Superorbital variability of X-ray and radio emission of Cyg X-1. I. Emission anisotropy of precessing sources - AstrophysicsReportar como inadecuado




Superorbital variability of X-ray and radio emission of Cyg X-1. I. Emission anisotropy of precessing sources - Astrophysics - Descarga este documento en PDF. Documentación en PDF para descargar gratis. Disponible también para leer online.

Abstract: We study theoretical interpretations of the 150-d superorbital modulationobserved in X-ray and radio emission of Cyg X-1 in the framework of modelsconnecting this phenomenon to precession. Precession changes the orientation ofthe emission source either disc or jet relative to the observer. This leadsto emission modulation due to an anisotropic emission pattern of the source ororientation-dependent amount of absorbing medium along the line of sight orboth. We consider, in particular, anisotropy patterns of blackbody-typeemission, thermal Comptonization in slab geometry, jet-outflow beaming, andabsorption in a coronal-type medium above the disc. We then fit these models tothe data from the RXTE-ASM, CGRO-BATSE, and the Ryle and Green Bank radiotelescopes, and find relatively small best-fit angles between the precessionand orbital planes, ~10-20 degrees. The thermal Comptonization model for theX-ray emission explains well the observed decrease of the variability amplitudefrom 1 to 300 keV as a result of a reduced anisotropy of the emission due tomultiple scatterings. Our modeling also yield the jet bulk velocity of~0.3-0.5c, which is in agreement with the previous constraint from the lackof an observed counterjet and lack of short-term X-ray-radio correlations.



Autor: A. Ibragimov 1,2, A. A. Zdziarski 3, J. Poutanen 1 1 Astronomy Division, University of Oulu, Finland, 2 Kazan State University, A

Fuente: https://arxiv.org/







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