The first observational run of the Advanced LIGO detectors, from September 12, 2015 to January 19, 2016, saw the first detections of gravitational waves from binary black hole mergers. In this paper we present full results from a search for binary black hole merger signals with total masses up to 100M⊙ and detailed implications from our observations of these systems. Our search, based on general-relativistic models of gravitational wave signals from binary black hole systems, unambiguously identified two signals, GW150914 and GW151226, with a significance of greater than 5σ over the observing period. It also identified a third possible signal, LVT151012, with substantially lower significance, which has a 87% probability of being of astrophysical origin. We provide detailed estimates of the parameters of the observed systems. Both GW150914 and GW151226 provide an unprecedented opportunity to study the two-body motion of a compact-object binary in the large velocity, highly nonlinear regime. We do not observe any deviations from general relativity, and place improved empirical bounds on several high-order post-Newtonian coefficients. From our observations we infer stellar-mass binary black hole merger rates lying in the range 9−240Gpc−3yr−1. These observations are beginning to inform astrophysical predictions of binary black hole formation rates, and indicate that future observing runs of the Advanced detector network will yield many more gravitational wave detections.

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Binary Black Hole Mergers in the First Advanced LIGO Observing Run

This is a comprehensive and richly illustrated textbook on the astrophysics of the interstellar and intergalactic medium--the gas and dust, as well as the electromagnetic radiation, cosmic rays, and magnetic and gravitational fields, present between the stars in a galaxy and also between galaxies themselves. Topics include radiative processes across the electromagnetic spectrum; radiative transfer; ionization; heating and cooling; astrochemistry; interstellar dust; fluid dynamics, including ionization fronts and shock waves; cosmic rays; distribution and evolution of the interstellar medium; and star formation. While it is assumed that the reader has a background in undergraduate-level physics, including some prior exposure to atomic and molecular physics, statistical mechanics, and electromagnetism, the first six chapters of the book include a review of the basic physics that is used in later chapters. This graduate-level textbook includes references for further reading, and serves as an invaluable resource for working astrophysicists. * Essential textbook on the physics of the interstellar and intergalactic medium * Based on a course taught by the author for more than twenty years at Princeton University * Covers radiative processes, fluid dynamics, cosmic rays, astrochemistry, interstellar dust, and more * Discusses the physical state and distribution of the ionized, atomic, and molecular phases of the interstellar medium * Reviews diagnostics using emission and absorption lines * Features color illustrations and detailed reference materials in appendices * Instructor's manual with problems and solutions (available only to teachers)

Physics of the Interstellar and Intergalactic Medium

Formation and evolution of binary and millisecond radio pulsars

A new generation of ground-based interferometric detectors for gravitational waves is currently under construction or has entered the commissioning phase (Laser Interferometer Gravitational-wave Observatory [LIGO], VIRGO, GEO600, TAMA300). The purpose of these detectors is to observe gravitational waves from astrophysical sources and help improve our understanding of the source origin and physical properties. In this paper we study the most promising candidate sources for these detectors: inspiraling double compact objects. We use population synthesis methods to calculate the properties and coalescence rates of compact object binaries: double neutron stars, black hole-neutron star systems, and double black holes. We also examine the formation channels available to double compact object binaries. We explicitly account for the evolution of low-mass helium stars and investigate the possibility of common-envelope evolution involving helium stars as well as two evolved stars. As a result we identify a significant number of new formation channels for double neutron stars, in particular, leading to populations with very distinct properties. We discuss the theoretical and observational implications of such populations, but we also note the need for hydrodynamical calculations to settle the question of whether such common-envelope evolution is possible. We also present and discuss the physical properties of compact object binaries and identify a number of robust, qualitative features as well as their origin. Using the calculated coalescence rates we compare our results to earlier studies and derive expected detection rates for LIGO. We find that our most optimistic estimate for the first LIGO detectors reach a couple of events per year and our most pessimistic estimate for advanced LIGO detectors exceed 10 events per year.

https://iopscience.iop.org/article/10.1086/340304/pdf

A Comprehensive Study of Binary Compact Objects as Gravitational Wave Sources: Evolutionary Channels, Rates, and Physical Properties

▪ Abstract In this article we first review the main physical effects to be considered in the building of evolutionary models of rotating stars on the Upper Main-Sequence (MS). The internal rotation...

The Evolution of Rotating Stars

Wolf-Rayet Stars and Interrelations with Other Massive Stars in Galaxies

Our galaxy is composed of billions of stars concentrated in the galactic plane, surrounded by interstellar gas, which is mainly composed of hydrogen. About half of the hydrogen is distributed uniformly in the galaxy; the other half is concentrated in interstellar clouds. We find atomic hydrogen in diffuse clouds (with a particle number density n = 10 cm−3); we find molecular hydrogen (H2) in dark clouds (n = 103 cm−3). Finally we have interstellar molecular clouds (n = 106 cm−3) which also contain more complex molecules.

The Formation of Stars

The WR and O-type star population predicted by massive star evolutionary synthesis

Fundamental Problems in the Theory of Stellar Evolution

The evolution of mass-losing stars that have M(ZAMS)/solar-M in the 50-100 range is examined. The stellar models used in this study include: (1) mass loss formalism for O, Of, and W-R stars; (2) the Roxburgh criterion for the convective core; and (3) a nuclear reaction network of 28 nuclides from H to Si-30 for analysis of energy production and chemical evolution during the H- and He-burning phases. The internal evolution of stars with solar masses of 50, 60, 80, and 100 is described by observing time variations of the stellar and convective core masses, and central temperature and density fluctuation during the H- and He-burning phases; the evolution of the models in the Hertzsprung-Russell diagram is studied. The formation of the chemical abundances in the convective core and surface of the stars is investigated. The composition of the stellar ejecta of the W-R stars is discussed. The data reveal that the computed evolutionary tracks and core and surface abundances correlate well with the observational data. 93 references.

C. De Loore

Papers

Wolf-Rayet Stars and Interrelations with Other Massive Stars in Galaxies

The Formation of Stars

The WR and O-type star population predicted by massive star evolutionary synthesis

Fundamental Problems in the Theory of Stellar Evolution

Nucleosynthesis and Evolution of Massive Stars with Mass Loss and Overshooting