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Explaining the spectrum of Sagittarius A* with a model of an accreting black hole

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Abstract

THE radio source at the centre of our Galaxy1, Sagittarius A* (Sgr A*), seems to be a low-luminosity version of active galactic nuclei—a massive black hole that is accreting gas from the surrounding region1,2. This idea is supported by observations of the gas and stars within 1 pc of Sgr A*, which appear to move under the influence of a large central mass1,3,4. A recent determination of the upper limit5,6 to the hard X-ray emission from the Galactic Centre has posed a problem for this picture, however, as the mass accretion rate implied by applying a standard accretion model to the X-ray data is far below that estimated from the observations of gas flows. Here we present a new model of accretion onto Sgr A*, in which most of the energy released is carried along with the gas and lost into the black hole of mass ∼7 x 105 solar masses, rather than appearing as radiation. The model fits the observed spectrum of Sgr A* from radio to hard X-ray wavelengths, and reconciles the low observed luminosity with a high mass-accretion rate.

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Authors and Affiliations

  1. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts, 02138, USA

    Ramesh Narayan, Insu Yi & Rohan Mahadevan

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  1. Ramesh Narayan
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  2. Insu Yi
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  3. Rohan Mahadevan
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Narayan, R., Yi, I. & Mahadevan, R. Explaining the spectrum of Sagittarius A* with a model of an accreting black hole. Nature 374, 623–625 (1995). https://doi.org/10.1038/374623a0

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  • DOI: https://doi.org/10.1038/374623a0

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