Protostars and Planets VI

When surrounded by a transparent emission region, black holes are expected to reveal a dark shadow caused by gravitational light bending and photon capture at the event horizon. To image and study this phenomenon, we have assembled the Event Horizon Telescope, a global very long baseline interferometry array observing at a wavelength of 1.3 mm. This allows us to reconstruct event-horizon-scale images of the supermassive black hole candidate in the center of the giant elliptical galaxy M87. We have resolved the central compact radio source as an asymmetric bright emission ring with a diameter of 42 +/- 3 mu as, which is circular and encompasses a central depression in brightness with a flux ratio greater than or similar to 10: 1. The emission ring is recovered using different calibration and imaging schemes, with its diameter and width remaining stable over four different observations carried out in different days. Overall, the observed image is consistent with expectations for the shadow of a Kerr black hole as predicted by general relativity. The asymmetry in brightness in the ring can be explained in terms of relativistic beaming of the emission from a plasma rotating close to the speed of light around a black hole. We compare our images to an extensive library of ray-traced general-relativistic magnetohydrodynamic simulations of black holes and derive a central mass of M = (6.5 +/- 0.7) x 10(9) M-circle dot. Our radio-wave observations thus provide powerful evidence for the presence of supermassive black holes in centers of galaxies and as the central engines of active galactic nuclei. They also present a new tool to explore gravity in its most extreme limit and on a mass scale that was so far not accessible.

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First M87 Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole

We review the properties and behavior of 20 X-ray binaries that contain a dynamically-confirmed black hole, 17 of which are transient systems. During the past decade, many of these transien...

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X-Ray Properties of Black-Hole Binaries

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.

Theory and Experiment in Gravitational Physics

Part I. Astronomical Background: 1. High energy astrophysics - an introduction 2. The stars and stellar evolution 3. The galaxies 4. Clusters of galaxies Part II. Physical Processes: 5. Ionisation losses 6. Radiation of accelerated charged particles and bremsstrahlung of electrons 7. The dynamics of charged particles in magnetic fields 8. Synchrotron radiation 9. Interactions of high energy photons 10. Nuclear interactions 11. Aspects of plasma physics and magnetohydrodynamics Part III. High Energy Astrophysics in our Galaxy: 12. Interstellar gas and magnetic fields 13. Dead stars 14. Accretion power in astrophysics 15. Cosmic rays 16. The origin of cosmic rays in our galaxy 17. The acceleration of high energy particles Part IV. Extragalactic High Energy Astrophysics: 18. Active galaxies 19. Black holes in the nuclei of galaxies 20. The vicinity of the black hole 21. Extragalactic radio sources 22. Compact extragalactic sources and superluminal motions 23. Cosmological aspects of high energy astrophysics Appendix References Index.

High Energy Astrophysics

WE have reported1 that the spectrum, colours and interstellar features in the star HD 226868, which is coincident with the X-ray star Cygnus X-1 and a radio star2,3, were those of a normal BOIb supergiant. We made measurements of the radial velocity of the star from August 1971 to October 1971 and find it to be a velocity variable, whose changes of velocity correlate with changes in the X-ray flux.

Cygnus X-1—a Spectroscopic Binary with a Heavy Companion ?

A collaboration between the Institute of Physics Publishing and Macmillan Reference Ltd, this work presents an extensive and comprehensive reference on astronomy and astrophysics. It has 800 contributors, over 2500 entries, is extensively cross-referenced - over 7500 links, and has extensive indexes - up to 12000 index entries. It should be of interest to undergraduates, graduate students, researchers and professionals, as well as to committed amateurs, librarians and lay people.

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Encyclopedia of Astronomy and Astrophysics

The optical properties of a sample of 53 active galactic nuclei (AGN) which exhibit an ultra-soft X-ray excess are examined. These AGN have been identified as part of the Ultra-Soft Survey (USS) which is selected from Einstein IPC sources. Optical spectra of 27 of these AGN are presented, from which continuum and line parameters are measured, including fluxes, line FWHM and equivalent widths. Accurate B and R magnitudes are measured from CCD images. A UV spectrum of one USS AGN, E0132-411, has been obtained with IUE and is combined with the optical and X-ray data to produce a multiwavelength spectrum. A large proportion of narrowline objects among the USS AGN is found. A comparison of the USS Hβ FWHM distribution with other X-ray selected samples confirms that the permitted lines of the USS AGN are biased to narrow widths

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Optical properties of active galaxies with ultra-soft X-ray spectra

The Lambda Orionis association has the photometric properties of a typical young cluster with an age of about 4 million yr. Its distance is 400 + or - 40 pc. Attention is drawn to the lack of a dense molecular cloud and associated infrared sources in this young grouping

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The Lambda Orionis association

PULSED optical emission has been detected from the Vela pulsar, PSR 0833–45. Double pulses were detected from an area which included Lasker's1 star M. The pulsed emission has a time-averaged blue magnitude of approximately 25.2 min.

Paul Murdin

Papers

Cygnus X-1—a Spectroscopic Binary with a Heavy Companion ?

Encyclopedia of Astronomy and Astrophysics

Optical properties of active galaxies with ultra-soft X-ray spectra

The Lambda Orionis association

Detection of optical pulses from the Vela pulsar