1,076 research outputs found
Black Hole-Neutron Star Mergers in Globular Clusters
We model the formation of black hole-neutron star (BH-NS) binaries via
dynamical interactions in globular clusters. We find that in dense, massive
clusters, 16-61% of the BH-NS binaries formed by interactions with existing BH
binaries will undergo mergers driven by the emission of gravitational
radiation. If the BHs are retained by the cluster after merging with a NS, the
BHs acquire subsequent NS companions and undergo several mergers. Thus, the
merger rate depends critically upon whether or not the BH is retained by the
cluster after the merger. Results from numerical relativity suggest that kick
imparted to a ~7 M_sun BH after it merges with a NS will greatly exceed the
cluster's escape velocity. In this case, the models suggest that the majority
of BH-NS mergers in globular clusters occur within 4 Gyrs of the cluster's
formation and would be unobservable by Advanced LIGO. For more massive BHs, on
the other hand, the post merger kick is suppressed and the BH is retained.
Models with 35 M_sun BHs predict Advanced LIGO detection rates in the range
0.04 - 0.7 per year. On the pessimistic end of this range, BH-NS mergers
resulting from binary-single star interactions in globular clusters could
account for an interesting fraction of all BH-NS mergers. On the optimistic
end, this channel may dominate the rate of detectable BH-NS mergers.Comment: 13 pages, 7 figures, 3 tabels, accepted for publication in MNRA
Dynamically formed black hole+millisecond pulsar binaries in globular clusters
The discovery of a binary comprising a black hole (BH) and a millisecond
pulsar (MSP) would yield insights into stellar evolution and facilitate
exquisitely sensitive tests of general relativity. Globular clusters (GCs) are
known to harbor large MSP populations and recent studies suggest that GCs may
also retain a substantial population of stellar mass BHs. We modeled the
formation of BH+MSP binaries in GCs through exchange interactions between
binary and single stars. We found that in dense, massive clusters most of the
dynamically formed BH+MSP binaries will have orbital periods of 2 to 10 days,
regardless of the mass of the BH, the number of BHs retained by the cluster,
and the nature of the GC's binary population. The size of the BH+MSP population
is sensitive to several uncertain parameters, including the BH mass function,
the BH retention fraction, and the binary fraction in GCs. Based on our models,
we estimate that there are dynamically formed BH+MSP binaries in
the Milky Way GC system, and place an upper limit on the size of this
population of . Interestingly, we find that BH+MSP binaries will be
rare even if GCs retain large BH populations.Comment: 15 pages, 5 figures, 2 tables, accepted for publication in MNRAS,
updated to match published versio
How England won North America: William Johnson and the Importance of Indian Allies in the French and Indian War
Apparatus and method for treating pollutants in a gas using hydrogen peroxide and UV light
An apparatus for treating pollutants in a gas may include a source of hydrogen peroxide, and a treatment injector for creating and injecting dissociated hydrogen peroxide into the flow of gas. The treatment injector may further include an injector housing having an inlet, an outlet, and a hollow interior extending therebetween. The inlet may be connected in fluid communication with the source of hydrogen peroxide so that hydrogen peroxide flows through the hollow interior and toward the outlet. At least one ultraviolet (UV) lamp may be positioned within the hollow interior of the injector housing. The at least one UV lamp may dissociate the hydrogen peroxide flowing through the tube. The dissociated hydrogen peroxide may be injected into the flow of gas from the outlet for treating pollutants, such as nitrogen oxides
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