期刊
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
卷 451, 期 4, 页码 4375-4383出版社
OXFORD UNIV PRESS
DOI: 10.1093/mnras/stv1218
关键词
accretion; accretion discs; black hole physics; X-rays: binaries; X-rays: galaxies
资金
- ERC
- Simons Foundation Fellows Program (US)
- Sackler Fellowship Program (Cambridge)
- STFC [ST/K000985/1] Funding Source: UKRI
- Science and Technology Facilities Council [1233534] Funding Source: researchfish
- UK Space Agency [ST/L005611/1] Funding Source: researchfish
The focusing optics of NuSTAR have enabled high signal-to-noise ratio spectra to be obtained from many X-ray bright active galactic nuclei (AGN) and galactic black hole binaries (BHB). Spectral modelling then allows robust characterization of the spectral index and upper energy cutoff of the coronal power-law continuum, after accounting for reflection and absorption effects. Spectral-timing studies, such as reverberation and broad iron line fitting, of these sources yield coronal sizes, often showing them to be small and in the range of 3 to 10 gravitational radii in size. Our results indicate that coronae are hot and radiatively compact, lying close to the boundary of the region in the compactness-temperature (I similar to - a) diagram which is forbidden due to runaway pair production. The coincidence suggests that pair production and annihilation are essential ingredients in the coronae of AGN and BHB and that they control the shape of the observed spectra.
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