New nearby hypervelocity stars and their spatial distribution from Gaia DR2. (arXiv:1907.06348v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Du_C/0/1/0/all/0/1">Cuihua Du</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Li_H/0/1/0/all/0/1">Hefan Li</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Yan_Y/0/1/0/all/0/1">Yepeng Yan</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Newberg_H/0/1/0/all/0/1">Heidi Jo Newberg</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Shi_J/0/1/0/all/0/1">Jianrong Shi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ma_J/0/1/0/all/0/1">Jun Ma</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Chen_Y/0/1/0/all/0/1">Yuqin Chen</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wu_Z/0/1/0/all/0/1">Zhenyu Wu</a>

Base on about 4,500 large tangential velocity
($V_mathrm{tan}>0.75V_mathrm{esc}$) with high-precision proper motions and
$5sigma$ parallaxes in Gaia DR2 5D information derived from parallax and
proper motion, we identify more than 600 high velocity stars with $50%$
unbound probability. Of these, 28 nearby (less than 6 kpc) late-type
Hypervelocity stars (HVSs) with over $99%$ possibility of unbound are
discovered. In order to search for the unbound stars from the full Gaia DR2 6D
phase space information derived from parallax, proper motion and radial
velocity, we also identify 28 stars from the total velocity
($V_mathrm{gc}>0.75V_mathrm{esc}$) that have probabilities greater than
$50%$ of being unbound from the Galaxy. Of these, only three have a nearly
$99%$ probabilities of being unbound. On the whole HVSs subsample, there is 12
sources reported by other surveys. We study the spatial distribution of angular
positions and angular separation of HVSs. We find the unbound HVSs are
spatially anisotropic that is most significant in the Galactic longitude at
more than $3sigma$ level, and lower unbound probability HVSs are
systematically more isotropic. The spatial distribution can reflect the origin
of HVSs and we discuss the possible origin link with the anisotropy.

Base on about 4,500 large tangential velocity
($V_mathrm{tan}>0.75V_mathrm{esc}$) with high-precision proper motions and
$5sigma$ parallaxes in Gaia DR2 5D information derived from parallax and
proper motion, we identify more than 600 high velocity stars with $50%$
unbound probability. Of these, 28 nearby (less than 6 kpc) late-type
Hypervelocity stars (HVSs) with over $99%$ possibility of unbound are
discovered. In order to search for the unbound stars from the full Gaia DR2 6D
phase space information derived from parallax, proper motion and radial
velocity, we also identify 28 stars from the total velocity
($V_mathrm{gc}>0.75V_mathrm{esc}$) that have probabilities greater than
$50%$ of being unbound from the Galaxy. Of these, only three have a nearly
$99%$ probabilities of being unbound. On the whole HVSs subsample, there is 12
sources reported by other surveys. We study the spatial distribution of angular
positions and angular separation of HVSs. We find the unbound HVSs are
spatially anisotropic that is most significant in the Galactic longitude at
more than $3sigma$ level, and lower unbound probability HVSs are
systematically more isotropic. The spatial distribution can reflect the origin
of HVSs and we discuss the possible origin link with the anisotropy.

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