of Galaxies · Physics 2018-03-21 T. Marchetti , O. Contigiani , E. M. Rossi , J. G. Albert , A. G. A. Brown , A. Sesana

The paucity of hypervelocity stars (HVSs) known to date has severely hampered their potential to investigate the stellar population of the Galactic Centre and the Galactic Potential. The first Gaia data release gives an opportunity to…

Astrophysics of Galaxies · Physics 2017-05-30 T. Marchetti , E. M. Rossi , G. Kordopatis , A. G. A. Brown , A. Rimoldi , E. Starkenburg , K. Youakim , R. Ashley

Several dozen hypervelocity star (HVS) candidates have been reported based on the second data release of Gaia (Gaia DR2). However, it has been proven that the radial velocities of some Gaia HVS candidates are not reliable. In this paper, we…

Solar and Stellar Astrophysics · Physics 2020-05-13 Jiao Li , Shi Jia , Yan Gao , Deng-Kai Jiang , Thomas Kupfer , Ulrich Heber , Chao Liu , Xue-Fei Chen , Zhan-Wen Han

Young massive stars in the halo are assumed to be runaway stars from the Galactic disk. Possible ejection scenarios are binary supernova ejections (BSE) or dynamical ejections from star clusters (DE). Hypervelocity stars (HVSs) are extreme…

Solar and Stellar Astrophysics · Physics 2018-12-05 Andreas Irrgang , Simon Kreuzer , Ulrich Heber

A dynamical encounter between a stellar binary and Sgr A* in the Galactic Centre (GC) can tidally separate the binary and eject one member with a velocity beyond the escape speed of the Milky Way. These hypervelocity stars (HVSs) can offer…

Astrophysics of Galaxies · Physics 2022-10-18 Fraser A. Evans , Tommaso Marchetti , Elena Maria Rossi

We search for high-velocity stars in the inner region of the Galactic bulge using a selected sample of red clump stars. Some of those stars might be considered hypervelocity stars (HVSs). Even though the HVSs ejection relies on an…

Astrophysics of Galaxies · Physics 2024-01-12 A. Luna , T. Marchetti , M. Rejkuba , N. W. C. Leigh , J. Alonso-García , A. Valenzuela Navarro , D. Minniti , L. C. Smith

The third data release (DR3) of the European Space Agency satellite Gaia provides coordinates, parallaxes, proper motions, and radial velocities for a sample of $\sim 34$ million stars. We use the combined 6-dimensional phase space…

Astrophysics of Galaxies · Physics 2022-07-06 Tommaso Marchetti , Fraser A. Evans , Elena Maria Rossi

We assemble a large sample of 12,784 high-velocity stars with total velocity $\it{V}_{\rm{GSR}}\ge {\rm 300}$ km s$^{-1}$, selected from RAVE DR5, SDSS DR12, LAMOST DR8, APOGEE DR16, GALAH DR2, and $Gaia$ EDR3. In this sample, 52 are…

Astrophysics of Galaxies · Physics 2023-06-28 Qing-Zheng Li , Yang Huang , Xiao-Bo Dong , Hua-Wei Zhang , Timothy C. Beers , Zhen Yuan

Hypervelocity stars (HVSs) travel so fast that they may leave the Galaxy. The tidal disruption of a binary system by the supermassive black hole in the Galactic center is widely assumed to be their ejection mechanism. To test the hypothesis…

Solar and Stellar Astrophysics · Physics 2018-07-18 Andreas Irrgang , Simon Kreuzer , Ulrich Heber , Warren Brown

Hypervelocity stars (HVSs) travel from the Galactic Centre across the dark matter halo of the Milky Way, where they are observed with velocities in excess of the Galactic escape speed. Because of their quasi-radial trajectories, they…

Astrophysics of Galaxies · Physics 2019-06-14 O. Contigiani , E. M. Rossi , T. Marchetti

Hypervelocity stars (HVSs) are stars ejected completely out of the Milky Way by three-body interactions with the massive black hole in the Galactic center. We describe 643 new spectroscopic observations from our targeted survey for HVSs. We…

Hypervelocity stars (HVSs) are stars with velocities exceeding their local escape velocities. Searching for HVSs and studying their origins can be an important way to study the properties of the Milky Way. In this paper, we utilize precise…

Astrophysics of Galaxies · Physics 2025-10-01 Haozhu Fu , Yang Huang , Huawei Zhang

Hypervelocity stars (HVSs) unbound to the Galaxy can be formed with extreme stellar interactions. Observational evidence comes from measurements of radial velocities (RVs) of objects crossing the Galactic halo and of tangential velocities…

Astrophysics of Galaxies · Physics 2024-05-22 Ralf-Dieter Scholz

Hypervelocity stars (HVSs) represent a unique class of objects capable of escaping the gravitational pull of the Milky Way due to extreme acceleration events, such as close encounters with the supermassive black hole at the Galactic center…

Astrophysics of Galaxies · Physics 2025-04-22 Yongkang Sun , Yang Huang , Jifeng Liu , Haozhu Fu , Huawei Zhang , Yinbi Li , Cuihua Du , Jianrong Shi , Xiao Kong

Base on about 4,500 large tangential velocity ($V_\mathrm{tan}>0.75V_\mathrm{esc}$) with high-precision proper motions and $5\sigma$ parallaxes in Gaia DR2 5D information derived from parallax and proper motion, we identify more than 600…

Astrophysics of Galaxies · Physics 2019-09-04 Cuihua Du , Hefan Li , Yepeng Yan , Heidi Jo Newberg , Jianrong Shi , Jun Ma , Yuqin Chen , Zhenyu Wu

Hypervelocity stars (HVSs) are stars ejected from the Galactic Centre (GC) through tidal interactions with the central supermassive black hole. Formed in the immediate vicinity of Sgr~A$^\ast$, these stars are accelerated to velocities high…

Astrophysics of Galaxies · Physics 2026-05-13 Manuel Cavieres , Sergey E. Koposov , Elena Maria Rossi , Zephyr Penoyre , Sill Verberne

Hypervelocity stars (HVS) move so fast that they are unbound to the Galaxy. When they were first discovered in 2005, dynamical ejection from the supermassive black hole (SMBH) in the Galactic Centre (GC) was suggested as their origin. The…

Solar and Stellar Astrophysics · Physics 2015-04-15 E. Ziegerer , M. Volkert , U. Heber , A. Irrgang , B. T. Gaensicke , S. Geier

We report the discovery of 3 new unbound hypervelocity stars (HVSs), stars traveling with such extreme velocities that dynamical ejection from a massive black hole (MBH) is their only suggested origin. We also detect a population of…

We report the discovery of two new unbound hypervelocity stars (HVSs) from the LAMOST spectroscopic surveys. They are respectively a B2V type star of ~ 7 M$_{\rm \odot}$ with a Galactic rest-frame radial velocity of 502 km/s at a…

Astrophysics of Galaxies · Physics 2017-10-04 Yang Huang , Xiaowei Liu , Huawei Zhang , Bingqiu Chen , Maosheng Xiang , Chun Wang , Haibo Yuan , Zhijia Tian , Yinbi Li , Bo Wang
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