Gravitational Waves from the Remnants of the First Stars
  Gravitational waves (GWs) provide a revolutionary tool to investigate yet
unobserved astrophysical objects. Especially the first stars, which are
believed to be more massive than present-day stars, might be indirectly
observable via the merger of their compact remnants. We develop a
self-consistent, cosmologically representative, semi-analytical model to
simulate the formation of the first stars. By extrapolating binary
stellar-evolution models at 10% solar metallicity to metal-free stars, we track
the individual systems until the coalescence of the compact remnants. We
estimate the contribution of primordial stars to the merger rate density and to
the detection rate of the Advanced Laser Interferometer Gravitational-Wave
Observatory (aLIGO). Owing to their higher masses, the remnants of primordial
stars produce strong GW signals, even if their contribution in number is
relatively small. We find a probability of $\gtrsim1\%$ that the current
detection GW150914 is of primordial origin. We estimate that aLIGO will detect
roughly 1 primordial BH-BH merger per year for the final design sensitivity,
although this rate depends sensitively on the primordial initial mass function
(IMF). Turning this around, the detection of black hole mergers with a total
binary mass of $\sim 300\,\mathrm{M}_\odot$ would enable us to constrain the
primordial IMF.
