Copyright by Athena Ranice Stacy 2011 - The University of Texas at ...

to carbon-enhanced metal-poor (CEMP) stars, those metal-poor halo stars
with unusually high carbon abundance (e.g. Frebel et al. 2007; Tumlinson
2007). If one of the members of a Pop III binary was an intermediate-mass star
(1 M⊙ < ∼ M∗ < ∼ 8 M⊙), then the companion might undergo carbon enhancement
through binary mass-transfer (e.g. Suda et al. 2004. This would occur when
the intermediate-mass star enters an asymptotic giant branch (AGB) phase
during which its C-rich ejecta can be captured by the companion. Furthermore,
another type of Pop III signature would arise if gamma-ray bursts (GRBs) were
able to form from very tight Pop III binaries. These may be detectable by Swift
(see Bromm and Loeb 2006; Belczynski et al. 2007).
On the other hand, if both members of a typical Pop III binary were
in the mass range to collapse directly into a black hole (M∗ > ∼ 260 M⊙), then
they could become massive black hole (MBH) binaries. Such a population of
MBH binaries may emit a gravitational wave (GW) signature detectable by
the future space-born Laser Interferometer Space Antenna (LISA). Previous
studies have already explored the possibility of GW detection of MBH binaries
formed through halo mergers during early structure formation (e.g. Wyithe
and Loeb 2003; Sesana et al. 2005). Sesana et al. (2005) find that high redshift
(z > ∼ 10) MBH binaries with masses < ∼ 10 3 M⊙ will be detectable by LISA.
MBH binaries formed from Pop III progenitors thus approach the range of
detectability by LISA, especially if the BHs continue to grow in mass through
accretion. Furthermore, Belczynski et al. (2004) predict that advanced LIGO
could also detect the GWs from Pop III MBH binary mergers. Madau and Rees
(2001) suggested a different type of Pop III MBH signal when they discussed
how an accreting primordial MBH could tidally capture a star and become a
detectable off-nuclear ultraluminous X-ray source. They conclude, however,
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