Close limit evolution of Kerr-Schild type initial data for binary black holes

We evolve the binary black hole initial data family proposed by Bishop {\em et al.} in the limit in which the black holes are close to each other. We present an exact solution of the linearized initial value problem based on their proposal and make use of a recently introduced generalized formalism for studying perturbations of Schwarzschild black holes in arbitrary coordinates to perform the evolution. We clarify the meaning of the free parameters of the initial data family through the results for the radiated energy and waveforms from the black hole collision.Comment: 8 pages, RevTex, four eps figure

Gravitational waves from quasi-spherical black holes

A quasi-spherical approximation scheme, intended to apply to coalescing black holes, allows the waveforms of gravitational radiation to be computed by integrating ordinary differential equations.Comment: 4 revtex pages, 2 eps figure

Initial data for a head on collision of two Kerr-like black holes with close limit

We prove the existence of a family of initial data for the Einstein vacuum equation which can be interpreted as the data for two Kerr-like black holes in arbitrary location and with spin in arbitrary direction. This family of initial data has the following properties: (i) When the mass parameter of one of them is zero or when the distance between them goes to infinity, it reduces exactly to the Kerr initial data. (ii) When the distance between them is zero, we obtain exactly a Kerr initial data with mass and angular momentum equal to the sum of the mass and angular momentum parameters of each of them. The initial data depends smoothly on the distance, the mass and the angular momentum parameters.Comment: 15 pages, no figures, Latex2

Open data from the third observing run of LIGO, Virgo, KAGRA, and GEO

The global network of gravitational-wave observatories now includes five detectors, namely LIGO Hanford, LIGO Livingston, Virgo, KAGRA, and GEO 600. These detectors collected data during their third observing run, O3, composed of three phases: O3a starting in 2019 April and lasting six months, O3b starting in 2019 November and lasting five months, and O3GK starting in 2020 April and lasting two weeks. In this paper we describe these data and various other science products that can be freely accessed through the Gravitational Wave Open Science Center at https://gwosc.org. The main data set, consisting of the gravitational-wave strain time series that contains the astrophysical signals, is released together with supporting data useful for their analysis and documentation, tutorials, as well as analysis software packages

Ice nucleation and freezing tolerance in New Zealand alpine and lowland weta, Hemideina spp. (Orthoptera; Stenopelmatidae)

Abstract.The alpine tree weta Hemidiena maori Pictet et Saussure (Orthoptera: Stenopelmatidae) is a large, flightless insect found above the treeline on many of the mountain ranges of the South Island of New Zealand. The population found on the Rock and Pillar Range, Central Otago has been identified as freezing tolerant with a haemolymph ice nucleating agent. The ability of H. maori to survive freezing is compared to the lowland weta Hemideina thoracica Walker and H. crassidens Blanchard, both of which are able to survive the formation of some ice in their bodies. Mortality is associated with time spent frozen in H. thoracica, and it is hypothesized that this species is killed when a critical proportion of its body water is frozen. All five subalpine and alpine populations of H. maori surveyed were found to be freezing tolerant. Comparison of temperatures of first nucleation and mean supercooling point of haemolymph droplets suggest that haemolymph ice nucleating activity varies between populations of H. maori. Hemideina maori collected from the Mt Cook region appear to lack a haemolymph ice nucleator. This population is nevertheless freezing tolerant, suggesting that the haemolymph ice nucleating agent described in H. maori is not essential for freezing tolerance. Hemideina crassidens and H. ricta Hutton, both of which are found in lowland habitats, also had high mean supercooling point and temperatures of first nucleation of haemolymph droplets, suggesting that these species also have a haemolymph ice nucleator. Comparison of ice nucleation characteristics of haemolymph and faecal material (representing gut contents) suggests that gut nucleators in H. maori may be at least as efficient as the haemolymph nucleator. It is concluded that freezing tolerance is probably not an adaptation to the alpine environment. This highlights the need for inter- and intraspecific comparative studies if physiological data are to be used to draw evolutionary conclusions