2015ApJ...806..124G -
Astrophys. J., 806, 124 (2015/June-2)
The fastest unbound stars in the universe.
GUILLOCHON J. and LOEB A.
Abstract (from CDS):
The discovery of hypervelocity stars (HVSs) leaving our galaxy with speeds of nearly 103 km/s has provided strong evidence of the existence of a massive compact object at the galaxy's center. HVSs ejected via the disruption of stellar binaries can occasionally yield a star with km/s; here we show that this mechanism can be extended to massive black hole (MBH) mergers, where the secondary star is replaced by a MBH with mass. We find that stars that are originally bound to the secondary MBH are frequently ejected with km/s, and occasionally with velocities Å105 km/s (one third the speed of light). For this reason we refer to stars ejected from these systems as ''semi-relativistic'' hypervelocity stars (SHSs). Bound to no galaxy, the velocities of these stars are so great that they can cross a significant fraction of the observable universe in the time since their ejection (several Gpc). We demonstrate that if a significant fraction of MBH mergers undergoes a phase in which their orbital eccentricity is ><≥0.5 and their periapse distance is tens of the primary's Schwarzschild radius, the space density of fast-moving ( km/s) SHSs may be as large as 103/Mpc3. Hundreds of SHSs will be giant stars that can be detected by future all-sky infrared surveys such as WFIRST or Euclid and proper motion surveys such as LSST, with spectroscopic follow-up being possible with the James Webb Space Telescope.
Abstract Copyright:
∼
Journal keyword(s):
black hole physics - gravitation
Simbad objects:
8
Full paper
View the references in ADS
To bookmark this query, right click on this link: simbad:2015ApJ...806..124G and select 'bookmark this link' or equivalent in the popup menu