Long-Term Evolution of Massive Black Hole Binaries. III. Binary Evolution in Collisional Nuclei

[Abridged] In galactic nuclei with sufficiently short relaxation times, binary supermassive black holes can evolve beyond their stalling radii via continued interaction with stars. We study this "collisional" evolutionary regime using both fully self-consistent N-body integrations and approximate Fokker-Planck models. The N-body integrations employ particle numbers up to 0.26M and a direct-summation potential solver; close interactions involving the binary are treated using a new implementation of the Mikkola-Aarseth chain regularization algorithm. Even at these large values of N, two-body scattering occurs at high enough rates in the simulations that they can not be simply scaled to the large-N regime of real galaxies. The Fokker-Planck model is used to bridge this gap; it includes, for the first time, binary-induced changes in the stellar density and potential. The Fokker-Planck model is shown to accurately reproduce the results of the N-body integrations, and is then extended to the much larger N regime of real galaxies. Analytic expressions are derived that accurately reproduce the time dependence of the binary semi-major axis as predicted by the Fokker-Planck model. Gravitational wave coalescence is shown to occur in <10 Gyr in nuclei with velocity dispersions below about 80 km/s. Formation of a core results from a competition between ejection of stars by the binary and re-supply of depleted orbits via two-body scattering. Mass deficits as large as ~4 times the binary mass are produced before coalescence. After the two black holes coalesce, a Bahcall-Wolf cusp appears around the single hole in one relaxation time, resulting in a nuclear density profile consisting of a flat core with an inner, compact cluster, similar to what is observed at the centers of low-luminosity spheroids.Comment: 21 page

How T.V. Promotes an Unrealistic Image of Romantic Relationships

This study aims to explore and prove that media (as defined in T.V. sitcoms and dramas) portrays an unrealistic expectation that is placed on romantic relationships. More specifically, it can affect the way people think and behave when it comes to marriages and serious relationships. Some may begin to compare their present relationship with a romantic relationship within the sitcoms and dramas. This study will. be used to promote awareness when making conscious and sensible decisions in regards to choosing partners. This will be done by conducting surveys that will exhibit the direct emotional effect of sitcoms and dramas on adolescents ranging from 15-18 years of age and young adults 20- 23. The findings used are derived from current T.V. sitcoms and dramas, with further consideration as to its effects on age, gender, race, and marital status

Using Wii technology to explore real spaces via virtual environments for people who are blind

Purpose - Virtual environments (VEs) that represent real spaces (RSs) give people who are blind the opportunity to build a cognitive map in advance that they will be able to use when arriving at the RS. Design - In this research study Nintendo Wii based technology was used for exploring VEs via the Wiici application. The Wiimote allows the user to interact with VEs by simulating walking and scanning the space. Finding - By getting haptic and auditory feedback the user learned to explore new spaces. We examined the participants' abilities to explore new simple and complex places, construct a cognitive map, and perform orientation tasks in the RS. Originality – To our knowledge, this finding presents the first virtual environment for people who are blind that allow the participants to scan the environment and by this to construct map model spatial representations

Spin Flips and Precession in Black-Hole-Binary Mergers

We use the `moving puncture' approach to perform fully non-linear evolutions of spinning quasi-circular black-hole binaries with individual spins not aligned with the orbital angular momentum. We evolve configurations with the individual spins (parallel and equal in magnitude) pointing in the orbital plane and 45-degrees above the orbital plane. We introduce a technique to measure the spin direction and track the precession of the spin during the merger, as well as measure the spin flip in the remnant horizon. The former configuration completes 1.75 orbits before merging, with the spin precessing by 98-degrees and the final remnant horizon spin flipped by ~72-degrees with respect to the component spins. The latter configuration completes 2.25 orbits, with the spins precessing by 151-degrees and the final remnant horizon spin flipped ~34-degrees with respect to the component spins. These simulations show for the first time how the spins are reoriented during the final stage of binary black hole mergers verifying the hypothesis of the spin-flip phenomenon. We also compute the track of the holes before merger and observe a precession of the orbital plane with frequency similar to the orbital frequency and amplitude increasing with time.Comment: Revtex4, 17 figures, 14 pages. Accepted for publication in PR

Model Atmospheres for Irradiated Giant Stars: Implications for the Galactic Center

Irradiation of a stellar atmosphere by an external source (e.g. an AGN) changes its structure and therefore its spectrum. Using a state-of-the-art stellar atmosphere code, we calculate the infrared spectra of such irradiated and transformed stars. We show that the original spectrum of the star, which is dominated by molecular bands, changes dramatically when irradiated even by a low-luminosity AGN ($L_{\rm X} = 10^{33}$ erg s$^{-1}$), becoming dominated by atomic lines in absorption. We study the changes in the spectrum of low-mass carbon- and oxygen-rich giant stars as they are irradiated by a modest AGN, similar to the one at the Galactic center (GC). The resulting spectra are similar to those of the faintest S-cluster stars observed in the GC. The spectrum of a star irradiated by a much brighter AGN, like that powered by a tidally disrupted star, is very different from that of any star currently observed near the GC. For the first time we have discovered that the structure of the atmosphere of an irradiated giant changes dramatically and induces a double inversion layer. We show that irradiation at the current level can explain the observed trend of CO band intensities decreasing as a function of increasing proximity to Sg $A^{*}$. This may indicate that (contrary to previous claims) there is no paucity of old giants in the GC, which coexist simultaneously with young massive stars.Comment: Submitted to ApJ; typo in name correcte

Large Merger Recoils and Spin Flips From Generic Black-Hole Binaries

We report the first results from evolutions of a generic black-hole binary, i.e. a binary containing unequal mass black holes with misaligned spins. Our configuration, which has a mass ratio of 2:1, consists of an initially non-spinning hole orbiting a larger, rapidly spinning hole (specific spin a/m = 0.885), with the spin direction oriented -45 degrees with respect to the orbital plane. We track the inspiral and merger for ~2 orbits and find that the remnant receives a substantial kick of 454 km/s, more than twice as large as the maximum kick from non-spinning binaries. The remnant spin direction is flipped by 103 degrees with respect to the initial spin direction of the larger hole. We performed a second run with anti-aligned spins, a/m = +-0.5 lying in the orbital plane that produces a kick of 1830 km/s off the orbital plane. This value scales to nearly 4000 km/s for maximally spinning holes. Such a large recoil velocity opens the possibility that a merged binary can be ejected even from the nucleus of a massive host galaxy.Comment: 4 pages. Accepted for publication in ApJ

Summary of Aerodynamic Vibration Effects on ALL Turret

The effects of the airborne environment on a pointing and tracking system using a turret external to an aircraft are summarized. The data covered a series of flight tests and a span of seven years. The two major airborne effects were shown to be direct pressure loading of optical elements and vibrations of the entire turret. The direct optical loading problem was minimized by fence designs for the turret