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Journal ArticleDOI

Observation of a Rapidly Pulsating Radio Source

01 Jan 1968-Nature (Nature Publishing Group)-Vol. 217, Iss: 5130, pp 709-713
TL;DR: In this article, the first report of a curious class of astronomical radio sources, distinguished by their rapid and extremely regular pulsations, was made by Hewish et al. They are now understood to be rapidly rotating, magnetized neutron stars, or pulsars.
Abstract: Unusual signals from pulsating radio sources have been recorded at the Mullard Radio Astronomy Observatory The radiation seems to come from local objects within the galaxy, and may be associated with oscillations of white dwarf or neutron stars 1968 saw the first report of a curious class of astronomical radio sources, distinguished by their rapid and extremely regular pulsations Hewish et al associated them with unusually stable oscillations in compact stars They are now understood to be rapidly rotating, magnetized neutron stars, or pulsars
Citations
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Journal ArticleDOI
TL;DR: A comprehensive survey of recent work on modified theories of gravity and their cosmological consequences can be found in this article, where the authors provide a reference tool for researchers and students in cosmology and gravitational physics, as well as a selfcontained, comprehensive and up-to-date introduction to the subject as a whole.

3,674 citations


Cites background from "Observation of a Rapidly Pulsating ..."

  • ...Pulsars are rapidly rotating neutron stars that emit a beam of electromagnetic radiation, and were first observed in 1967 [604]....

    [...]

Journal ArticleDOI
TL;DR: A new and complete catalog of the main properties of the 1509 pulsars for which published information currently exists, which includes all spin-powered pulsars, as well as anomalous X-ray pulsars and soft gamma-ray repeaters showing coherent pulsed emission.
Abstract: We have compiled a new and complete catalog of the main properties of the 1509 pulsars for which published information currently exists. The catalog includes all spin-powered pulsars, as well as anomalous X-ray pulsars and soft gamma-ray repeaters showing coherent pulsed emission, but excludes accretion-powered systems. References are given for all data listed. We have also developed a new World Wide Web interface for accessing and displaying either tabular or plotted data with the option of selecting pulsars to be displayed via logical conditions on parameter expressions. The Web interface has an expert mode giving access to a wider range of parameters and allowing the use of custom databases. For users with locally installed software and database on Unix or Linux systems, the catalog may be accessed from a command-line interface. C-language functions to access specified parameters are also available. The catalog is updated from time to time to include new information.

2,985 citations

Journal ArticleDOI
TL;DR: A binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors.
Abstract: On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of $\sim 1.7\,{\rm{s}}$ with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg2 at a luminosity distance of ${40}_{-8}^{+8}$ Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 $\,{M}_{\odot }$. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at $\sim 40\,{\rm{Mpc}}$) less than 11 hours after the merger by the One-Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ~10 days. Following early non-detections, X-ray and radio emission were discovered at the transient's position $\sim 9$ and $\sim 16$ days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC 4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta.

2,746 citations

Journal ArticleDOI
M. P. van Haarlem1, Michael W. Wise2, Michael W. Wise1, A. W. Gunst1  +219 moreInstitutions (27)
TL;DR: In dit artikel zullen the authors LOFAR beschrijven: van de astronomische mogelijkheden met de nieuwe telescoop tot aan een nadere technische beshrijving of het instrument.
Abstract: LOFAR, the LOw-Frequency ARray, is a new-generation radio interferometer constructed in the north of the Netherlands and across europe. Utilizing a novel phased-array design, LOFAR covers the largely unexplored low-frequency range from 10-240 MHz and provides a number of unique observing capabilities. Spreading out from a core located near the village of Exloo in the northeast of the Netherlands, a total of 40 LOFAR stations are nearing completion. A further five stations have been deployed throughout Germany, and one station has been built in each of France, Sweden, and the UK. Digital beam-forming techniques make the LOFAR system agile and allow for rapid repointing of the telescope as well as the potential for multiple simultaneous observations. With its dense core array and long interferometric baselines, LOFAR achieves unparalleled sensitivity and angular resolution in the low-frequency radio regime. The LOFAR facilities are jointly operated by the International LOFAR Telescope (ILT) foundation, as an observatory open to the global astronomical community. LOFAR is one of the first radio observatories to feature automated processing pipelines to deliver fully calibrated science products to its user community. LOFAR's new capabilities, techniques and modus operandi make it an important pathfinder for the Square Kilometre Array (SKA). We give an overview of the LOFAR instrument, its major hardware and software components, and the core science objectives that have driven its design. In addition, we present a selection of new results from the commissioning phase of this new radio observatory.

2,067 citations

Book
01 Jan 1981
TL;DR: In this paper, the authors provide a complete treatment of techniques for analyzing gravitation theory and experience, taking into account the Dicke framework, basic criteria for the viability of a gravitation theories, experimental tests of the Einstein equivalence principle, Schiff's conjecture, and a model theory devised by Lightman and Lee (1973).
Abstract: New technological advances have made it feasible to conduct measurements with precision levels which are suitable for experimental tests of the theory of general relativity. This book has been designed to fill a new need for a complete treatment of techniques for analyzing gravitation theory and experience. The Einstein equivalence principle and the foundations of gravitation theory are considered, taking into account the Dicke framework, basic criteria for the viability of a gravitation theory, experimental tests of the Einstein equivalence principle, Schiff's conjecture, and a model theory devised by Lightman and Lee (1973). Gravitation as a geometric phenomenon is considered along with the parametrized post-Newtonian formalism, the classical tests, tests of the strong equivalence principle, gravitational radiation as a tool for testing relativistic gravity, the binary pulsar, and cosmological tests.

1,692 citations

References
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Journal ArticleDOI

6,521 citations

Journal ArticleDOI
01 Dec 1964-Nature
TL;DR: In this article, the authors used the black-body equations to calculate the increased radiation appropriate to the observed brightness increase in the star over a 1,000 A.u. band-width at 5,400 A.U.
Abstract: Previous observations 4 of flares on EV Lacertae in yellow and blue light have ~hown that 1/(yellow)/J/(blue) = 0·23 at maximum light, and this has been used as tho correction factor. The estimates of tho optical and radio energies in the flares on the three stars are given in Table 2. The optical energies havo been obtained by using the black-body equations to calculate the increased radiation appropriate to the observed brightness increase in the star over a 1,000 A.u. band-width at 5,400 A.u. The apparent photovisual magnitudes mpv quoted in Table 2 are for the combined light of both components of the binary in the case of UV Ceti, and it is assumed that the stars radiate uniformly into TC steradians. The energies are based on a stellar radius of 0·080 for UV Ceti and for radii typical of dM5e stars in the case of EV L acortao and Ross 882.

366 citations

Journal ArticleDOI
TL;DR: In this article, the authors discuss the association of solar cosmic rays with flare association, solar particle acceleration, recurrence and low energy solar particle events, and discuss the effects of solar particle particle acceleration.
Abstract: Solar cosmic rays, discussing flare association, solar particle acceleration, recurrence and low energy solar particle events

54 citations

Journal ArticleDOI
20 Feb 1965-Nature
TL;DR: In this paper, it was shown that the importance of the early cooling by emission of neutrinos from the Urca process has been underestimated in the foregoing investigations, and the calculations of Miss Tsuruta indicate that a neutron star will rapidly cool to 3 or 4 × 106 °K, but that after 105 years its surface temperature will still be about 2 × 106°K.
Abstract: WITH the discovery of X-ray sources in the sky1,2, speculation has arisen that they might be associated with neutron or hyperon stars formed during the internal collapse which triggers off supernova explosions (probably of type I). Rates of cooling of neutron star models have been calculated by Morton3, Chiu and Salpeter4,5, and Tsuruta6. It appears (J. Bahcall, personal communication) that the importance of the early cooling by emission of neutrinos from the ‘Urca’ process has been underestimated in the foregoing investigations. With rough allowance for this effect, the calculations of Miss Tsuruta indicate that a neutron star will rapidly cool to 3 or 4 × 106 °K, but that after 105 years its surface temperature will still be about 2 × 106 °K.

37 citations