Abstract
THE peculiar emission line object SS433 has recently been the subject of interest following new spectrophotometric observations by Margon et al.1, and previous suggestions identifying it with the supernova remnant (SNR) W50 (ref. 2) and also with the X-ray source A1909+04 (ref. 3). Margon et al.1 report “three very strong (equivalent widths 50–150 Å) broad emission features in the green, red and IR, which change in intensity, profile and wavelength daily.” In this note we propose that the reported red and IR lines (at ∼6,000 Å and ∼7,400 Å, respectively) are Doppler-shifted Hα lines which are emitted from a ring of matter orbiting around a ∼106 M⊙ black hole. (The green line at ∼5,200 Å may be the redshifted Hβ line.) The ring itself may be part of an accretion disk and its radius is ∼20–25 gravitational radii (Rg ≡ 2GM/c2). The intensity of an emission line per observed Doppler-shifted frequency interval in such a ring is maximal at the two extreme ends of the spectrum4, in any case of emission constant along the ring. These maxima are quite sharp; in the non-relativistic case, we have dIv/dv∝{v02−(∂v)2}−½ where ∂v is the frequency shift and v0 depends on the radius of the ring and on its inclination with respect to us. Also, due to the gravitational redshift in our case, the centre-of-mass of the red and IR lines emitted from such ring is additionally redshifted.
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AMITAI-MILCHGRUB, A., PIRAN, T. & SHAHAM, J. SS433—a massive black hole?. Nature 279, 505 (1979). https://doi.org/10.1038/279505a0
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DOI: https://doi.org/10.1038/279505a0
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