Journal
ASTRONOMY & ASTROPHYSICS
Volume 483, Issue 2, Pages L21-L24Publisher
EDP SCIENCES S A
DOI: 10.1051/0004-6361:200809767
Keywords
stars : individual : HD 271791; stars : distances; stars : early-type; stars : atmospheres; Galaxy : center; Galaxy : halo
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Context. Young, massive stars have been found in the distant Galactic halo. Dynamical ejection from the Galactic disc has been suggested as the origin of these run-away stars. The so-called hyper-velocity stars have been found to travel so fast that they are unbound to the Galaxy. Only a supermassive black hole ( SMBH) appears to be able to accelerate the stars to such high velocities, which suggests that the Galactic centre is their place of origin. Aims. We revisit the run-away B star HD 271791 to determine its nature and origin. Methods. High-resolution optical echelle spectra are analysed using LTE model atmospheres. Based on proper-motion measurements, the 3D kinematic of the star is investigated by means of numerical experiments. Results. HD 271791 is found to be a massive (11 M circle dot), rapidly-rotating B-type star. Its chemical composition is found to be consistent with that of the sun. Its Galactic rest-frame velocity exceeds the Galactic escape velocity. Conclusions. According to its space velocity, HD 271791 qualifies as a hyper-velocity star. Its kinematic constrains the place of birth to the outer Galactic disc and rules out the Galactic centre. HD 271791 is also too young (< 30 Myr) to have originated in the Galactic centre. This challenges the SMBH paradigm for the origin of hyper-velocity stars.
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