101 research outputs found

    Observation of Gravitational Waves from a Binary Black Hole Merger

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    On September 14, 2015 at 09:50:45 UTC the two detectors of the Laser Interferometer Gravitational-Wave Observatory simultaneously observed a transient gravitational-wave signal. The signal sweeps upwards in frequency from 35 to 250 Hz with a peak gravitational-wave strain of 1.0 × 10−21. It matches the waveform predicted by general relativity for the inspiral and merger of a pair of black holes and the ringdown of the resulting single black hole. The signal was observed with a matched-filter signal-to-noise ratio of 24 and a false alarm rate estimated to be less than 1 event per 203 000 years, equivalent to a significance greater than 5.1σ. The source lies at a luminosity distance of 410þ160 −180 Mpc corresponding to a redshift z ¼ 0.09þ0.03 −0.04 . In the source frame, the initial black hole masses are 36þ5 −4M⊙ and 29þ4 −4M⊙, and the final black hole mass is 62þ4 −4M⊙, with 3.0þ0.5 −0.5M⊙c2 radiated in gravitational waves. All uncertainties define 90% credible intervals. These observations demonstrate the existence of binary stellar-mass black hole systems. This is the first direct detection of gravitational waves and the first observation of a binary black hole merger

    Comparative demography of two commensal macaques in India: Implications for population status and conservation

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    Rhesus and bonnet macaques are among the most common primates found in India and have been categorised as being of Least Concern by the IUCN. Despite the wealth of information on their ecology and behaviour, little attention has been paid to their demography or population status. We studied the demographic status of the two species along their common distribution zone in western, central and south-eastern India. Bonnet macaques were largely found in forest areas whereas rhesus macaques were observed more often in human-dominated habitats. The troop sizes of the two species also tended to be largest in different habitats, bonnet macaques in forested areas and rhesus macaques in urban areas. We suggest that the presence of large numbers of rhesus macaques in anthropogenic areas in south-eastern India is not a natural phenomenon but has been caused by human intervention. The bonnet macaque population has decreased in number in the common distribution zone, and as this species, unlike the rhesus macaque, is endemic to India, we strongly recommend the need to reassess its conservation status
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